4-Channel DAS with 16-Bit, Bipolar Input,
Simultaneous Sampling ADC
Data Sheet
AD7605-4
Rev. 0 Document Feedback
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FEATURES
4 simultaneously sampled inputs
True bipolar analog input ranges: ±10 V (maximum),
±5 V (maximum)
Single 5 V analog supply and 2.5 V to 5 V VDRIVE (nominal)
Fully integrated data acquisition solution
Analog input clamp protection
Input buffer with 1 MΩ analog input impedance
Second-order antialiasing analog filter
On-chip accurate reference and reference buffer
16-bit ADC with 300 kSPS on all channels
Flexible parallel/serial interface
Serial peripheral interface (SPI)/QSPI/MICROWIRE/DSP
compatible
Performance
7 kV ESD rating on analog input pins
Standby mode: 25 mW (typical)
64-lead LQFP package
APPLICATIONS
Power line monitoring and protection systems
Multiphase motor control
Instrumentation and control systems
Multiaxis positioning systems
Data acquisition systems (DAS)
GENERAL DESCRIPTION
The AD7605-41 is a 4-channel, 16-bit, simultaneous sampling,
analog-to-digital data acquisition system (DAS). The device
contains analog input clamp protection, a second-order antialias-
ing filter, a track-and-hold amplifier, a 16-bit charge redistribution
successive approximation analog-to-digital converter (ADC), a
2.5 V reference and reference buffer, and high speed serial and
parallel interfaces.
The AD7605-4 operates from a single 5 V supply and can
accommodate ±10 V and ±5 V true bipolar input signals while
sampling at throughput rates of up to 300 kSPS for all channels.
The input clamp protection circuitry can tolerate voltages up to
±16.5 V. The AD7605-4 has 1 MΩ analog input impedance,
regardless of sampling frequency. The single-supply operation,
on-chip filtering, and high input impedance eliminate the need
for driver op amps and external bipolar supplies.
The AD7605-4 is SPI, QSPI™, MICROWIRE™, and digital signal
processor (DSP) compatible.
Table 1. High Resolution, Bipolar Input, Simultaneous
Sampling DAS Solutions
Resolution
(Bits)
Single-Ended
Inputs
True Differential
Inputs
No. of Simultaneous
Sampling Channels
18 AD7608 AD7609 8
16 AD7606 8
AD7606-6 6
AD7606-4 4
AD7605-4 4
14 AD7607 8
FUNCTIONAL BLOCK DIAGRAM
Figure 1.
1 Protected by U.S. Patent No. 8,072,360 B2.
V1
V1GND
R
FB
1MΩ
1MΩ R
FB
CLAMP
CLAMP
SECOND-
ORDE R LPF
T/H
V2
V2GND
R
FB
1MΩ
1MΩ R
FB
CLAMP
CLAMP
SECOND-
ORDE R LPF
T/H
V3
V3GND
R
FB
1MΩ
1MΩ R
FB
CLAMP
CLAMP
SECOND-
ORDE R LPF
T/H
V4
V4GND
R
FB
1MΩ
1MΩ R
FB
CLAMP
CLAMP
SECOND-
ORDE R LPF
T/H
4:1
MUX
AGND
BUSY
FRSTDATA
CONVS T A CONVS T B RESET RANGE
CONTROL
INPUTS
CLK O SC
REFIN/REFOUT
REF SELECT
AGND
DB7/D
OUT
A
DB8/D
OUT
B
RD/SCLK
CS
PAR/SER/ BYTE SEL
V
DRIVE
16-BIT
SAR PARALLEL/
SERIAL
INTERFACE
2.5V
REF
REFCAPB REFCAPA
SERIAL
PARALLEL
REGCAP
2.5V
LDO
REGCAP
2.5V
LDO
AV
CC
AV
CC
DB0 TO DB1 5 /BYTE SEL
AD7605-4
13503-001
AD7605-4 Data Sheet
Rev. 0 | Page 2 of 27
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Timing Specifications .................................................................. 5
Absolute Maximum Ratings ............................................................ 9
Thermal Resistance ...................................................................... 9
ESD Caution .................................................................................. 9
Pin Configuration and Function Descriptions ........................... 10
Typical Performance Characteristics ........................................... 13
Ter m ino lo g y .................................................................................... 17
Theory of Operation ...................................................................... 18
Converter Details ........................................................................ 18
Analog Input ............................................................................... 18
ADC Transfer Function ............................................................. 19
Internal/External Reference ...................................................... 20
Typical Connection Diagram ................................................... 21
Power-Down Modes .................................................................. 21
Conversion Control ................................................................... 22
Applications Information .............................................................. 23
Parallel Interface (PAR/SER/BYTE SEL = 0) .......................... 23
Parallel Byte (PAR/SER/BYTE SEL = 1,
DB15/BYTE SEL = 1) ................................................................ 23
Serial Interface (PAR/SER/BYTE SEL = 1) ............................. 24
Reading During Conversion ..................................................... 24
Layout Guidelines....................................................................... 25
Outline Dimensions ....................................................................... 27
Ordering Guide .......................................................................... 27
REVISION HISTORY
9/2016—Revision 0: Initial Version
Data Sheet AD7605-4
Rev. 0 | Page 3 of 27
SPECIFICATIONS
VREF = 2.5 V external/internal, AVCC = 4.75 V to 5.25 V, VDRIVE = 2.3 V to 5.25 V, fSAMPLE = 300 kSPS, TA = TMIN to TMAX, unless otherwise noted.
Table 2.
Parameter Test Conditions/Comments Min Typ Max Unit
DYNAMIC PERFORMANCE fIN = 1 kHz sine wave, unless otherwise
noted
Signal-to-Noise Ratio (SNR) ±10 V range 86.5 90 dB
±5 V range 86 89 dB
Signal-to-(Noise + Distortion) (SINAD)
Ratio
±10 V range 86.5 90 dB
±5 V range
86
89
dB
Dynamic Range ±10 V range 90.5 dB
±5 V range 90 dB
Total Harmonic Distortion (THD) −107 −95 dB
Spurious-Free Dynamic Range (SFDR) −108 dB
Intermodulation Distortion (IMD) fa = 1 kHz, fb = 1.1 kHz
Second-Order Terms
−110
dB
Third-Order Terms −106 dB
Channel-to-Channel Isolation fIN on unselected channels up to 160 kHz −95 dB
ANALOG INPUT FILTER
Full Power Bandwidth −3 dB, ±10 V range 23 kHz
−3 dB, ±5 V range 15 kHz
−0.1 dB, ±10 V range 10 kHz
−0.1 dB, ±5 V range 5 kHz
t
GROUP DELAY
±10 V range
11
µs
±5 V range 15 µs
DC ACCURACY
Resolution
No missing codes
16
Bits
Differential Nonlinearity ±0.5 ±0.99 LSB1
Integral Nonlinearity ±0.5 ±2 LSB
Total Unadjusted Error (TUE) ±10 V range ±6 LSB
±5 V range ±12 LSB
Positive Full-Scale (PFS) Error External reference ±8 ±32 LSB
Internal reference ±8 LSB
Drift External reference ±2 ppm/°C
Internal reference ±7 ppm/°C
Matching ±10 V range 5 32 LSB
±5 V range 16 40 LSB
Bipolar Zero Code Error
±10 V range
±1
±6
LSB
±5 V range ±3 ±12 LSB
Drift ±10 V range 10 µV/°C
±5 V range 5 µV/°C
Matching ±10 V range 1 8 LSB
±5 V range 6 22 LSB
Negative Full-Scale (NFS) Error
External reference
±8
±32
LSB
Internal reference ±8 LSB
Drift External reference ±4 ppm/°C
Internal reference ±8 ppm/°C
Matching ±10 V range 5 32 LSB
±5 V range
16
40
LSB
AD7605-4 Data Sheet
Rev. 0 | Page 4 of 27
Parameter Test Conditions/Comments Min Typ Max Unit
ANALOG INPUT
Input Voltage Range RANGE = 1 ±10 V
RANGE = 0 ±5 V
Analog Input Current Input voltage (VIN) = 10 V 9 µA
V
IN
= 5 V
2.5
µA
Input Capacitance 5 pF
Input Impedance 1 MΩ
REFERENCE INPUT/OUTPUT
Reference Input Voltage Range 2.475 2.5 2.525 V
DC Leakage Current ±1 µA
Input Capacitance REF SELECT = 1 7.5 pF
Reference Output Voltage REFIN/REFOUT 2.49 to
2.505
V
Reference Temperature Coefficient ±10 ppm/°C
LOGIC INPUTS
Input Voltage
High (VINH) 0.7 × VDRIVE V
Low (VINL) 0.3 × VDRIVE V
Input Current (IIN) ±2 µA
Input Capacitance (CIN) 5 pF
LOGIC OUTPUTS
Output Voltage
High (VOH) ISOURCE = 100 µA VDRIVE − 0.2 V
Low (VOL) ISINK = 100 µA 0.2 V
Floating State
Leakage Current ±1 ±20 µA
Output Capacitance 5 pF
Output Coding Twos complement 16 Bits
CONVERSION RATE
Conversion Time All four channels included 2 µs
Track-and-Hold Acquisition Time 1 µs
Throughput Rate Per channel, all four channels included 300 kSPS
POWER REQUIREMENTS
AVCC 4.75 5 5.25 V
VDRIVE 2.5 V to 5 V nominal 2.3 5.25 V
Total Current, I
TOTAL
Digital inputs = 0 V or V
DRIVE
Normal Mode
Static 10 12 mA
Operational fSAMPLE = 300 kSPS 12 15.2 mA
Standby Mode 5 8 mA
Shutdown Mode 2 6 µA
Power Dissipation
Normal Mode
Static 52 61 mW
Operational fSAMPLE = 300 kSPS 71 80 mW
Standby Mode 25 42 mW
Shutdown Mode 10 31.5 µW
1 LSB means least significant bit. With a ±5 V input range, 1 LSB = 152.58 µV. With a ±10 V input range, 1 LSB = 305.175 µV.
