a
AD9833
Low Power 20 mW 2.3 V to 5.5 V
Programmable Waveform Generator
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved.
FEATURES
Digitally Programmable Frequency and Phase
20 mW Power Consumption at 3 V
0 MHz to 12.5 MHz Output Frequency Range
28-Bit Resolution (0.1 Hz @ 25 MHz Ref Clock)
Sinusoidal/Triangular/Square Wave Outputs
2.3 V to 5.5 V Power Supply
No External Components Required
3-Wire SPI
®
Interface
Extended Temperature Range: –40ⴗC to +105ⴗC
Power-Down Option
10-Lead MSOP Package
APPLICATIONS
Frequency Stimulus/Waveform Generation
Liquid and Gas Flow Measurement
Sensory Applications—Proximity, Motion, and Defect
Detection
Line Loss/Attenuation
Test and Medical Equipment
Sweep/Clock Generators
TDR
FUNCTIONAL BLOCK DIAGRAM
SERIAL INTERFACE
AND
CONTROL LOGIC
SCLK SDATA
FSYNC
CONTROL REGISTER
PHASE1 REG
PHASE0 REG
MUX
SIN
ROM
⌺10-BIT DAC
MUX
FREQ0 REG
FREQ1 REG
12
ON-BOARD
REFERENCE
AGND DGND VDD
AD9833
PHASE
ACCUMULATOR
(28-BIT)
REGULATOR
CAP/2.5V
2.5V
AVDD/
DVDD
MUX
DIVIDE
BY 2
MSB
MUX
FULL-SCALE
CONTROL COMP
VOUT
R
200⍀
MCLK
GENERAL DESCRIPTION
The AD9833 is a low power programmable waveform generator
capable of producing sine, triangular, and square wave outputs.
Waveform generation is required in various types of sensing,
actuation, and time domain reflectometry applications. The output
frequency and phase are software programmable, allowing easy
tuning. No external components are needed. The frequency regis-
ters are 28 bits; with a 25 MHz clock rate, resolution of 0.1 Hz
can be achieved. Similarly, with a 1 MHz clock rate, the AD9833
can be tuned to 0.004 Hz resolution.
The AD9833 is written to via a 3-wire serial interface. This serial
interface operates at clock rates up to 40 MHz and is compatible
with DSP and microcontroller standards. The device operates
with a power supply from 2.3 V to 5.5 V.
The AD9833 has a power-down function (SLEEP). This allows
sections of the device that are not being used to be powered down,
thus minimizing the current consumption of the part, e.g., the DAC
can be powered down when a clock output is being generated.
The AD9833 is available in a 10-lead MSOP package.
REV. A–2–
AD9833–SPECIFICATIONS
*
(VDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, TA = TMIN to TMAX, RSET = 6.8 k⍀ for
VOUT, unless otherwise noted.)
Parameter Min Typ Max Unit Test Conditions/Comments
SIGNAL DAC SPECIFICATIONS
Resolution 10 Bits
Update Rate 25 MSPS
V
OUT
Max 0.65 V
V
OUT
Min 38 mV
V
OUT
TC 200 ppm/∞C
DC Accuracy
Integral Nonlinearity ±1.0 LSB
Differential Nonlinearity ±0.5 LSB
DDS SPECIFICATIONS
Dynamic Specifications
Signal-to-Noise Ratio 55 60 dB
f
MCLK
= 25 MHz, f
OUT
= f
MCLK
/4096
Total Harmonic Distortion –66 –56 dBc f
MCLK
= 25 MHz, f
OUT
=
f
MCLK
/4096
Spurious-Free Dynamic Range (SFDR)
Wideband (0 to Nyquist) –60 dBc f
MCLK
= 25 MHz, f
OUT
= f
MCLK
/50
Narrow Band (±200 kHz) –78 dBc f
MCLK
= 25 MHz, f
OUT
= f
MCLK
/50
Clock Feedthrough –60 dBc
Wake-Up Time 1 ms
LOGIC INPUTS
V
INH
, Input High Voltage 1.7 V 2.3 V to 2.7 V Power Supply
2.0 V 2.7 V to 3.6 V Power Supply
2.8 V 4.5 V to 5.5 V Power Supply
V
INL
, Input Low Voltage 0.5 V 2.3 V to 2.7 V Power Supply
0.7 V 2.7 V to 3.6 V Power Supply
0.8 V 4.5 V to 5.5 V Power Supply
I
INH
/I
INL
, Input Current 10 mA
C
IN
, Input Capacitance 3 pF
POWER SUPPLIES
f
MCLK
= 25 MHz, f
OUT
= f
MCLK
/4096
VDD 2.3 5.5 V
I
DD
4.5 5.5 mA
I
DD
Code Dependent. See TPC 2.
Low Power Sleep Mode 0.5 mA DAC Powered Down,
MCLK Running
*Operating temperature range is as follows: B Version: –40∞C to +105∞C; typical specifications are at 25∞C.
Specifications subject to change without notice.
