1 GSPS Quadrature Digital Upconverter
with 18-Bit I/Q Data Path and 14-Bit DAC
Data Sheet
AD9957
Rev. C
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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Fax: 781.461.3113 ©2007–2012 Analog Devices, Inc. All rights reserved.
FEATURES
1 GSPS internal clock speed (up to 400 MHz analog output)
Integrated 1 GSPS 14-bit DAC
250 MSPS input data rate
Phase noise ≤ −125 dBc/Hz (400 MHz carrier @ 1 kHz offset)
Excellent dynamic performance >80 dB narrow-band SFDR
8 programmable profiles for shift keying
Sin(x)/(x) correction (inverse sinc filter)
Reference clock multiplier
Internal oscillator for a single crystal operation
Software and hardware controlled power-down
Integrated RAM
Phase modulation capability
Multichip synchronization
Easy interface to Blackfin SPORT
Interpolation factors from 4× to 252×
Interpolation DAC mode
Gain control DAC
Internal divider allows references up to 2 GHz
1.8 V and 3.3 V power supplies
100-lead TQFP_EP package
APPLICATIONS
HFC data, telephony, and video modems
Wireless base station transmissions
Broadband communications transmissions
Internet telephony
GENERAL DESCRIPTION
The AD9957 functions as a universal I/Q modulator and agile
upconverter for communications systems where cost, size, power
consumption, and dynamic performance are critical. The AD9957
integrates a high speed, direct digital synthesizer (DDS), a high
performance, high speed, 14-bit digital-to-analog converter (DAC),
clock multiplier circuitry, digital filters, and other DSP functions
onto a single chip. It provides baseband upconversion for data
transmission in a wired or wireless communications system.
The AD9957 is the third offering in a family of quadrature
digital upconverters (QDUCs) that includes the AD9857 and
AD9856. It offers performance gains in operating speed, power
consumption, and spectral performance. Unlike its predecessors,
it supports a 16-bit serial input mode for I/Q baseband data.
The device can alternatively be programmed to operate either as
a single tone, sinusoidal source or as an interpolating DAC.
The reference clock input circuitry includes a crystal oscillator,
a high speed, divide-by-two input, and a low noise PLL for
multiplication of the reference clock frequency.
The user interface to the control functions includes a serial port
easily configured to interface to the SPORT of the Blackfin®
DSP and profile pins to enable fast and easy shift keying of any
signal parameter (phase, frequency, or amplitude).
FUNCTIONAL BLOCK DIAGRAM
FORMAT AND
INTERPOLATE
NCO
I
Q
REF E RE NCE CLOCK INPUT
I/Q DATADATA
FOR
XMIT
REF E RE NCE CLOCK
INP UT CIRCUIT RY
TIMING
AND
CONTROL
14-BI T DAC
USER INTE R FACE
06384-001
AD9957
Figure 1.
AD9957 Data Sheet
Rev. C | Page 2 of 64
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 4
Specifications ..................................................................................... 5
Electrical Specifications ............................................................... 5
Absolute Maximum Ratings ............................................................ 8
ESD Caution .................................................................................. 8
Pin Configuration and Function Descriptions ............................. 9
Typical Performance Characteristics ........................................... 12
Modes of Operation ....................................................................... 16
Overview ...................................................................................... 16
Quadrature Modulation Mode ................................................. 17
BlackFin Interface (BFI) Mode ................................................. 18
Interpolating DAC Mode .......................................................... 19
Single Tone Mode ....................................................................... 20
Signal Processing ............................................................................ 21
Parallel Data Clock (PDCLK) ................................................... 21
Transmit Enable Pin (TxEnable) .............................................. 21
Input Data Assembler ................................................................ 22
Inverse CCI Filter ....................................................................... 23
Fixed Interpolator (4×) .............................................................. 23
Programmable Interpolating Filter .......................................... 24
QDUC Mode ........................................................................... 24
BFI Mode ................................................................................. 24
Quadrature Modulator .............................................................. 25
DDS Core ..................................................................................... 25
Inverse Sinc Filter ....................................................................... 25
Output Scale Factor (OSF) ........................................................ 26
14-Bit DAC .................................................................................. 26
Auxiliary DAC ........................................................................ 26
RAM Control .................................................................................. 27
RAM Overview ........................................................................... 27
RAM Segment Registers ............................................................ 27
RAM State Machine ................................................................... 27
RAM Trigger (RT) Pin ............................................................... 27
Load/Retrieve RAM Operation ................................................ 28
RAM Playback Operation ......................................................... 28
Overview of RAM Playback Modes ......................................... 29
RAM Ramp-Up Mode ........................................................... 29
RAM Bidirectional Ramp Mode .......................................... 30
RAM Continuous Bidirectional Ramp Mode .................... 32
RAM Continuous Recirculate Mode ................................... 33
Clock Input (REF_CLK) ................................................................ 34
REFCLK Overview ..................................................................... 34
Crystal Driven REF_CLK ......................................................... 34
Direct Driven REF_CLK ........................................................... 34
Phase-Locked Loop (PLL) Multiplier ...................................... 35
PLL Charge Pump ...................................................................... 36
External PLL Loop Filter Components ................................... 36
PLL Lock Indication .................................................................. 36
Additional Features ........................................................................ 37
Output Shift Keying (OSK) ....................................................... 37
Manual OSK ............................................................................ 37
Automatic OSK ....................................................................... 37
Profiles ......................................................................................... 38
I/O_UPDATE Pin ...................................................................... 38
Automatic I/O Update ............................................................... 38
Power-Down Control ................................................................ 39
General-Purpose I/O (GPIO) Port .......................................... 39
Synchronization of Multiple Devices ........................................... 40
Overview ..................................................................................... 40
Clock Generator ......................................................................... 40
Data Sheet AD9957
Rev. C | Page 3 of 64
Sync Generator ............................................................................ 40
Sync Receiver ............................................................................... 41
Setup/Hold Validation ................................................................ 42
Synchronization Example .......................................................... 44
I/Q Path Latency ......................................................................... 45
Example .................................................................................... 45
Power Supply Partitioning ............................................................. 46
3.3 V Supplies .............................................................................. 46
DVDD_I/O (Pin 11, Pin 15, Pin 21, Pin 28, Pin 45, Pin 56,
Pin 66) ...................................................................................... 46
AVDD (Pin 74 to Pin 77 and Pin 83) ................................... 46
1.8 V Supplies .............................................................................. 46
DVDD (Pin 17, Pin 23, Pin 30, Pin 47, Pin 57, Pin 64) ..... 46
AVDD (Pin 3) .......................................................................... 46
AVDD (Pin 6) .......................................................................... 46
AVDD (Pin 89 and Pin 92) .................................................... 46
Serial Programming ........................................................................ 47
Control Interface—Serial I/O .................................................... 47
General Serial I/O Operation .................................................... 47
Instruction Byte ........................................................................... 47
Instruction Byte Information Bit Map ................................. 47
Serial I/O Port Pin Descriptions ............................................... 47
SCLK—Serial Clock................................................................ 47
CS—Chip Select Bar ............................................................... 47
SDIO—Serial Data Input/Output ......................................... 47
SDO—Serial Data Out ........................................................... 48
I/O_RESET—Input/Output Reset ........................................ 48
I/O_UPDATE—Input/Output Update ................................ 48
Serial I/O Timing Diagrams ...................................................... 48
MSB/LSB Transfers ..................................................................... 48
I/O_UPDATE, SYNC_CLK, and System Clock
Relationships ................................................................................ 49
Register Map and Bit Descriptions ............................................... 50
Register Map ................................................................................ 50
Register Bit Descriptions............................................................ 55
Control Function Register 1 (CFR1) .................................... 55
Control Function Register 2 (CFR2) .................................... 56
Control Function Register 3 (CFR3) .................................... 58
Auxiliary DAC Control Register ........................................... 58
I/O Update Rate Register ....................................................... 58
RAM Segment Register 0 ....................................................... 58
RAM Segment Register 1 ....................................................... 59
Amplitude Scale Factor (ASF) Register ............................... 59
Multichip Sync Register ......................................................... 59
Profile Registers ........................................................................... 60
Profile<7:0> Register—Sing le Tone ...................................... 60
Profile<7:0> Register—QDUC ............................................. 60
RAM Register .......................................................................... 60
GPIO Configuration Register ............................................... 60
GPIO Data Register ................................................................ 60
Outline Dimensions ........................................................................ 61
Ordering Guide ........................................................................... 61
AD9957 Data Sheet
Rev. C | Page 4 of 64
REVISION HISTORY
4/12—Re v. B to Rev. C
Changes to Table 1 ............................................................................ 7
Changes to Table 3 .......................................................................... 11
Change to Sync Generator Section ............................................... 41
Changes to Sync Receiver Section and Setup/Hold Validation
Section .............................................................................................. 42
Changes to Table 13 ........................................................................ 50
Changes to Table 19 ........................................................................ 57
Changes to Table 26 ........................................................................ 59
10/10—Re v. A to Rev. B
Changes to Data Rate in Features Section ..................................... 1
Changes to Specifications Section .................................................. 6
Added EPAD Notation to Figure 4 and Table 3 ........................... 9
Changes to XTAL_SEL Pin Description ...................................... 11
Changes to BlackFin Interface (BFI) Mode Section .................. 18
Changes to Figure 30 and Figure 31 ............................................. 22
Changes to Programmable Interpolating Filter Section ............ 24
Changes to Fifth Paragraph of Quadrature Modulator Section...... 25
Changes to RAM Segment Registers Section ............................. 27
Changes to RAM Playback Operation Section ........................... 28
Changes to Control Interface—Serial I/O Section ..................... 47
Added to I/O_UPDATE, SYNC_CLK, and System Clock
Relationships Section and Figure 64 ............................................ 49
Changes to Default Values of Profile 0 Register—Single Tone
(0x0E) and Profile 0 Register—QDUC (0x0E) in Table 14 ....... 51
Changes to Default Values in Table 15 ......................................... 52
Changes to Default Values in Table 16 ......................................... 53
Changes to Default Values in Table 17 ......................................... 54
Updated Outline Dimensions ....................................................... 61
1/08—Re v. 0 to Rev. A
Changes to REFCLK Multiplier Specification ............................... 3
Changes to I/O_Update/Profile<2:0>/RT Timing
Characteristics and I/Q Input Timing Characteristics ................. 5
Replaced Pin Configuration and Function Descriptions
Section ................................................................................................. 8
Changes to Figure 25 Through Figure 29.................................... 15
Deleted Table 4, Renumbered Sequentially ................................ 20
Changes to DDS Core Section ...................................................... 24
Changes to Figure 47 and Table 6................................................. 33
Replaced Synchronization of Multiple Devices Section ............ 39
Added I/Q Path Latency Section .................................................. 44
Added Power Supply Partitioning Section .................................. 45
Changes to General Serial I/O Operation Section ..................... 46
Changes to Table 13 ....................................................................... 48
Changes to Table 14 ....................................................................... 49
Changes to Table 19 ....................................................................... 54
Changes to Table 20 ....................................................................... 56
Changes to GPIO Configuration Register and
GPIO Data Register Sections ........................................................ 58
5/07—Revision 0: Initial Version
Data Sheet AD9957
Rev. C | Page 5 of 64
SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
AVDD (1.8V) and DVDD (1.8V) = 1.8 V ± 5%, AVDD (3.3V) = 3.3 V ± 5%, DVDD_I/O (3.3V) = 3.3 V ± 5%, T = 25°C, RSET = 10 kΩ,
IOUT = 20 mA, external reference clock frequency = 1000 MHz with REFCLK multiplier disabled, unless otherwise noted.
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
REF_CLK INPUT CHARACTERISTICS
Frequency Range
REFCLK Multiplier
Disabled
60
10001
MHz
Enabled 3.2 60 MHz
Maximum REFCLK Input Divider Frequency Full temperature range 1500 1900 MHz
Minimum REFCLK Input Divider Frequency Full temperature range 25 35 MHz
External Crystal 25 MHz
Input Capacitance 3 pF
Input Impedance (Differential)
2.8
kΩ
Input Impedance (Single-Ended) 1.4 kΩ
Duty Cycle REFCLK multiplier disabled 45 55 %
REFCLK multiplier enabled 40 60 %
REF_CLK Input Level Single-ended 50 1000 mV p-p
Differential
100
2000
mV p-p
REFCLK MULTIPLIER VCO GAIN CHARACTERISTICS
VCO Gain (KV) @ Center Frequency VCO0 range setting 429 MHz/V
VCO1 range setting
500
MHz/V
VCO2 range setting 555 MHz/V
VCO3 range setting 750 MHz/V
VCO4 range setting 789 MHz/V
VCO5 range setting2 850 MHz/V
REFCLK_OUT CHARACTERISTICS
Maximum Capacitive Load 20 pF
Maximum Frequency 25 MHz
DAC OUTPUT CHARACTERISTICS
Full-Scale Output Current 8.6 20 31.6 mA
Gain Error −10 +10 %FS
Output Offset
2.3
µA
Differential Nonlinearity 0.8 LSB
Integral Nonlinearity 1.5 LSB
Output Capacitance 5 pF
Residual Phase Noise @ 1 kHz Offset, 20 MHz AOUT
REFCLK Multiplier Disabled −152 dBc/Hz
Enabled @ 20×
−140
dBc/Hz
Enabled @ 100× −140 dBc/Hz
AC Voltage Compliance Range −0.5 +0.5 V
SPURIOUS-FREE DYNAMIC RANGE (SFDR SINGLE TONE)
fOUT = 20.1 MHz −70 dBc
fOUT = 98.6 MHz −69 dBc
fOUT = 201.1 MHz −61 dBc
fOUT = 397.8 MHz −54 dBc
AD9957 Data Sheet
Rev. C | Page 6 of 64
Parameter Test Conditions/Comments Min Typ Max Unit
NOISE SPECTRAL DENSITY (NSD)
Single Tone
fOUT = 20.1 MHz −167 dBm/Hz
fOUT = 98.6 MHz −162 dBm/Hz
f
OUT
= 201.1 MHz
−157
dBm/Hz
fOUT = 397.8 MHz −151 dBm/Hz
TWO-TONE INTERMODULATION DISTORTION (IMD) I/Q rate = 62.5 MSPS; 16× interpolation
f
OUT
= 25 MHz
−82
dBc
fOUT = 50 MHz −78 dBc
fOUT = 100 MHz −73 dBc
MODULATOR CHARACTERISTICS
Input Data
Error Vector Magnitude 2.5 Msymbols/s, QPSK, 4× oversampled 0.53 %
270.8333 ksymbols/s, GMSK, 32×
oversampled
0.77 %
2.5 Msymbols/s, 256-QAM, 4×
oversampled
0.35 %
WCDMA—FDD (TM1), 3.84 MHz Bandwidth,
5 MHz Channel Spacing
Adjacent Channel Leakage Ratio (ACLR) IF = 143.88 MHz −78 dBc
Carrier Feedthrough
−78
dBc
SERIAL PORT TIMING CHARACTERISTICS
Maximum SCLK Frequency
70
Mbps
Minimum SCLK Pulse Width Low 4 ns
High 4 ns
Maximum SCLK Rise/Fall Time 2 ns
Minimum Data Setup Time to SCLK 5 ns
Minimum Data Hold Time to SCLK 0 ns
Maximum Data Valid Time in Read Mode 11 ns
I/O_UPDATE/PROFILE<2:0>/RT TIMING CHARACTERISTICS
Minimum Pulse Width
High
1
SYNC_CLK
cycle
Minimum Setup Time to SYNC_CLK 1.75 ns
Minimum Hold Time to SYNC_CLK 0 ns
I/Q INPUT TIMING CHARACTERISTICS
Maximum PDCLK Frequency 250 MHz
Minimum I/Q Data Setup Time to PDCLK 1.75 ns
Minimum I/Q Data Hold Time to PDCLK 0 ns
Minimum TxEnable Setup Time to PDCLK 1.75 ns
Minimum TxEnable Hold Time to PDCLK
0
ns
MISCELLANEOUS TIMING CHARACTERISTICS
Wake-Up Time3 1
Fast Recovery Mode 8 SYSCLK cycles4
Full Sleep Mode 150 μs
Minimum Reset Pulse Width High 5 SYSCLK cycles4
DATA LATENCY (PIPELINE DELAY)
Data Latency Single Tone Mode
Frequency, Phase-to-DAC Output 79 SYSCLK cycles4
Data Sheet AD9957
Rev. C | Page 7 of 64
Parameter Test Conditions/Comments Min Typ Max Unit
CMOS LOGIC INPUTS
Voltage
Logic 1 2.0 V
Logic 0 0.8 V
Current
Logic 1 90 150 µA
Logic 0 90 150 µA
Input Capacitance 2 pF
XTAL_SEL INPUT
Logic 1 Voltage 1.25 V
Logic 0 Voltage 0.6 V
Input Capacitance 2 pF
CMOS LOGIC OUTPUTS 1 mA load
Voltage
Logic 1 2.8 V
Logic 0 0.4 V
POWER SUPPLY CURRENT
DVDD_I/O (3.3V) Pin Current Consumption QDUC mode 16 mA
DVDD (1.8V) Pin Current Consumption
QDUC mode
610
mA
AVDD (3.3V) Pin Current Consumption QDUC mode 28 mA
AVDD (1.8V) Pin Current Consumption QDUC mode 105 mA
POWER CONSUMPTION
Single Tone Mode 800 mW
Continuous Modulation 8× interpolation 1400 1800 mW
Inverse Sinc Filter Power Consumption 150 200 mW
Full Sleep Mode 12 40 mW
1 The system clock is limited to 750 MHz maximum in BFI mode.
2 The gain value for VCO range Setting 5 is measured at 1000 MHz.
3 Wake-up time refers to the recovery from analog power-down modes. The longest time required is for the Reference Clock Multiplier PLL to relock to the reference.
4 SYSCLK cycle refers to the actual clock frequency used on-chip by the DDS. If the reference clock multiplier is used to multiply the external reference clock frequency,
the SYSCLK frequency is the external frequency multiplied by the reference clock multiplication factor. If the reference clock multiplier and divider are not used, the
SYSCLK frequency is the same as the external reference clock frequency.
AD9957 Data Sheet
Rev. C | Page 8 of 64
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
AVDD (1.8V), DVDD (1.8V) Supplies 2 V
AVDD (3.3V), DVDD_I/O (3.3V) Supplies
4 V
Digital Input Voltage −0.7 V to +4 V
XTAL_SEL −0.7 V to +2.2 V
Digital Output Current 5 mA
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +85°C
θJA 22°C/W
θJC 2.8°C/W
Maximum Junction Temperature 150°C
Lead Temperature, Soldering (10 sec) 300°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
06384-003
AVOID OVERDRIVING DIGITAL INP UTS.
FORWARD BIAS ING E S D DIO DE S M AY
COUPLE DIGITAL NOISE ONTO PO W ER
PINS.
DIGITAL INP UTS
INPUT
DVDD_I/O
Figure 2. Equivalent Input Circuit
06384-055
MUST TERMINATE OUTPUTS TO AGND
FOR CURRENT FL OW. DO NOT EXCEED
THE OUTPUT VOLTAG E COMP LIANCE
RATING.
IOUT IOUT
DAC OUTPUT S
AVDD
Figure 3. Equivalent Output Circuit
ESD CAUTION
Data Sheet AD9957
Rev. C | Page 9 of 64
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
26
27
28
29
30
55
54
53
52
51
TQF P -100 ( E _PAD)
TOP VIEW
(Not t o S cale)
AD9957
D16
D15
DVDD_I /O ( 3.3V)
DGND
DVDD (1.8V)
5
4
3
2
7
6
9
8
1
11
10
16
15
14
13
18
17
20
19
22
21
12
24
23
25
32
33
34
35
36
38
39
40
41
42
43
44
45
46
47
48
49
50
31
37
D14
D13
D12
D11
D10
D9
D8
D7
D6
PDCLK
TxENABLE/FS
DGND
D5/SPORT I-DATA
D4/SPORT Q-DATA
D3
DVDD_I /O ( 3.3V)
DVDD (1.8V)
D2
D1
D0
80 IOUT
79 AGND
78 AGND
77 AVDD ( 3.3V)
76 AVDD ( 3.3V)
75 AVDD ( 3.3V)
74 AVDD ( 3.3V)
73 AGND
72 NC
71 I/O_RESET
70 CS
69 SCLK
68 SDO
67 SDIO
66 DVDD_I /O ( 3.3V)
65 DGND
64 DVDD (1.8V)
63 DGND
62 DGND
61 NC
60 OSK
59 I/O_UPDATE
58 DGND
57 DVDD (1.8V)
56 DVDD_I /O ( 3.3V)
SYNC_CLK
PROFILE0
PROFILE1
PROFILE2
RT
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
NC
NC
NC
NC
AGND
XTAL_SEL
REFCLK_OUT
NC
AVDD ( 1.8V)
REF_CLK
REF_CLK
AVDD ( 1.8V)
AGND
NC
NC
AGND
DAC_RSET
AVDD ( 3.3V)
AGND
IOUT
NC
PLL_LOOP_FILTER
AVDD ( 1.8V)
AGND
AGND
AVDD ( 1.8V)
SYNC_IN+
SYNC_IN–
SYNC_OUT+
SYNC_OUT–
DVDD_I /O ( 3.3V)
SYNC_SMP_ERR
DGND
MASTER_RESET
DVDD_I /O ( 3.3V)
DGND
DVDD (1.8V)
EXT_PWR_DWN
PLL_LOCK
CCI_OVFL
DVDD_I /O ( 3.3V)
DGND
DVDD (1.8V)
NC
D17
06384-004
PIN 1
INDICATOR
NOTES
1. NC = NO CO NNE CT.
2. EXPOSED PAD SHOUL D BE S OL DE RE D TO GRO UND.
Figure 4. Pin Configuration
AD9957 Data Sheet
Rev. C | Page 10 of 64
Table 3. Pin Function Descriptions
Pin No. Mnemonic I/O1 Description
1, 24, 61, 72, 86,
87, 93, 97 to 100
NC Not Connected. Allow device pin to float.