Data Sheet AD7605-4
Rev. 0 | Page 5 of 27
TIMING SPECIFICATIONS
AVCC = 4.75 V to 5.25 V, VDRIVE = 2.3 V to 5.25 V, VREF = 2.5 V external reference/internal reference, TA = TMIN to TMAX, unless otherwise noted.
Note that throughout this data sheet, multifunction pins, such as RD/SCLK, are referred to either by the entire pin name or by a single
function of the pin, for example, RD, when only that function is relevant.
Table 3.
VINL = 0.1 × VDRIVE and
VINH = 0.9 × VDRIVE
Logic Input Levels
VINL = 0.3 × VDRIVE and
VINH = 0.7 × VDRIVE
Logic Input Levels
Parameter Min Typ Max Min Typ Max Unit Description
PARALLEL/SERIAL/BYTE MODE See Figure 2 and Figure 3
tCYCLE 3.33 3.33 μs 1/throughput rate, parallel mode, reading during or
after conversion; or serial mode: VDRIVE = 3.3 V to
5.25 V, reading during a conversion using DOUTA and
DOUTB lines
tCONV 2 2.08 2 2.08 μs Conversion time
tWAKE-UP STANDBY 100 100 μs
STBY rising edge to CONVST x rising edge; power-
up time from standby mode; not shown in Figure 2
or Figure 3
tWAKE-UP SHUTDOWN Not shown in Figure 2 or Figure 3
Internal Reference 30 30 ms
STBY rising edge to CONVST x rising edge; power-
up time from shutdown mode
External Reference 13 13 ms
STBY rising edge to CONVST x rising edge; power-
up time from shutdown mode
tRESET 50 50 ns RESET high pulse width
t1 40 45 ns CONVST x high to BUSY high
t2 25 25 ns Minimum CONVST x low pulse
t3 25 25 ns Minimum CONVST x high pulse
t4 0 0 ns
BUSY falling edge to CS falling edge setup time
t5 0.5 0.5 ms Maximum delay allowed between CONVST A and
CONVST B rising edges
t6 25 25 ns
Maximum time between last CS rising edge and BUSY
falling edge
t7 25 25 ns Minimum delay between RESET low to CONVST x high
PARALLEL/BYTE READ
OPERATION
See Figure 4, Figure 5, and Figure 7
t8 0 0 ns
CS to RD setup time
t9 0 0 ns
CS to RD hold time
t10 RD low pulse width
16 19 ns VDRIVE above 4.75 V
21 24 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
32 37 ns VDRIVE above 2.3 V
t11 15 15 ns
RD high pulse width
t12 22 22 ns
CS high pulse width; CS and RD linked
t13 Delay from CS until DB15 to DB0 three-state disabled
16 19 ns VDRIVE above 4.75 V
20 24 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
30 37 ns VDRIVE above 2.3 V
t14 Data access time after RD falling edge
16 19 ns VDRIVE above 4.75 V
21 24 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
32 37 ns VDRIVE above 2.3 V
AD7605-4 Data Sheet
Rev. 0 | Page 6 of 27
VINL = 0.1 × VDRIVE and
VINH = 0.9 × VDRIVE
Logic Input Levels
VINL = 0.3 × VDRIVE and
VINH = 0.7 × VDRIVE
Logic Input Levels
Parameter Min Typ Max Min Typ Max Unit Description
t15 6 6 ns Data hold time after RD falling edge
t16 6 6 ns CS to DB15 to DB0 hold time
t17 22 22 ns Delay from CS rising edge to DB15 to DB0 three-
state enabled
SERIAL READ OPERATION See Figure 6
fSCLK Frequency of serial read clock
23.5 20 MHz VDRIVE above 4.75 V
17 15 MHz VDRIVE above 3.3 V
14.5 12.5 MHz VDRIVE above 2.7 V
11.5
10
MHz
V
DRIVE
above 2.3 V
t18 Delay from CS until DOUTA/DOUTB three-state
disabled/delay from CS until MSB valid
15 18 ns VDRIVE above 4.75 V
20 23 ns VDRIVE above 3.3 V
30 35 ns VDRIVE = 2.3 V to 2.7 V
t19 Data access time after SCLK rising edge
17 20 ns VDRIVE above 4.75 V
23 26 ns VDRIVE above 3.3 V
27 32 ns VDRIVE above 2.7 V
34 39 ns VDRIVE above 2.3 V
t20 0.4 × tSCLK 0.4 × tSCLK ns SCLK low pulse width
t
21
0.4 × t
SCLK
0.4 × t
SCLK
ns
SCLK high pulse width
t22 7 7 ns SCLK rising edge to DOUTA/DOUTB valid hold time
t23 22 22 ns CS rising edge to DOUTA/DOUTB three-state enabled
FRSTDATA OPERATION See Figure 4 and Figure 7
t24 Delay from CS falling edge until FRSTDATA three-
state disabled
15 18 ns VDRIVE above 4.75 V
20 23 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
30 35 ns VDRIVE above 2.3 V
t25 Delay from CS falling edge until FRSTDATA high,
serial mode
15 18 ns VDRIVE above 4.75 V
20 23 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
30 35 ns VDRIVE above 2.3 V
t26 Delay from RD falling edge to FRSTDATA high
16 19 ns VDRIVE above 4.75 V
20 23 ns VDRIVE above 3.3 V
25 30 ns VDRIVE above 2.7 V
30 35 ns VDRIVE above 2.3 V
t27 Delay from RD falling edge to FRSTDATA low
19 22 ns VDRIVE = 3.3 V to 5.25V
24 29 ns VDRIVE = 2.3 V to 2.7V
t28 Delay from 16th SCLK falling edge to FRSTDATA low
17 20 ns VDRIVE = 3.3 V to 5.25V
22 27 ns VDRIVE = 2.3 V to 2.7V
t
29
24
29
ns
CS rising edge until FRSTDATA three-state enabled
Data Sheet AD7605-4
Rev. 0 | Page 7 of 27
Timing Diagrams
Figure 2. CONVST x Timing—Reading After a Conversion
Figure 3. CONVST x Timing—Reading During a Conversion
Figure 4. Parallel Mode, Separate CS and RD Pulses
Figure 5. CS and RD, Linked Parallel Mode
t
CYCLE
t
3
t
5
t
2
t
4
t
1
t
7
t
RESET
t
CONV
CONVS T A,
CONVS T B
CONVS T A,
CONVS T B
BUSY
CS
RESET
13503-002
t
CYCLE
t
3
t
5
t
6
t
2
t
1
t
CONV
CONVS T A,
CONVS T B
CONVS T A,
CONVS T B
BUSY
CS
t
7
t
RESET
RESET
13503-003
DATA:
DB15 TO DB0
FRSTDATA
CS
RD
INVALID V1 V2 V3 V4
t10
t8
t13
t24 t26 t27
t14
t11
t15
t9
t16
t17
t29
13503-004
DATA:
DB15 TO DB0
FRSTDATA
CS AND RD
V1 V2 V3 V4
t
12
t
13
t
16
t
17
13503-005
AD7605-4 Data Sheet
Rev. 0 | Page 8 of 27
Figure 6. Serial Read Operation
Figure 7. Parallel Byte Mode Read Operation
SCLK
D
OUT
A,
D
OUT
B
FRSTDATA
CS
DB15 DB14 DB13 DB1 DB0
t
18
t
19
t
21
t
20
t
22
t
23
t
29
t
28
t
25
13503-006
DATA:
DB7 TO DB0
FRSTDATA
CS
RD
INVALID HIGH
BYTE V1 LOW
BYTE V1 HIGH
BYTE V4 LOW
BYTE V4
t
8
t
13
t
14
t
24
t
26
t
27
t
11
t
17
t
29
t
16
t
9
t
15
t
10
13503-007
Data Sheet AD7605-4
Rev. 0 | Page 9 of 27
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 4.
Parameter Rating
AVCC to AGND −0.3 V to +7 V
VDRIVE to AGND −0.3 V to AVCC + 0.3 V
Analog Input Voltage to AGND1 ±16.5 V
Digital Input Voltage to AGND −0.3 V to VDRIVE + 0.3 V
Digital Output Voltage to AGND −0.3 V to VDRIVE + 0.3 V
REFIN/REFOUT to AGND −0.3 V to AVCC + 0.3 V
Input Current to Any Pin Except Supplies1 ±10 mA
Operating Temperature Range −40°C to +85°C
Storage Temperature Range −65°C to +150°C
Junction Temperature 150°C
Pb/Sn Temperature, Soldering
Reflow (10 sec to 30 sec) 240 (+0)°C
Pb-Free Temperature, Soldering Reflow
260 (+0)°C
ESD
All Pins Except Analog Inputs 2 kV
Analog Input Pins Only 7 kV
1 Transient currents of up to 100 mA do not cause silicon controlled rectifier
(SCR) latch-up.
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
THERMAL RESISTANCE
Thermal performance is directly linked to printed circuit board
(PCB) design and operating environment. Careful attention to
PCB thermal design is required.
θJA is the natural convection junction to ambient thermal
resistance, measured in a one cubic foot sealed enclosure. θJC is
the junction to case thermal resistance.
Table 5. Thermal Resistance
Package Type θJA1 θJC1 Unit
ST-64-2 45.5 9.5 °C/W
1 The thermal resistance specifications are based on the device being
mounted to a JEDEC 2P2S compliant, 4-layer PCB, as per JEDEC Standard
JESD51-7.