VOUT
COMP
12
AD9833
10-BIT DAC
SIN
ROM
20pF
10nF
VDD
REGULATOR
100nF
CAP/2.5V
Figure 1. Test Circuit Used to Test Specifications
–3–REV. A
AD9833
TIMING CHARACTERISTICS
*
Parameter Limit at T
MIN
to T
MAX
Unit Test Conditions/Comments
t
1
40 ns min MCLK Period
t
2
16 ns min MCLK High Duration
t
3
16 ns min MCLK Low Duration
t
4
25 ns min SCLK Period
t
5
10 ns min SCLK High Duration
t
6
10 ns min SCLK Low Duration
t
7
5ns min FSYNC to SCLK Falling Edge Setup Time
t
8 min
10 ns min FSYNC to SCLK Hold Time
t
8 max
t
4
– 5 ns max
t
9
5ns min Data Setup Time
t
10
3ns min Data Hold Time
t
11
5ns min SCLK High to FSYNC Falling Edge Setup Time
*Guaranteed by design, not production tested.
Specifications subject to change without notice.
MCLK
t2
t1
t3
Figure 2. Master Clock
SCLK
FSYNC
SDATA
t5t4
t6
t7t8
t10
t9
D15 D14 D2 D1 D0 D15 D14
t11
Figure 3. Serial Timing
(VDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, unless otherwise noted.)
REV. A–4–
AD9833
ABSOLUTE MAXIMUM RATINGS*
(T
A
= 25∞C, unless otherwise noted.)
VDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6 V
VDD to DGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6 V
AGND to DGND . . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.3 V
CAP/2.5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.75 V
Digital I/O Voltage to DGND . . . . . . –0.3 V to VDD + 0.3 V
Analog I/O Voltage to AGND . . . . . . –0.3 V to VDD + 0.3 V
Operating Temperature Range
Industrial (B Version) . . . . . . . . . . . . . . . –40∞C to +105∞C
Storage Temperature Range . . . . . . . . . . . . –65∞C to +150∞C
Maximum Junction Temperature . . . . . . . . . . . . . . . . . 150∞C
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate
on the human body and test equipment and can discharge without detection. Although the AD9833
features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to
high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid
performance degradation or loss of functionality.
ORDERING GUIDE
Model Temperature Range Package Description Package Option Branding
AD9833BRM –40∞C to +105∞C10-Lead MSOP RM-10 DJB
AD9833BRM-REEL –40∞C to +105∞C10-Lead MSOP RM-10 DJB
AD9833BRM-REEL7 –40∞C to +105∞C10-Lead MSOP RM-10 DJB
EVAL-AD9833EB Evaluation Board
MSOP Package
JA
Thermal Impedance . . . . . . . . . . . . . . . . . . . . 206∞C/W
JC
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 44∞C/W
Lead Temperature, Soldering (10 sec) . . . . . . . . . . . . . 300∞C
IR Reflow, Peak Temperature . . . . . . . . . . . . . . . . . . . . 220∞C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
REV. A
AD9833
–5–
PIN FUNCTION DESCRIPTIONS
Pin Number Mnemonic Function
Power Supply
2VDD Positive Power Supply for the Analog and the Digital Interface Sections. The
on-board 2.5 V regulator is also supplied from VDD. VDD can have a value
from 2.3 V to 5.5 V. A 0.1 mF and a 10 mF decoupling capacitor should be
connected between VDD and AGND.
3CAP/2.5 V The digital circuitry operates from a 2.5 V power supply. This 2.5 V is generated
from VDD using an on-board regulator (when VDD exceeds 2.7 V). The
regulator requires a decoupling capacitor of typically 100 nF, which is connected
from CAP/2.5 V to DGND. If VDD is equal to or less than 2.7 V, CAP/2.5 V
should be tied directly to VDD.
4DGND Digital Ground.
9AGND Analog Ground.
Analog Signal and Reference
1COMP A DAC Bias Pin. This pin is used for decoupling the DAC bias voltage.
10 VOUT Voltage Output. The analog and digital output from the AD9833 is available at
this pin. An external load resistor is not required because the device has a
200 W resistor on board.
Digital Interface and Control
5MCLK Digital Clock Input. DDS output frequencies are expressed as a binary fraction
of the frequency of MCLK. The output frequency accuracy and phase noise
are determined by this clock.
6SDATA Serial Data Input. The 16-bit serial data-word is applied to this input.
7SCLK Serial Clock Input. Data is clocked into the AD9833 on each falling SCLK edge.
8FSYNC Active Low Control Input. This is the frame synchronization signal for the input
data. When FSYNC is taken low, the internal logic is informed that a new word is
being loaded into the device.
PIN CONFIGURATION
1
AD9833
COMP
VDD
CAP/2.5V
DGND
MCLK
VOUT
AGND
FSYNC
SCLK
SDATA
2
3
4
5
10
9
8
7
6
TOP VIEW
(Not to Scale)
REV. A–6–
AD9833–Typical Performance Characteristics
MCLK (MHz)
I
DD
(mA)
5.5
5.0
3.0
3.5
4.0
4.5
051015 20 25
5V
3V
T
A
= 25ⴗC
TPC 1. Typical Current Consumption
vs. MCLK Frequency
–45
–40
–70
–50
–55
–60
–65
5791113151719212325
MCLK FREQUENCY (MHz)
SFDR (dBc)
SFDR dB MCLK/7
SFDR dB MCLK/50
VDD = 3V
T
A
= 25ⴗC
TPC 4. Wideband SFDR vs.