2 PLL_LOOP_FILTER I PLL-Loop Filter Compensation. See External PLL Loop Filter Components section.
3, 6, 89, 92 AVDD (1.8V) I Analog Core VDD. 1.8 V analog supplies.
74 to 77, 83 AVDD (3.3V) I Analog DAC VDD. 3.3 V analog supplies.
17, 23, 30, 47, 57,
64
DVDD (1.8V) I Digital Core VDD. 1.8 V digital supplies.
11, 15, 21, 28, 45,
56, 66
DVDD_I/O (3.3V) I Digital Input/Output VDD. 3.3 V digital supplies.
4, 5, 73, 78, 79,
82, 85, 88, 96
AGND
I
Analog Ground.
13, 16, 22, 29, 46,
58, 62, 63, 65
DGND I Digital Ground.
7 SYNC_IN+ I Synchronization Signal, Digital Input (Rising Edge Active). Synchronization signal from
external master to synchronize internal subclocks. See the Synchronization of Multiple
Devices section.
8 SYNC_IN− I Synchronization Signal, Digital Input (Falling Edge Active). Synchronization signal from
external master to synchronize internal subclocks. See the Synchronization of Multiple
Devices section.
9 SYNC_OUT+ O Synchronization Signal, Digital Output (Rising Edge Active). Synchronization signal from
internal device subclocks to synchronize external slave devices. See the Synchronization of
Multiple Devices section.
10 SYNC_OUT− O Synchronization Signal, Digital Output (Falling Edge Active). Synchronization signal from
internal device subclocks to synchronize external slave devices. See the Synchronization of
Multiple Devices section.
12 SYNC_SMP_ERR O Synchronization Sample Error, Digital Output (Active High). A high on this pin indicates
that the AD9957 did not receive a valid sync signal on SYNC_IN+/SYNC_IN−. See the
Synchronization of Multiple Devices section.
14 MASTER_RESET I Master Reset, Digital Input (Active High). This pin clears all memory elements and sets
registers to default values.
18 EXT_PWR_DWN I External Power-Down, Digital Input (Active High). A high level on this pin initiates the
currently programmed power-down mode. See the Power-Down Control section for
further details. If unused, tie to ground.
19 PLL_LOCK O PLL Lock, Digital Output (Active High). A high on this pin indicates that the clock multiplier
PLL has acquired lock to the reference clock input.
20 CCI_OVFL O CCI Overflow Digital Output, Active High. A high on this pin indicates a CCI filter overflow.
This pin remains high until the CCI overflow condition is cleared.
25 to 27, 31 to
39, 42 to 44, 48
to 50
D<17:0>
I/O
Parallel Data Input Bus (Active High). These pins provide the interleaved, 18-bit, digital, I
and Q vectors for the modulator to upconvert. Also used for a GPIO port in Blackfin
interface mode.
42 SPORT I-DATA I In Blackfin interface mode, this pin serves as the I-data serial input.
43 SPORT Q-DATA I In Blackfin interface mode, this pin serves as the Q-data serial input.
40 PDCLK O Parallel Data Clock, Digital Output (Clock). See the Signal Processing section for details.
41
TxENABLE/FS
I
Transmit Enable, Digital Input (Active High). See the Signal Processing section for details.
In Blackfin interface mode, this pin serves as the FS input to receive the RFS output signal
from the Blackfin.
51 RT I RAM Trigger, Digital Input (Active High). This pin provides control for the RAM amplitude
scaling function. When this function is engaged, a high sweeps the amplitude from the
beginning RAM address to the end. A low sweeps the amplitude from the end RAM
address to the beginning. If unused, connect to ground or supply.
52 to 54 PROFILE<2:0> I Profile Select Pins, Digital Inputs (Active High). These pins select one of eight
phase/frequency profiles for the DDS core (single tone or carrier tone). Changing the state
of one of these pins transfers the current contents of all I/O buffers to the corresponding
registers. State changes should be set up to the SYNC_CLK pin.
55
SYNC_CLK
O
Output System Clock/4, Digital Output (Clock). The I/O_UPDATE and PROFILE<2:0> pins
should be set up to the rising edge of this signal.
Data Sheet AD9957
Rev. C | Page 11 of 64
Pin No. Mnemonic I/O1 Description
59 I/O_UPDATE I/O Input/Output Update; Digital Input Or Output (Active High) Depending on the Internal I/O
Update Active Bit. A high on this pin indicates a transfer of the contents of the I/O buffers
to the corresponding internal registers.
60 OSK I Output Shift Keying, Digital Input (Active High). When using OSK (manual or automatic),
this pin controls the OSK function. See the Output Shift Keying (OSK) section of the data
sheet for details. When not using OSK, tie this pin high.
67 SDIO I/O Serial Data Input/Output, Digital Input/Output (Active High). This pin can be either
unidirectional or bidirectional (default), depending on configuration settings. In
bidirectional serial port mode, this pin acts as the serial data input and output. In
unidirectional, it is an input only.
68
SDO
O
Serial Data Output, Digital Output (Active High). This pin is only active in unidirectional
serial data mode. In this mode, it functions as the output. In bidirectional mode, this pin is
not operational and should be left floating.
69 SCLK I Serial Data Clock. Digital clock (rising edge on write, falling edge on read). This pin
provides the serial data clock for the control data path. Write operations to the AD9957
use the rising edge. Readback operations from the AD9957 use the falling edge.
70 CS I Chip Select, Digital Input (Active Low). Bringing this pin low enables the AD9957 to detect
serial clock rising/falling edges. Bringing this pin high causes the AD9957 to ignore input
on the serial data pins.
71 I/O_RESET I Input/Output Reset, Digital Input (Active High). Rather than resetting the entire device
during a failed communication cycle, when brought high, this pin resets the state machine
of the serial port controller and clears any I/O buffers that have been written since the last
I/O update. When unused, tie this pin to ground to avoid accidental resets.
80 IOUT O Open-Source DAC Complementary Output Source. Analog output, current mode. Connect
through 50 Ω to AGND.
81 IOUT O Open-Source DAC Output Source. Analog output, current mode. Connect through 50 Ω to
AGND.
84
DAC_RSET
O
Analog Reference Pin. This pin programs the DAC output full-scale reference current.
Attach a 10 kΩ resistor to AGND.
90 REF_CLK I Reference Clock Input. Analog input. See the REFCLK Overview section for more details.
91 REF_CLK I Complementary Reference Clock Input. Analog input. See the REFCLK Overview section
for more details.
94
REFCLK_OUT
O
Reference Clock Output. Analog output. See the REFCLK Overview section for more
details.
95 XTAL_SEL I Crystal Select (1.8 V Logic). Analog input (active high). Driving the XTAL_SEL pin high enables
the internal oscillator to be used with a crystal resonator. If unused, connect it to AGND.
(EPAD) Exposed Pad
(EPAD)
The EPAD should be soldered to ground.
1 I = input, O = output.
AD9957 Data Sheet
Rev. C | Page 12 of 64
TYPICAL PERFORMANCE CHARACTERISTICS
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0Hz 50MHz/DIV S TO P 500M Hz
06384-048
1
1
Figure 5. 15.625 kHz Quadrature Tone, Carrier = 102 MHz,
CCI = 16, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0MHz 50MHz/DIV S TO P 500M Hz
06384-050
1
1
Figure 6. 15.625 kHz Quadrature Tone, Carrier = 222 MHz,
CCI = 16, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0Hz 50MHz/DIV S TO P 500M Hz
06384-052
1
1
Figure 7. 15.625 kHz Quadrature Tone, Carrier = 372 MHz,
CCI = 16, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 102M Hz 5kHz/DIV SP AN 50kHz
06384-049
1
1
Figure 8. Narrow-Band View of Figure 5
(with Carrier and Lower Sideband Suppression)
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 222M Hz 5kHz/DIV SP AN 50kHz
06384-051
1
1
Figure 9. Narrow-Band View of Figure 6
(with Carrier And Lower Sideband Suppression)
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 372M Hz 5kHz/DIV SP AN 50kHz
06384-053
1
1
Figure 10. Narrow-Band View of Figure 7
(with Carrier and Lower Sideband Suppression)
Data Sheet AD9957
Rev. C | Page 13 of 64
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0Hz 50MHz/DIV S TO P 500M Hz
06384-044
Figure 11. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 102 MHz, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0MHz 50MHz/DIV S TO P 500M Hz
06384-045
Figure 12. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 222 MHz, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 ST ART 0Hz 50MHz/DIV S TO P 500M Hz
06384-046
Figure 13. QPSK, 7.8125 Msymbols/s, 4x Oversampled Raised Cosine,
α = 0.25, CCI = 8, Carrier = 372 MHz, fS = 1 GHz
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 102M Hz 2MHz/DIV S P AN 20M Hz
06384-041
Figure 14. Narrow-Band View of Figure 11
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 222M Hz 2MHz/DIV S P AN 20M Hz
06384-042
Figure 15. Narrow-Band View of Figure 12
0
–20
–10
–50
–40
–30
–80
–70
–60
–90
–100 CENT E R 372M Hz 2MHz/DIV S P AN 20M Hz
06384-043
Figure 16. Narrow-Band View of Figure 13
AD9957 Data Sheet
Rev. C | Page 14 of 64
–50
–55
–60
–65
–75
–70
06384-058
SF DR ( dBc)
FRE QUENCY OUT ( M Hz )
SFDR WITHOUT PLL
SFDR WITH PLL
050 100 150 200 250 300 350 400
Figure 17. Wideband SFDR vs. Output Frequency in Single Tone Mode,
PLL with REFCLK = 15.625 MHz × 64
400 450300250 350200150100500
06384-059
SF DR ( dBc)
FRE QUENCY OUT ( M Hz )
–75
–70
–65
–60
–55
–45
–50
LOW SUPPLY
HIGH SUPP LY
Figure 18. SFDR vs. Output Frequency and Supply (±5%) in Single Tone
Mode, REFCLK = 1 GHz
400 450300250 350200150100500
06384-060
SF DR ( dBc)
FRE QUENCY OUT ( M Hz )
–75
–70
–65
–60
–55
–50
–40°C
+85°C
Figure 19. SFDR vs. Frequency and Temperature in Single Tone Mode,
REFCLK = 1 GHz
–90
–100
–120
–110
–140
–150
–130
–170
–160
10 100 1k 10k 100k 100M1M 10M
06384-061
MAG NITUDE ( dBc/ Hz )
FREQUENCY OFFSET (Hz)
f
OUT
= 20.1M Hz
f
OUT
= 98.6M Hz
f
OUT
= 201.1M Hz
f
OUT
= 397.8M Hz
Figure 20. Residual Phase Noise, System Clock = 1 GHz
–90
–100
–110
–120
–130
–140
–150
–16010 100 1k 10k 100k 1M 10M 100M
06384-054
MAG NITUDE ( dBc/ Hz )
FREQUENCY OFFSET (Hz)
f
OUT = 20. 1M Hz
f
OUT = 397. 8M Hz
f
OUT = 98. 6M Hz
f
OUT = 201. 1M Hz
Figure 21. Residual Phase Noise Using the REFCLK Multiplier,
REFCLK = 50 MHz with 20x Multiplication, System Clock = 1 GHz
1200
200
400
600
800
1000
0
100 200 300 400 500 600 700 800 900 1000
06384-062
POWER DISSIPATI O N (mW)
SYSTEM CLOCK FREQUENCY (MHz)
DVDD 3. 3V
AVDD 3. 3V
AVDD 1. 8V
DVDD 1. 8V
Figure 22. Power Dissipation vs. System Clock (PLL Disabled)
Data Sheet AD9957
Rev. C | Page 15 of 64
1200
200
400
600
800
1000
0
400 500 600 700 800 900 1000
06384-063
POWER DISSIPATI O N (mW)
SYSTEM CLOCK FREQUENCY (MHz)
DVDD 1. 8V
AVDD 1. 8V
AVDD 3. 3V
DVDD 3. 3V
Figure 23. Power Dissipation vs. System Clock (PLL Enabled)
06384-064
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
CENT E R 143.86MHz S P AN 25.5MHz2.55MHz/DIV
Tx CHANNE L
BANDWIDTH: 3.84MHz
ADJACENT CHANNE L
BANDWIDTH: 3.84MHz
SPACING: 3M Hz
ADJACENT CHANNE L
BANDWIDTH: 3.84MHz
SPACING: 10M Hz
PO WER: –11.88d Bm
LOWE R: –78.27d B
UPPE R: –78.50dB
LOWE R: –81.42d B
UPPE R: –81.87dB
W-CDMA SGFF FWD
Figure 24. Typical ACLR for Wideband CDMA
AD9957 Data Sheet
Rev. C | Page 16 of 64
MODES OF OPERATION
OVERVIEW
The AD9957 has three basic operating modes.
• Quadrature modulation (QDUC) mode (default)
• Interpolating DAC mode
• Single tone mode
The active mode is selected via the operating mode bits in
Control Function Register 1 (CFR1). Single tone mode allows
the device to operate as a sinusoidal generator with the DDS
driving the DAC directly.
Interpolating DAC mode bypasses the DDS, allowing the user
to deliver baseband data to the device at a sample rate lower
than that of the DAC. An internal chain of rate interpolation
filters the user data and upsamples to the DAC sample rate.
Combined, the filters provide for programmable rate interpola-
tion while suppressing spectral images and retaining the original
baseband spectrum.
QDUC mode employs both the DDS and the rate interpolation
filters. In this case, two parallel banks of rate interpolation
filters allow baseband processing of in-phase and quadrature
(I/Q) signals with the DDS providing the carrier signal to be
modulated by the baseband signals. A detailed block diagram of
the AD9957 is shown in Figure 25.
The inverse sinc filter is available in all three modes.
06384-005
PDCLK
I/Q IN
EXT_PWR_DWN
DAC_RSET
IOUT
IOUT
TxENABLE
FTW
PW
DAC GAIN
θ
INVERSE
SINC
FILTER
CLOCK
FTW PW
8
SYSCLK
PLL
÷2
CLOCK MO DE
REF_CLK
REF_CLK
REFCLK_OUT
XTAL_SEL
PARAL LEL DATA
TIMI NG AND CO NTRO L
AD9957
ω
cos (ωt+θ)
sin (ωt+θ)
SYNC_OUT
SYNC_IN
PLL_LOCK
PLL_LOOP_FILTER
MASTER_RESET
22
CCI_OVFL
OSK
DDS AUX
DAC
8-BIT
POWER
DOWN
CONTROL
RT
RAM
PROFILE
SERIAL I/O
PORT
I/O_UPDATE
PROGRAMMING
REGISTERS
3I Q ISQS
18
DATA AS S E M BLER AND F ORMATT E R
I
Q
IS
QS
BLACKFIN INT E RFACE
18
18
16
16
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
OSK
INTERNAL CLO CK TI M ING AND CONTROL
DAC
14-BIT
OUTPUT
SCALE
FACTOR
SDIO
CS
I/O_RESET
SCLK
SDO
Figure 25. Detailed Block Diagram
Data Sheet AD9957
Rev. C | Page 17 of 64
QUADRATURE MODULATION MODE
A block diagram of the AD9957 operating in QDUC mode is
shown in Figure 26; grayed items are inactive. The parallel input
accepts 18-bit I- and Q-words in time-interleaved fashion. That
is, an 18-bit I-word is followed by an 18-bit Q-word, then the
next 18-bit I-word, and so on. One 18-bit I-word and one 18-bit
Q-word together comprise one internal sample. The data assem-
bler and formatter de-interleave the I- and Q-words so that each
sample propagates along the internal data pathway in parallel
fashion. Both I and Q data paths are active; the parallel data
clock (PDCLK) serves to synchronize the input of I/Q data to
the AD9957.
The PROFILE and I/O_UPDATE pins are also synchronous to
the PDCLK.
The DDS core provides a quadrature (sine and cosine) local
oscillator signal to the quadrature modulator, where the
interpolated I and Q samples are multiplied by the respective
phase of the carrier and summed together, producing a
quadrature modulated data stream. This data stream is routed
through the inverse sinc filter (optionally), and the output
scaling multiplier. Then it is applied to the 14-bit DAC to
produce the quadrature modulated analog output signal.
06384-006
PDCLK
I/Q IN
EXT_PWR_DWN
DAC_RSET
IOUT
IOUT
TxENABLE
DAC GAIN
OUTPUT
SCALE
FACTOR
θ
INVERSE
SINC
FILTER
CLOCK
FTW PW
8
SYSCLK
PLL
÷2
CLOCK MO DE
REF_CLK
REF_CLK
REFCLK_OUT
XTAL_SEL
AD9957
ω
cos (ωt+θ)
sin (ωt+θ)
SYNC_OUT
SYNC_IN
PLL_LOCK
PLL_LOOP_FILTER
MASTER_RESET
22
OSK
DDS AUX
DAC
8-BIT
POWER
DOWN
CONTROL
18
DATA ASSEMBLER AND FORMATTER
I
Q
IS
QS
BLACKFIN INT E R FACE
18
18
16
16
INVERSE
CCI
INVERSE
CCI
OSK
INTERNAL CLO CK TI M ING AND CONTROL
DAC
14-BIT
CCI_OVFL
FTW
PW
PARAL LEL DATA
TIMI NG AND CO NTRO L
RT
RAM
PROFILE
SERIAL I/O
PORT
I/O_UPDATE
PROGRAMMING
REGISTERS
3I Q ISQS
HALF-BAND
FILTERS (4×)
CCI
(1× T O 63×)
HALF-BAND
FILTERS (4×)
CCI
(1× T O 63×)
SDIO
CS
I/O_RESET
SCLK
SDO
Figure 26. Quadrature Modulation Mode
AD9957 Data Sheet
Rev. C | Page 18 of 64
BLACKFIN INTERFACE (BFI) MODE
A subset of the QDUC mode is the Blackfin interface (BFI)
mode, shown in Figure 27; grayed items are inactive. In this
mode, a separate I and Q serial bit stream is applied to the
baseband data port instead of parallel data-words. The two
serial inputs provide for 16-bit I- and Q-words (unlike the
18-bit words in normal QDUC mode). The serial bit streams
are delivered to the Blackfin interface. The Blackfin interface
converts the 16-bit serial data into 16-bit parallel data to
propagate down the signal processing chain.
The Blackfin interface includes an additional pair of half-band
filters in both I and Q signal paths (not shown explicitly in the
diagram). The two half-band filters increase the interpolation
of the baseband data by a factor of four, relative to the normal
QDUC mode.
The synchronization of the serial data occurs through the
PDCLK signal. In BFI mode, the PDCLK signal is effectively
the bit clock for the serial data.
Note that the system clock is limited to 750 MHz in BFI mode.
06384-007
PDCLK
I/Q IN
EXT_PWR_DWN
DAC_RSET
IOUT
IOUT
TxENABLE
DAC GAIN
θ
INVERSE
SINC
FILTER
CLOCK
FTW PW
8
SYSCLK
PLL
÷2
CLOCK MO DE
REF_CLK
REF_CLK
REFCLK_OUT
XTAL_SEL
AD9957
ω
cos (ωt+θ)
sin (ωt+θ)
SYNC_OUT
SYNC_IN
PLL_LOCK
PLL_LOOP_FILTER
MASTER_RESET
22
OSK
DDS AUX
DAC
8-BIT
POWER
DOWN
CONTROL
2
DATA ASSEMBLER AND FORMATTER
I
Q
IS
QS
BLACKFIN INT E R FACE
18
18
16
16
INVERSE
CCI
INVERSE
CCI
OSK
INTERNAL CLO CK TI M ING AND CONTROL
DAC
14-BIT
CCI_OVFL
OSK
FTW
PW
PARAL LEL DATA
TIMI NG AND CO NTRO L
RT
RAM
PROFILE
SERIAL I/O
PORT
I/O_UPDATE
PROGRAMMING
REGISTERS
3I Q ISQS
HALF-BAND
FILTERS (4×)
CCI
(1× T O 63×)
HALF-BAND
FILTERS (4×)
CCI
(1× T O 63×)
OUTPUT
SCALE
FACTOR
SDIO
CS
I/O_RESET
SCLK
SDO
Figure 27. Quadrature Modulation Mode, Blackfin Interface
Data Sheet AD9957
Rev. C | Page 19 of 64
INTERPOLATING DAC MODE
A block diagram of the AD9957 operating in interpolating DAC
mode is shown in Figure 28; grayed items are inactive. In this
mode, the Q data path, DDS, and modulator are all disabled; only
the I data path is active.