ESD CAUTION
AD7605-4 Data Sheet
Rev. 0 | Page 10 of 27
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 8. Pin Configuration
Table 6. Pin Function Descriptions1
Pin No. Type2 Mnemonic Description
1, 37, 38,
48
P AVCC Analog Supply Voltage, 4.75 V to 5.25 V. This supply voltage is applied to the internal front-end
amplifiers and to the ADC core. Decouple these supply pins to AGND.
2, 3, 4, 5,
26, 35, 40,
41, 47
GND AGND Analog Ground. These pins are the ground reference points for all analog circuitry on the AD7605-4.
Refer all analog input signals and external reference signals to these pins. Connect all AGND pins to
the AGND plane of a system.
6 DI PAR/SER/
BYTE SEL
Parallel Interface Selection Input (PAR). This pin is a logic input. If this pin is tied to a logic low, the
parallel interface is selected. Parallel byte interface mode is selected when this pin is logic high and
DB15/BYTE SEL is logic high (see Table 8).
Serial Interface Selection Input (SER). If this pin is tied to a logic high, the serial interface is selected.
In serial mode, the RD/SCLK pin functions as the serial clock input. The DB7/DOUTA pin and the
DB8/DOUTB pin function as serial data outputs. When the serial interface is selected, tie the parallel
output data bit pins (Pin 16 to Pin 22, and Pin 27 to Pin 33) to ground.
Parallel Byte Interface Selection Input (BYTE SEL). In byte mode, DB15/BYTE SEL, in conjunction
with PAR/SER/BYTE SEL, selects the parallel byte mode of operation (see Table 8). DB14/HBEN
functions as the high byte enable (HBEN) pin. DB7 to DB0 transfer the 16-bit conversion results in
two RD/SCLK operations, with DB0 as the LSB of the data transfers.
7
DI
STBY Standby Mode Input. This pin places the AD7605-4 into one of two power-down modes: standby
mode or shutdown mode. The power-down mode entered depends on the state of the RANGE pin, as
shown in Table 7. When in standby mode, all circuitry, except the on-chip reference, regulators, and
regulator buffers, is powered down. When in shutdown mode, all circuitry is powered down.
8 DI RANGE Analog Input Range Selection. RANGE is a logic input. The polarity on this pin determines the input
range of the analog input channels. If this pin is tied to a logic high, the analog input range is ±10 V
for all channels. If this pin is tied to a logic low, the analog input range is ±5 V for all channels. A logic
change on this pin has an immediate effect on the analog input range. Changing this pin during a
conversion is not recommended for fast throughput rate applications. See the Analog Input
section for more information.
AD7605-4
TOP VIEW
(No t t o Scal e)
64 63 62 61 60 59 58 57
V1GND
56 55 54 53 52 51 50 49
V3
AGND
V4
AGND
V2
V1
PIN 1
AGND
AGND
V2GND
AGND
AGND
V3GND
V4GND
AGND
AGND
DB13
DB12
DB11
DB14/HBEN
V
DRIVE
DB1
17 18 19 20 21 22 23 24 25
AGND
26 27 28 29 30 31 32
DB2
DB3
DB4
DB5
DB6
DB7/D
OUT
A
DB9
DB10
DB8/D
OUT
B
AGND
AV
CC 1
3
4
FRSTDATA
7
6
5
AGND
2
8
9
10
12
13
14
15
16
11
DB0
BUSY
CONVS T B
CONVS T A
RANGE
RESET
RD/SCLK
CS
PAR/SER/BYTE SEL
AGND
AGND
STBY
DECOUP LI NG CAPACIT OR PIN
POWER SUPPLY
ANALOG INPUT
GRO UND P IN
DIGITAL OUTPUT
DIGITAL INPUT
REF ERE NCE INPUT/ OUT P UT
DB15/BYTE S E L
REFIN/REFOUT
48
46
45
42
43
44
47
41
40
39
37
36
35
34
33
38
AGND
AV
CC
REFGND
REFCAPA
AGND
AGND
AGND
REFCAPB
REFGND
REGCAP
REGCAP
AV
CC
AV
CC
REF SELECT
13503-010
Data Sheet AD7605-4
Rev. 0 | Page 11 of 27
Pin No. Type2 Mnemonic Description
9 DI CONVST A
Conversion Start Input A. CONVST A is a logic input. Use this logic input to initiate conversions on
the analog input channels. For simultaneous sampling of all input channels, CONVST A and CONVST
B can be shorted together, and a single convert start signal can be applied. Alternatively, CONVST A
can be used to initiate simultaneous sampling of V1 and V2. When the CONVST A pin transitions from
low to high, the front-end track-and-hold circuitry for the respective analog input is set to hold.
10 DI CONVST B Conversion Start Input B. CONVST B is a logic input. Use this logic input to initiate conversions on
the analog input channels. For simultaneous sampling of all input channels, CONVST A and CONVST
B can be shorted together, and a single convert start signal can be applied. CONVST B can be used
to initiate simultaneous sampling on V3 and V4. When the CONVST B pin transitions from low to
high, the front-end track-and-hold circuitry for the respective analog input is set to hold.
11
DI
RESET
Reset Input. When set to logic high, the rising edge of RESET resets the AD7605-4. The device
receives a RESET pulse after power-up. The RESET high pulse is typically 50 ns wide. If a RESET pulse is
applied during a conversion, the conversion is aborted. If a RESET pulse is applied during a read,
the contents of the output registers reset to all zeros.
12 DI RD/SCLK Parallel Data Read Control Input When the Parallel Interface Is Selected (RD). When both CS and RD are
logic low in parallel mode, the output bus is enabled.
Serial Clock Input When the Serial Interface Is Selected (SCLK). In serial mode, this pin acts as the
serial clock input for data transfers. The CS falling edge takes the DOUTA and DOUTB data output lines
out of three-state and clocks out the MSB of the conversion result. The rising edge of SCLK clocks
all subsequent data bits onto the DOUTA and DOUTB serial data outputs. For more information, see
the Conversion Control section.
13 DI CS Chip Select. This active low logic input frames the data transfer. When both CS and RD are logic low
in parallel mode, the DB[15:0] output bus is enabled and the conversion result is output on the
parallel data bus lines. In serial mode, CS frames the serial read transfer and clocks out the MSB of
the serial output data.
14 DO BUSY Busy Output. This pin transitions to a logic high after both CONVST A and CONVST B rising edges
and indicates that the conversion process has started. The BUSY output remains high until the
conversion process for all channels is complete. The falling edge of the BUSY pin signals that the
conversion data is being latched into the output data registers and is available to read after a
period of time, t4. Any data read while BUSY is high must be completed before the falling edge of
BUSY occurs. Rising edges on CONVST A or CONVST B have no effect while the BUSY signal is high.
15 DO FRSTDATA Digital Output. The FRSTDATA output signal indicates when the first channel, V1, is being read back on
the parallel, byte, or serial interface. When the CS input is high, the FRSTDATA output pin is in
three-state. The falling edge of CS takes FRSTDATA out of three-state. In parallel mode, the falling
edge of RD corresponding to the result of V1, then sets the FRSTDATA pin high, indicating that the
result from V1 is available on the output data bus. The FRSTDATA output returns to a logic low
following the next falling edge of RD. In serial mode, FRSTDATA goes high on the falling edge of CS
because this clocks out the MSB of V1 on DOUTA. FRSTDATA returns low on the 16th SCLK falling edge
after the CS falling edge. See the Conversion Control section for more details.
16 to 22 DO DB0 to DB6 Parallel Output Data Bits, DB0 to DB6. When PAR/SER/BYTE SEL = 0, these pins act as three-state
parallel digital input/output pins. When CS and RD are low, these pins are used to output DB6 to DB0
of the conversion result. When PAR/SER/BYTE SEL = 1, tie these pins to AGND. When operating in
parallel byte interface mode, DB7 to DB0 outputs the 16-bit conversion result in two RD operations.
DB7 (Pin 24) is the MSB; DB0 is the LSB.
23 P VDRIVE Logic Power Supply Input. The voltage supplied at this pin, 2.3 V to 5.25 V, determines the
operating voltage of the interface. This pin is nominally at the same supply as the supply of the
host interface (that is, DSP and field-programmable gate array (FPGA)).
24 DO DB7/DOUTA Parallel Output Data Bit 7 (DB7). When PAR/SER/BYTE SEL = 0, this pins acts as a three-state parallel
digital input/output pin. When CS and RD are low, this pin outputs DB7 of the conversion result.
Serial Interface Data Output Pin (D
OUT
A). When PAR/SER/BYTE SEL = 1, this pin functions as D
OUT
A
and outputs serial conversion data (see the Conversion Control section for more details). When
operating in parallel byte mode, DB7 is the MSB of the byte.
25 DO DB8/DOUTB Parallel Output Data Bit 8 (DB8). When PAR/SER/BYTE SEL = 0, this pin acts as a three-state parallel
digital input/output pin. When CS and RD are low, this pin outputs DB8 of the conversion result.
Serial Interface Data Output Pin (DOUTB). When PAR/SER/BYTE SEL = 1, this pin functions as DOUTB and
outputs serial conversion data (see the Conversion Control section for more details).
27 to 31 DO DB9 to
DB13
Parallel Output Data Bits, DB9 to DB13. When PAR/SER/BYTE SEL = 0, these pins act as three-state
parallel digital input/output pins. When CS and RD are low, these pins are used to output DB13 to DB9
of the conversion result. When PAR/SER/BYTE SEL = 1, tie these pins to AGND.
AD7605-4 Data Sheet
Rev. 0 | Page 12 of 27
Pin No. Type2 Mnemonic Description
32 DO/DI DB14/
HBEN
Parallel Output Data Bit 14 (DB14). When PAR/ SER/BYTE SEL = 0, this pin acts as a three-state parallel
digital output pin. When CS and RD are low, this pin outputs DB14 of the conversion result.