MCLK Frequency
500
1000
700
650
600
550
850
750
800
900
950
–40 25 105
TEMPERATURE (ⴗC)
WAKE-UP TIME (␮s)
5.5V
2.3V
TPC 7. Wake-Up Time vs.
Temperature
f
OUT (Hz)
5.5
3.0
4.0
4.5
5.0
IDD (mA)
3.5
3V
5V
TA = 25ⴗC
110100 1k 10k 100k 1M
TPC 2. Typical I
DD
vs. f
OUT
for
f
MCLK
= 25 MHz
f
OUT
/
f
MCLK
–30
–90
–80
–70
–60
–50
–40
0.001 0.01 0.1 1
SFDR (dB)
10 100
0
–20
–10
MCLK 1MHz
MCLK 10MHz
MCLK 18MHz
MCLK 25MHz
VDD = 3V
T
A
= 25ⴗC
TPC 5. Wideband SFDR vs.
f
OUT
/f
MCLK
for Various MCLK
Frequencies
TEMPERATURE (ⴗC)
V
REFOUT
(V)
1.150
1.125
–40 105
1.100
25
1.175
1.200
1.250
1.225
LOWER RANGE
UPPER RANGE
TPC 8. V
REFOUT
vs. Temperature
0 25 5101520
MCLK FREQUENCY (MHz)
SFDR (dBc)
–65
–60
–90
–70
–75
–80
–85
SFDR dB MCLK/7 SFDR dB MCLK/50
AVDD = 3V
T
A
= 25ⴗC
TPC 3. Narrow-Band SFDR
vs. MCLK Frequency
MCLK FREQUENCY (MHz)
1.0 5.0 10 12.5 25
SNR (dB)
–60
–65
–70
–50
–55
–40
–45
TA = 25ⴗC
VDD = 3V
fOUT = MCLK/4096
TPC 6. SNR vs. MCLK Frequency
REV. A
AD9833
–7–
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
0100k
RWB 100 ST 100 SEC
VWB 30
TPC 9. f
MCLK
= 10 MHz,
f
OUT
= 2.4 kHz, Frequency
Word = 000FBA9
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
0100k
RWB 100 ST 100 SEC
VWB 30
TPC 12. f
MCLK
= 25 MHz,
f
OUT
= 6 kHz, Frequency
Word = 000FBA9
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
012.5M
RWB 1K ST 100 SEC
VWB 300
TPC 15. f
MCLK
= 25 MHz,
f
OUT
= 2.4 MHz, Frequency
Word = 189374D
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
05M
RWB 1K ST 50 SEC
VWB 300
TPC 10. f
MCLK
= 10 MHz,
f
OUT
= 1.43 MHz = f
MCLK
/7,
Frequency Word = 2492492
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
01M
RWB 300 ST 100 SEC
VWB 100
TPC 13. f
MCLK
= 25 MHz,
f
OUT
= 60 kHz, Frequency
Word = 009D495
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
012.5M
RWB 1K ST 100 SEC
VWB 300
TPC 16. f
MCLK
= 25 MHz,
f
OUT
= 3.857 MHz = f
MCLK
/7,
Frequency Word = 2492492
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
05M
RWB 1K ST 50 SEC
VWB 300
TPC 11. f
MCLK
= 10 MHz,
f
OUT
= 3.33 MHz = f
MCLK
/3,
Frequency Word = 5555555
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
012.5M
RWB 1K ST 100 SEC
VWB 300
TPC 14. f
MCLK
= 25 MHz,
f
OUT
= 600 kHz, Frequency
Word = 0624DD3
FREQUENCY (Hz)
dB
0
–20
–50
–90
–100
–80
–70
–60
–40
–30
–10
012.5M
RWB 1K ST 100 SEC
VWB 300
TPC 17. f
MCLK
= 25 MHz,
f
OUT
= 8.333 MHz = f
MCLK
/3,
Frequency Word = 5555555
REV. A–8–
AD9833
TERMINOLOGY
Integral Nonlinearity
This is the maximum deviation of any code from a straight line
passing through the endpoints of the transfer function. The end-
points of the transfer function are zero scale, a point 0.5 LSB
below the first code transition (000 . . . 00 to 000 . . . 01),
and full scale, a point 0.5 LSB above the last code transition
(111 . . . 10 to 111 . . . 11). The error is expressed in LSBs.
Differential Nonlinearity
This is the difference between the measured and ideal 1 LSB
change between two adjacent codes in the DAC. A specified differ-
ential nonlinearity of ±1 LSB maximum ensures monotonicity.
Output Compliance
The output compliance refers to the maximum voltage that can be
generated at the output of the DAC to meet the specifications.
When voltages greater than that specified for the output compli-
ance are generated, the AD9833 may not meet the specifications
listed in the data sheet.
Spurious-Free Dynamic Range
Along with the frequency of interest, harmonics of the fundamental
frequency and images of these frequencies are present at the output
of a DDS device. The spurious-free dynamic range (SFDR) refers
to the largest spur or harmonic present in the band of interest.