As in quadrature modulation mode, the PDCLK pin functions
as a clock, synchronizing the input of data to the AD9957.
No modulation takes place in the interpolating DAC mode;
therefore, the spectrum of the data supplied at the parallel port
remains at baseband. However, a sample rate conversion takes
place based on the programmed interpolation rate. The inter-
polation hardware processes the signal, effectively performing
an oversample with a zero-stuffing operation. The original
input spectrum remains intact and the images that otherwise
would occur from the sample rate conversion process are
suppressed by the interpolation signal chain.
06384-008
PDCLK
I/Q IN
EXT_PWR_DWN
DAC_RSET
IOUT
IOUT
TxENABLE
DAC GAIN
θ
INVERSE
SINC
FILTER
CLOCK
FTW PW
8
SYSCLK
PLL
÷2
CLOCK MO DE
REF_CLK
REF_CLK
REFCLK_OUT
XTAL_SEL
PARAL LEL DATA
TIMI NG AND CO NTRO L
AD9957
ω
cos (ωt+θ)
sin (ωt+θ)
SYNC_OUT
SYNC_IN
PLL_LOCK
PLL_LOOP_FILTER
MASTER_RESET
22
DDS AUX
DAC
8-BIT
POWER
DOWN
CONTROL
18
DATA ASSEMBLER AND FORMATTER
I
Q
IS
QS
BLACKFIN INT E R FACE
18
18
16
16
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
OSK
INTERNAL CLO CK TI M ING AND CONTROL
DAC
14-BIT
FTW
PW
OSK
RT
RAM
PROFILE
SERIAL I/O
PORT
I/O_UPDATE
PROGRAMMING
REGISTERS
3I Q ISQS
OUTPUT
SCALE
FACTOR
CCI_OVFL
SDIO
CS
I/O_RESET
SCLK
SDO
Figure 28. Interpolating DAC Mode
AD9957 Data Sheet
Rev. C | Page 20 of 64
SINGLE TONE MODE
A block diagram of the AD9957 operating in single tone mode
is shown in Figure 29; grayed items are inactive. In this mode,
both I and Q data paths are disabled from the 18-bit parallel
data port up to, and including, the modulator. The internal
DDS core produces a single frequency signal based on the
programmed tuning word. The user may select either the
cosine or sine output of the DDS. The sinusoid at the DDS
output can be scaled using a 14-bit amplitude scale factor (ASF)
and optionally routed through the inverse sinc filter.
Single tone mode offers the output shift keying (OSK) function.
It provides the ability to ramp the amplitude scale factor between
zero and an arbitrary preset value over a programmable time
interval.
06384-009
PDCLK
I/Q IN
EXT_PWR_DWN
DAC_RSET
IOUT
IOUT
TxENABLE
FTW
PW
DAC GAIN
θ
INVERSE
SINC
FILTER
CLOCK
FTW PW
8
SYSCLK
PLL
÷2
CLOCK MO DE
REF_CLK
REF_CLK
REFCLK_OUT
XTAL_SEL
PARAL LEL DATA
TIMI NG AND CO NTRO L
AD9957
ω
cos (ωt+θ)
sin (ωt+θ)
SYNC_OUT
SYNC_IN
PLL_LOCK
PLL_LOOP_FILTER
MASTER_RESET
22
CCI_OVFL
OSK
DDS AUX
DAC
8-BIT
POWER
DOWN
CONTROL
RT
RAM
PROFILE
SERIAL I/O
PORT
I/O_UPDATE
PROGRAMMING
REGISTERS
3I Q ISQS
10
DATA ASSEMBLER AND FORMATTER
I
Q
IS
QS
BLACKFIN INT E R FACE
18
18
16
16
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
HALF-BAND
FILTERS (4×)
INVERSE
CCI
CCI
(1× T O 63×)
OSK
INTERNAL CLO CK TI M ING AND CONTROL
DAC
14-BIT
OUTPUT
SCALE
FACTOR
SDIO
CS
I/O_RESET
SCLK
SDO
Figure 29. Single Tone Mode
Data Sheet AD9957
Rev. C | Page 21 of 64
SIGNAL PROCESSING
For a better understanding of the operation of the AD9957, it
is helpful to follow the signal path in quadrature modulation
mode from the parallel data port to the output of the DAC,
examining the function of each block (see Figure 26).
The internal system clock (SYSCLK) signal that generates from
the timing source provided to the REF_CLK pins provides all
timing within the AD9957.
PARALLEL DATA CLOCK (PDCLK)
The AD9957 generates a signal on the PDCLK pin, which is a
clock signal that runs at the sample rate of the parallel data port.
PDCLK serves as a data clock for the parallel port in QDUC
and interpolating DAC modes; in BFI mode, it is a bit clock.
Normally, the device uses the rising edges on PDCLK to latch
the user-supplied data into the data port. Alternatively, the
PDCLK Invert bit selects the falling edges as the active edges.
Furthermore, the PDCLK enable bit is used to switch off the
PDCLK signal. Even when the output signal is turned off via the
PDCLK enable bit, PDCLK continues to operate internally. The
device uses PDCLK internally to capture parallel data. Note that
PDCLK is Logic 0 when disabled.
In QDUC mode, the AD9957 expects alternating I- and Q-
data-words at the parallel port (see Figure 31). Each active edge
of PDCLK captures one 18-bit word; therefore, there are two
PDCLK cycles per I/Q pair. In BFI mode, the AD9957 expects
two serial bit streams, each segmented into 16-bit words with
PDCLK indicating each new bit. In either case, the output clock
rate is fPDCLK as explained in the Input Data Assembler section.
In QDUC applications that require a consistent timing relation-
ship between the internal SYSCLK signal and the PDCLK signal,
the PDCLK rate control bit is used to slightly alter the operation
of PDCLK. When this bit is set, the PDCLK rate is reduced by
a factor of two. This causes rising edges on PDCLK to latch
incoming I-words and falling edges to latch incoming Q-words.
Again, the edge polarity assignment is reversible via the PDCLK
Invert bit.
TRANSMIT ENABLE PIN (TxENABLE)
The AD9957 accepts a user-generated signal applied to the
TxENABLE pin that gates the user supplied data. Polarity of
the TxENABLE pin is set using the TxENABLE invert bit (see
the Register Map section for details). When TxENABLE is true,
the device latches data into the device on the expected edge of
PDCLK (based on the PDCLK invert bit). When TxENABLE
is false, the device ignores the data supplied to the port, even
though the PDCLK may continue to operate. Furthermore,
when the TxENABLE pin is held false, then the device either
forces the 18-bit data-words to Logic 0s, or it retains the last
value present on the data port prior to TxENABLE switching
to the false state (see the data assembler hold last value bit in
the Register Map section).
Alternatively, rather than operating the TxENABLE pin as a
gate for framing bursts of data, it can be driven with a clock
signal operating at the parallel port data rate. When driven by
a clock signal, the transition from the false to true state must
meet the required setup and hold times on each cycle to ensure
proper operation.
In QDUC mode, on the false-to-true edge of TxENABLE, the
device is ready to receive the first I-word. The first I-word is
latched into the device coincident with the active edge of PDCLK.
The next active edge of PDCLK latches in a Q-word, and so on,
until TxENABLE is returned to a static false state. The user may
reverse the ordering of the I- and Q-words via the Q-First Data
Pairing bit. Furthermore, the user must ensure that an even
number of data words are delivered to the device as it must
capture both an I- and a Q-word before the data is processed
along the signal chain.
In interpolating DAC mode, TxENABLE operation is similar to
QDUC mode, but without the need for I/Q data pairing; the
even-number-of-PDCLK-cycles rule does not apply.
In BFI mode, operation of the TxENABLE pin is similar except
that instead of the false-to-true edge marking the first I-word,
it marks the first I and Q bits in a serial frame. The user must
ensure that all 16-bits of a serial frame are delivered because the
device must capture a full 16-bit I- and Q-word before the data
is processed along the signal chain.
The timing relationships between TxENABLE, PDCLK, and
DATA are shown in Figure 30, Figure 31, and Figure 32.
AD9957 Data Sheet
Rev. C | Page 22 of 64
tDH
I
0
TxENABLE
PDCLK
D<17:0> I
K
I
K – 1
I
3
I
2
I
1
06384-010
tDH
tDS
tDS
Figure 30. 18-Bit Parallel Port Timing Diagram—Interpolating DAC Mode
t
DH
I
0
TxENABLE
PDCLK
D<17:0> Q
N
I
N
Q
1
I
1
Q
0
06384-011
t
DH
t
DS
t
DS
Figure 31. 18-Bit Parallel Port Timing Diagram—Quadrature Modulation Mode
TxENABLE
PDCLK
I DATA
Q DATA Q
0
Q
1
Q
2
Q
3
Q
4
Q
6
Q
5
Q
7
Q
8
Q
9
Q
10
Q
11
Q
12
Q
13
Q
14
Q
15
I
0
I
1
I
2
I
3
I
4
I
6
I
5
I
7
I
8
I
9
I
10
I
11
I
12
I
13
I
14
I
15
I
16n – 1
Q
16n – 1
06384-012
Figure 32. Dual Serial I/Q Bit Stream Timing Diagram, BFI Mode
INPUT DATA ASSEMBLER
The input to the AD9957 is an 18-bit parallel data port in
QDUC mode or interpolating DAC mode. In BFI mode, it
operates as a dual serial data port.
In QDUC mode, it is assumed that two consecutive 18-bit
words represent the real (I) and imaginary (Q) parts of a
complex number of the form, I + jQ. The 18-bit words are
supplied to the input of the AD9957 at a rate of
R
f
f
SYSCLK
PDCLK
2
=
for QDUC mode
where:
fSYSCLK (for all of the PDCLK equations in this section) is the
sample rate of the DAC.
R (for all of the PDCLK equations in this section) is the
interpolation factor of the programmable interpolation filter.
When the PDCLK rate control bit is active in QDUC mode,
however, the frequency of PDCLK becomes
R
f
f
SYSCLK
PDCLK
4
=
with PDCLK rate control active
In the interpolating DAC mode, the rate of PDCLK is the same
as QDUC mode with the PDCLK rate control bit active, that is,
R
f
f
SYSCLK
PDCLK
4
=
for interpolating DAC mode
In BFI mode, the 18-bit parallel input converts to a dual serial
input that is, one pin is assigned as the serial input for the I-words
and one pin is assigned as the serial input for the Q-words. The
other 16 pins are not used. Furthermore, each I- and Q-word
has a 16-bit resolution. fPDCLK is the bit rate of the I- and Q-data
streams and is given by
R
f
fSYSCLK
PDCLK = for BFI mode
Data Sheet AD9957
Rev. C | Page 23 of 64
Encoding and pulse shaping of symbols must be implemented
before the data is presented to the input of the AD9957. Data
delivered to the input of the AD9957 may be formatted as either
twos complement or offset binary (see the Data Format bit in
Table 13). In BFI mode, the bit sequence order can be set to
either MSB-first or LSB-first (via the Blackfin Bit Order bit).
INVERSE CCI FILTER
The inverse cascaded comb integrator (CCI) filter predistorts
the data, compensating for the slight attenuation gradient imposed
by the CCI filter (see the Programmable Interpolating Filter
section). Data entering the first half-band filter occupies a maxi-
mum bandwidth of ½ fIQ as defined by Nyquist (where fIQ is the
sample rate at the input of the first half-band filter); see Figure 33.
If the CCI filter is used, the inband attenuation gradient can pose a
problem for applications requiring an extremely flat pass band.
For example, if the spectrum of the data supplied to the AD9957
occupies a significant portion of the ½ fDATA region, the higher
frequencies of the data spectrum are slightly more attenuated
than the lower frequencies (the worst-case overall droop from
f = 0 to ½ fDATA is <0.8 dB). The inverse CCI filter has a response
characteristic that is the inverse of the CCI filter response over
the ½ fIQ region.
INBAND
ATTENUATION
GRADIENT
CCI FILT ER RESPONSE
½fIQ
fIQ 4fIQ f
06384-013
Figure 33. CCI Filter Response
The product of the two responses yields an extremely flat
pass band (±0.05 dB over the baseband Nyquist bandwidth)
eliminating the inband attenuation gradient introduced by the
CCI filter. The cost is a slight attenuation of the input signal
(approximately 0.5 dB for a CCI interpolation rate of 2, and
0.8 dB for higher interpolation rates).
The inverse CCI filter can be bypassed using the appropriate bit
in the register map; it is automatically bypassed if the CCI inter-
polation rate is 1×. When bypassed, power to the stage turns off
to reduce power consumption.
FIXED INTERPOLATOR (4×)
This block is a fixed 4× rate interpolator, implemented as a
cascade of two half-band filters. Together, the sampling rate
of these two filters increases by a factor of four while preserving
the spectrum of the baseband signal applied at the input. Both
are linear phase filters; virtually no phase distortion is intro-
duced within their pass bands. Their combined insertion loss
is 0.01 dB, preserving the relative amplitude of the input signal.
The filters are designed to deliver a composite performance that
yields a usable pass band of 40% of the input sample rate. Within
that pass band, ripple does not exceed 0.002 dB peak-to-peak.
The stop band extends from 60% to 340% of the input sample
rate and offers a minimum of 85 dB attenuation. Figure 34 and
Figure 35 show the composite response of the two half-band filters.
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
10
00.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
06384-014
(dB)
f
I
Figure 34. Half-Band 1 and Half-Band 2 Composite Response
(Frequency Scaled to Input Sample Rate of Half-Band 1)
–0.010
–0.008
0.008
–0.006
0.006
–0.004
0.004
–0.002
0.002
0
0.010
00.1 0.2 0.3 0.4 0.5
06384-015
(dB)
fI
Figure 35. Composite Pass-Band Detail
(Frequency Scaled to Input Sample Rate of Half-Band 1)
In BFI mode, there are two additional half-band filters resident,
yielding a total fixed interpolation factor of 16×. The extra BFI
filters use the same filter tap coefficient values as the QDUC
half-band filters, but their data pathway is 16 bits (instead of
18 bits as with the QDUC half-band filters). As such, baseband
quantization noise is higher in BFI mode.
AD9957 Data Sheet
Rev. C | Page 24 of 64
Knowledge of the frequency response of the half-band filters is
essential to understanding their impact on the spectral properties
of the input signal. This is especially true when using the quad-
rature modulator to upconvert a baseband signal containing
complex data symbols that have been pulse shaped.
Consider that a complex symbol is represented by a real (I) and
an imaginary (Q) component, thus requiring two digital words
to represent a single complex sample of the form I + jQ. The
sample rate associated with a sequence of complex symbols is
referred to as fSYMBOL. If pulse shaping is applied to the symbols,
the sample rate must be increased by some integer factor, M
(a consequence of the pulse shaping process). This new sample
rate (fIQ) is related to the symbol rate by
fIQ = MfSYMBOL
where fIQ is the rate at which complex samples must be supplied
to the input of the first half-band filter in both (I and Q) signal
paths. This rate should not be confused with the rate at which
data is supplied to the AD9957.
Typically, pulse shaping is applied to the baseband symbols via
a filter having a raised cosine response. In such cases, an excess
bandwidth factor (α, 0 ≤ α ≤ 1) is used to modify the bandwidth
of the data. For α = 0, the data bandwidth corresponds to fSYMBOL/2;
for α = 1, the data bandwidth extends to fSYMBOL. Figure 36 shows
the relationship between α, the bandwidth of the raised cosine
response, and the response of the first half-band filter.
f
f
f
TY P ICAL S P E CTRUM OF A RANDOM S Y M BOL S E QUENCE
RAIS E D COSI NE
SPECTRAL MASK
SAMPLE RATE FOR
2× OVERSAMPLED
PULSE SHAPING
INPUT SAMPLE
RATE OF FIRST
HALF-BAND
FILTER
HALF-BAND
FILTER
RESPONSE INPUT SAMPLE
RATE OF FIRST
HALF-BAND
FILTER
NYQUIST
BAND
WIDTH
½f
SYMBOL
f
SYMBOL
2
f
SYMBOL
3
f
SYMBOL
½f
SYMBOL
0.4
f
IQ
f
IQ
2
f
IQ
½f
IQ
f
SYMBOL
2
f
SYMBOL
4
f
SYMBOL
α = 1
α = 0 α = 0.5
06384-016
Figure 36. Effect of the Excess Bandwidth Factor (α)
The responses in Figure 36 reflect the specific case of M = 2 (the
interpolation factor for the pulse shaping operation). Increasing
Factor M shifts the location of the fIQ point on the half-band
response portion of the diagram to the right, as it must remain
aligned with the corresponding MfSYMBOL point on the frequency
axis of the raised cosine spectral diagram. However, if fIQ shifts
to the right, so does the half-band response, proportionally.
The result is that the raised cosine spectral mask always lies
within the flat portion (dc to 0.4 fIQ) of the pass band response
of the first half-band filter, regardless of the choice of α so long
as M > 2. Therefore, for M > 2, the first half-band filter has
absolutely no negative impact on the spectrum of the baseband
signal when raised cosine pulse shaping is employed. For the
case of M = 2, a problem can arise. This is highlighted by the
shaded area in the tail of the α = 1 trace on the raised cosine
spectral mask diagram. Notice that this portion of the raised
cosine spectral mask extends beyond the flat portion of the
half-band response and causes unwanted amplitude and phase
distortion as the signal passes through the first half-band filter.
To avoid this, simply ensure that α ≤ 0.6 when M = 2.
PROGRAMMABLE INTERPOLATING FILTER
The programmable interpolator is implemented as a low-pass
CCI filter. It is programmable by a 6-bit control word, giving a
range of 2× to 63× interpolation.
The programmable interpolator is bypassed when programmed
for an interpolation factor of 1. When bypassed, power to the
stage is removed and the inverse CCI filter is also bypassed,
because its compensation is not needed.
The output of the programmable interpolator is the data from
the 4× interpolator further upsampled by the CCI filter, accord-
ing to the rate chosen by the user. This results in the upsampling of
the input data by a factor of 8× to 252× in steps of four.
The transfer function of the CCI interpolating filter is
( )
( )
5
1
0
2
=∑
−
=
−
R
k
fkπj
e
fH
(1)
where R is the programmed interpolation factor, and f is the
frequency normalized to fSYSCLK.
Note that minimum R requirements exist depending on the
mode and frequency of fSYSCLK. The minimum R setting is
defined under the follo wing conditions.
QDUC Mode
If fSYSCLK is between 500 MSPS to 1 GSPS, then the minimum R is 2.
If fSYSCLK is less than 500 MSPS, then the minimum R is 1.
BFI Mode
If fSYSCLK is between 500 MSPS to 750 MSPS, then the minimum
R is 3.
If fSYSCLK is between 250 MSPS to 500 MSPS, then the minimum
R is 2.
If fSYSCLK is less than 250 MSPS, then the minimum R is 1.
Data Sheet AD9957
Rev. C | Page 25 of 64
QUADRATURE MODULATOR
The digital quadrature modulator stage shifts the frequency of
the baseband spectrum of the incoming data stream up to the
desired carrier frequency (a process known as upconversion).
At this point, the baseband data, which was delivered to the
device at an I/Q sample rate of fIQ, has been upsampled to a rate
equal to the frequency of SYSCLK, making the data sampling
rate equal to the sampling rate of the carrier signal.
The frequency of the carrier signal is controlled by a direct
digital synthesizer (DDS). The DDS very precisely generates the
desired carrier frequency from the internal reference clock
(SYSCLK). The carrier is applied to the I and Q multipliers in
quadrature fashion (90° phase offset) and summed, yielding a
data stream that represents the quadrature modulated carrier.
The modulation is performed digitally, avoiding the phase
offset, gain imbalance, and crosstalk issues commonly associated
with analog modulators. Note that the modulated, so-called
signal is a number stream sampled at the rate of SYSCLK, the
same rate at which the DAC is clocked.
The orientation of the modulated signal with respect to the
carrier is controlled by a spectral invert bit. This bit resides in
each of the eight profile registers. By default, the time domain
output of the quadrature modulator takes the form
I(t) × cos(ωt) − Q(t) × sin(ωt) (2)
When the spectral invert bit is asserted, it becomes
I(t) × cos(ωt) + Q(t) × sin(ωt) (3)
DDS CORE
The direct digital synthesizer (DDS) block generates sine
and/or cosine signals. In single tone mode, the DDS generates
either a digital sine or cosine waveform based on the select DDS
sine output bit. In QDUC mode, the DDS generates the quadra-
ture carrier reference signal that digitally modulates the I/Q
baseband signal.