High Byte Enable (HBEN). When PAR/SER/BYTE SEL = 1 and DB15/BYTE SEL = 1, the AD7605-4
operates in parallel byte interface mode. In parallel byte mode, the HBEN pin selects whether the
most significant byte (MSB) or the least significant byte (LSB) of the conversion result is output first.
When HBEN = 1, the MSB is output first, followed by the LSB.
When HBEN = 0, the LSB is output first, followed by the MSB.
In serial mode, tie this pin to AGND.
33 DO/DI DB15/
BYTE SEL
Parallel Output Data Bit 15 (DB15). When PAR/SER/BYTE SEL = 0, this pin acts as a three-state
parallel digital output pin. When CS and RD are low, this pin outputs DB15 of the conversion result.
Parallel Byte Mode Select (BYTE SEL). When PAR/SER/BYTE SEL = 1, the BYTE SEL pin selects
between serial interface mode and parallel byte interface mode (see Table 8). When PAR/SER/BYTE
SEL = 1 and DB15/BYTE SEL = 0, the AD7605-4 operates in serial interface mode. When PAR/
SER/BYTE SEL = 1 and DB15/BYTE SEL = 1, the AD7605-4 operates in parallel byte interface mode.
34 DI REF SELECT Internal/External Reference Selection Input. REF SELECT is a logic input. If this pin is set to logic high,
the internal reference is selected and enabled. If this pin is set to logic low, the internal reference is
disabled and an external reference voltage must be applied to the REFIN/REFOUT pin.
36, 39 CAP REGCAP Decoupling Capacitor Pin for Voltage Output from Internal Regulator. Decouple these output pins
separately to AGND using a 1 μF capacitor. The voltage on these pins is in the range of 2.5 V to
2.7 V.
42 REF REFIN/
REFOUT
Reference Input (REFIN)/Reference Output (REFOUT). The on-chip reference of 2.5 V is available on
this pin for external use if the REF SELECT pin is set to logic high. Alternatively, the internal
reference can be disabled by setting the REF SELECT pin to logic low, and an external reference of
2.5 V can be applied to this input (see the Internal/External Reference section). Decoupling is
required on this pin for both the internal and external reference options. Apply a 10 μF capacitor
from this pin to ground close to the REFGND pins.
43, 46 GND REFGND Reference Ground Pins. Connect these pins to AGND.
44, 45
CAP
REFCAPA,
REFCAPB
Reference Buffer Output Force/Sense Pins. These pins must be connected together and decoupled
to AGND using a low effective series resistance (ESR), 10 μF ceramic capacitor. The voltage on these
pins is typically 4.5 V.
49 AI V1 Analog Input 1. This pin is a single-ended analog input. The analog input range of this channel is
determined by the RANGE pin.
50, 52 AI GND V1GND,
V2GND
Analog Input Ground Pin 1 and Pin 2. These pins correspond to Analog Input Pin V1 and Analog
Input Pin V2. Connect all analog input ground pins to the AGND plane of a system.
51 AI V2 Analog Input 2. This pin is a single-ended analog input. The analog input range of this channel is
determined by the RANGE pin.
53, 54, 55,
56
GND AGND Analog Ground. These pins are the ground reference points for all analog circuitry on the AD7605-4.
Refer all analog input signals and external reference signals to these pins. Connect all the AGND
pins to the AGND plane of a system.
57 AI V3 Analog Input 3. This pin is a single-ended analog input. The analog input range of this channel is
determined by the RANGE pin.
58 AI GND V3GND Analog Input Ground Pin 3. Connect all analog input ground pins to the AGND plane of a system.
59 AI V4 Analog Input 4. This pin is a single-ended analog input.
60 AI GND V4GND Analog Input Ground Pin 4. Connect all analog input ground pins to the AGND plane of a system.
61, 62, 63,
64
AGND AGND Analog Ground. These pins are the ground reference points for all analog circuitry on the AD7605-4.
Refer all analog input signals and external reference signals to these pins. Connect all the analog
ground pins to the AGND plane of a system.
1 Note that throughout this data sheet, multifunction pins, such as RD/SCLK, are referred to either by the entire pin name or by a single function of the pin, for example,
RD, when only that function is relevant.
2 P is power supply, DI is digital input, DO is digital output, REF is reference input/output, CAP is decoupling capacitor pin, AI is analog input, and GND is ground.
Data Sheet AD7605-4
Rev. 0 | Page 13 of 27
TYPICAL PERFORMANCE CHARACTERISTICS
AVCC = 5 V, V DRIVE = 5 V, ±10 V range, internal reference, TA = 25°C, unless otherwise noted.
Figure 9. FFT Plot, ±10 V Range
Figure 10. FFT Plot, ±5 V Range
Figure 11. Typical INL, ±10 V Range
Figure 12. Typical DNL, ±10 V Range
Figure 13. Typical INL, ±5 V Range
Figure 14. Typical DNL, ±5 V Range
0
–180
–160
–140
–120
–100
–80
–60
–40
–20
AMPLITUDE ( dB)
INPUT F RE QUENCY ( Hz )
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
±10V RANG E
fSAMPLE = 300kSPS
fIN = 1kHz
SNR = 90. 3dB
THD = –109.8d B
13503 -011
0
2349
4699
7048
9397
11746
14096
16445
18794
21143
23493
25842
28191
30541
32890
35239
37588
39938
42287
44636
46986
49335
51684
54033
56383
58732
61081
63430
65780
68129
70478
72828
75177
77526
79875
82225
84574
86923
89273
91622
93971
96320
98670
101019
103368
105717
108067
110416
112765
115115
117464
119813
122162
124512
126861
129210
131560
133909
136258
138607
140957
143306
145655
148004
150354
0
–180
–160
–140
–120
–100
–80
–60
–40
–20
AMPLITUDE ( dB)
INPUT F RE QUENCY ( Hz )
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
±5V RANG E
fSAMPLE = 300kSPS
fIN = 1kHz
SNR = 89. 6dB
THD = –113.5d B
13503 -012
0
2349
4699
7048
9397
11746
14096
16445
18794
21143
23493
25842
28191
30541
32890
35239
37588
39938
42287
44636
46986
49335
51684
54033
56383
58732
61081
63430
65780
68129
70478
72828
75177
77526
79875
82225
84574
86923
89273
91622
93971
96320
98670
101019
103368
105717
108067
110416
112765
115115
117464
119813
122162
124512
126861
129210
131560
133909
136258
138607
140957
143306
145655
148004
150354
2.0
060k50k40k30k20k10k
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
1.5
INL (LSB)
CODE
AVCC, VDRIVE = 5V
f
SAMPLE = 300kSPS
TA = 25° C
INTERNAL RE FERE NCE
±10V RANG E
13503-013
1.0
060k50k40k30k20k10k
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.4
0.2
0.6
0.8
DNL ( LSB)
CODE
13503-014
AVCC, VDRIVE = 5V
f
SAMPLE = 300kSPS
TA = 25° C
INTERNAL RE FERE NCE
±10V RANG E
2.0
065,53657,34449,15240,96032,76824,57616,3848192
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
1.5
INL (LSB)
CODE
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
±5V RANG E
fSAMPLE = 300kSPS
TA = 25° C
13503-015
1.00
065,53657,34449,15240,96032,76824,57616,3848192
–1.00
–0.75
–0.50
–0.25
0
0.25
0.50
0.75
DNL ( LSB)
CODE
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
±5V RANG E
fSAMPLE = 300kSPS
TA = 25° C
13503-016
AD7605-4 Data Sheet
Rev. 0 | Page 14 of 27
Figure 15. NFS Error vs. Temperature
Figure 16. PFS Error vs. Temperature
Figure 17. NFS and PFS Error Matching
Figure 18. PFS and NFS Error vs. Source Resistance
Figure 19. Bipolar Zero Code Error vs. Temperature
Figure 20. Bipolar Zero Code Error Matching Between Channels
20
15
10
5
0
–5
–10
–15
–40 –25 –10 520 35 50 65 80
–20
NFS ERROR (LSB)
TEMPERATURE (°C)
13503-017
200kSPS
AVCC, VDRIVE = 5V
EXT E RNAL REFERE NCE
±5V RANG E
±10V RANG E
20
15
10
5
0
–5
–10
–15
–40 –25 –10 520 35 50 65 80
–20
PFS ERROR (LSB)
TEMPERATURE (°C)
13503-118
200kSPS
AVCC, VDRIVE = 5V
EXT E RNAL REFERE NCE
±5V RANG E
±10V RANG E
10
–40 –25 –10 520 35 50 65 80
–10
–9
–6
–4
–2
0
2
4
6
8
NFS AND PFS CHANNE L MATCHI NG (LSB)
TEMPERATURE (°C)
13503-018
±10V RANG E
AVCC, VDRIVE = 5V
EXT E RNAL REFERE NCE
PFS ERROR
NFS ERROR
10
8
6
4
2
0
0120k100k80k60k40k20k
–2
PF S AND NFS E RROR (%FS)
SOURCE RESISTANCE (Ω)
13503-019
AVCC, VDRIVE = 5V
f
SAMPLE = 200kSPS
TA = 25° C
EXT E RNAL REFERE NCE
SOURCE RE S ISTANCE IS M ATCHED ON
THE VxGND I NP UT
±10V AND ±5V RANGE
1.0
–40 –25 –10 520 35 50 65 80
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
BIPOL AR ZERO CO DE E RROR (LSB)
TEMPERATURE (°C)
13503-023
200kSPS
AVCC, VDRIVE = 5V
EXT E RNAL REFERE NCE
±5V RANG E
±10V RANG E
4
3
2
1
0
–1
–2
–3
–40 –25 –10 520 35 50 65 80
–4
BIPOL AR ZERO CO DE E RROR MATCHI NG (LSB)
TEMPERATURE (°C)
13503-024
200kSPS
AVCC, VDRIVE = 5V
EXT E RNAL REFERE NCE
±5V RANG E
±10V RANG E
Data Sheet AD7605-4
Rev. 0 | Page 15 of 27
Figure 21. THD vs. Input Frequency for Various Source Impedances,
±10 V Range
Figure 22. THD vs. Input Frequency for Various Source Impedances,
±5 V Range
Figure 23. Channel to Channel Isolation