The wideband SFDR gives the magnitude of the largest harmonic
or spur relative to the magnitude of the fundamental frequency
in the 0 to Nyquist bandwidth. The narrow-band SFDR gives the
attenuation of the largest spur or harmonic in a bandwidth of
±200 kHz about the fundamental frequency.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the rms sum of
harmonics to the rms value of the fundamental. For the AD9833,
THD is defined as
THD log 2
2
3
2
4
2
5
2
6
2
1
=++++
20 VVVVV
V
where V
1
is the rms amplitude of the fundamental and V
2
, V
3
,
V
4
, V
5
, and V
6
are the rms amplitudes of the second through
sixth harmonics.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the measured output signal
to the rms sum of all other spectral components below the Nyquist
frequency. The value for SNR is expressed in decibels.
Clock Feedthrough
There will be feedthrough from the MCLK input to the analog
output. Clock feedthrough refers to the magnitude of the MCLK
signal relative to the fundamental frequency in the AD9833’s
output spectrum.
THEORY OF OPERATION
Sine waves are typically thought of in terms of their magnitude
form a(t) = sin(t). However, these are nonlinear and not easy
to generate except through piecewise construction. On the other
hand, the angular information is linear in nature. That is, the
phase angle rotates through a fixed angle for each unit of time.
The angular rate depends on the frequency of the signal by the
traditional rate of = 2f.
MAGNITUDE
PHASE
+1
0
–1
2p
0
2␲4␲
6␲
2␲4␲6␲
Figure 4. Sine Wave
Knowing that the phase of a sine wave is linear and given a
reference interval (clock period), the phase rotation for that
period can be determined.
DDPhase t=w
Solving for
wp==DDPhase t f/2
Solving for f and substituting the reference clock frequency for
the reference period
1/ ft
MCLK
=
()
D
f Phase f
MCLK
=¥D/2p
The AD9833 builds the output based on this simple equation. A
simple DDS chip can implement this equation with three major
subcircuits: numerically controlled oscillator + phase modulator,
SIN ROM, and digital-to-analog converter.
Each of these subcircuits is discussed in the following section.
CIRCUIT DESCRIPTION
The AD9833 is a fully integrated direct digital synthesis (DDS)
chip. The chip requires one reference clock, one low precision
resistor, and decoupling capacitors to provide digitally created
sine waves up to 12.5 MHz. In addition to the generation of this
RF signal, the chip is fully capable of a broad range of simple
and complex modulation schemes. These modulation schemes
are fully implemented in the digital domain, allowing accurate
and simple realization of complex modulation algorithms
using DSP techniques.
The internal circuitry of the AD9833 consists of the following
main sections: a numerically controlled oscillator (NCO),
frequency and phase modulators, SIN ROM, a digital-to-analog
converter, and a regulator.
REV. A
AD9833
–9–
Numerically Controlled Oscillator Plus Phase Modulator
This consists of two frequency select registers, a phase accumu-
lator, two phase offset registers, and a phase offset adder. The
main component of the NCO is a 28-bit phase accumulator.
Continuous time signals have a phase range of 0 to 2. Outside
this range of numbers, the sinusoid functions repeat themselves
in a periodic manner. The digital implementation is no different.
The accumulator simply scales the range of phase numbers into
a multibit digital word. The phase accumulator in the AD9833 is
implemented with 28 bits. Therefore, in the AD9833, 2 = 2
28
.
Likewise, the Phase term is scaled into this range of numbers
0< Phase < 2
28
– 1. With these substitutions, the previous
equation becomes
f Phase f /
MCLK
=¥228
where 0 < Phase < 2
28
– 1.
The input to the phase accumulator can be selected either from
the FREQ0 register or FREQ1 register, and is controlled by
the FSELECT bit. NCOs inherently generate continuous phase
signals, thus avoiding any output discontinuity when switching
between frequencies.
Following the NCO, a phase offset can be added to perform phase
modulation using the 12-bit phase registers. The contents of
one of these phase registers is added to the most significant bits
of the NCO. The AD9833 has two phase registers; their resolu-
tion is 2/4096.
SIN ROM
To make the output from the NCO useful, it must be converted
from phase information into a sinusoidal value. Since phase infor-
mation maps directly into amplitude, the SIN ROM uses the digital
phase information as an address to a look-up table and converts
the phase information into amplitude. Although the NCO contains
a 28-bit phase accumulator, the output of the NCO is truncated
to 12 bits. Using the full resolution of the phase accumulator is
impractical and unnecessary, as this would require a look-up
table of 2
28
entries. It is necessary only to have sufficient phase
resolution such that the errors due to truncation are smaller than
the resolution of the 10-bit DAC. This requires that the SIN ROM
have two bits of phase resolution more than the 10-bit DAC.
The SIN ROM is enabled using the MODE bit (D1) in the
control register. This is explained further in Table XI.
Digital-to-Analog Converter
The AD9833 includes a high impedance current source 10-bit
DAC. The DAC receives the digital words from the SIN ROM
and converts them into the corresponding analog voltages.