The DDS output frequency is tuned using registers accessed via
the serial I/O port. This allows for both precise tuning and
instantaneous changing of the carrier frequency.
The equation relating output frequency (fOUT) of the DDS to the
frequency tuning word (FTW) and the system clock (fSYSCLK) is
SYSCLK
OUT f
FTW
f
=32
2
(4)
where FTW is a decimal number from 0 to 2,147,483,647 (231 − 1).
Solving for FTW yields
=
SYSCLK
OUT
f
f
roundFTW
32
2
(5)
where the round() function means to round the result to the
nearest integer. For example, for fOUT = 41 MHz and fSYSCLK =
122.88 MHz, then FTW = 1,433,053,867 (0x556AAAAB).
In single tone mode, the DDS frequency, phase, and amplitude
are all programmable via the serial I/O port. The amplitude
is controlled by means of a digital multiplier using a 14-bit
fractional scale value called the amplitude scale factor (ASF).
The LSB weight is 2−14, yielding a multiplier range of 0 to
0.99993896484375 (1 − 2−14). To bypass the ASF multiplier,
program the appropriate control register bit (see the details of
CFR2<24> in the Register Bit Descriptions section). When
bypassed, the ASF multiplier clocks are disabled to conserve
power. The phase offset is controlled by means of a digital adder
that uses a 14-bit offset value called the phase offset word (POW).
The adder is situated between the phase accumulator and the
angle-to-amplitude conversion logic in the DDS core. The adder
applies the POW to the instantaneous phase values produced by
the DDS phase accumulator. The adder is MSB aligned with the
phase accumulator yielding an LSB weight of 2−14 (which equates to
a resolution of ~0.022° or ~0.000383 radians). Both the ASF and
the POW are available for each of the eight profiles.
INVERSE SINC FILTER
The sampled carrier data stream is the input to the digital-to-
analog converter. The DAC output spectrum is shaped by the
characteristic sin(x)/x (or sinc) envelope, due to the intrinsic
zero-order hold effect associated with DAC-generated signals.
The shape of the sinc envelope is well known and can be
compensated for. This compensation is provided by the inverse
sinc filter preceding the DAC.
The inverse sinc filter is implemented as a digital FIR filter. Its
response characteristic very nearly matches the inverse of the
sinc envelope, as shown in Figure 37 (along with the sinc
envelope for comparison).
The inverse sinc filter is enabled through a bit in the register
map. The filter tap coefficients are listed in Table 4. The filter
predistorts the data prior to its arrival at the DAC to compensate
for the sinc envelope that otherwise distorts the spectrum.
When the inverse sinc filter is enabled, it introduces a ~3.0 dB
insertion loss. The inverse sinc compensation is effective for
output frequencies up to 40% (nominally) of the DAC sample rate.
Table 4. Inverse Sinc Filter Tap Coefficients
Tap No. Tap Value Tap No.
1 −35 7
2 +134 6
3 −562 5
4 +6729 4
AD9957 Data Sheet
Rev. C | Page 26 of 64
In Figure 37, it can be seen that the sinc envelope introduces a
frequency dependent attenuation that can be as much as 4 dB at
the Nyquist frequency (half of the DAC sample rate). Without
the inverse sinc filter, the DAC output also suffers from the
frequency dependent droop of the sinc envelope. The inverse
sinc filter effectively flattens the droop to within ±0.05 dB as
shown in Figure 38, which shows the corrected sinc response
with the inverse sinc filter enabled.
1
0
–1
–2
–3
–4 00.1 0.2 0.40.3 0.5
06384-017
(dB)
FRE QUENCY RE LAT IVE TO DAC S AM P LE RAT E
INVERSE
SINC
SINC
Figure 37. Sinc and Inverse Sinc Responses
–2.8
–2.9
–3.0
–3.1 00.1 0.2 0.40.3 0.5
06384-018
(dB)
FRE QUENCY RE LAT IVE TO DAC S AM P LE RAT E
COMPENSATED RESPONSE
Figure 38. DAC Response with Inverse Sinc Compensation
OUTPUT SCALE FACTOR (OSF)
In QDUC and interpolating DAC modes, the output amplitude
is controlled using an 8-bit digital multiplier. The 8-bit multiplier
value is called the output scale factor (OSF) and is programmed
via the appropriate control registers. It is available for each of
the eight profiles. The LSB weight is 2−7, which yields a multiplier
range of 0 to 1.9921875 (2 − 2−7). The gain extends to nearly a
factor of 2 to provide a means to overcome the intrinsic loss
through the modulator when operating in the quadrature
modulation mode.
In interpolating DAC mode, the OSF should not be programmed
to exceed unity, as clipping can result. Programming the 8-bit
multiplier to unity gain (0x80) bypasses the stage and reduces
power consumption.
14-BIT DAC
The AD9957 incorporates an integrated 14-bit current-output
DAC. The output current is delivered as a balanced signal using
two outputs. The use of balanced outputs reduces the amount of
common-mode noise at the DAC output, increasing signal-to-
noise ratio. An external resistor (RSET) connected between the
DAC_RSET pin and AGND establishes a reference current. The
full-scale output current of the DAC (IOUT) is a scaled version of
the reference current (see the Auxiliary DAC section that
follows).
Proper attention should be paid to the load termination to keep
the output voltage within the specified compliance range, as
voltages developed beyond this range cause excessive distortion
and can damage the DAC output circuitry.
Auxiliary DAC
The full-scale output current of the main DAC (IOUT) is con-
trolled by an 8-bit auxiliary DAC. An 8-bit code word stored in
the appropriate register map location sets IOUT according to the
following equation:
+= 96
1
4.86 CODE
R
I
SET
OUT
(6)
where:
RSET is the value of the RSET resistor (in ohms).
CODE is the 8-bit value supplied to the auxiliary DAC (default
is 127).
For example, with RSET = 10,000 and CODE = 127, IOUT = 20.07 mA.
Data Sheet AD9957
Rev. C | Page 27 of 64
RAM CONTROL
RAM OVERVIEW
The AD9957 has an integrated 1024 × 32-bit RAM. This RAM
is only accessible when the AD9957 is operating in QDUC or
interpolating DAC mode. The RAM has two fundamental
modes of operation: data entry/retrieve mode and playback
mode. The mode is selected by programming the RAM Enable
bit in CFR1 via the serial I/O port.
Data entry/retrieve mode is used to load or read back the RAM
contents via the serial I/O port. Playback mode is used to deliver
RAM data to one of two internal destinations: the baseband
scaling multipliers (see Figure 25, the IS and QS labels) or the
baseband signal chain (see Figure 25, the I and Q labels). In
both cases, the RAM can be used to apply an arbitrary, time-
varying waveform to the selected destination. A block diagram
of the RAM and its control elements is shown in Figure 39.
The external parallel data port is disabled when the baseband
signal chain serves as the RAM playback destination.
RAM 32
10
Q
STATE
MACHINE SCLK
SDIO
SDO
CS
I/O_RESET
RT
END ADDRES S
ST ART ADDRESS
10
10
ADDRESS S TEP RATE
16 RAM MODE
3
CLK
BASEBAND DATA CLOCK
I16
IS
Q
QS
DDS CL OCK
UP/ DOWN COUNT E R
I CHANNE L
Q CHANNE L
RAM
SEGMENT
REGISTERS
SERIAL I/O PORT
ADDRESS
DATA
U/D 32
(MSBs)
(LSBs)
16
06384-019
Figure 39. RAM Block Diagram
In Figure 39, the serial I/O port is used to program the contents
of the two RAM segment registers as well as to load and retrieve
the RAM contents. The state machine takes care of incrementing
or decrementing the RAM address locations and controlling the
timing of the RAM address and data for proper operation. The
I-channel and Q-channel multiplexers route RAM data to base-
band scaling multipliers (IS/QS) or directly to the baseband
signal chain (I/Q) when the RAM is used in playback mode.
The state of the RAM playback destination bit determines the
destination of the RAM data during playback.
An I/O update (or a profile change) is necessary to enact a state
change of the RAM enable or RAM playback destination bits, or
any of the RAM segment register bits.
The 32-bit RAM data bus is partitioned so that the 16 MSBs are
designated as I-channel bits and the 16 LSBs are designated as
Q-channel bits. In playback mode, when driving data directly
into the baseband signal chain, the 16-bit data-words are
considered to be signed (that is, twos complement) values. The
16-bit I-and Q-words are MSB aligned with the 18-bit I and Q
baseband data path. The two remaining LSBs of each 18-bit
baseband channel are driven by the MSB of the respective
channel. This ensures correct polarity coding when the 16-bit I
and Q data from the RAM translates into 18-bit words for the
baseband signal chain. Alternatively, when the RAM is driving
the baseband scaling multipliers in playback mode, the RAM
data is considered to represent unsigned, fractional values with a
range of 0 to 1 − 2−16.
RAM SEGMENT REGISTERS
Two dedicated registers (RAM Segment Register 0 and RAM
Segment Register 1) control the operation of the RAM. Each
contains the following:
• 10-bit start address word
• 10-bit end address word
• 16-bit address step rate word
• 3-bit RAM playback mode word
When programming these registers, the user must ensure that
the end address is greater than the start address.
With the RAM segment registers, the user can arbitrarily partition
the RAM into two independent memory segments. The segment
boundaries are specified with the start and end address words
in each RAM segment register. The playback rate is controlled
by the address step rate word (only meaningful when the base-
band scaling multipliers serve as the playback destination). If the
baseband signal chain serves as the RAM playback destination,
the 16-bit address step rate words must be set to 1. The playback
mode of the RAM is controlled via the RAM playback mode word.
RAM STATE MACHINE
The state machine acts as an address generator for the RAM. It
is clocked by either the serial I/O port (when the RAM is operating
in the load/retrieve mode) or the baseband data clock (when
the RAM is in playback mode). The state machine uses the
RAM mode bits of the active RAM segment register to establish
the proper sequence through the specified address range.
RAM TRIGGER (RT) PIN
The RAM state machine monitors the RT pin for logic state tran-
sitions. Any state transition triggers the state machine into action.
The direction of the logic state transition on the RT pin deter-
mines which RAM segment register the state machine uses for
playback instructions. RAM Segment Register 0 is used if the
state machine detects a 0-to-1 transition; RAM Segment Register 1
is used if a 1-to-0 transition is detected.
AD9957 Data Sheet
Rev. C | Page 28 of 64
LOAD/RETRIEVE RAM OPERATION
Loading or retrieving the RAM contents is a three-step process.
1. Program the RAM segment registers with start and end
addresses defining the boundaries of each independent
RAM segment.
2. Toggle the RT pin with the appropriate transition to select
the desired RAM segment register.
3. Using the serial I/O port, write (or read) the address range
specified by the selected RAM segment register.
Figure 40 shows the RAM block diagram when used for loading
or retrieve operations.
RAM 32
10
Q
STATE
MACHINE
RT
END ADDRES S
ST ART ADDRESS
10
10
ADDRESS S TEP RATE
16 RAM MODE
3
CLK
BASEBAND DATA CLOCK
I16
IS
Q
QS
DDS CL OCK
UP/ DOWN COUNT E R
I CHANNE L
Q CHANNE L
SERIAL I/O PORT
ADDRESS
DATA
U/D 32
(MSBs)
(LSBs)
16
06384-020
NOTES
1. NONESS E NTI AL F UNCTI ONAL COMP ONENTS ARE RE NDE RE D IN GRAY .
RAM
SEGMENT
REGISTERS
SCLK
SDIO
SDO
CS
I/O_RESET
Figure 40. RAM Load/Retrieve Operation
During a load or retrieve operation, the state machine controls
an up/down counter to step through the required RAM locations.
The counter is synchronized with the serial I/O port so that the
serial/parallel conversion of the 32-bit words is correctly timed
with the generation of the appropriate RAM address to properly
execute the desired read or write operation. The up/down
counter always increments through the address range during
serial I/O port operations.
Because the RAM segment registers are completely independent,
it is possible to define overlapping address ranges. However,
doing so causes the overlapping address locations to be over-
written by the most recent write operation. It is recommended
that the user avoid defining overlapping address ranges.
RAM PLAYBACK OPERATION
When the RAM has been loaded, it can be used for playback
operation. The destination of the playback data is selected via
the RAM playback destination bit. The active RAM segment
register is selected by the appropriate transition of the RT pin.
The active RAM segment register directs the internal state
machine by defining the RAM address range occupied by the
data and the RAM playback mode. It also defines the playback
rate when the playback destination is the baseband scaling
multipliers.
Although RAM load/retrieve operations via the serial I/O port
take precedence over playback, it is recommended that the user
not attempt RAM access via the serial I/O port when the RAM
enable bit is set.
Figure 41 is a block diagram showing the functional compo-
nents used for RAM playback operation when the internal
destination is the baseband scaling multipliers.
RAM 32
10
Q
STATE
MACHINE
RT
END ADDRES S
ST ART ADDRESS
10
10
ADDRESS S TEP RATE
16 RAM MODE
3
CLK
BASEBAND DATA CLOCK
I16
IS
Q
QS
DDS CL OCK
UP/ DOWN COUNT E R
I CHANNE L
Q CHANNE L
RAM
SEGMENT
REGISTERS
SERIAL I/O PORT
ADDRESS
DATA
U/D 32
(MSBs)
(LSBs)
16
06384-021
NOTES
1. NONESS E NTI AL F UNCTI ONAL COMP ONENTS ARE RE NDE RE D IN GRAY .
SCLK
SDIO
SDO
CS
I/O_RESET
Figure 41. RAM Playback to Baseband Scaling Multipliers
During playback to the baseband scaling multipliers, the
address step rate word in the active RAM segment register sets
the rate at which RAM data samples are delivered to the
multipliers. The following equations define the RAM sample
rate and sample interval (Δt):
RM
f
RateSampleRAM SYSCLK
4
=
SYSCLK
f
RM
t
4
=∆
where:
R is the rate interpolation factor for the CCI filter.
M is the 16-bit value of the address step rate word stored in the
active RAM segment register.
If the RAM enable bit is set and the baseband scaling multi-
pliers are selected as the playback destination, then assertion
of an I/O update or profile change causes the multipliers to be
driven with a static value of zero. A subsequent state change on
the RT pin causes the multipliers to be driven by the data played
back from the RAM instead of the static zero value.
Figure 42 is a block diagram showing RAM playback operation
when the internal destination is the baseband data path. During
playback to the baseband data path, the state machine increments/
decrements the RAM address at the baseband data rate (the
address step rate must be set to 1).
Data Sheet AD9957
Rev. C | Page 29 of 64
RAM 32
10
Q
STATE
MACHINE
RT
END ADDRES S
ST ART ADDRESS
10
10
ADDRESS S TEP RATE
16 RAM MODE
3
CLK
BASEBAND DATA CLOCK
I16
IS
Q
QS
DDS CL OCK
UP/ DOWN COUNT E R
I CHANNE L
Q CHANNE L
RAM
SEGMENT
REGISTERS
SERIAL I/O PORT
ADDRESS
DATA
U/D 32
(MSBs)
(LSBs)
16
06384-022
NOTES
1. NONESS E NTI AL F UNCTI ONAL COMP ONENTS ARE RE NDE RE D IN GRAY .
SCLK
SDIO
SDO
CS
I/O_RESET
Figure 42. RAM Playback to Baseband Data Path
OVERVIEW OF RAM PLAYBACK MODES
The RAM is operational in any one of four different
playback modes.
• Ramp-up
• Bidirectional ramp
• Continuous bidirectional ramp
• Continuous recirculate
RAM playback is only functional when the AD9957 is pro-
grammed for either the QDUC or interpolating DAC mode.
The RAM playback mode is selected via the 3-bit RAM play-
back mode word located in each of the RAM segment registers.
Thus, the RAM playback mode is segment dependent. The
RAM playback mode bits are detailed in Table 5.
Table 5. RAM Playback Modes
RAM Playback Mode
Bits<2:0> RAM Playback Mode
001 Ramp-up
010 Bidirectional ramp
011 Continuous bidirectional
ramp
100 Continuous recirculate
000, 101, 110, 111
Not Valid
The continuous bidirectional ramp and continuous recirculate
modes are not available when the baseband scaling multipliers
serve as the destination of RAM playback.
RAM Ramp-Up Mode
In ramp-up mode, upon assertion of an I/O update or a state
change on the RT pin, the RAM begins playback operation
using the parameters programmed into the selected RAM seg-
ment register. Data is extracted from RAM over the specified
address range contained in the start address and end address of
the active RAM segment register. The data is delivered at the
appropriate rate and to the destination as specified by the RAM
playback destination bit.
The playback rate is governed by the timer internal to the RAM
state machine and its period (Δt) is determined by the state of the
RAM playback destination bit as detailed in the RAM playback
operation section.
The internal state machine begins extracting data from the
RAM at the start address and continues to extract data until it
reaches the end address. Upon reaching this address, the state
machine halts.
A graphic representation of the ramp-up mode appears in
Figure 43. The upper trace shows the progression of the RAM
address from the start address to the end address for the active
RAM segment register. The address value advances by one with
each timeout of the timer internal to the state machine. The circled
numbers indicate specific events, explained as follows:
Event 1—an I/O update or state transition on the RT pin. This
event initializes the state machine to the start address of the active
RAM segment register.
Event 2—the state machine reaches the end address of the active
RAM segment register and halts.
ST ART ADDRESS
RAM
ADDRESS
END ADDRES S
1
1 PDCL K CY CLE
OR
M DDS CLOCK CY CLES
Δ
t
I/O_UPDATE OR
RT TRANSITION
2
1
06384-023
Figure 43. Ramp-Up Timing Diagram
AD9957 Data Sheet
Rev. C | Page 30 of 64
RAM Bidirectional Ramp Mode
This mode is unique in that the RAM segment playback mode
word of both RAM segment registers must be programmed for
RAM bidirectional ramp mode.
In bidirectional ramp mode, upon assertion of an I/O update,
the RAM readies for playback operation using the parameters
programmed into RAM Segment Register 0. The data is deliv-
ered at the appropriate rate and to the destination as specified
by the RAM playback destination bit.
The playback rate is governed by the timer that is internal to the
RAM state machine, and its period (Δt) is determined by the
state of the RAM playback destination bit as detailed in the
RAM Playback Operation section.
Playback begins upon a 0 to 1 logic transition on the RT pin.
This instructs the state machine to increment through the
address range specified in RAM Segment Register 0 starting
with the start address. As long as the RT pin remains Logic 1,
the state machine continues to play back the RAM data until it
reaches the end address, at which point the state machine halts.
A Logic 1 to Logic 0 transition on the RT pin instructs the state
machine to switch to RAM Segment Register 1 and to decrement
through the address range starting with the end address. As
long as the RT pin remains Logic 0, the state machine continues
to play back the RAM data until it reaches the start address, at
which point the state machine halts.
It is important to note that RAM Segment Register 1 is played
back in reverse order for bidirectional ramp mode. This must
be kept in mind when the RAM contents are loaded via the
serial I/O port when bidirectional ramp mode is the intended
playback mode.
A graphic representation of the bidirectional ramp mode
appears in Figure 44. It demonstrates the action of the state
machine in response to the RT pin. If the RT pin changes states
before the state machine reaches the programmed start or end
address, the internal timer is restarted and the direction of the
address counter reversed.
1 2 3 4 5 6 7 8
06384-024
1
RAM SEGMENT 01 0 1 0
Δt
Δt
ΔtΔt
Δt
ST ART ADDRESS NUM BE R 1
ST ART ADDRESS NUM BE R 0
END ADDRES S NUM BE R 1
END ADDRES S
NUMBER 0
RAM
ADDRESS
RAM
ADDRESS
RT
PIN
1 PDCL K CY CLE
OR
M DDS CLOCK CY CLES
I/O_UPDATE
Figure 44. Bidirectional Ramp Timing Diagram
Data Sheet AD9957
Rev. C | Page 31 of 64
The circled numbers in Figure 44 indicate specific events,
explained as follows:
Event 1—an I/O update or profile change activates the RAM
bidirectional ramp mode.
Event 2—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0 and
begins incrementing the RAM address counter.
Event 3—the RT pin remained at Logic 1 long enough for the
state machine to reach the end address of RAM Segment
Register 0, at which point the address counter is halted.
Event 4—the RT pin switches to Logic 0. The state machine
initializes to the end address of RAM Segment Register 1, resets
the internal timer, and begins decrementing the RAM address
counter.
Event 5—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0,
resets the internal timer, and begins incrementing the RAM
address counter.
Event 6—the RT pin switches to Logic 0. The state machine
initializes to the end address of RAM Segment Register 1, resets
the internal timer, and begins decrementing the RAM address
counter.
Event 7—the RT pin remained at Logic 0 long enough for the
state machine to reach the start address of RAM Segment
Register 1, at which point the address counter is halted.