Figure 24. REFOUT Voltage vs. Temperature for
Different Supply Voltages
–40
–50
–60
–70
–80
–90
–100
–110
1k 100k10k
–120
THD ( dB)
INPUT F RE QUENCY ( Hz )
13503-021
±10V RANG E
AVCC, VDRIVE = +5V
f
SAMPLE = 200kSPS
RSOURCE MATCHE D ON Vx AND V xGND I NP UTS
105kΩ
48.7kΩ
23.7kΩ
10kΩ
5kΩ
1.2kΩ
100Ω
51Ω
0Ω
1k 100k10k
THD ( dB)
INPUT F RE QUENCY ( Hz )
13503-122
±5V RANG E
AVCC, VDRIVE = +5V
f
SAMPLE = 200kSPS
RSOURCE MATCHE D ON Vx AND V xGND I NP UTS
105kΩ
48.7kΩ
23.7kΩ
10kΩ
5kΩ
1.2kΩ
100Ω
51Ω
0Ω
–40
–50
–60
–70
–80
–90
–100
–110
–120
–50
–60
–70
–80
–90
–100
–110
–120
–130
016014012010080604020
–140
CHANNEL TO CHANNE L I S OL ATI ON (dB)
NOI S E FREQUENCY ( kHz )
13503-025
±10V RANG E
±5V RANG E
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
RECOMMENDE D DE COUPLI NG USE D
f
SAMPLE = 150kSPS
TA = 25° C
INTERF E RE R ON AL L UNSE LECTED CHANNE LS
2.5010
2.5005
2.5000
2.4995
2.4990
2.4985
–40 –25 –10 520 35 50 65 80
2.4980
REFOUT VOLTAGE (V)
TEMPERATURE (°C)
13503-029
AVCC = 4.75V
AVCC = 5V AVCC = 5.25V
AD7605-4 Data Sheet
Rev. 0 | Page 16 of 27
Figure 25. Analog Input Current vs. Input Voltage for Various Temperatures
Figure 26. Power Supply Rejection Ratio (PSRR)
Figure 27. Histogram of Codes (Six Codes)
8
–10 –8 –6 –4 –2 1086420
–10
–8
–6
–4
–2
0
2
4
6
ANALOG INPUT CURRENT (µA)
INPUT VOLTAGE (V)
13503-028
–40°C
+25°C
+85°C
AVCC, VDRIVE = 5V
f
SAMPLE = 300kSPS
140
011001000
900800700600
500400300200100
60
70
80
90
100
110
120
130
POWER S UP P LY RE JE CTI ON RAT IO ( dB)
AVCC NO ISE FREQUENCY ( kHz )
13503-030
AVCC, VDRIVE = 5V
INTERNAL RE FERE NCE
RECOMMENDE D DE COUPLI NG USE D
f
SAMPLE = 200kSPS
TA = 25° C
±10V RANG E
±5V RANG E
1000
0
100
200
300
400
500
600
700
800
900
NUMBER OF OCCURENCE S
CODE (LS B)
–3 –2 –1 0 1
928 887
3
0 3 2
2
131 97
13503-047
f
SAMPLE = 200kSPS
AVCC = 5V
VDRIVE = 2.5V
Data Sheet AD7605-4
Rev. 0 | Page 17 of 27
TERMINOLOGY
Integral Nonlinearity (INL)
INL is the maximum deviation from a straight line passing
through the endpoints of the ADC transfer function. The
endpoints of the transfer function are zero scale, at ½ LSB below
the first code transition; and full scale, at ½ LSB above the last
code transition.
Differential Nonlinearity (DNL)
DNL is the difference between the measured and the ideal 1
LSB change between any two adjacent codes in the ADC.
Bipolar Zero Code Error
Bipolar zero code error is the deviation of the midscale
transition (all 1s to all 0s) from the ideal, which is 0 V − ½ LSB.
Bipolar Zero Code Error Matching
Bipolar zero code error matching is the absolute difference in
bipolar zero code error between any two input channels.
Positive Full-Scale Error
Positive full-scale error is the deviation of the actual last code
transition from the ideal last code transition (10 V − 1½ LSB
(9.99954) and 5 V − 1½ LSB (4.99977)) after bipolar zero code
error is adjusted out. The positive full-scale error includes the
contribution from the internal reference buffer.
Positive Full-Scale Error Matching
Positive full-scale error matching is the absolute difference in
positive full-scale error between any two input channels.
Negative Full-Scale Error
Negative full-scale error is the deviation of the first code
transition from the ideal first code transition (−10 V + ½ LSB
(−9.99984) and −5 V + ½ LSB (−4.99992)) after the bipolar zero
code error is adjusted out. The negative full-scale error includes
the contribution from the internal reference buffer.
Negative Full-Scale Error Match
Negative full-scale error match is the absolute difference in
negative full-scale error between any two input channels.
Signal-to-(Noise + Distortion) Ratio (SINAD)
SINAD is the measured ratio of signal-to-(noise + distortion) at
the output of the ADC. The signal is the rms amplitude of the
fundamental. Noise is the sum of all nonfundamental signals
up to half the sampling frequency (fS/2, excluding dc).
The ratio depends on the number of quantization levels in
the digitization process: the more levels, the smaller the
quantization noise.
The theoretical signal-to-(noise + distortion) ratio for an ideal
N-bit converter with a sine wave input is given by
Signal-to-(Noise + Distortion) = (6.02 N + 1.76) dB
Thus, for a 16-bit converter, the ideal signal-to-(noise +
distortion) is 98 dB.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of the harmonics to the
fundamental. For the AD7605-4, it is defined as
THD (dB) =
20log
1
6
5
4
32
V
V
V
VVVVVV
2
9
2
8
2
7
22222
+
++++++
where:
V2 to V9 are the rms amplitudes of the second through ninth
harmonics.
V1 is the rms amplitude of the fundamental.
Peak Harmonic or Spurious Noise
Peak harmonic or spurious noise is the ratio of the rms value of
the next largest component in the ADC output spectrum (up to
fS/2, excluding dc) to the rms value of the fundamental. Normally,
the value of this specification is determined by the largest
harmonic in the spectrum, but for ADCs where the harmonics
are buried in the noise floor, it is determined by a noise peak.
Intermodulation Distortion (IMD)
With inputs consisting of sine waves at two frequencies, fa and fb,
any active device with nonlinearities creates distortion products
at sum and difference frequencies of mfa ± nfb, where m, n = 0,
1, 2, 3. Intermodulation distortion terms are those for which
neither m nor n is equal to 0. For example, the second-order
terms include (fa + fb) and (fa − fb), and the third-order terms
include (2fa + fb), (2fa − fb), (fa + 2fb), and (fa − 2fb).
The calculation of the intermodulation distortion is per the
THD specification, where it is the ratio of the rms sum of the
individual distortion products to the rms amplitude of the sum
of the fundamentals expressed in decibels (dB).
Power Supply Rejection Ratio (PSRR)
Variations in power supply affect the full-scale transition but not
the linearity of the converter. Power supply rejection is the
maximum change in full-scale transition point due to a change
in power supply voltage from the nominal value. The PSRR is
defined as the ratio of the power in the ADC output at full-scale
frequency, f, to the power of a 100 mV p-p sine wave applied to
the ADC’s VDD and VSS supplies of Frequency fS.
PSRR (dB) = 10 log (Pf/PfS)
where:
Pf is equal to the power at Frequency f in the ADC output.
PfS is equal to the power at Frequency fS coupled onto the AVCC
supply.
Channel to Channel Isolation
Channel to channel isolation is a measure of the level of crosstalk
between all input channels. It is measured by applying a full-scale
sine wave signal, up to 160 kHz, to all unselected input channels
and then determining the degree to which the signal attenuates
in the selected channel with a 1 kHz sine wave signal applied (see
Figure 23).
AD7605-4 Data Sheet
Rev. 0 | Page 18 of 27
THEORY OF OPERATION
Note that throughout this data sheet, multifunction pins, such
as RD/SCLK, are referred to either by the entire pin name or by
a single function of the pin, for example, RD, when only that
function is relevant.
CONVERTER DETAILS
The AD7605-4 is a data acquisition system that employs a high
speed, low power, charge redistribution, successive approxima-
tion register (SAR) ADC and allows the simultaneous sampling
of four analog input channels. The analog inputs on the AD7605-4
can accept true bipolar input signals. The RANGE pin selects
either ±10 V or ±5 V as the input range. The AD7605-4 operates
from a single 5 V supply.
The AD7605-4 contains input clamp protection, input signal
scaling amplifiers, a second-order anti-aliasing filter, track-and-
hold amplifiers, an on-chip reference, reference buffers, a high
speed ADC, a digital filter, and high speed parallel and serial
interfaces. Sampling on the AD7605-4 is controlled using the
CONVST x signals.
ANALOG INPUT
Analog Input Ranges
The AD7605-4 can handle true bipolar, single-ended input
voltages. The logic level on the RANGE pin determines the
analog input range of all analog input channels. If this pin
is tied to a logic high, the analog input range is ±10 V for all
channels. If this pin is tied to a logic low, the analog input range
is ±5 V for all channels. A logic change on this pin has an
immediate effect on the analog input range; however, there is
typically a settling time of approximately 80 μs, in addition to
the normal acquisition time requirement. The recommended
practice is to hardwire the RANGE pin according to the desired
input range for the system signals.