The DAC is configured for single-ended operation. An external
load resistor is not required since the device has a 200 W resis-
tor on board. The DAC generates an output voltage of typically
0.6 V p-p.
Regulator
VDD provides the power supply required for the analog section
and the digital section of the AD9833. This supply can have a
value of 2.3 V to 5.5 V.
The internal digital section of the AD9833 is operated at 2.5 V.
An on-board regulator steps down the voltage applied at VDD
to 2.5 V. When the applied voltage at the VDD pin of the AD9833
is equal to or less than 2.7 V, the CAP/2.5 V and VDD pins
should be tied together, thus bypassing the on-board regulator.
FUNCTIONAL DESCRIPTION
Serial Interface
The AD9833 has a standard 3-wire serial interface that is com-
patible with SPI
®
, QSPI
™
, MICROWIRE
™
, and DSP interface
standards.
Data is loaded into the device as a 16-bit word under the control
of a serial clock input, SCLK. The timing diagram for this opera-
tion is given in Figure 3.
The FSYNC input is a level triggered input that acts as a frame
synchronization and chip enable. Data can be transferred into
the device only when FSYNC is low. To start the serial data
transfer, FSYNC should be taken low, observing the minimum
FSYNC to SCLK falling edge setup time, t
7
. After FSYNC goes
low, serial data will be shifted into the device’s input shift register
on the falling edges of SCLK for 16 clock pulses. FSYNC may
be taken high after the 16th falling edge of SCLK, observing
the minimum SCLK falling edge to FSYNC rising edge time, t
8
.
Alternatively, FSYNC can be kept low for a multiple of 16 SCLK
pulses and then brought high at the end of the data transfer. In
this way, a continuous stream of 16-bit words can be loaded while
FSYNC is held low, FSYNC only going high after the 16th SCLK
falling edge of the last word loaded.
The SCLK can be continuous, or alternatively the SCLK can
idle high or low between write operations but must be high
when FSYNC goes low (t
11
).
Powering Up the AD9833
The flow chart in Figure 7 shows the operating routine for the
AD9833. When the AD9833 is powered up, the part should be
reset. This will reset appropriate internal registers to zero to pro-
vide an analog output of midscale. To avoid spurious DAC outputs
while the AD9833 is being initialized, the RESET bit should be
set to 1 until the part is ready to begin generating an output.
RESET does not reset the phase, frequency, or control registers.
These registers will contain invalid data, and therefore should be
set to a known value by the user. The RESET bit should then
be set to 0 to begin generating an output. The data will appear
on the DAC output eight MCLK cycles after RESET is set to 0.
Latency
Associated with each asynchronous write operation in the AD9833
is a latency. If a selected frequency/phase register is loaded with
a new word, there is a delay of seven to eight MCLK cycles before
the analog output will change. (There is an uncertainty of one
MCLK cycle, as it depends on the position of the MCLK rising
edge when the data is loaded into the destination register.)
REV. A–10–
AD9833
Control Register
The AD9833 contains a 16-bit control register that sets up the
AD9833 as the user wants to operate it. All control bits, except
MODE, are sampled on the internal negative edge of MCLK.
Table II describes the individual bits of the control register.
The different functions and the various output options from
the AD9833 are described in more detail in the section
following Table II.
SIN
ROM
PHASE
ACCUMULATOR
(28-BIT)
AD9833
(LOW POWER)
10-BIT DAC
0
MUX
1
SLEEP12
SLEEP1
RESET
MODE + OPBITEN
DIV2
OPBITEN
VOUT
1
MUX
0
DIGITAL
OUTPUT
(ENABLE)
DIVIDE
BY 2
DB15
0
DB14
0
DB13
B28
DB12
HLB
DB11
FSELECT
DB10
PSELECT
DB9
0
DB8
RESET
DB7
SLEEP1
DB6
SLEEP12
DB5
OPBITEN
DB4
0
DB3
DIV2
DB2
0
DB1
MODE
DB0
0
Figure 5. Function of Control Bits
Table II. Description of Bits in the Control Register
Bit Name Function
D13 B28 Two write operations are required to load a complete word into either of the frequency registers.
B28 = 1 allows a complete word to be loaded into a frequency register in two consecutive writes. The first write
contains the 14 LSBs of the frequency word, and the next write will contain the 14 MSBs. The first two bits of
each 16-bit word define the frequency register to which the word is loaded and should, therefore, be the same
for both of the consecutive writes. Refer to Table IV for the appropriate addresses. The write to the frequency
register occurs after both words have been loaded, so the register never holds an intermediate value. An example
of a complete 28-bit write is shown in Table V.
When B28 = 0, the 28-bit frequency register operates as two 14-bit registers, one containing the 14 MSBs and
the other containing the 14 LSBs. This means that the 14 MSBs of the frequency word can be altered independent
of the 14 LSBs, and vice versa. To alter the 14 MSBs or the 14 LSBs, a single write is made to the appropriate
frequency address. The control bit D12 (HLB) informs the AD9833 whether the bits to be altered are the
14 MSBs or 14 LSBs.
D12 HLB This control bit allows the user to continuously load the MSBs or LSBs of a frequency register while ignoring
the remaining 14 bits. This is useful if the complete 28-bit resolution is not required. HLB is used in conjunction
with D13 (B28). This control bit indicates whether the 14 bits being loaded are being transferred to the 14 MSBs
or 14 LSBs of the addressed frequency register. D13 (B28) must be set to 0 to be able to change the MSBs and
LSBs of a frequency word separately. When D13 (B28) = 1, this control bit is ignored.