Event 8—the RT pin switches to Logic 1. The state machine
initializes to the start address of RAM Segment Register 0,
resets the internal timer, and begins incrementing the RAM
address counter.
AD9957 Data Sheet
Rev. C | Page 32 of 64
ST ART ADDRESS
RAM
ADDRESS
END ADDRES S
1
1 PDCL K CY CLE
OR
M DDS CLOCK CY CLES
Δ
t
I/O_UPDATE OR
RT TRANSITION
23
1
Δ
t
06384-025
Figure 45. Continuous Bidirectional Ramp Timing Diagram
RAM Continuous Bidirectional Ramp Mode
In continuous bidirectional ramp mode, upon assertion of an
I/O update or a state change on the RT pin, the RAM begins
playback operation using the parameters programmed into the
selected RAM segment register. Data is extracted from RAM
over the specified address range contained in the start address
and end address. The data is delivered at the appropriate rate
and to the destination as specified by the RAM playback
destination bit.
The playback rate is governed by the timer internal to the RAM
state machine and its period (Δt) is determined by the state of
the RAM playback destination bit as detailed in the RAM
Playback Operation section.
After initialization, the internal state machine begins extracting
data from the RAM at the start address of the active RAM segment
register and increments the address counter until it reaches the
end address, at which point the state machine reverses the direc-
tion of the address counter and begins decrementing through
the address range. Whenever one of the terminal addresses is
reached, the state machine reverses the address counter; the
process continues indefinitely.
Note that a change in state of the RT pin aborts the current
waveform and the newly selected RAM segment register is used
to initiate a new waveform.
A graphic representation of the continuous bidirectional ramp
mode is shown in Figure 45. The circled numbers in Figure 45
indicate specific events, explained as follows:
Event 1—an I/O update or state change on the RT pin has
activated the RAM continuous bidirectional ramp mode. The
state machine initializes to the start address of the active RAM
segment register. The state machine begins incrementing
through the specified address range.
Event 2—the state machine reaches the end address of the active
RAM segment register.
Event 3—the state machine reaches the start address of the
active RAM segment register.
The continuous bidirectional ramp continues indefinitely until
the next I/O update or state change on the RT pin.
Data Sheet AD9957
Rev. C | Page 33 of 64
06384-026
ST ART ADDRESS
END ADDRES S
1
1234 5
RAM ADRES S
Δt
1 PDCL K CY CLE
OR
M DDS CLOCK CY CLES
I/O_UPDATE OR
RT TRANSITION
Figure 46. Continuous Recirculate Timing Diagram
RAM Continuous Recirculate Mode
The continuous recirculate mode mimics ramp-up mode,
except that when the state machine reaches the end address of
the active RAM segment register, it does not halt. Instead, the
next timeout of the internal timer causes the state machine to
jump to the start address of the active RAM segment register.
This process continues indefinitely until an I/O update or state
change on the RT pin. A state change on the RT pin aborts the
current waveform and the newly selected RAM segment register
initiates a new waveform.
A graphic representation of the continuous recirculate mode is
shown in Figure 46.
The circled numbers in Figure 46 indicate specific events, which
are explained as follows:
Event 1—an I/O update or state change on the RT pin occurs.
This initializes the state machine to the start address of the
active RAM segment register and causes the state machine to
begin incrementing the address counter at the appropriate rate.
Event 2—the state machine reaches the end address of the active
RAM segment register.
Event 3—the state machine switches to the start address of the
active RAM segment register. The state machine continues to
increment the address counter.
Event 4—the state machine again reaches the end address of the
active RAM segment register.
Event 5—the state machine switches to the start address of the
active RAM segment register. The state machine continues to
increment the address counter.
Event 4 and Event 5 repeat until an I/O update or state change
occurs on the RT pin.
AD9957 Data Sheet
Rev. C | Page 34 of 64
CLOCK INPUT (REF_CLK)
REFCLK OVERVIEW
The AD9957 supports a number of options for producing the
internal SYSCLK signal (that is, the DAC sample clock) via the
REF_CLK/REF_CLK input pins. The REF_CLK input can be
driven directly from a differential or single-ended source, or it
can accept a crystal connected across the two input pins. There
is also an internal phase-locked loop (PLL) multiplier that can
be independently enabled. A block diagram of the REF_CLK
functionality is shown in Figure 47. The various input configu-
rations are controlled by means of the XTAL_SEL pin and
control bits in the CFR3 register. Figure 47 also shows how the
CFR3 control bits are associated with specific functional blocks.
REF_CLK
REF_CLK
PLL
VCO
SELECT
DIVIDE
CHARGE
PUMP
OUTIN
PLL_LOOP_FILTERENABLE
PLL_LOOP_FILTER
DRV0
CFR3
<29:28>
REFCLK_OUT
XTAL_SEL
REFCLK
INPUT
SELECT
LOGIC
SYSCLK
ICP
CFR3
<21:19>
N
CFR3
<7:1>
VCO SEL
CFR3
<26:24>
÷2
REF CLK INP UT
DIV IDER BYP AS S
CFR3<15>
PL L ENABL E
CFR3
<8>
REF CLK INP UT
DIVIDER RESETB
CFR3<14>
94
95 2
90
91
0
1
0
1
2
2
7
3
0
1
06384-028
Figure 47. REF_CLK Block Diagram
The PLL enable bit is used to choose between the PLL path or
the direct input path. When the direct input path is selected, the
REF_CLK/REF_CLK pins must be driven by an external signal
source. Input frequencies up to 2 GHz are supported. For input
frequencies greater than 1 GHz, the input divider must be
enabled for proper operation of the device.
When the PLL is enabled, a buffered clock signal is available at
the REFCLK_OUT pin. This clock signal is the same frequency
as the REF_CLK input. This is especially useful when a crystal
is connected, because it gives the user a replica of the crystal
clock for driving other external devices. The REFCLK_OUT
buffer is controlled by two bits as listed in Table 6.
Table 6. REFCLK_OUT Buffer Control
CFR3<29:28> REFCLK_OUT Buffer
00 Disabled
01 Low output current
10 Medium output current
11 High output current
CRYSTAL DRIVEN REF_CLK
When using a crystal at the REF_CLK input, the resonant
frequency should be approximately 25 MHz. Figure 48 shows
the recommended circuit configuration.
06384-027
REF_CLK
REF_CLK
39pF39pF
XTAL
90
91
Figure 48. Crystal Connection Diagram
DIRECT DRIVEN REF_CLK
When driving the REF_CLK/REF_CLK inputs directly from a
signal source, either single-ended or differential signals can be
used. With a differential signal source, the REF_CLK/REF_CLK
pins are driven with complementary signals and ac-coupled
with 0.1 µF capacitors. With a single-ended signal source, either a
single-ended-to-differential conversion can be employed or the
REF_CLK input can be driven single-ended directly. In either case,
0.1 µF capacitors are used to ac couple both REF_CLK/REF_CLK
pins to avoid disturbing the internal dc bias voltage of ~1.35 V.
See Figure 49 for more details.
The REF_CLK/REF_CLK input resistance is ~2.5 kΩ differential
(~1.2 kΩ single-ended). Most signal sources have relatively low
output impedances. The REF_CLK/REF_CLK input resistance is
relatively high; therefore, its effect on the termination impedance
is negligible and can usually be chosen to be the same as the output
impedance of the signal source. The bottom two examples in
Figure 49 assume a signal source with a 50 Ω output impedance.
Data Sheet AD9957
Rev. C | Page 35 of 64
06384-029
TERMINATION
REF_CLK
DIFFE RE NTI AL SOURCE,
DIFFERENTIAL INPUT.
SI NGLE - E NDE D S OURCE,
DIFFERENTIAL INPUT.
SI NGLE - E NDE D S OURCE,
SI NGLE - E NDE D INPUT.
90
91
0.1µF
0.1µF
PECL,
LVPECL,
OR
LVDS
DRIVER
REF_CLK
90
91
50Ω
0.1µF
0.1µF
BALUN
(1:1)
REF_CLK
REF_CLK
REF_CLK
REF_CLK
90
91
0.1µF
0.1µF
50Ω
Figure 49. Direct Connection Diagram
PHASE-LOCKED LOOP (PLL) MULTIPLIER
An internal phase-locked loop (PLL) provides users of the
AD9957 the option to use a reference clock frequency that is
significantly lower than the system clock frequency. The PLL
supports a wide range of programmable frequency multiplica-
tion factors (12× to 127×) as well as a programmable charge
pump current and external loop filter components (connected
via the PLL_LOOP_FILTER pin). These features add an extra
layer of flexibility to the PLL, allowing optimization of phase
noise performance and flexibility in frequency plan develop-
ment. The PLL is also equipped with a PLL_LOCK pin.
The PLL output frequency range (fSYSCLK) is constrained to the
range of 420 MHz ≤ fSYSCLK ≤ 1 GHz by the internal VCO. In
addition, the user must program the VCO to one of six operating
ranges such that fSYSCLK falls within the specified range. Figure 50
and Figure 51 summarize these VCO ranges.
Figure 50 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for all devices from the available population. The implication is
that multiple devices chosen at random from the population and
operated under widely varying conditions may require different
values to be programmed into CFR3<26:24> to operate at the
same frequency. For example, Part A chosen randomly from the
population, operating in an ambient temperature of −10°C with
a system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 100b. Whereas Part B chosen randomly from the
population, operating in an ambient temperature of 90°C with a
system clock frequency of 900 MHz may require CFR3<26:24>
to be set to 101b. If a frequency plan is chosen such that the
system clock frequency operates within one set of boundaries
(as shown in Figure 51), the required value in CFR3<26:24> is
consistent from part to part.
Figure 51 shows the boundaries of the VCO frequency ranges
over the full range of temperature and supply voltage variation
for an individual device selected from the population. Figure 51
shows that the VCO frequency ranges for a single device always
overlap when operated over the full range of conditions.
In conclusion, if a user wants to retain a single default value for
CFR3<26:24>, a frequency that falls into one of the ranges
found in Figure 50 should be selected. Additionally, for any
given individual device, the VCO frequency ranges overlap,
meaning that any given device exhibits no gaps in its frequency
coverage across VCO ranges over the full range of conditions.
06384-057
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
395 495 595 695 795 895 995
FLOW = 400
FHIGH = 460
FLOW = 455
FHIGH = 530
FLOW = 530
FHIGH = 615
FLOW = 760
FHIGH = 875
FLOW = 920
FHIGH = 1030
FLOW = 650
FHIGH = 790
(MHz)
Figure 50. VCO Ranges Including Atypical Wafer Process Skew
335 435 535 635 735 835 935 1035 1135
VCO0
VCO1
VCO2
VCO3
VCO4
VCO5
06384-056
FLOW = 342
FHIGH = 522
FLOW = 402
FHIGH = 602
FLOW = 469
FHIGH = 709
FLOW = 574
FHIGH = 904
(MHz)
FLOW = 646
FHIGH = 966
FLOW = 810
FHIGH = 1180
Figure 51. Typical VCO Ranges
Table 7. VCO Range Bit Settings
VCO SEL Bits
(CFR3<26:24>) VCO Range
000 VCO0
001 VCO1
010 VCO2
011 VCO3
100 VCO4
101
VCO5
110 PLL Bypassed
111 PLL Bypassed
AD9957 Data Sheet
Rev. C | Page 36 of 64
PLL CHARGE PUMP
The charge pump current (ICP) is programmable to provide the
user with additional flexibility to optimize the PLL performance.
Table 8 lists the bit settings vs. the nominal charge pump
current.
Table 8. PLL Charge Pump Current
ICP (CFR3<21:19>) Charge Pump Current, ICP (μA)
000 212
001 237
010 262
011
287
100 312
101 337
110 363
111 387
EXTERNAL PLL LOOP FILTER COMPONENTS
The PLL_LOOP_FILTER pin provides a connection interface to
attach the external loop filter components. The ability to use
custom loop filter components gives the user more flexibility to
optimize the PLL performance. The PLL and external loop filter
components are shown in Figure 52.
PFD CP
PLL_LOOP_FILTER
VCO
÷N
PLL OUT
PLL IN
AVDD
REF CLK PL L
2
R1
C1
C2
06384-030
Figure 52. REFCLK PLL External Loop Filter
In the prevailing literature, this configuration yields a third-
order, Type II PLL. To calculate the loop filter component
values, begin with the feedback divider value (N), the gain of
the phase detector (KD), and the gain of the VCO (KV) based on
the programmed VCO SEL bit settings (see Table 1 for KV). The
loop filter component values depend on the desired open-loop
bandwidth (fOL) and phase margin (φ), as follows:
( )
+= φKK
Nfπ
R1
VD
OL
sin
1
1 (7)
( )
( )
2
2
tan
OL
VD
fN
KK
C1 π
φ
=
(8)
( )
( )
−
=φ
φ
fπN
KK
C2
OL
VD
cos
sin1
)2(
2
(9)
where:
KD equals the programmed value of ICP.
KV is taken from Table 1.
Ensure that proper units are used for the variables in Equation 7
through Equation 9. ICP must be in amps, not μA as appears in
Table 8; KV must be in Hz/V, not MHz/V as listed in Tabl e 1; the
loop bandwidth (fOL) must be in Hz; the phase margin (φ) must
be in radians.
For example, suppose the PLL is programmed such that
ICP = 287 μA, KV = 625 MHz/V, and N = 25. If the desired loop
bandwidth and phase margin are 50 kHz and 45°, respectively,
the loop filter component values are R1 = 52.85 Ω, C1 = 145.4 nF,
and C2 = 30.11 nF.
PLL LOCK INDICATION
When the PLL is in use, the PLL_LOCK pin provides an active
high indication that the PLL has locked to the REFCLK input
signal. When the PLL is bypassed, the PLL_LOCK pin defaults
to Logic 0.
Data Sheet AD9957
Rev. C | Page 37 of 64
ADDITIONAL FEATURES
OUTPUT SHIFT KEYING (OSK)
The OSK function (Figure 53) is only available in single tone
mode. It allows the user to control the output signal amplitude
of the DDS. Both manual and automatic modes are available.
06384-031
OS K E NABLE
AMPLITUDE S CALE FACT OR
(ASF<15:2>)
AMPLITUDE RAM P RATE
(ASF<31:16>)
AMPLITUDE STEP SIZ E
(ASF<1:0>)
MANUAL OSK EX TERNAL
AUTO OS K E NABLE
OSK
DDS CL OCK
TO DDS
AMPLITUDE
CONTROL
PARAMETER
60
LOAD ARR AT I/ O_UPDATE
OSK
CONTROLLER
14
16
14
2
Figure 53. OSK Block Diagram
The operation of the OSK function is governed by four control
register bits, the external OSK pin, and the entire 32 bits of the
ASF register. The primary control for the OSK block is the OSK
enable bit. When this bit is set, the OSK function is enabled;
otherwise, the OSK function is disabled. When disabled, the
other OSK input controls are ignored and the internal clocks are
shut down to conserve power.
When the OSK function is enabled, automatic and manual
operation is selected via the Select Auto-OSK bit. When this bit
is set, the automatic mode is active; otherwise, the manual
mode is active.
Manual OSK
In manual mode, output amplitude is varied by successive write
operations to the amplitude scale factor portion of the ASF
register. The rate at which amplitude changes can be applied to
the output signal is limited by the speed of the serial I/O port.
In manual mode, the OSK pin functionality depends on the
state of the manual OSK external control bit. It is either inoperative
or used to switch the output amplitude between the programmed
amplitude scale factor value and zero. When operational, a Logic 0
on the OSK pin forces the output amplitude to zero whereas a
Logic 1 on the OSK pin causes the output amplitude to be scaled
by the amplitude scale factor value.
Automatic OSK
In automatic mode, the OSK function automatically generates
a linear amplitude vs. time profile (or amplitude ramp). The
amplitude ramp is controlled via three parameters, as follows:
• The maximum amplitude scale factor
• The amplitude step size
• The time interval between steps
The amplitude ramp parameters reside in the 32-bit ASF
register and are programmed via the serial I/O port. The
amplitude step interval is set using the 16-bit amplitude ramp
rate portion of the ASF register (Bits<31:16>). The maximum
amplitude scale factor is set using the 14-bit amplitude scale
factor in the ASF register (Bits<15:2>). The amplitude step size
is set using the 2-bit amplitude step size portion of the ASF
register (Bits<1:0>). The direction of the ramp (positive or
negative slope) is controlled by the external OSK pin. When
the OSK pin is a Logic 1, the slope is positive; otherwise, it is
negative.
The step interval is controlled by a 16-bit programmable timer
that is clocked at a rate of ¼ fSYSCLK. The timer period sets the
interval between amplitude steps. The step time interval (Δt)
is given by
SYSCLK
f
M
t
4
=∆
where M is the 16-bit number stored in the amplitude ramp rate
portion of the ASF register. For example, if fSYSCLK = 750 MHz
and M = 23,218 (0x5AB2), then Δt ≈ 123.8293 μs.
The output of the OSK function is a 14-bit unsigned data bus
that controls the amplitude of the DDS output (as long as the
OSK enable bit is Logic 1). When the OSK pin is Logic 1, the
OSK output value starts at 0 and increments by the programmed
amplitude step size until it reaches the programmed maximum
amplitude value. When the OSK pin is Logic 0, the OSK output
starts at its present value and decrements by the programmed
amplitude step size until it reaches 0.
The OSK output does not necessarily attain the maximum
amplitude—the OSK pin may switch to Logic 0 before attaining
the maximum value.
The OSK output does not necessarily reach a value of zero—the
OSK pin may switch to Logic 1 before attaining the zero value.
The OSK output is initialized to 0 at power-up. It is also set to 0
when the OSK enable bit is Logic 0 or when the OSK enable bit
is Logic 1, but the Select Auto-OSK bit is Logic 0.
The amplitude step size of the OSK output is set by the ampli-
tude step size bits in the ASF register according to the values
listed in Table 9. The step size refers to the LSB weight of the
14-bit OSK output.
The OSK output cannot exceed the maximum amplitude value
programmed into the ASF register.
AD9957 Data Sheet
Rev. C | Page 38 of 64
Table 9. OSK Amplitude Step Size
ASF<1:0> Amplitude Step Size
00 1
01 2
10 4
11 8
As mentioned earlier, the step interval is controlled by a 16-bit
programmable timer. Normally, this timer is loaded with the
programmed timing value whenever the timer expires, thus
initiating a new timing cycle. However, three events cause the
timer to have its timing value reloaded prior to the timer expiring.
One such event is when the Select Auto-OSK bit is transitioned
from a Logic 0 state to a Logic 1 state followed by an I/O update. A
second such event is a change of state in the OSK pin. The third
event is dependent on the status of the Load ARR @ I/O Update
bit. If this bit is Logic 0, no action occurs; otherwise, when the
I/O_UPDATE pin is asserted (or a profile change occurs), the
timer resets to its initial starting point.
PROFILES
Each of the three operating modes of the AD9957 support the
use of profiles, which consist of a group of registers containing
pertinent operating parameters for a particular operating mode.
Profiles enable rapid switching between parameter sets. Profile
parameters are programmed via the serial I/O port. Once pro-
grammed, a specific profile is activated by means of three
external pins (PROFILE<2:0>). A particular profile is activated
by providing the appropriate logic levels to the profile control
pins per the settings listed in Table 10.
Table 10. Profile Control Pins
PROFILE<2:0> Active Profile
000 0
001 1
010 2
011 3
100 4
101 5
110 6
111 7
Consider an application of basic two-tone frequency shift
keying (FSK) where binary data is transmitted by selecting
between two different frequencies: a mark frequency (Logic 1)
and a space frequency (Logic 0). To accommodate FSK, the
Profile 0 register is programmed with the appropriate frequency
tuning word for a space, and the Profile 1 register is programmed
with the appropriate frequency tuning word for a mark. Then,
with the PROFILE1 and PROFILE2 pins tied to Logic 0, the
PROFILE0 pin is used to transmit the data bits. The logic state
of the PROFILE0 pin causes the appropriate mark and space
frequencies to be generated.
I/O_UPDATE PIN
By default, the I/O_UPDATE pin is an input that serves as a
strobe signal to allow synchronous update of the device operating
parameters. For example, frequency, phase, and amplitude con-
trol words for the DDS can be programmed using the serial I/O
port. However, the serial I/O port is an asynchronous interface;
consequently, programming of the device operating parameters
using the I/O port is not synchronized with the internal timing.
Using the pin, I/O_UPDATE, the user can synchronize the
application of certain programmed operating parameters with
external circuitry when new parameters are programmed into
the I/O registers. A rising edge on I/O_UPDATE initiates transfer
of the register contents to the internal workings of the device.
The transfer of programmed data from the programming
registers to the internal hardware is also accomplished by
changing the state of the profile pins.
AUTOMATIC I/O UPDATE
The AD9957 offers an option whereby the I/O update function
is asserted automatically rather than relying on an external
signal supplied by the user. This feature is enabled by setting the
Internal I/O Update Active bit in CFR2.