During normal operation, keep the applied analog input voltage
within the analog input range selected via the RANGE pin. A
RESET pulse must be applied after power up to ensure the
analog input channels are configured for the range selected.
When in one of the two power-down modes, it is recommended
to tie the analog inputs to AGND. The overvoltage clamp
protection is designed to protect against transient overvoltage
conditions only; do not keep the clamp protection circuitry
active for extended periods (see the Analog Input Clamp
Protection section).
Analog Input Impedance
The analog input impedance of the AD7605-4 is 1 MΩ. This
fixed input impedance does not vary with sampling frequency.
This high analog input impedance eliminates the need for a
driver amplifier in front of the AD7605-4, allowing direct
connection to the source or sensor. With the need for a driver
amplifier eliminated, bipolar supplies (which are often a source
of noise in a system) can be removed from the signal chain.
Analog Input Clamp Protection
Figure 28 shows the analog input structure of the AD7605-4.
Each analog input contains clamp protection circuitry. Despite
single 5 V supply operation, this analog input clamp protection
allows an input overvoltage of up to ±16.5 V.
Figure 28. Analog Input Circuitry
Figure 29 shows the input clamp current vs. the source voltage
characteristic of the clamp circuit. For input voltages of up
to ±16.5 V, no current flows in the clamp circuit. For input
voltages greater than ±16.5 V, the AD7605-4 clamp circuitry
turns on.
Figure 29. Input Protection Clamp Profile
Place a series resistor on the analog input channels to limit the
current to ±10 mA for input voltages greater than ±16.5 V. In an
application where there is a series resistance on an analog input
channel, Vx, a corresponding resistance is required on the
analog input ground channel, VxGND (see Figure 30). If there
is no corresponding resistor on the VxGND channel, an offset
error occurs on that channel. It is recommended that the input
overvoltage clamp protection circuitry be used to protect the
AD7605-4 against transient overvoltage events. It is not
recommended to leave the AD7605-4 in a condition where the
clamp protection circuitry is active in normal or power-down
conditions for extended periods because doing so may degrade
the bipolar zero code error performance of the AD7605-4.
Figure 30. Input Resistance Matching on the Analog Input of the AD7605-4
1MΩ
CLAMPVx
1MΩ
CLAMP
V
xGND
SECOND-
ORDER
LPF
RFB
RFB
13503-032
30
–50
–40
–30
–20
–10
0
10
20
–20–15–10–5 0 5 101520
INPUT CLAMP CURRENT (mA)
SOURCE VOLTAGE (V)
13503-033
AV
CC
, V
DRIVE
= 5V
T
A
= 25°C
1MΩ
CLAMP
Vx
1MΩ
CLAMP
VxGND
RFB
RFB
C
R
R
A
NALO
G
INPUT
SIGNAL
AD7605-4
13503-034
Data Sheet AD7605-4
Rev. 0 | Page 19 of 27
Analog Input Antialiasing Filter
An analog antialiasing filter (a second-order Butterworth) is also
provided on the AD7605-4. Figure 31 and Figure 32 show the
frequency and phase response, respectively, of the analog
antialiasing filter. In the ±5 V range, the −3 dB frequency is
typically about 15 kHz. In the ±10 V range, the −3 dB frequency
is typically about 23 kHz.
Figure 31. Analog Antialiasing Filter Frequency Response
Figure 32. Analog Antialias Filter Phase Response
Track-and-Hold Amplifiers
The track-and-hold amplifiers on the AD7605-4 allow the ADC
to accurately acquire an input sine wave of full-scale amplitude to
16-bit resolution. The track-and-hold amplifiers sample their
respective inputs simultaneously on the rising edge of CONVST x.
The aperture time for the track-and-hold (that is, the delay time
between the external CONVST x signal and the track-and-hold
actually going into hold) is well matched, by design, across all
track-and-holds on one device and from device to device. This
matching allows more than one AD7605-4 device to be sampled
simultaneously in a system.
The end of the conversion process across all channels is indicated
by the falling edge of BUSY; it is at this point that the track-and-
holds return to track mode, and the acquisition time for the next
set of conversions begins.
The conversion clock for the device is internally generated, and
the conversion time for all channels is 2 µs on the AD7605-4.
The BUSY signal returns low after all four conversions are
completed, to indicate the end of the conversion process. On the
falling edge of BUSY, the track-and-hold amplifiers return to
track mode. New data can be read from the output register via
the parallel interface, parallel byte interface, or serial interface
after BUSY goes low; or, alternatively, data from the previous
conversion can be read while BUSY is high. Reading data from
the AD7605-4 while a conversion is in progress has little effect
on performance and allows a faster throughput to be achieved.
In parallel mode at VDRIVE > 3.3 V, the SNR is reduced by ~1.5
dB when reading during a conversion.
ADC TRANSFER FUNCTION
The output coding of the AD7605-4 is twos complement. The
designed code transitions occur midway between successive
integer LSB values, that is, 1/2 LSB and 3/2 LSB. The LSB size is
FSR/65,536 for the AD7605-4. The ideal transfer characteristic
for the AD7605-4 is shown in Figure 33.
Figure 33. Transfer Characteristics
The LSB size is dependent on the analog input range selected.
5
0
–5
–10
–15
–20
–25
–30
–35
–40
100 1k 10k 100k
ATTENUAT IO N ( dB)
INPUT F RE QUENCY ( Hz )
13503-035
±10V RANG E
±5V RANG E
AV
CC
, V
DRIVE
= 5V
fSAMPLE
= 200kSPS
T
A
= 25° C
±10V RANG E –0.1dB –3dB
–40 10,303 24,365Hz
+25 9619 23,389Hz
+85 9326 22,607Hz
±5V RANG E –0.1dB –3dB
–40 5225 16,162Hz
+25 5225 15,478Hz
+85 4932 14,990Hz
18
16
14
12
10
8
6
4
2
0
–2
–4
–6
10 100k10k1k
–8
PHASE DELAY (µs)
INPUT F RE QUENCY ( Hz )
13503-036
AVCC, VDRIVE = 5V
f
SAMPLE = 200kSPS
TA = 25° C
±5V RANG E
±10V RANG E
011...111
011...110
000...001
000...000
111...111
100...010
100...001
100...000
–FS + 1/2LSB 0V – 1/2LSB +FS – 3/ 2LSB
ADC CODE
ANALOG INPUT
+FS MIDSCALE –FS LSB
±10V RANG E +10V 0V –10V 305µV
±5V RANG E +5V 0V –5V 152µV
+FS – (–FS)
216
LS B =
VIN
5V REF
2.5V
±5V CO DE = × 32,768 ×
VIN
10V REF
2.5V
±10V CO DE = × 32,768 ×
13503-037
AD7605-4 Data Sheet
Rev. 0 | Page 20 of 27
INTERNAL/EXTERNAL REFERENCE
The AD7605-4 contains an on-chip 2.5 V band gap reference.
The REFIN/REFOUT pin allows access to the 2.5 V reference
that generates the on-chip 4.5 V reference internally, or it allows
an external reference of 2.5 V to be applied to the AD7605-4. An
externally applied reference of 2.5 V is also amplified to 4.5 V,
using the internal buffer. This 4.5 V buffered reference is the
reference used by the SAR ADC.
The REF SELECT pin is a logic input pin that allows the user to
select between the internal reference and an external reference.
If this pin is set to logic high, the internal reference is selected
and enabled. If this pin is set to logic low, the internal reference
is disabled and an external reference voltage must be applied
to the REFIN/REFOUT pin. The internal reference buffer is
always enabled. After a reset, the AD7605-4 operates in the
reference mode selected by the REF SELECT pin. Decoupling is
required on the REFIN/REFOUT pin for both the internal and
external reference options. A 10 µF ceramic capacitor is
required on the REFIN/REFOUT pin.
The AD7605-4 contains a reference buffer configured to
amplify the REFIN/REFOUT voltage to 4.5 V, as shown in
Figure 34. The REFCAPA and REFCAPB pins must be shorted
together externally, and a ceramic capacitor of 10 F applied to
REFGND, to ensure that the reference buffer is in closed-loop
operation. The reference voltage available at the REFIN/REFOUT
pin is 2.5 V.
When the AD7605-4 is configured in external reference mode,
the REFIN/REFOUT pin is a high input impedance pin. For
applications using multiple devices, the following configura-
tions are recommended, depending on the application
requirements.
External Reference Mode
One ADR421 external reference can be used to drive the
REFIN/REFOUT pins of all AD7605-4 devices (see Figure 35).
In this configuration, decouple each REFIN/REFOUT pin of
the AD7605-4 with at least a 100 nF decoupling capacitor.
Internal Reference Mode
Use one AD7605-4 device, configured to operate in the internal
reference mode, to drive the remaining AD7605-4 devices,
which are configured to operate in external reference mode (see
Figure 36). Decouple the REFIN/REFOUT pin of the AD7605-4
that is configured in internal reference mode, using a 10 µF
ceramic decoupling capacitor. For the other AD7605-4 devices,
configured in external reference mode, use at least a 100 nF
decoupling capacitor on their REFIN/REFOUT pins.
Figure 34. Reference Circuitry
Figure 35. Single External Reference Driving Multiple AD7605-4 REFIN/RFOUT Pins
Figure 36. Internal Reference Driving Multiple AD7605-4 REFIN/REFOUT Pins
BUF
SAR
2.5V
REF
REFCAPA
REFIN/REFOUT
REFCAPB 10µF
13503-038
AD7605-4
REF SELECT
REFIN/REFOUT
AD7605-4
REF SELECT
REFIN/REFOUT
100nF
0.1µF
100nF
AD7605-4
REF SELECT
REFIN/REFOUT
100nF
ADR421
13503-040
AD7605-4
REF SELECT
REFIN/REFOUT
+10µF
AD7605-4
REF SELECT
REFIN/REFOUT
100nF
AD7605-4
REF SELECT
REFIN/REFOUT
100nF
V
DRIVE
13503-039
Data Sheet AD7605-4
Rev. 0 | Page 21 of 27
TYPICAL CONNECTION DIAGRAM
Figure 37 shows the typical connection diagram for the AD7605-4.