HLB = 1 allows a write to the 14 MSBs of the addressed frequency register.
HLB = 0 allows a write to the 14 LSBs of the addressed frequency register.
D11 FSELECT The FSELECT bit defines whether the FREQ0 register or the FREQ1 register is used in the phase accumulator.
D10 PSELECT The PSELECT bit defines whether the PHASE0 register or the PHASE1 register data is added to the output of
the phase accumulator.
D9 Reserved This bit should be set to 0.
D8 RESET RESET = 1 resets internal registers to 0, which corresponds to an analog output of midscale.
RESET = 0 disables RESET. This function is explained further in Table IX.
D7 SLEEP1 When SLEEP1 = 1, the internal MCLK clock is disabled, the DAC output will remain at its present value as
the NCO is no longer accumulating.
When SLEEP1 = 0, MCLK is enabled. This function is explained further in Table X.
To inform the AD9833 that the contents of the control register
will be altered, D15 and D14 must be set to 0 as shown below.
Table I. Control Register
D15 D14 D13 D0
00 CONTROL BITS
REV. A
AD9833
–11–
Table II. Description of Bits in the Control Register (continued)
Bit Name Function
D6 SLEEP12 SLEEP12 = 1 powers down the on-chip DAC. This is useful when the AD9833 is used to output the MSB of
the DAC data.
SLEEP12 = 0 implies that the DAC is active. This function is explained further in Table X.
D5 OPBITEN The function of this bit, in association with D1 (MODE), is to control what is output at the VOUT pin. This is
explained further in Table XI.
When OPBITEN = 1, the output of the DAC is no longer available at the VOUT pin. Instead, the MSB (or
MSB/2) of the DAC data is connected to the VOUT pin. This is useful as a coarse clock source. The bit DIV2
controls whether it is the MSB or MSB/2 that is output.
When OPBITEN = 0, the DAC is connected to VOUT. The MODE bit determines whether it is a sinusoidal
or a ramp output that is available.
D4 Reserved This bit must be set to 0.
D3 DIV2 DIV2 is used in association with D5 (OPBITEN). This is explained further in Table XI.
When DIV2 = 1, the MSB of the DAC data is passed directly to the VOUT pin.
When DIV2 = 0, the MSB/2 of the DAC data is output at the VOUT pin.
D2 Reserved This bit must be set to 0.
D1 MODE This bit is used in association with OPBITEN (D5). The function of this bit is to control what is output at
the VOUT pin when the on-chip DAC is connected to VOUT. This bit should be set to 0 if the control bit
OPBITEN = 1. This is explained further in Table XI.
When MODE = 1, the SIN ROM is bypassed, resulting in a triangle output from the DAC.
When MODE = 0, the SIN ROM is used to convert the phase information into amplitude information, which
results in a sinusoidal signal at the output.
D0 Reserved This bit must be set to 0.
The analog output from the AD9833 is
f FREQREG
MCLK /228 ¥
where FREQREG is the value loaded into the selected frequency
register. This signal will be phase shifted by
2 4096p/¥PHASEREG
where PHASEREG is the value contained in the selected
phase register. Consideration must be given to the relationship of
the selected output frequency and the reference clock frequency
to avoid unwanted output anomalies.
The flow chart in Figure 9 shows the routine for writing to the
frequency and phase registers of the AD9833.
Writing to a Frequency Register
When writing to a frequency register, Bits D15 and D14 give
the address of the frequency register.
Table IV. Frequency Register Bits
D15 D14 D13 D0
01MSB 14 FREQ0 REG Bits LSB
10MSB 14 FREQ1 REG Bits LSB
Frequency and Phase Registers
The AD9833 contains two frequency registers and two phase
registers, which are described in Table III.
Table III. Frequency/Phase Registers
Register Size Description
FREQ0 28 Bits Frequency Register 0. When the FSELECT
bit = 0, this register defines the output fre-
quency as a fraction of the MCLK frequency.
FREQ1 28 Bits Frequency Register 1. When the FSELECT
bit = 1, this register defines the output fre-
quency as a fraction of the MCLK frequency.
PHASE0 12 Bits Phase Offset Register 0. When the PSELECT
bit = 0, the contents of this register are added
to the output of the phase accumulator.
PHASE1 12 Bits Phase Offset Register 1. When the PSELECT
bit = 1, the contents of this register are added
to the output of the phase accumulator.
REV. A–12–
AD9833
RESET Function
The RESET function resets appropriate internal registers to 0
to provide an analog output of midscale. RESET does not reset
the phase, frequency, or control registers. When the AD9833 is
powered up, the part should be reset. To reset the AD9833, set
the RESET bit to 1. To take the part out of reset, set the bit to 0.
A signal will appear at the DAC to output eight MCLK cycles
after RESET is set to 0.