When this feature is active, the I/O_UPDATE pin becomes an
output pin. It generates an active high pulse each time an inter-
nal I/O update occurs. The duration of the pulse is approximately
12 cycles of SYSCLK. This I/O update strobe can be used to
notify an external controller that the device has generated an
I/O update internally.
The repetition rate of the internal I/O update is programmed
via the serial I/O port. Two parameters control the repetition
rate. The first parameter consists of the two I/O update rate
control bits in CFR2. The second parameter is the 32-bit word
in the I/O update rate register that sets the range of an internal
counter.
The I/O update rate control bits establish a divide by 1, 2, 4, or 8
of a clock signal that runs at ¼ fSYSCLK. The output of the divider
clocks the aforementioned 32-bit internal counter. The repetition
rate of the I/O update is given by
B
f
fA
SYSCLK
UPDATEOI 2
_/
where:
A is the value of the 2-bit word comprising the I/O update rate
control bits.
B is the value of the 32-bit word stored in the I/O update rate
register.
If B is programmed to 0x0003 or less, the I/O_UPDATE pin no
longer pulses, but assumes a static Logic 1 state.
Data Sheet AD9957
Rev. C | Page 39 of 64
POWER-DOWN CONTROL
The AD9957 offers the ability to independently power down four
specific sections of the device. Power-down functionality applies
to the digital core, DAC, auxiliary DAC, and REFCLK input.
A power-down of the digital core disables the ability to update
the serial I/O port. However, the digital power-down bit can
still be cleared via the serial port to prevent the possibility of a
nonrecoverable state.
Software power-down is controlled through four independent
power-down bits in CFR1. Software control requires forcing the
EXT_PWR_DWN pin to a Logic 0 state. In this case, setting the
desired power-down bits (via the serial I/O port) powers down
the associated functional block; clearing the bits restores the
function.
Alternatively, all four functions can be simultaneously powered
down via external hardware control through the EXT_PWR_DWN
pin. Forcing this pin to Logic 1 powers down all four circuit
blocks, regardless of the state of the power-down bits. That is,
the independent power-down bits in CFR1 are ignored and
overridden when EXT_PWR_DWN is Logic 1.
Based on the state of the external power-down control bit, the
EXT_PWR_DWN pin produces either a full power-down or a
fast recovery power-down. The fast recovery power-down mode
maintains power to the DAC bias circuitry and the PLL, VCO,
and input section of the REFCLK circuitry. Although the fast
recovery power-down does not conserve as much power as the
full power-down, it allows the device to very quickly awaken
from the power-down state.
GENERAL-PURPOSE I/O (GPIO) PORT
The GPIO function is only available when the AD9957 is pro-
grammed for QDUC mode and the Blackfin interface mode is
active. Because the Blackfin serial interface uses only two of
the 18 parallel data port pins (D<5:4>), the remaining 16 pins
(D<17:6> and D<3:0>) are available as a GPIO port.
Each of these 16 pins is assigned a unique bit in both the 16-bit
GPIO configuration register and the 16-bit GPIO data register.
The status of each bit in the GPIO configuration register assigns
the associated pin as either a GPIO input or output (0 = input,
1 = output) based on the data listed in Table 11.
When a GPIO pin is programmed as an output, the logic state
written to the associated bit of the GPIO data register (via the
serial I/O port) appears at the GPIO pin. When a GPIO pin is
programmed as an input, the logic state of the GPIO pin can be
read (via the serial I/O port) in the associated bit position in the
GPIO data register. Note that the GPIO data register does not
require an I/O update.
Table 11. GPIO Pins vs. Configuration and Data Register Bits
Pin Label Configuration Bit Data Bit
D17 15 15
D16 14 14
D15 13 13
D14 12 12
D13 11 11
D12 10 10
D11
9
9
D10 8 8
D9 7 7
D8 6 6
D7 5 5
D6 4 4
D3 3 3
D2 2 2
D1 1 1
D0 0 0
AD9957 Data Sheet
Rev. C | Page 40 of 64
SYNCHRONIZATION OF MULTIPLE DEVICES
OVERVIEW
The internal clocks of the AD9957 provide the timing for the
propagation of data along the baseband signal processing path.
These internal clocks are derived from the internal system clock
(SYSCLK) and are all submultiples of the SYSCLK frequency.
The logic state of all of these clocks in aggregate during any
given SYSCLK cycle defines a unique clock state. The clock state
advances with each cycle of SYSCLK, but the sequence of clock
states is periodic. By definition, multiple devices are synchro-
nized when their clock states match and they transition between
states simultaneously. Clock synchronization allows the user to
asynchronously program multiple devices, but synchronously
activate the programming by applying a coincident I/O update
to all devices. It also allows multiple devices to operate in unison
when the parallel port is in use with either the QDUC or inter-
polating DAC mode (see Figure 59) or when the dual serial port
(BlackFin interface) is in use.
The function of the synchronization logic in the AD9957 is to
force the internal clock generator to a predefined state coincident
with an external synchronization signal applied to the SYNC_IN
pins. Forcing multiple devices to the same clock state coincident
with the same external signal is, by definition, synchronization.
Figure 54 is a block diagram of the synchronization function.
The synchronization logic consists of two independent blocks, a
sync generator and a sync receiver, both of which use the local
SYSCLK signal for internal timing.
SYNC
GENERATOR
REF_CLK
5
SYSCLK
INTERNAL
CLOCKS
6
5
4
SYNC
RECEIVER
SYNC
GENERATOR
ENABLE
SYNC
GENERATOR
DELAY
SYNC
POLARITY
90
91
9
10 SYNC_OUT
REF_CLK
INPUT
CIRCUITRY
7
8
12
SYNC_IN
SYNC_SMP_ERR
SYNC
VALIDATION
DELAY
SYNC S TATE
PRESET VALUE SYNC
TIMING
VALIDATION
DISABLE
CLOCK
GENERATOR
SETUP AND
HOLD VALIDATION
SYNC
RECEIVER
ENABLE
SYNC
RECEIVER
DELAY
06384-032
INP UT DEL AY
AND EDG E
DETECTION
Figure 54. Synchronization Circuit Block Diagram
The synchronization mechanism relies on the premise that the
REFCLK signal appearing at each device is edge aligned with all
others resulting from the external REFCLK distribution system
(see Figure 59).
CLOCK GENERATOR
The clock generator provides the necessary timing for the inter-
nal workings of the AD9957. The goal of the synchronization
mechanism is to force the clock generator to a known state
coincident with an external synchronization signal. The clock
generator consists of three separate clock trees (see Figure 55).
The first is a common clock generator that is active for all
programmed modes of operation (single tone, QDUC, or
interpolating DAC). The common clock generates the
SYNC_CLK signal that appears at Pin 55. The second clock
generator is active when the device is programmed for the
interpolating DAC mode or quadrature modulation mode using
the parallel data port. It uses the SYSCLK/2 output of the common
clock as its primary timing source. The third clock generator is
active when the device is programmed for quadrature modulation
mode using the BlackFin interface.
6
SYSCLK
PDCLK
6
COMM ON CL OCK
GENERATOR
SYNC_CLK
CLO CK GENE RATO R FO R
QUADRAT URE M ODUL ATI ON MODE
WI TH T HE BLACKF IN I NTERF ACE
SYNC
PULSE
SYNC STAT E
PRESET VALUE
CLOCK GENERATOR FOR INTERPOLATING
DAC MODE OR Q UADRATURE M ODUL ATION
MODE WI TH T HE P ARALL E L DATA P ORT
÷2 ÷2
÷2
÷2÷2÷2÷2÷R
÷R
06384-065
Figure 55. Clock Generator
SYNC GENERATOR
The sync generator block is shown in Figure 56. It is activated
via the Sync Generator Enable bit. It allows for one AD9957 in a
group to function as a master timing source with the remaining
devices slaved to the master.
Data Sheet AD9957
Rev. C | Page 41 of 64
SYSCLK
SYNC
GENERATOR
ENABLE
SYNC
GENERATOR
DELAY
SYNC
POLARITY
SYNC_OUT
0
1
D Q
R
PROGAMMABLE
DELAY
÷16 ÷2R
5
9
10
LVDS
DRIVER
06384-033
Figure 56. Sync Generator
The sync generator produces an LVDS-compatible clock signal
with a 50% duty cycle that appears at the SYNC_OUT pins. The
frequency of the SYNC_OUT signal can be one of two possible
rates. With the AD9957 programmed for any of the following
modes:
• Single tone mode
• Quadrature modulation mode with the CCI filter bypassed
(that is, interpolation factor is 1)
• Interpolating DAC mode with the CCI filter bypassed (that
is, interpolation factor is 1)
The frequency of SYNC_OUT is given by:
16
_
SYSCLK
OUTSYNC
f
f=
With the AD9957 programmed for the QDUC or interpolating
DAC mode and with the CCI filter not bypassed (that is, R>1)
the frequency of SYNC_OUT is given by
R
f
fSYSCLK
OUTSYNC
32
_=
where R is the programmed interpolation factor of the CCI filter.
The signal at the SYNC_OUT pins is edge aligned with either
the rising or falling edge of the internal SYSCLK signal as deter-
mined by the Sync Polarity bit. Because the SYNC_OUT signal is
synchronized with the internal SYSCLK of the master device, the
master device SYSCLK serves as the reference timing source for
all slave devices.
The user can adjust the output delay of the SYNC_OUT signal
in steps of ~75 ps by programming the 5-bit sync generator
delay word via the serial I/O port. The programmable output
delay facilitates added edge timing flexibility to the overall
synchronization mechanism.
SYNC RECEIVER
The sync receiver block (shown in Figure 57) is activated via the
Sync Receiver Enable bit. The sync receiver consists of three
subsections: the input delay and edge detection block, the
internal clock generator block, and the setup-and-hold valida-
tion block.
The clock generator block remains operational even when the
sync receiver is not enabled.
The sync receiver accepts an LVDS-compatible signal at the
SYNC_IN pins. Typically, the signal applied to the SYNC_IN
pins originates from the SYNC_OUT of another AD9957
functioning as a master timing unit. The sync receiver expects a
periodic synchronization pulse that meets certain frequency
requirements based on the operating mode of the AD9957.
When programmed for single tone mode, the frequency of
SYNC_IN must satisfy
M
f
f
SYSCLK
INSYNC
4
_
=
where M is any integer greater than zero. When programmed
for quadrature modulation mode (using the parallel data port)
or interpolating DAC mode, the frequency of SYNC_IN must
satisfy
( )
MR
f
fSYSCLK
INSYNC +
=16
_
where R is the programmed CCI interpolation factor and M is
any integer greater than or equal to zero. When programmed
for quadrature modulation mode using the BlackFin interface,
the frequency of SYNC_IN must satisfy
( )
MR
f
f
SYSCLK
INSYNC
+
=32
_
where R is the programmed CCI interpolation factor and M is
any integer greater than or equal to zero.
AD9957 Data Sheet
Rev. C | Page 42 of 64
LVDS
RECEIVER
PROGAMMABLE
DELAY
5INTERNAL
CLOCKS
CLOCK
STATE
6
SYNC S TATE
PRESET VALUE
SYNC PULSE
SYSCLK
SETUP AND HO LD
VALIDATION
4
Q0
LOAD
QN
DEL AY E D S Y NC- IN SI GNAL
SYNC
RECEIVER
DELAY
SYNC
RECEIVER
ENABLE
SYNC_SMP_ERR
SYNC_IN+
SYNC_IN–
7
8
12
RISING EDGE
DETECTOR
AND
STROBE
GENERATOR
SYNC
TIMING
VALIDATION
DISABLE
SYNC
VALIDATION
DELAY
06384-034
CLOCK
GENERATOR
P
R
E
S
E
T
.
.
..
.
.
Figure 57. Sync Receiver
When a device other than another AD9957 provides the
SYNC_IN signal it must be LVDS compatible. Furthermore,
although SYNC_IN is typically considered to be a periodic
clock signal, it is not an absolute requirement. It is feasible to
drive the SYNC_IN pins with a single synchronization pulse as
long as its edge transition meets the setup/hold timing required
for the internally generated sync pulse (as detailed later in this
section). However, using a periodic SYNC_IN signal has the
distinct advantage that should any of the devices arbitrarily lose
synchronization it automatically resynchronizes with the arrival
of the next SYNC_IN edge.
The 5-bit sync receiver delay word in the multichip sync register
delays the SYNC_IN signal in steps of ~75 ps. This provides the
ability to time align the arrival of the SYNC_IN signal to
multiple devices by compensating for unequal propagation times.
The edge detection logic in the sync receiver generates a
synchronization pulse (sync pulse) having a duration of one
SYSCLK cycle with a repetition rate equal to that of the signal
applied to the SYNC_IN pins. To produce the sync pulse, the
strobe generator samples the delayed rising edge of the SYNC_IN
signal with the rising edge of the local SYSCLK. The generation
of this sync pulse is crucial to the operation of the synchroniza-
tion mechanism, because it performs the task of placing the
clock generator into a known state. The sync pulse presets the
R-divider stage of the internal clock generator, which behaves as
a presettable downcounter (see Figure 55). The programmable
6-bit sync state preset value word in the multichip sync register
establishes the preset state. The preset state is only active for a
single SYSCLK period, after which the clock generator is free to
cycle through its state sequence until the next sync pulse arrives
(see Figure 55). In addition to presetting the R-divider, the sync
pulse also synchronously presets the other dividers to a proper
state in order to preserve the cadence of the clock tree.
The ability to program the clock state preset value provides the
flexibility to synchronize devices, but with specific relative clock
state offsets by assigning a different sync state preset value word
to each device in a group. This flexibility is limited, however,
because the sync state preset value must adhere to certain
bounds to satisfy internal timing requirements. Regardless of
the programmed sync state preset value, the preset value is
internally constrained to the range, 2 to R, where R is the CCI
filter interpolation factor. A programmed value of 0 or 1 is forced
to 2, whereas a programmed value greater than R is forced to R.
SETUP/HOLD VALIDATION
Synchronization of the AD9957 internal clock generator with
other external devices relies on the ability of the sync receiver’s
edge detection circuit to generate a valid sync pulse. This
requires proper sampling of the rising edge of the delayed
SYNC_IN signal with the rising edge of the local SYSCLK. If the
edge timing of these signals fails to meet the setup or hold time
requirements of the internal latches in the edge detection
circuitry, the proper generation of a sync pulse is in jeopardy.
The setup-and-hold validation block (see Figure 58) gives the
user a means to validate that proper edge timing exists between
the two signals. The Sync Timing Validation Disable bit in
Control Function Register 2 controls whether or not the setup-
and-hold validation block is active.
The validation block makes use of a specified time window
(programmable in increments of ~75 ps via the 4-bit sync
validation delay word in the multichip sync register). The setup
validation and hold validation circuits use latches identical to
those in both the rising edge detector and strobe generator. The
programmable time window skews the timing between the local
SYSCLK signal and the delayed sync-in signal. If the hold valida-
tion and setup validation circuits fail to produce the same logic
states, it is an indication of a possible setup or hold violation.
The check logic of Figure 58 monitors the state of the setup and
hold validation latches. If they are not equal (that is, a potential
setup/hold violation exists), a Logic 1 is stored in an internal
validation result latch; otherwise, a Logic 0 is stored. The state
of validation result latch appears at the SYNC_SMP_ERR pin.
Data Sheet AD9957
Rev. C | Page 43 of 64
The validation result latch is in a reset state whenever the sync
receiver is disabled, which forces the SYNC_SMP_ERR pin to a
Logic 0 state. To reset the validation result latch when the sync
receiver is active, however, requires the use of the Sync Timing
Validation Disable bit in the multichip sync register. To make a
setup/hold validation measurement is a two-step process. First,
write a Logic 1 to the sync timing validation disable bit. Then,
to make a measurement, write a Logic 0. The first action resets
the validation result latch and holds it in a reset state; the
second action releases the reset state and enables the validation
result latch to capture a setup/hold validation measurement.
Each time a new setup/hold validation check is desired, this
two-step procedure must be performed.
Because the programmed value of the sync validation delay
establishes the time window for a setup/hold measurement,
the amount of delay is an important consideration for proper
operation of the validation block. The value chosen should
represent a small fraction of the SYSCLK period. For example,
if the SYSCLK frequency is 1 GHz (1000 ps period), then a
reasonable sync validation delay value is 4 (~300 ps). This
allows the validation block to ensure that the local SYSCLK
and the delayed SYNC_IN edges exhibit at least 300 ps of
timing separation. Choosing too large a value can cause the
validation block to indicate a setup/hold violation when one
does not exist. Choosing too small a value can cause the
validation block to miss a setup/hold violation when one
actually exists.
SYNC
PULSE
SYSCLK DELAY
CHECK L OGIC
4
4
SYNC V ALIDATI ON
DELAY
SYNC_SMP_ERR
SYNC RECEIVER
SYNC TIMING VALIDATION DISABLE
SETUP
VALIDATION
HOLD
VALIDATION
12
SETUP AND HO LD VALI DATI ON
TO
CLOCK
GENERATION
LOGIC
FROM
SYNC
RECEIVER
DELAY
LOGIC
D Q
D Q
D Q
DELAY
RISING EDGE
DETECTOR
AND ST ROBE
GENERATOR
06384-036
4
Figure 58. Sync Timing Validation Block
AD9957 Data Sheet
Rev. C | Page 44 of 64
SYNCHRONIZATION EXAMPLE
To accomplish the synchronization of multiple devices provide
each AD9957 with a SYNC_IN signal that is edge aligned across
all the devices. If the SYNC_IN signal is edge aligned at all devices,
and all devices have the same sync receiver delay and sync state
preset value, then they all have matching clock states (that is,
they are synchronized). Figure 59 shows this concept with three
AD9957s in synchronization. One device operates as a master
timing unit with the others synchronized to the master.
The master device must have its SYNC_IN pins included as part
of the synchronization distribution and delay equalization mecha-
nism. This ensures that the master maintains synchronous timing
with the other units.
The synchronization mechanism begins with the clock distribu-
tion and delay equalization block, which ensures that all devices
receive an edge-aligned REFCLK signal. However, even though
the REFCLK signal is edge aligned among all devices, this alone
does not guarantee that the clock state of each internal clock
generator is coordinated with the others. This is the role of the
synchronization and delay equalization block. This block accepts
the SYNC_OUT signal generated by the master device and
redistributes it to the SYNC_IN input of the slave units (as well
as feeding it back to the master). The goal of the redistributed
SYNC_OUT signal from the master device is to deliver an edge-
aligned SYNC_IN signal to all of the sync receivers.
Assuming that all devices share the same REFCLK edge timing
(due to the clock distribution and delay equalization block) and
that all devices share the same SYNC_IN edge timing (due to
the synchronization and delay equalization block), then all
devices should be generating an internal sync pulse in unison
(assuming all have the same value for the sync receiver delay).
With the further stipulation that all devices have the same sync
state preset value, then the synchronized sync pulses cause all of
the devices to assume the same predefined clock state simultane-
ously. That is, all devices have their internal clocks fully
synchronized.
CLOCK
SOURCE
SYNC
IN SYNC
OUT
REF_CLK
AD9957
NUMBER 1 MASTER DEVICE
FPGA
DATA
FPGA
DATA
FPGA
DATA
EDGE
ALIGNED
AT RE F_CLK
INPUTS
EDGE
ALIGNED
AT S Y NC_IN
INPUTS.
PDCLK
SYNC
IN SYNC
OUT
REF_CLK
AD9957
NUMBER 2
PDCLK
SYNC
IN SYNC
OUT
REF_CLK
AD9957
NUMBER 3
PDCLK
(FOR EXAMPL E, AD951x)
CLOCK DISTRIBUTION
AND
DELAY EQUALIZATION
SYNCHRONIZATION
DIS TRIBUTI ON AND
DELAY EQUALIZATION
(FOR EXAMPL E AD951x)
06384-035
Figure 59. Multichip Synchronization Example
Data Sheet AD9957
Rev. C | Page 45 of 64
I/Q PATH LATENCY
The I/Q latency through the AD9957 is easiest to describe in
terms of system clock (SYSCLK) cycles and is a function of the
AD9957 configuration (that is, which mode and which optional
features are engaged). The I/Q latency is primarily affected by
the programmable CCI rate.
The values in Table 12 should be considered estimates because
observed latency may be data dependent. The latency was
calculated using the linear delay model for FIR filters. N = CCI
rate (programmable interpolation rate, 2 to 63, 1 if bypassed).
In BFI mode, the latency through the AD9957 may not be con-
stant for multiple transmissions. This is due to the relationship
between the phase of the clock that drives the first half-band
filter and the frame sync signal coming from the Blackfin,
which is unknown and denoted as x in Table 12. The design
successfully transfers data from the data assembler logic to the
signal process path by updating a parallel register at the proper
time. The data is transferred from the parallel register to the
signal processing chain and all timing has been verified regard-
less of the phase relationship between the updating of the parallel
register and the signal processing clock.