There are four AVCC supply pins on the device. Decouple each of
the four pins using a 100 nF capacitor at each supply pin and a
10 μF capacitor at the supply source. The AD7605-4 can operate
with the internal reference or an externally applied reference. In
this configuration, the AD7605-4 is configured to operate with
the internal reference. When using a single AD7605-4 device on
the board, decouple the REFIN/REFOUT pin with a 10 μF
capacitor. Refer to the Internal/External Reference section when
using an application with multiple AD7605-4 devices. The
REFCAPA and REFCAPB pins are shorted together and
decoupled with a 10 μF ceramic capacitor.
The VDRIVE supply is connected to the same supply as the
processor. The VDRIVE voltage controls the voltage value of the
output logic signals. For layout, decoupling, and grounding
hints, see the Layout Guidelines section.
After supplies are applied to the AD7605-4, apply a reset to
ensure that the device is configured for the correct mode of
operation.
POWER-DOWN MODES
Two power-down modes are available on the AD7605-4: standby
mode and shutdown mode. The STBY pin controls whether the
AD7605-4 is in normal mode or in one of the two power-down
modes.
The power-down mode is selected through the state of the
RANGE pin when the STBY pin is low. Table 7 shows the
configurations required to choose the desired power-down mode.
When the AD7605-4 is placed in standby mode, the current
consumption is 8 mA maximum and the power-up time is
approximately 100 μs because the capacitor on the REFCAPA
and REFCAPB pins must charge up. In standby mode, the on-chip
reference and regulators remain powered up, and the amplifiers
and ADC core are powered down.
When the AD7605-4 is placed in shutdown mode, the current
consumption is 6 μA maximum and power-up time is
approximately 13 ms (external reference mode). In shutdown
mode, all circuitry is powered down. When the AD7605-4 is
powered up from shutdown mode, a RESET signal must be
applied to the AD7605-4 after the required power-up time has
elapsed.
Table 7. Power-Down Mode Selection
Power-Down Mode STBY Setting RANGE Setting
Standby 0 1
Shutdown 0 0
Figure 37. Typical Connection Diagram
AV
CC
AGND
V
DRIVE
+
REFIN/REFOUT
DB0 TO DB15/BYTESEL
CONVST A, CONVST B
CS
RD/SCLK
BUSY
RESET
AD7605-4
1µF
10µF 100nF
DIGITAL SUPPLY
VOLTAGE +2.3V TO +5.25V
A
NALOG SUPPLY
VOLTAGE 5V
1
FOUR ANALOG
INPUTS V1 TO V4
PARALLEL
INTERFACE
1
DECOUPLING SHOWN ON THE AV
CC
PIN APPLIES TO EACH AV
CC
PIN (PIN 1, PIN 37, PIN 38, PIN 48).
DECOUPLING CAPACITOR CAN BE SHARED BETWEEN AV
CC
PIN 37 AND PIN 38.
2
DECOUPLING SHOWN ON THE REGCAP PIN APPLIES TO EACH REGCAP PIN (PIN 36, PIN 39).
REGCAP
2
+
10µF
REFCAPA
REFCAPB
100nF
V1
PAR/SER/BYTE SEL
STBY
REF SELECT
RANGE
V2
V3
V4
REFGND
V1GND
V2GND
V3GND
V4GND
V
DRIVE
V
DRIVE
13503-041
MICROPROCESSOR/
MICROCONVERTER/
DSP
AD7605-4 Data Sheet
Rev. 0 | Page 22 of 27
CONVERSION CONTROL
Simultaneous Sampling on All Analog Input Channels
The AD7605-4 allows simultaneous sampling of all analog input
channels. All channels are sampled simultaneously when both
CONVST x pins (CONVST A, CONVST B) are tied together. A
single CONVSTx signal is used to control both CONVST x
inputs. The rising edge of this common CONVST x signal
initiates simultaneous sampling on all analog input channels.
The AD7605-4 contains an on-chip oscillator that performs the
conversions. The conversion time for all ADC channels is tCONV.
The BUSY signal indicates to the user when conversions are in
progress, so when the rising edge of CONVST x is applied, BUSY
goes logic high and transitions low at the end of the entire
conversion process. The falling edge of the BUSY signal is used
to place all track-and-hold amplifiers back into track mode. The
falling edge of BUSY also indicates that the new data can now
be read from the parallel bus (DB15 to DB0), the DOUTA and
DOUTB serial data lines, or the parallel byte bus, DB7 to DB0.
Simultaneously Sampling Two Sets of Channels
The AD7605-4 also allows the analog input channels to be
sampled simultaneously in two sets. This feature can be used in
power line protection and measurement systems to compensate
for phase differences introduced by potential transformers
(PTs) and current transformers (CTs). In a 50 Hz system,
simultaneous sampling allows up to 9° of phase compensation; and
in a 60 Hz system, it allows up to 10° of phase compensation.
Simultaneous sampling is accomplished by pulsing the two
CONVST x pins independently. CONVST A initiates simultane-
ous sampling of the first set of channels (V1 and V2); and
CONVST B initiates simultaneous sampling on the second set
of analog input channels (V3 and V4), as shown in Figure 38.
On the rising edge of CONVST A, the track-and-hold amplifiers
for the first set of channels are placed into hold mode. On the
rising edge of CONVST B, the track-and-hold amplifiers for the
second set of channels are placed into hold mode. The conversion
process begins after both rising edges of CONVST x occur;
therefore, BUSY goes high on the rising edge of the later
CONVST x signal. In Tabl e 3, t5 indicates the maximum
allowable time between the CONVST x sampling points.
There is no change to the data read process when using two
separate CONVST x signals.
Connect all unused analog input channels to AGND. The results
for any unused channels are still included in the data read because
all channels are always converted.
Figure 38. Simultaneous Sampling on Channel Sets While Using Independent CONVST A and CONVST B Signals—Parallel Mode
CONVS T A
CONVS T B
BUSY
CS, RD
DATA: DB15 TO DB0
FRSTDATA
V1 V2 V3 V4
t
5
t
CONV
V1 AND V2 T RACK-AND-HO LD
ENT ER HOL D V3 AND V4 TRACK-AND- HOL D
ENT ER HOL D
AD7605-4 CO NV ERTS
ON ALL 4 CHANNE LS
13503-042
Data Sheet AD7605-4
Rev. 0 | Page 23 of 27
APPLICATIONS INFORMATION
The AD7605-4 provides three interface options: a parallel
interface, a high speed serial interface, and a parallel byte
interface. The required interface mode is selected via the
PAR/SER/BYTE SEL and DB15/BYTE SEL pins.
Table 8. Interface Mode Selection
PAR/SER/BYTE SEL
Setting
DB15/BYTE SEL
Setting Interface Mode
0 0 Parallel
1 0 Serial
1 1 Parallel byte
Operation of the interface modes is discussed in the following
sections.
PARALLEL INTERFACE (PAR/SER/BYTE SEL = 0)
Data can be read from the AD7605-4 via the parallel data bus
with standard CS and RD signals. To read the data over the
parallel bus, tie the PAR/SER/BYTE SEL pin low. The CS and
RD input signals are internally gated to enable the conversion
result onto the data bus. The data lines, DB15 to DB0, leave
their high impedance state when both CS and RD are logic low.
Figure 39. AD7605-4 Interface Diagram—One AD7605-4 Device Using the
Parallel Bus, with CS and RD/SCLK Shorted Together
The rising edge of the CS input signal three-states the bus, and
the falling edge of the CS input signal takes the bus out of the
high impedance state. CS is the control signal that enables the
data lines; it is the function that allows multiple AD7605-4
devices to share the same parallel data bus.
The CS signal can be permanently tied low, and the RD signal
can be used to access the conversion results as shown in Figure 4.
A read operation of new data can take place after the BUSY
signal goes low (see Figure 2); or, alternatively, a read operation
of data from the previous conversion process can take place
while BUSY is high (see Figure 3).
The RD/SCLK pin is used to read data from the output
conversion results register. Applying a sequence of RD pulses to
the RD/SCLK pin of the AD7605-4 clocks the conversion
results out from each channel onto the parallel bus, DB15 to
DB0, in ascending order. The first RD signal falling edge after
BUSY goes low clocks out the conversion result from Channel V1.
The next RD signal falling edge updates the bus with the V2
conversion result, and so on.
When the RD signal is logic low, it enables the data conversion
result from each channel to be transferred to the digital host
(DSP, FPGA).
When there is only one AD7605-4 device in a system/board and
it does not share the parallel bus, data can be read using just one
control signal from the digital host. The CS and RD signals can
be tied together, as shown in Figure 5. In this case, the data bus
comes out of three-state on the falling edge of the CS/RD signal.
The combined CS and RD signal allows the data to be clocked
out of the AD7605-4 and to be read by the digital host. In this
case, CS frames the data transfer of each data channel.