Table IX. Applying RESET
RESET Bit Result
0No Reset Applied
1Internal Registers Reset
SLEEP Function
Sections of the AD9833 that are not in use can be powered
down to minimize power consumption. This is done using the
SLEEP function. The parts of the chip that can be powered
down are the internal clock and the DAC. The bits required for
the SLEEP function are outlined in Table X.
Table X. Applying the SLEEP Function
SLEEP1 Bit SLEEP12 Bit Result
00 No Power-Down
01 DAC Powered Down
10 Internal Clock Disabled
11 Both the DAC Powered Down
and the Internal Clock Disabled
DAC Powered Down
This is useful when the AD9833 is used to output the MSB of
the DAC data only. In this case, the DAC is not required so it
can be powered down to reduce power consumption.
Internal Clock Disabled
When the internal clock of the AD9833 is disabled, the DAC
output will remain at its present value as the NCO is no longer
accumulating. New frequency, phase, and control words can be
written to the part when the SLEEP1 control bit is active. The
synchronizing clock is still active, which means that the selected
frequency and phase registers can also be changed using the
control bits. Setting the SLEEP1 bit to 0 enables the MCLK.
Any changes made to the registers while SLEEP1 was active will
be seen at the output after a certain latency.
VOUT Pin
The AD9833 offers a variety of outputs from the chip, all of which
are available from the VOUT pin. The choice of outputs are the
MSB of the DAC data, a sinusoidal output, or a triangle output.
The OPBITEN (D5) and MODE (D1) bits in the control
register are used to decide which output is available from the
AD9833. This is explained further below and also in Table XI.
MSB of the DAC Data
The MSB of the DAC data can be output from the AD9833. By
setting the OPBITEN (D5) control bit to 1, the MSB of the DAC
data is available at the VOUT pin. This is useful as a coarse
clock source. This square wave can also be divided by two before
being output. The DIV2 (D3) bit in the control register controls
the frequency of this output from the VOUT pin.
If the user wants to change the entire contents of a frequency regis-
ter, two consecutive writes to the same address must be performed
since the frequency registers are 28 bits wide. The first write will
contain the 14 LSBs, while the second write will contain the 14 MSBs.
For this mode of operation, the control bit B28 (D13) should
be set to 1. An example of a 28-bit write is shown in Table V.
Table V. Writing 00FC00 to FREQ0 REG
SDATA Input Result of Input Word
0010 0000 0000 0000 Control Word Write (D15, D14 = 00),
B28 (D13) = 1, HLB (D12) = X
0100 0000 0000 0000 FREQ0 REG Write (D15, D14 = 01),
14 LSBs = 0000
0100 0000 0011 1111 FREQ0 REG Write (D15, D14 = 01),
14 MSBs = 003F
In some applications, the user does not need to alter all 28 bits
of the frequency register. With coarse tuning, only the 14 MSBs
are altered, while with fine tuning, only the 14 LSBs are altered.
By setting the control bit B28 (D13) to 0, the 28-bit frequency
register operates as two, 14-bit registers, one containing the
14 MSBs and the other containing the 14 LSBs. This means that
the 14 MSBs of the frequency word can be altered independent
of the 14 LSBs, and vice versa. Bit HLB (D12) in the control
register identifies which 14 bits are being altered. Examples of
this are shown in Tables VI and VII.
Table VI. Writing 3FFF to the 14 LSBs of FREQ1 REG
SDATA Input Result of Input Word
0000 0000 0000 0000 Control Word Write (D15, D14 = 00),
B28 (D13) = 0; HLB (D12) = 0,
i.e. LSBs
1011 1111 1111 1111 FREQ1 REG Write (D15, D14 = 10),
14 LSBs = 3FFF
Table VII. Writing 00FF to the 14 MSBs of FREQ0 REG
SDATA Input Result of Input Word
0001 0000 0000 0000 Control Word Write (D15, D14 = 00),
B28 (D13) = 0, HLB (D12) = 1,
i.e., MSBs
0100 0000 1111 1111 FREQ0 REG Write (D15, D14 = 01),
14 MSBs = 00FF
Writing to a Phase Register
When writing to a phase register, Bits D15 and D14 are set to 11.
Bit D13 identifies which phase register is being loaded.
Table VIII. Phase Register Bits
D15 D14 D13 D12 D11 D0
110 XMSB 12 PHASE0 Bits LSB
111 XMSB 12 PHASE1 Bits LSB
REV. A
AD9833
–13–
Sinusoidal Output
The SIN ROM is used to convert the phase information from
the frequency and phase registers into amplitude information
that results in a sinusoidal signal at the output. To have a
sinusoidal output from the VOUT pin, set the MODE (D1) bit to 0
and the OPBITEN (D5) bit to 0.
Triangle Output
The SIN ROM can be bypassed so that the truncated digital output
from the NCO is sent to the DAC. In this case, the output is no
longer sinusoidal. The DAC will produce a 10-bit linear trian-
gular function. To have a triangle output from the VOUT pin,
set the MODE (D1) bit = 1.
Note that the SLEEP12 bit must be 0 (i.e., the DAC is enabled)
when using this pin.