Example
Quadrature modulation mode = 18-bit parallel data
Reference clock multiplier = bypassed
Input scale multiplier = off
Inverse CCI = off
CCI rate = 20
Inverse SINC = on
Output scale = off
Latency = (16 × 20) + (4 × 20) + (4 × 20) + (69 × 20) +
(4 × 20 + 8) + 22 + 8 + 2 + 8 = 1988 SYSCLKs
Table 12.
Stage Quadrature Modulation Mode—Parallel Quadrature Modulation Mode—BFI Interpolation DAC Mode
Input Demuxplexer 16N (16 + x)N 28N
where x = 0 to 15
Input Scale Multiplier Active: 8N Not available in BFI mode Active: 8N
Bypassed: 4N Bypassed: 4N
Inverse CCI Filter
Active: 8
N
Active: 8
N
Active: 8
N
Bypassed: 4N Bypassed: 4N Bypassed: 4N
Half-Band Filters 69N 345N 69N
CCI Filter Active: 4N + 8 Active: 4N + 8 Active: 4N + 8
Bypass: 2N + 4 Bypass: 2N + 4 Bypass: 2N + 4
Modulator 22 22 0
Inverse Sinc Filter Active: 8 Active: 8 Active: 8
Bypass: 2 Bypass: 2 Bypass: 2
Output Scale Multiplier Active: 12 Active: 12 Active: 12
Bypass: 2 Bypass: 2 Bypass: 2
DAC Interface 8 8 8
AD9957 Data Sheet
Rev. C | Page 46 of 64
POWER SUPPLY PARTITIONING
The AD9957 features multiple power supplies, and their power
consumption varies with its configuration. This section covers
which power supplies can be grouped together and how the
power consumption of each block varies with frequency.
The values quoted in this section are for comparison only. Refer
to Tabl e 1 for exact values. With each group, bypass capacitors of
1 μF in parallel with a 10 μF capacitor should be used.
The recommendations here are for typical applications, for
which there are four groups of power supplies: 3.3 V digital,
3.3 V analog, 1.8 V digital, and 1.8 V analog.
Applications demanding the highest performance may require
additional power supply isolation.
3.3 V SUPPLIES
DVDD_I/O (Pin 11, Pin 15, Pin 21, Pin 28, Pin 45, Pin 56,
Pin 66)
These 3.3 V supplies can be grouped together. The power
consumption on these pins varies dynamically with serial port
activity.
AVDD (Pin 74 to Pin 77 and Pin 83)
These are 3.3 V DAC power supplies that typically consume
about 28 mA. At a minimum, a ferrite bead should be used to
isolate these from other 3.3 V supplies, with a separate regulator
being ideal. The current consumption of these supplies consist
mainly of biasing current and do not vary with frequency.
1.8 V SUPPLIES
DVDD (Pin 17, Pin 23, Pin 30, Pin 47, Pin 57, Pin 64)
These pins can be grouped together. Their current consumption
increases linearly with the system clock frequency. A system
clock of 1 GHz produces a typically current consumption of
610 mA in QDUC mode. There is also a slight (~5%) increase
as fOUT increases from 50 MHz to 400 MHz.
AVDD (Pin 3)
This 1.8 V supply powers the REFCLK multiplier (PLL) and
consumes about 7 mA. For applications demanding the highest
performance with the PLL enabled, this supply should be
isolated from other 1.8 V AVDD supplies with a separate
regulator. For less demanding applications this supply can be
run off the same regulator as Pin 89, Pin 92 with a ferrite bead
to isolate Pin 3 from Pin 89, and Pin 89.
The loop filter for the PLL should directly connect to Pin 3. If
the PLL is bypassed, pin 3 should still be powered, but isolation
is not critical.
AVDD (Pin 6)
This pin can be grouped together with the DVDD 1.8V supply
pins. For the highest performance, a ferrite bead should be used
for isolation, with a separate regulator being ideal.
AVDD (Pin 89 and Pin 92)
This 1.8 V supply for the REFCLK input consumes about
15 mA. The supply can be run off the same as Pin 3 with a
ferrite bead to isolate Pin 3 from Pin 89 and Pin 92. At a
minimum, a ferrite bead should be used to isolate these from
other 1.8 V supplies. However, for applications demanding the
highest performance, a separate regulator is recommended.
Data Sheet AD9957
Rev. C | Page 47 of 64
SERIAL PROGRAMMING
CONTROL INTERFACE—SERIAL I/O
The AD9957 serial port is a flexible, synchronous serial commu-
nications port allowing easy interface to many industry-standard
microcontrollers and microprocessors.
The interface allows read/write access to all registers that configure
the AD9957. MSB-first or LSB-first transfer formats are sup-
ported. In addition, the serial interface port can be configured
as a single pin input/output (SDIO) allowing a two-wire interface,
or it can be configured as two unidirectional pins for input/output
(SDIO/SDO), enabling a 3-wire interface. Two optional pins
(I/O_RESET and CS) enable greater flexibility for designing
systems with the AD9957.
GENERAL SERIAL I/O OPERATION
There are two phases to a serial communications cycle. The first
is the instruction phase to write the instruction byte into the
AD9957. The instruction byte contains the address of the regis-
ter to be accessed (see the Register Map and Bit Descriptions
section) and defines whether the upcoming data transfer is a
write or read operation.
For a write cycle, Phase 2 represents the data transfer between
the serial port controller to the serial port buffer. The number
of bytes transferred is a function of the register being accessed.
For example, when accessing the Control Function Register 2
(Address 0x01), Phase 2 requires that four bytes be transferred.
Each bit of data is registered on each corresponding rising edge
of SCLK. The serial port controller expects that all bytes of the
register be accessed; otherwise, the serial port controller is put
out of sequence for the next communication cycle. However,
one way to write fewer bytes than required is to use the I/O_RESET
pin feature. The I/O_RESET pin function can be used to abort
an I/O operation and reset the pointer of the serial port con-
troller. After an I/O reset, the next byte is the instruction byte.
Note that every completed byte written prior to an I/O reset is
preserved in the serial port buffer. Partial bytes written are not
preserved. At the completion of any communication cycle, the
AD9957 serial port controller expects the next eight rising
SCLK edges to be the instruction byte for the next communi-
cation cycle.
After a write cycle, the programmed data resides in the serial
port buffer and is inactive. I/O_UPDATE transfers data from
the serial port buffer to active registers. The I/O update can
either be sent after each communication cycle or when all serial
operations are complete. In addition, a change in profile pins
can initiate an I/O update.
For a read cycle, Phase 2 is the same as the write cycle with the
following differences: Data is read from the active registers, not
the serial port buffer, and data is driven out on the falling edge
of SCLK.
Note that to read back any profile register (0x0E to 0x15), the
three external profile pins must be used. For example, if the
profile register is Profile 5 (0x13) then PROFILE<0:2> pins
must equal 101.This is not required to write to profile registers.
INSTRUCTION BYTE
The instruction byte contains the following information as
shown in the instruction byte bit map.
Instruction Byte Information Bit Map
MSB LSB
D7 D6 D5 D4 D3 D2 D1 D0
R/W X X A4 A3 A2 A1 A0
R/W—Bit 7 of the instruction byte determines whether a read
or write data transfer occurs after the instruction byte write.
Logic 1 indicates a read operation. Cleared indicates a write
operation.
X, X—Bit 6 and Bit 5 of the instruction byte are don’t cares.
A4, A3, A2, A1, A0—Bit 4, Bit 3, Bit 2, Bit 1, and Bit 0 of the
instruction byte determine which register is accessed during the
data transfer portion of the communications cycle.
SERIAL I/O PORT PIN DESCRIPTIONS
SCLK—Serial Clock
The serial clock pin is used to synchronize data to and from the
AD9957 and to run the internal state machines.
CS—Chip Select Bar
An active low input that allows more than one device on the
same serial communications line. The SDO and SDIO pins go
to a high impedance state when this input is high. If driven high
during any communications cycle, that cycle is suspended until
CS is reactivated low. Chip select (CS) can be tied low in
systems that maintain control of SCLK.
SDIO—Serial Data Input/Output
Data is always written into the AD9957 on this pin. However,
this pin can be used as a bidirectional data line. Bit 1 of CFR1,
Register Address 0x00, controls the configuration of this pin.
The default is cleared, which configures the SDIO pin as
bidirectional.
AD9957 Data Sheet
Rev. C | Page 48 of 64
SDO—Serial Data Out
Data is read from this pin for protocols that use separate lines
for transmitting and receiving data. In the case where the
AD9957 operates in a single bidirectional I/O mode, this pin
does not output data and is set to a high impedance state.
I/O_RESET—Input/Output Reset
I/O_RESET synchronizes the I/O port state machines without
affecting the addressable registers contents. An active high
input on the I/O_RESET pin causes the current communication
cycle to abort. After I/O_RESET returns low (Logic 0), another
communication cycle can begin, starting with the instruction
byte write.
I/O_UPDATE—Input/Output Update
The I/O_UPDATE initiates the transfer of written data from
the I/O port buffer to active registers. I/O_UPDATE is active
on the rising edge and its pulse width must be greater than one
SYNC_CLK period. It is either an input or output pin depending
on the programming of the Internal I/O Update Active bit.
SERIAL I/O TIMING DIAGRAMS
Figure 60 through Figure 63 provide basic examples of the tim-
ing relationships between the various control signals of the serial
I/O port. Most of the bits in the register map are not transferred
to their internal destinations until assertion of an I/O update,
which is not included in the timing diagrams that follow.
MSB/LSB TRANSFERS
The AD9957 serial port can support both most significant bit
(MSB) first or least significant bit (LSB) first data formats. This
functionality is controlled by Bit 0 in Control Function Register 1
(0x00). The default format is MSB first. If LSB first is active,
all data, including the instruction byte, must follow LSB-first
convention. Note that the highest number found in the bit range
column for each register is the MSB and the lowest number is
the LSB for that register (see the Register Map and Bit
Descriptions section and Table 13).
06384-037
I7
SDIO
INSTRUCT IO N CY CLE DATA TRANS FER CY CLE
SCLK
CS
I6I5I4I3I2I1I0D7D6D5D4D3D2D1D0
Figure 60. Serial Port Write Timing—Clock Stall Low
06384-038
D
O7
INS TRUCTIO N CY CLE DATA T RANS FER CY CLE
DON' T CARE
I
7
I
6
I
5
I
4
I
3
I
2
I
1
I
0
SDIO
SCLK
CS
SDO D
O6
D
O5
D
O4
D
O3
D
O2
D
O1
D
O0
Figure 61. 3-Wire Serial Port Read Timing—Clock Stall Low
06384-039
I7
SDIO
INSTRUCT IO N CY CLE DATA T RANS FER CY CLE
SCLK
CS
I6I5I4I3I2I1I0D7D6D5D4D3D2D1D0
Figure 62. Serial Port Write Timing—Clock Stall High
06384-040
I7
SDIO
INSTRUCT IO N CY CLE DATA T RANS FER CY CLE
SCLK
CS
I6I5I4I3I2I1I0DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
Figure 63. 2-Wire Serial Port Read Timing—Clock Stall High
Data Sheet AD9957
Rev. C | Page 49 of 64
I/O_UPDATE, SYNC_CLK, AND SYSTEM CLOCK
RELATIONSHIPS
The I/O_UPDATE pin is used to transfer data from the serial
I/O buffer to the active registers in the device. Data in the buffer
is inactive.
SYNC_CLK is a rising edge active signal. It is derived from the
system clock and a divide-by-4 frequency divider. SYNC_CLK,
which is externally provided, can be used to synchronize
external hardware to the AD9957 internal clocks.
I/O_UPDATE initiates the start of a buffer transfer. It can
be sent synchronously or asynchronously relative to the
SYNC_CLK. If the setup time between these signals is met,
then constant latency (pipeline) to the DAC output exists.
For example, if repetitive changes to phase offset via the SPI
port is desired, the latency of those changes to the DAC output
is constant; otherwise, a time uncertainty of one SYNC_CLK
period is present.
By default, the I/O_UPDATE pin is an input that serves as a
strobe signal to allow synchronous update of the device oper-
ating parameters. A rising edge on I/O_UPDATE initiates
transfer of the register contents to the internal workings of
the device. Alternatively, the transfer of programmed data from
the programming registers to the internal hardware can be
accomplished by changing the state of the PROFILE[2:0] pins.
The timing diagram shown in Figure 64 depicts when the data
in the buffer is transferred to the active registers.
SYNC_CLK
SYSCLK
A B
NN + 1
N – 1
DATA IN
REGISTERS
DATA IN
I/O BUFFERS NN + 1 N + 2
I/O_UPDATE
THE DE V ICE REGI S TERS AN I/ O UPDAT E AT POI NT A. THE DAT A IS TRANSFERRE D FRO M THE ASY NCHRONO US LY LO ADE D I/O BUF FERS AT POINT B.
06384-161
Figure 64. I/O_UPDATE Transferring Data from I/O Buffer to Active Registers
AD9957 Data Sheet
Rev. C | Page 50 of 64
REGISTER MAP AND BIT DESCRIPTIONS
REGISTER MAP
Note that the highest number found in the Bit Range column for each register in the following tables is the MSB and the lowest number is
the LSB for that register.
Table 13. Control Registers
Register
Name
(Serial
Address)
Bit
Range
(Internal
Address)
Bit 7
(MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Bit 0
(LSB)
Default
Value
Control
Function
Register 1
CFR1
(0x00)
<31:24> RAM
Enable
Open RAM
Playback
Destination
Open Operating Mode 0x00
<23:16> Manual
OSK
External
Control
Inverse
Sinc Filter
Enable
Clear CCI Open Select
DDS
Sine
Output
0x00
<15:8> Open Autoclear
Phase
Accumulator
Open Clear Phase
Accumulator
Load ARR @
I/O Update
OSK
Enable
Select
Auto-
OSK
0x00
<7:0>
Digital
Power-
Down
DAC Power-
Down
REFCLK Input
Power-Down
Aux DAC
Power-Down
External
Power-Down
Control
Auto
Power-Down
Enable
SDIO
Input
Only
LSB First
0x00
Control
Function
Register 2
CFR2
(0x01)
<31:24> Blackfin
Interface
Mode
Active
Blackfin Bit
Order
Blackfin
Early Frame
Sync Enable
Open Enable
Profile
Registers
as ASF
Source
0x00
<23:16> Internal
I/O
Update
Active
SYNC_CLK
Enable
Open Read
Effective
FTW
0x40
<15:8> I/O Update Rate Control PDCLK Rate
Control
Data Format PDCLK
Enable
PDCLK
Invert
TxEnable
Invert
Q-First
Data
Pairing
0x08
<7:0> Open Data
Assembler
Hold Last
Value
Sync Timing
Validation
Disable
Open 0x20
Control
Function
Register 3
CFR3
(0x02)
<31:24> Open DRV0<1:0> Open VCO SEL<2:0> 0x1F
<23:16> Open ICP<2:0> Open 0x3F
<15:8> REFCLK
Input
Divider
Bypass
REFCLK
Input
Divider
ResetB
Open PLL
Enable
0x40
<7:0> N<6:0> Open 0x00
Auxiliary
DAC
Control
Register
(0x03)
<31:24> Open 0x00
<23:16> Open 0x00
<15:8> Open 0x7F
<7:0> FSC<7:0> 0x7F
I/O Update
Rate
Register
(0x04)
<31:24>
I/O Update Rate<31:24>
0xFF
<23:16> I/O Update Rate<23:16> 0xFF
<15:8> I/O Update Rate<15:8> 0xFF
<7:0> I/O Update Rate<7:0> 0xFF
Data Sheet AD9957
Rev. C | Page 51 of 64
Table 14. RAM, ASF, Multichip Sync, and Profile 0 Registers
Register Name
(Serial Address)
Bit Range
(Internal
Address)
Bit 7
(MSB) Bit 6 Bit5
Bit
4 Bit 3 Bit 2 Bit 1
Bit 0
(LSB)
Default
Value
RAM Segment
Register 0 (0x05)
<47:40> RAM Address Step Rate 0<15:8>
<39:32> RAM Address Step Rate 0<7:0>
<31:24> RAM End Address 0<9:2>
<23:16> RAM End
Address 0<1:0>
Open
<15:8>
RAM Start Address 0<9:2>
<7:0> RAM Start
Address 0<1:0>
Open RAM Playback Mode 0<2:0>
RAM Segment
Register 1 (0x06)
<47:40> RAM Address Step Rate 1<15:8>
<39:32> RAM Address Step Rate 1<7:0>
<31:24> RAM End Address 1<9:2>
<23:16> RAM End
Address 1<1:0>
Open
<15:8> RAM Start Address 1<9:2>
<7:0> RAM Start
Address 1<1:0>
Open RAM Playback Mode 1<2:0>
Amplitude Scale
Factor (ASF)
Register
(0x09)
<31:24> Amplitude Ramp Rate<15:8> 0x00
<23:16> Amplitude Ramp Rate<7:0> 0x00
<15:8> Amplitude Scale Factor<13:6> 0x00
<7:0> Amplitude Scale Factor<5:0> Amplitude Step Size<1:0> 0x00
Multichip Sync
Register (0x0A)
<31:24> Sync Validation Delay<3:0> Sync
Receiver
Enable
Sync
Generator
Enable
Sync
Generator
Polarity
Open 0x00
<23:16> Sync State Preset Value<5:0> Open 0x00
<15:8>
Sync Generator Delay<4:0>
Open
0x00
<7:0> Sync Receiver Delay<4:0> Open 0x00
Profile 0
Register—Single
Tone (0x0E)
<63:56> Open Amplitude Scale Factor<13:8> 0x08
<55:48> Amplitude Scale Factor<7:0> 0xB5
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 0
Register—QDUC
(0x0E)
<63:56> CCI Interpolation Rate<7:2> Spectral Invert Inverse
CCI Bypass
0x00
<55:48> Output Scale Factor 0x00
<47:40>
Phase Offset Word<15:8>
0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
AD9957 Data Sheet
Rev. C | Page 52 of 64
Table 15. Profile 1, Profile 2, and Profile 3 Registers
Register
Name
(Serial
Address)
Bit Range
(Internal
Address)
Bit 7
(MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Bit 0
(LSB)
Default
Value
Profile 1
Register—
Single Tone
(0x0F)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48> Amplitude Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 1
Register—
QDUC (0x0F)
<63:56> CCI Interpolation Rate<7:2> Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24>
Frequency Tuning Word<31:24>
0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 2
Register—
Single Tone
(0x10)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48> Amplitude Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 2
Register—
QDUC (0x10)
<63:56> CCI Interpolation Rate<7:2> Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 3
Register—
Single Tone
(0x11)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48>
Amplitude Scale Factor<7:0>
0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 3
Register—
QDUC
(0x11)
<63:56> CCI Interpolation Rate<7:2> Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16>
Frequency Tuning Word<23:16>
0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Data Sheet AD9957
Rev. C | Page 53 of 64
Table 16. Profile 4, Profile 5, and Profile 6 Registers
Register
Name
(Serial
Address)
Bit
Range
(Internal
Address) Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB)
Default
Value
Profile 4
Register—
Single Tone
(0x12)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48>
Amplitude Scale Factor<7:0>
0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24>
Frequency Tuning Word<31:24>
0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 4
Register—
QDUC
(0x12)
<63:56> CCI Interpolation Rate<7:2> Spectral Invert Inverse CCI Bypass 0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 5
Register—
Single Tone
(0x13)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48> Amplitude Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0>
Frequency Tuning Word<7:0>
0x00
Profile 5
Register—
QDUC
(0x13)
<63:56> CCI Interpolation Rate<7:2> Spectral Invert Inverse CCI Bypass 0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40>
Phase Offset Word<15:8>
0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16>
Frequency Tuning Word<23:16>
0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 6
Register—
Single Tone
(0x14)
<63:56> Open Amplitude Scale Factor<13:8> 0x00
<55:48> Amplitude Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 6
Register—
QDUC
(0x14)
<63:56> CCI Interpolation Rate<7:2> Spectral Invert Inverse CCI Bypass 0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
AD9957 Data Sheet
Rev. C | Page 54 of 64
Table 17. Profile 7, RAM, GPIO Configuration, and GPIO Data Registers
Register Name
(Serial Address)
Bit Range
(Internal
Address)
Bit 7
(MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
Bit 0
(LSB)
Default
Value
Profile 7
Register—
Single Tone
(0x15)
<63:56>
Open
Amplitude Scale Factor<13:8>
0x00
<55:48> Amplitude Scale Factor<7:0> 0x00
<47:40> Phase Offset Word<15:8> 0x00
<39:32>
Phase Offset Word<7:0>
0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16> Frequency Tuning Word<23:16> 0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
Profile 7
Register—
QDUC (0x15)
<63:56> CCI Interpolation Rate<7:2> Spectral
Invert
Inverse CCI
Bypass
0x00
<55:48> Output Scale Factor<7:0> 0x00
<47:40>
Phase Offset Word<15:8>
0x00
<39:32> Phase Offset Word<7:0> 0x00
<31:24> Frequency Tuning Word<31:24> 0x00
<23:16>
Frequency Tuning Word<23:16>
0x00
<15:8> Frequency Tuning Word<15:8> 0x00
<7:0> Frequency Tuning Word<7:0> 0x00
RAM Register
(0x16)
<31:0>
RAM Word<31:0>
GPIO
Configuration
Register (0x18)
<15:0> GPIO Configuration<15:0> 0x00
GPIO Data
Register (0x19)
<15:0> GPIO Data<15:0> 0x00
Data Sheet AD9957
Rev. C | Page 55 of 64
REGISTER BIT DESCRIPTIONS
The serial I/O port registers span an address range of 0 to 25
(0x00 to 0x19 in hexadecimal notation). This represents a total
of 26 registers. However, six of these registers are unused, yielding
a total of 20 available registers. The unused registers are 7, 8, 11
to 13, and 23 (0x07 to 0x08, 0x0B to 0x0D, and 0x17).