PARALLEL BYTE (PAR/SER/BYTE SEL = 1,
DB15/BYTE SEL = 1)
Parallel byte interface mode operates much like the parallel
interface mode, except that each channel conversion result is read
out in two 8-bit transfers. Therefore, eight RD pulses are required
to read all four conversion results from the AD7605-4. To
configure the AD7605-4 to operate in parallel byte mode, tie the
PAR/SER/BYTE SEL and DB15/BYTE SEL pins to logic high
(see Table 8). In parallel byte mode, DB7 to DB0 are used to
transfer the data to the digital host. DB0 is the LSB of the data
transfer, and DB7 is the MSB of the data transfer. In parallel
byte mode, the DB14/HBEN pin functions as HBEN. When
DB14/HBEN is tied to logic high, the most significant byte
(MSB) of the conversion result is output first, followed by the
LSB of the conversion result. When DB14/HBEN is tied to logic
low, the LSB of the conversion result is output first, followed by
the MSB of the conversion result. The FRSTDATA pin remains
high until the entire 16 bits of the conversion result from V1 are
read from the AD7605-4.
AD7605-4
14
BUSY
12
RD/SCLK
[33:27]
[25:24]
[22:16]
DB15 TO DB0
13
CS
DIGITAL
HOST
INTERRUPT
13503-043
AD7605-4 Data Sheet
Rev. 0 | Page 24 of 27
SERIAL INTERFACE (PAR/SER/BYTE SEL = 1)
To read data back from the AD7605-4 over the serial interface,
the PAR/SER/BYTE SEL pin must be tied high. The CS and
SCLK signals are used to transfer data from the AD7605-4. The
AD7605-4 has two serial data output pins, DOUTA and DOUTB.
Data can be read back from the AD7605-4 using one or both of
these DOUTx lines. For the AD7605-4, conversion results from
Channel V1 and Channel V2 first appear on DOUTA, and
conversion results from Channels V3 and Channel V4 first
appear on DOUTB.
The CS falling edge takes the data output lines, DOUTA and DOUTB,
out of three-state and clocks out the MSB of the conversion
result. The rising edge of SCLK clocks all subsequent data bits
onto the serial data outputs, DOUTA and DOUTB. The CS input
can be held low for the entire serial read operation, or it can be
pulsed to frame each channel read of 16 SCLK cycles. Figure 40
shows a read of four simultaneous conversion results using two
DOUTx lines on the AD7605-4. In this case, a 32 SCLK transfer is
used to access data from the AD7605-4, and CS is held low to
frame all the 32 SCLK cycles.
Data can also be clocked out using just one DOUTx line, in which
case it is recommended that DOUTA be used to access all conver-
sion data because the channel data is output in ascending order.
For the AD7605-4 to access all four conversion results on the
DOUTA line, a total of 64 SCLK cycles is required. These 64 SCLK
cycles can be framed by one CS signal, or each group of 16 SCLK
cycles can be individually framed by the CS signal. The disad-
vantage of using just the one DOUTA line is that the throughput
rate is reduced if reading occurs after conversion. Leave the
unused DOUTB line unconnected in serial mode.
If DOUTB is used as the single data output line, the channel results
are output in the following order: V3, V4, V1, and V2; however,
the FRSTDATA indicator returns low after V3 is read on DOUTB.
Figure 6 shows the timing diagram for reading one channel of
data, framed by the CS signal, from the AD7605-4 in serial
mode. The SCLK input signal provides the clock source for the
serial read operation. The AD7605-4 can be accessed while
the CS signal is held low.
The falling edge of CS takes the bus out of three-state and clocks
out the MSB of the 16-bit conversion result. This MSB is valid
on the first falling edge of the SCLK after the CS falling edge.
The subsequent 15 data bits are clocked out of the AD7605-4 on
the SCLK rising edge. Data is valid on the SCLK falling edge. To
access each conversion result, 16 clock cycles must be provided to
the AD7605-4.
The FRSTDATA output signal indicates when the first channel,
V1, is being read back. When the CS input is high, the FRSTDATA
output pin is in three-state. In serial mode, the falling edge
of CS takes FRSTDATA out of three-state and sets the
FRSTDATA pin high, indicating that the result from V1 is
available on the DOUTA output data line. The FRSTDATA output
returns to a logic low following the 16th SCLK falling edge. If all
channels are read on DOUTB, the FRSTDATA output does not go
high when V1 is being output on this serial data output pin. The
FRSTDATA output goes high only when V1 is available on
DOUTA (when V3 is available on DOUTB for the AD7605-4).
READING DURING CONVERSION
Data can be read from the AD7605-4 while BUSY is high and
the conversions are in progress. Reading during conversions has
little effect on the performance of the converter. A parallel read,
parallel byte read, or serial read can be performed during
conversions. Figure 3 shows the timing diagram for reading
while BUSY is high in parallel or serial mode. Reading during
conversions allows the full throughput rate to be achieved when
using the serial interface with VDRIVE greater than 4.75 V.
Data can be read from the AD7605-4 at any time other than on
the falling edge of BUSY because the output data registers are
updated with the new conversion data on the BUSY falling
edge. Observe Time t6, as outlined in Table 3, in this condition.
Figure 40. Serial Interface with Two DOUTx Lines
V1 V2
V3 V4
SCLK
D
OUT
A
D
OUT
B
CS
32
13503-044
Data Sheet AD7605-4
Rev. 0 | Page 25 of 27
LAYOUT GUIDELINES
Design the PCB that houses the AD7605-4 so that the analog and
digital sections are separated and confined to different areas of the
board.
Use at least one ground plane. It can be common or split
between the digital and analog sections. In the case of the split
plane, join the digital and analog ground planes in only one
place, preferably as close as possible to the AD7605-4.
If the AD7605-4 is in a system where multiple devices require
analog to digital ground connections, make the connection at
only one point: establish a star ground point as close as possible
to the AD7605-4. Good connections must be made to the
ground plane. Avoid sharing one connection for multiple
ground pins. Use individual vias or multiple vias to the ground
plane for each ground pin.
Avoid running digital lines under the devices because doing so
couples noise onto the die. Allow the analog ground plane to
run under the AD7605-4 to avoid noise coupling. Shield fast
switching signals like CONVST A, CONVST B, or clocks with
digital ground to avoid radiating noise to other sections of the
board, and never run them near analog signal paths. Avoid
crossover of digital and analog signals. Route traces on layers in
close proximity on the board at right angles to each other to
reduce the effect of feedthrough through the board.
For the power supply lines to the AVCC and VDRIVE pins on the
AD7605-4, use as large a trace as possible to provide low
impedance paths and to reduce the effect of glitches on the
power supply lines. Where possible, use supply planes and make
good connections between the AD7605-4 supply pins and the
power tracks on the board. Use a single via or multiple vias for
each supply pin.
Good decoupling is also important to lower the supply impedance
presented to the AD7605-4 and to reduce the magnitude of the
supply spikes. Place the decoupling capacitors close to (ideally,
right up against) these pins and their corresponding ground
pins. Place the decoupling capacitors for the REFIN/REFOUT
pin and the REFCAPA and REFCAPB pins as close as possible
to their respective AD7605-4 pins; and, where possible, place
them on the same side of the board as the AD7605-4 device.
Figure 41 shows the recommended decoupling on the top layer
of the AD7605-4 board. Figure 42 shows bottom layer decoupling,
which is used for the four AVCC pins and the VDRIVE pin decoupling.
Where the ceramic 100 nF capacitors for the AVCC pins are
placed close to their respective device pins, a single 100 nF
capacitor can be shared between Pin 37 and Pin 38.
Figure 41. Top Layer Decoupling REFIN/REFOUT,
REFCAPA, REFCAPB, and REGCAP Pins
Figure 42. Bottom Layer Decoupling
To ensure good device to device performance matching in
a system that contains multiple AD7605-4 devices, a symmetrical
layout between the AD7605-4 devices is important.
13503-054
13503-055
AD7605-4 Data Sheet
Rev. 0 | Page 26 of 27
Figure 43 shows a layout with two AD7605-4 devices. The AVCC
supply plane runs to the right of both devices, and the VDRIVE
supply track runs to the left of the two devices. The reference
chip is positioned between the two devices, and the reference
voltage track runs north to Pin 42 of U1 and south to Pin 42 of
U2. A solid ground plane is used.
These symmetrical layout principles can also be applied to a system
that contains more than two AD7605-4 devices. The AD7605-4
devices can be placed in a north to south direction, with the
reference voltage located midway between the devices and the
reference track running in the north to south direction, similar
to Figure 43.
Figure 43. Layout for Multiple AD7605-4 Devices—Top Layer and
Supply Plane Layer
AVCC
U2
U1
AVCC
U2
U1
13503-056
Data Sheet AD7605-4
Rev. 0 | Page 27 of 27
OUTLINE DIMENSIONS
Figure 44. 64-Lead Low Profile Quad Flat Package [LQFP]
(ST-64-2)
Dimensions shown in millimeters
ORDERING GUIDE
Model1, 2 Temperature Range Package Description Package Option
AD7605-4BSTZ
−40°C to +85°C
64-Lead Low Profile Quad Flat Package [LQFP]
ST-64-2
AD7605-4BSTZ-RL −40°C to +85°C 64-Lead Low Profile Quad Flat Package [LQFP] ST-64-2
EVAL-AD7605-4SDZ Evaluation Board
EVAL-SDP-CB1Z Controller Board
1 Z = RoHS Compliant Part.
2 The EVAL-AD7605-4SDZ evaluation board requires the EVAL-SDP-CB1Z controller board to allow connection to a PC and full evaluation using the included evaluation
software.
COMPLIANT TO JE DE C S TANDARDS MS-026-BCD
051706-A
TOP VIEW
(PINS DOW N)
1
16
17 33
32
48
49
64
0.27
0.22
0.17
0.50
BSC
LE AD PIT CH
12.20
12.00 SQ
11.80
PIN 1
1.60
MAX
0.75
0.60
0.45
10.20
10.00 SQ
9.80
VIEW A
0.20
0.09
1.45
1.40
1.35
0.08
COPLANARITY
VIEW A
ROTAT E D 90° CCW
SEATING
PLANE
0.15
0.05
7°
3.5°
0°
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