The number of bytes assigned to the registers varies. That is, the
registers are not of uniform depth; each contains the number
of bytes necessary for its particular function. Additionally, the
registers are assigned names according to their functionality.
In some cases, a register is given a mnemonic descriptor. For
example, the register at Serial Address 0x00 is named Control
Function Register 1 and is assigned the mnemonic CFR1.
The following section provides a detailed description of each bit
in the AD9957 register map. For cases in which a group of bits
serve a specific function, the entire group is considered as a
binary word and described in aggregate.
This section is organized in sequential order of the serial
addresses of the registers. Following each subheading are the
individual bit descriptions for that particular register. The
location of the bit(s) in the register are indicated by <A> or
<A:B>, where A and B are bit numbers. The notation, <A:B>,
specifies a range of bits from most significant to least significant
bit position. For example, <5:2> means bit positions 5 down to
2, inclusive, with Bit 0 identifying the LSB of the register.
Unless otherwise stated, programmed bits are not transferred to
their internal destinations until the assertion of an I/O update or
profile change.
Control Function Register 1 (CFR1)
Address 0x00, four bytes are assigned to this register.
Table 18. Bit Descriptions for CFR1 Register
Bit (s)
Mnemonic
Description
31 RAM Enable 0: disables RAM playback functionality (default).
1: enables RAM playback functionality.
30:29 Open
28 RAM Playback
Destination
Ineffective unless CFR1<31> = 1.
0: RAM playback data routed to baseband scaling multipliers (default).
1: RAM playback data routed to baseband I/Q data path.
27:26 Open
25:24 Operating Mode 00: quadrature modulation mode (default).
01: single tone mode.
1x: interpolating DAC mode.
23 Manual OSK
External Control
Ineffective unless CFR1<9:8> = 10b.
0: OSK pin inoperative (default).
1: OSK pin enabled for manual OSK control (see the Output Shift Keying (OSK) section).
22 Inverse Sinc Filter
Enable
0: inverse sinc filter bypassed (default).
1: inverse sinc filter active.
21 Clear CCI This bit is automatically cleared by the serial I/O port controller. This operation requires several internal clock
cycles to complete, during which time the data supplied to the CCI input by the baseband signal chain is
ignored. The inputs are forced to all zeros to flush the CCI data path, after which the CCI accumulators are reset.
0: normal operation of the CCI filter (default).
1: initiates an asynchronous reset of the accumulators in the CCI filter.
20:17 Open
16 Select DDS Sine
Output
Ineffective unless CFR1<25:24> = 01b.
0: cosine output of the DDS is selected (default).
1: sine output of the DDS is selected.
15:14 Open
13 Autoclear Phase
Accumulator
0: normal operation of the DDS phase accumulator (default).
1: synchronously resets the DDS phase accumulator any time I/O_UPDATE is asserted or a profile
change occurs.
12 Open
11
Clear Phase
Accumulator
0: normal operation of the DDS phase accumulator (default).
1: asynchronous, static reset of the DDS phase accumulator.
10 Load ARR @ I/O
Update
0: normal operation of the OSK amplitude ramp rate timer (default).
1: OSK amplitude ramp rate timer reloaded any time I/O_UPDATE is asserted or a profile change occurs.
AD9957 Data Sheet
Rev. C | Page 56 of 64
Bit (s) Mnemonic Description
9 OSK (Output Shift
Keying) Enable
0: OSK disabled (default).
1: OSK enabled.
8 Select Auto-OSK Ineffective unless CFR1<9> = 1.
0: manual OSK enabled (default).
1: automatic OSK enabled.
7 Digital Power-
Down
This bit is effective without the need for an I/O update.
0: clock signals to the digital core are active (default).
1: clock signals to the digital core are disabled.
6 DAC Power-Down 0: DAC clock signals and bias circuits are active (default).
1: DAC clock signals and bias circuits are disabled.
5
REFCLK Input
Power-Down
This bit is effective without the need for an I/O update.
0: REFCLK input circuits and PLL are active (default).
1: REFCLK input circuits and PLL are disabled.
4 Auxiliary DAC
Power-Down
0: auxiliary DAC clock signals and bias circuits are active (default).
1: auxiliary DAC clock signals and bias circuits are disabled.
3 External Power-
Down Control
0: assertion of the EXT_PWR_DWN pin affects full power-down (default).
1: assertion of the EXT_PWR_DWN pin affects fast recovery power-down.
2 Auto Power-Down
Enable
Ineffective when CFR1<25:24> = 01b.
0: disable power-down (default).
1: when the TxEnable pin is Logic 0, the baseband signal processing chain is flushed of residual data and
the clocks are automatically stopped. Clocks restart when the TxENABLE pin is a Logic 1.
1 SDIO Input Only 0: configures the SDIO pin for bidirectional operation; 2-wire serial programming mode (default).
1: configures the serial data I/O pin (SDIO) as an input only pin; 3-wire serial programming mode.
0 LSB First 0: configures the serial I/O port for MSB first format (default).
1: configures the serial I/O port for LSB first format.
Control Function Register 2 (CFR2)
Address 0x01, four bytes are assigned to this register.
Table 19. Bit Descriptions for CFR2 Register
Bit (s) Mnemonic Description
31 Blackfin Interface
Mode Active
Valid only when CFR1<25:24> = 00b (quadrature modulation mode).
0: Pin D<17:0> configured as an 18-bit parallel port (default).
1: Pin D<5:4> configured as a dual serial port compatible with the Blackfin serial interface. Pin D<17:6>
and Pin D<3:0> become available as a 16-bit GPIO port.
30 Blackfin Bit Order Valid only when CFR2<31> = 1.
0: the dual serial port (BFI) configured for MSB first operation (default).
1: the dual serial port (BFI) configured for LSB first operation.
29
Blackfin Early
Frame Sync
Enable
Valid only when CFR2<31> = 1.
0: the dual serial port (BFI) configured to be compatible with Blackfin late frame sync operation (default).
1: the dual serial port (BFI) configured to be compatible with Blackfin early frame sync operation.
28:25 Open
24 Enable Profile
Registers as ASF
Source
Valid only when CFR1<25:24> = 01b (single tone mode) and CFR1<9>=0 (OSK disabled).
0: amplitude scale factor bypassed (unity gain).
1: the active profile register determines the amplitude scale factor.
23 Internal I/O
Update Active
This bit is effective without the need for an I/O update.
0: serial I/O programming is synchronized with external assertion of the I/O_UPDATE pin, which is
configured as an input pin (default).
1: serial I/O programming is synchronized with an internally generated I/O update signal (the internally
generated signal appears at the I/O_UPDATE pin, which is configured as an output pin).
22 SYNC_CLK Enable 0: the SYNC_CLK pin is disabled; static Logic 0 output.
1: the SYNC_CLK pin generates a clock signal at ¼ fSYSCLK; use of synchronization of the serial I/O port
(default).
Data Sheet AD9957
Rev. C | Page 57 of 64
Bit (s) Mnemonic Description
21:17 Open
16 Read Effective
FTW
0: a serial I/O port read operation of the FTW register reports the contents of the FTW register (default).
1: a serial I/O port read operation of the FTW register reports the actual 32-bit word appearing at the input to
the DDS phase accumulator.
15:14 I/O Update Rate
Control
Ineffective unless CFR2<23> = 1. Sets the prescale ratio of the divider that clocks the I/O update timer as
follows:
00: divide-by-1 (default).
01: divide-by-2.
10: divide-by-4.
11: divide-by-8.
13
PDCLK Rate
Control
Ineffective unless CFR2<31> = 0 and CFR1<25:24> = 00b.
0: PDCLK operates at the input data rate (default).
1: PDCLK operates at ½ the input data rate; useful for maintaining a consistent relationship between I/Q
words at the parallel data port and the internal clocks of the baseband signal processing chain.
12 Data Format 0: the data-words applied to Pin D<17:0> are expected to be coded as twos complement (default).
1: the data-words applied to Pin D<17:0> are expected to be coded as offset binary.
11 PDCLK Enable 0: the PDCLK pin is disabled and forced to a static Logic 0 state; the internal clock signal continues to operate
and provide timing to the data assembler.
1: the internal PDCLK signal appears at the PDCLK pin (default).
10 PDCLK Invert 0: normal PDCLK polarity; Q-data associated with Logic 1, I-data with Logic 0 (default).
1: inverted PDCLK polarity.
9
TxEnable Invert
0: normal TxENABLE polarity; Logic 0 is standby, Logic 1 is transmit (default).
1: inverted TxENABLE polarity; Logic 0 is transmit, Logic 1 is standby.
8 Q-First Data
Pairing
0: an I/Q data pair is delivered as I-data first, followed by Q-data (default).
1: an I/Q data pair is delivered as Q-data first, followed by I-data.
7 Open
6 Data Assembler
Hold Last Value
Ineffective when CFR1<25:24> = 01b.
0: when the TxENABLE pin is false, the data assembler ignores the input data and internally forces zeros on
the baseband signal path (default).
1: when the TxENABLE pin is false, the data assembler ignores the input data and internally forces the last
value received on the baseband signal path.
5 Sync Timing
Validation Disable
0: enables the setup and hold validation circuit to take a measurement; the measurement result appears at
the SYNC_SMP_ERR pin; a Logic 1 at this pin indicates a potential setup/hold violation whereas a Logic 0
indicates that a setup/hold violation has not been detected; the measurement result is latched and held until
this bit is set to a Logic 1.
1: resets the setup and hold validation measurement circuit forcing the SYNC_SMP_ERR pin to a static Logic 0
condition (default); the measurement circuit is effectively disabled until this bit is restored to a Logic 0 state.
4:0 Open
AD9957 Data Sheet
Rev. C | Page 58 of 64
Control Function Register 3 (CFR3)
Address 0x02, four bytes are assigned to this register.
Table 20. Bit Descriptions for CFR3 Register
Bit (s) Mnemonic Description
31:30 Open
29:28
DRV0
Controls REFCLK_OUT pin (see Table 6 for details); default is 01b.
27 Open
26:24 VCO SEL Selects frequency band of the VCO in the REFCLK PLL (see Table 7 for details); default is 111b.
23:22 Open
21:19 ICP Selects the charge pump current in the REFCLK PLL (see Table 8 for details); default is 111b.
18:16 Open
15 REFCLK Input Divider
Bypass
0: input divider is selected (default).
1: input divider is bypassed.
14 REFCLK Input Divider
ResetB
0: input divider is reset.
1: input divider operates normally (default).
13:9 Open
8
PLL Enable
0: REFCLK PLL bypassed (default).
1: REFCLK PLL enabled.
7:1 N This 7-bit number is divide modulus of the REFCLK PLL feedback divider; default is 0000000b.
0 Open
Auxiliary DAC Control Register
Address 0x03, four bytes are assigned to this register.
Table 21. Bit Descriptions for Auxiliary DAC Control Register
Bit(s) Mnemonic Description
31:8 Open
7:0 FSC This 8-bit number controls the full-scale output current of the main DAC (see the Auxiliary DAC section);
default is 0xFF.
I/O Update Rate Register
Address 0x04, four bytes are assigned to this register. This register is effective without the need for an I/O update.
Table 22. Bit Descriptions for I/O Update Rate Register5
Bit(s) Mnemonic Description
31:0 I/O Update Rate Ineffective unless CFR2<23> = 1. This 32-bit number controls the automatic I/O update rate (see the
Automatic I/O Update section); default is 0xFFFFFFFF.
RAM Segment Register 0
Address 0x05, six bytes are assigned to this register. This register is effective without the need for an I/O update. This register is only
active if CFR1<31> = 1 and there is a Logic 0-to-Logic 1 transition on the RT pin.
Table 23. Bit Descriptions for RAM Segment Register 0
Bit(s) Mnemonic Description
47:32 RAM Address Step
Rate 0
This 16-bit number controls the rate at which the RAM state machine steps through the specified RAM
address range.
31:22 RAM End Address 0 This 10-bit number identifies the ending address for the RAM state machine.
21:16 Open
15:6 RAM Start Address 0 This 10-bit number identifies the starting address for the RAM state machine.
5:3 Open
2:0 RAM Playback Mode 0 This 3-bit number identifies the playback mode for the RAM state machine (see Table 5).
Data Sheet AD9957
Rev. C | Page 59 of 64
RAM Segment Register 1
Address 0x06, six bytes are assigned to this register. This register is only active if CFR1<31> = 1 and there is a Logic 1 to Logic 0 transition
on the RT pin.
Table 24. Bit Descriptions for RAM Segment Register 1
Bit(s) Mnemonic Description
47:32
RAM Address Step
Rate 1
This 16-bit number controls the rate at which the RAM state machine steps through the specified RAM
address range.
31:22 RAM End Address 1 This 10-bit number identifies the ending address for the RAM state machine.
21:16 Open
15:6 RAM Start Address 1 This 10-bit number identifies the starting address for the RAM state machine.
5:3 Open
2:0
RAM Playback Mode 1
This 3-bit number identifies the playback mode for the RAM state machine (see Table 5).
Amplitude Scale Factor (ASF) Register
Address 0x09, four bytes are assigned to this register. This register is only active if CFR1<9> = 1.
Table 25. Bit Descriptions for ASF Register
Bit(s) Mnemonic Description
31:16 Amplitude Ramp Rate Ineffective unless CFR1<8> = 1. This 16-bit number controls the rate at which the OSK controller
updates amplitude changes to the DDS.
15:2 Amplitude Scale Factor If CFR1<8> = 0 and CFR1<23> = 0, then this 14-bit number is the amplitude scale factor for the DDS.
If CFR1<8> = 0 and CFR1<23> = 1, then this 14-bit number is the amplitude scale factor for the DDS
when the OSK pin is Logic 1.
If CFR1<8> = 1, then this 14-bit number sets a ceiling on the maximum allowable amplitude scale factor
for the DDS.
1:0
Amplitude Step Size
Ineffective unless CFR1<8> = 1. This 2-bit number controls the step size for amplitude changes to the
DDS (see Table 9).
Multichip Sync Register
Address 0x0A, four bytes are assigned to this register.
Table 26. Bit Descriptions for the Multichip Sync Register
Bit(s)
Mnemonic
Description
31:28 Sync Validation Delay Default is 0000b. This 4-bit number sets the timing skew (in ~75 ps increments) between SYSCLK and
the delayed sync-in signal for the synchronization validation block in the synchronization receiver.
27 Sync Receiver Enable 0: synchronization clock receiver disabled (default).
1: synchronization clock receiver enabled.
26 Sync Generator Enable 0: synchronization clock generator disabled (default).
1: synchronization clock generator enabled.
25 Sync Generator Polarity 0: synchronization clock generator coincident with the rising edge of the system clock (default).
1: synchronization clock generator coincident with the falling edge of the system clock.
24 Open
23:18 Sync State Preset Value Default is 000000b. This 6-bit number is the state that the internal clock generator assumes when it
receives a sync pulse.
17:16 Open
15:11
Sync Generator Delay
Default is 00000b. This 5-bit number sets the output delay (in ~75 ps increments) of the synchronization
generator.
10:8 Open
7:3 Sync Receiver Delay Default is 00000b. This 5-bit number sets the delay input delay (in ~75 ps increments) of the
synchronization receiver.
2:0 Open
AD9957 Data Sheet
Rev. C | Page 60 of 64
PROFILE REGISTERS
There are eight consecutive serial I/O addresses (0x0E to 0x15)
dedicated to device profiles. All eight profile registers are either
single tone profiles or QDUC profiles depending on the device
operating mode specified by CFR1<25:24>. During operation,
the active profile register is determined via the external
PROFILE<2:0> pins.
Single tone profiles control: DDS frequency (32 bits), DDS
phase offset (16 bits), and DDS amplitude scaling (14 bits).
QDUC profiles control: DDS frequency (32 bits), DDS phase
offset (16 bits), output amplitude scaling (8 bits), CCI filter
interpolation factor, inverse CCI bypass, and spectral invert.
The QDUC profiles also selectively apply to the interpolating
DAC operating mode: only output scaling, CCI filter interpola-
tion factor, and inverse CCI bypass apply; all others (DDS
frequency, output amplitude scaling, and spectral invert) are
ignored.
Profile<7:0> Register—Single Tone
Address 0x0E to 0x15, eight bytes are assigned to this register.
Table 27. Bit Descriptions for Profile<7:0> Registers—Single Tone
Bit(s) Mnemonic Description
63:62 Open
61:48 Amplitude Scale Factor This 14-bit number controls the DDS output amplitude.
47:32 Phase Offset Word This 16-bit number controls the DDS phase offset.
31:0 Frequency Tuning Word This 32-bit number controls the DDS frequency.
Profile<7:0> Register—QDUC
Address 0x0E to 0x15, eight bytes are assigned to this register.
Table 28. Bit Descriptions for Profile<7:0> Registers—QDUC
Bit(s) Mnemonic Description
63:58 CC Interpolation Rate This 6-bit number is the rate interpolation factor for the CCI filter.
57 Spectral Invert 0: the modulator output takes the form: I(t) × cos(ct) – Q(t) × sin(ct).
1: the modulator output takes the form: I(t) × cos(ct) + Q(t) × sin(ct).
56 Inverse CCI Bypass 0: the inverse CCI filter is enabled.
1: the inverse CCI filter is bypassed.
55:48 Output Scale Factor This 8-bit number controls the output amplitude.
47:32 Phase Offset Word This 16-bit number controls the DDS phase offset.
31:0
Frequency Tuning Word
This 32-bit number controls the DDS frequency.
RAM Register
Address 0x16, four bytes are assigned to this register.
Table 29. Bit Descriptions for RAM Register
Bit(s) Mnemonic Description
31:0 RAM Word The number of 32-bit words written to RAM is defined by the start and end address in
RAM Segment Register 0 or RAM Segment Register 1.
GPIO Configuration Register
Address 0x18, two bytes are assigned to this register.
Table 30. Bit Descriptions for GPIO Configuration Register
Bit(s) Mnemonic Description
15:0 GPIO Configuration See the General-Purpose I/O (GPIO) Port section for details.
GPIO Data Register
Address 0x19, two bytes are assigned to this register.
Table 31. Bit Descriptions for GPIO Data Register
Bits Mnemonic Description
15:0 GPIO Data Read or write based on the contents of the GPIO Configuration register. See the
General-Purpose I/O (GPIO) Port section for details.
Data Sheet AD9957
Rev. C | Page 61 of 64
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC S TANDARDS MS-026-AE D- HD
1
2526 50
76
100 75
51
14.00 BSC S Q
16.00 BSC S Q
0.75
0.60
0.45
1.20
MAX
1.05
1.00
0.95
0.20
0.09
0.08 MAX
COPLANARITY
VIEW A
ROTAT E D 90
°
CCW
SEATING
PLANE
0° MIN
7°
3.5°
0°
0.15
0.05
VIEW A
PIN 1
TOP VIEW
(PINS DO W N)
0.27
0.22
0.17
0.50 BSC
LEAD P ITCH
1
25
2650
76 100
75
51
BOTTOM VIEW
(PI NS UP)
5.00 SQ
EXPOSED
PAD
042209-A
FO R P ROPER CONNECT IO N OF
THE EXPOSED PAD, REFER TO
THE P IN CONFIGURAT ION AND
FUNCT ION DE S CRIPT IO NS
SECTION OF THIS DATA SHEET.
Figure 65. 100-Lead Thin Quad Flat Package, Exposed Pad [TQFP_EP]
(SV-100-4)
Dimensions shown in millimeters
ORDERING GUIDE
Model1 Temperature Range Package Description Package Option
AD9957BSVZ −40°C to +85°C 100-Lead Thin Quad Flat Package Exposed Pad [TQFP_EP] SV-100-4
AD9957BSVZ-REEL −40°C to +85°C 100-Lead Thin Quad Flat Package Exposed Pad [TQFP_EP] SV-100-4
AD9957/PCBZ Evaluation Board
1 Z = RoHS Compliant Part.
AD9957 Data Sheet
Rev. C | Page 62 of 64
NOTES
Data Sheet AD9957
Rev. C | Page 63 of 64
NOTES