Table XI. Various Outputs from VOUT
OPBITEN Bit MODE Bit DIV2 Bit VOUT Pin
00XSinusoid
01XTriangle
100DAC Data MSB/2
101DAC Data MSB
11XReserved
VOUT MAX
VOUT MIN
2␲4␲6␲
Figure 6. Triangle Output
APPLICATIONS
Because of the various output options available from the part, the
AD9833 can be configured to suit a wide variety of applications.
One of the areas where the AD9833 is suitable is in modulation
applications. The part can be used to perform simple modu-
lation, such as FSK. More complex modulation schemes, such as
GMSK and QPSK, can also be implemented using the AD9833.
In an FSK application, the two frequency registers of the AD9833
are loaded with different values. One frequency will represent
the space frequency, while the other will represent the mark
frequency. Using the FSELECT bit in the control register of the
AD9833, the user can modulate the carrier frequency between
the two values.
The AD9833 has two phase registers; this enables the part to
perform PSK. With phase shift keying, the carrier frequency
is phase shifted, the phase being altered by an amount that is
related to the bit stream being input to the modulator.
The AD9833 is also suitable for signal generator applications.
Because the MSB of the DAC data is available at the VOUT
pin, the device can be used to generate a square wave.
With its low current consumption, the part is suitable for appli-
cations in which it can be used as a local oscillator.
GROUNDING AND LAYOUT
The printed circuit board that houses the AD9833 should be
designed so that the analog and digital sections are separated
and confined to certain areas of the board. This facilitates the
use of ground planes that can be separated easily. A minimum
etch technique is generally best for ground planes since it gives
the best shielding. Digital and analog ground planes should be
joined in one place only. If the AD9833 is the only device requiring
an AGND to DGND connection, then the ground planes should
be connected at the AGND and DGND pins of the AD9833. If
the AD9833 is in a system where multiple devices require AGND
to DGND connections, the connection should be made at one
point only, a star ground point that should be established as
close as possible to the AD9833.
Avoid running digital lines under the device as these will couple
noise onto the die. The analog ground plane should be allowed to
run under the AD9833 to avoid noise coupling. The power supply
lines to the AD9833 should use as large a track as possible to
provide low impedance paths and reduce the effects of glitches
on the power supply line. Fast switching signals, such as clocks,
should be shielded with digital ground to avoid radiating noise
to other sections of the board. Avoid crossover of digital and
analog signals. Traces on opposite sides of the board should run
at right angles to each other. This will reduce the effects of
feedthrough through the board. A microstrip technique is by far
the best but is not always possible with a double-sided board. In
this technique, the component side of the board is dedicated to
ground planes, while signals are placed on the other side.
Good decoupling is important. The AD9833 should have supply
bypassing of 0.1 µF ceramic capacitors in parallel with 10 µF
tantalum capacitors. To achieve the best from the decoupling
capacitors, they should be placed as close as possible to the
device, ideally right up against the device.
Proper operation of the comparator requires good layout strategy.
The strategy must minimize through proper layout of the PCB
the parasitic capacitance between V
IN
and the SIGN BIT OUT
pin by adding isolation using a ground plane. For example, in a
4-layer board, the C
IN
signal could be connected to the top layer
and the SIGN BIT OUT connected to the bottom layer, so that
isolation is provided by the power and ground planes between.
REV. A–14–
AD9833
DATA WRITE
SEE FIGURE 9
SELECT DATA
SOURCES
WAIT 8/9 MCLK
CYCLES
V
OUT
= V
REF
ⴛ 18 ⴛ R
LOAD
/R
SET
ⴛ (1 + (SIN(2␲(FREQREG ⴛ
fMCLK
ⴛ
t
/2
28
+ PHASEREG/2
12
))))
DAC OUTPUT
CHANGE PHASE?
CHANGE FREQUENCY?
CHANGE DAC OUTPUT
FROM SIN TO RAMP?
CHANGE OUTPUT TO
A DIGITAL SIGNAL?
CHANGE
PSELECT?
CHANGE PHASE
REGISTER?
CHANGE
FSELECT?
CHANGE FREQUENCY
REGISTER?
CONTROL REGISTER
WRITE
(SEE TABLE XI)
INITIALIZATION
SEE FIGURE 8 BELOW
NO
NO
NO
NO
YES
NO
YES
YES
NO
YES
YES
YES
YES
YES
Figure 7. Flow Chart for AD9833 Initialization and Operation
INITIALIZATION
APPLY RESET
(CONTROL REGISTER WRITE)
RESET = 1
WRITE TO FREQUENCY AND PHASE REGISTERS
FREQ0 REG = F
OUT0
/
fMCLK
ⴛ 2
28
FREQ1 REG = F
OUT1
/
fMCLK
ⴛ 2
28
PHASE0 AND PHASE1 REG = (PHASESHIFT ⴛ 2
12
) / 2␲
(SEE FIGURE 9)
SET RESET = 0
SELECT FREQUENCY REGISTERS
SELECT PHASE REGISTERS
(CONTROL REGISTER WRITE)
RESET BIT = 0
FSELECT = SELECTED FREQUENCY REGISTER
PSELECT = SELECTED PHASE REGISTER
Figure 8. Initialization
REV. A
AD9833
–15–
NO
WRITE 14 MSBs OR LSBs
TO A FREQUENCY REGISTER?
(CONTROL REGISTER WRITE)
B28 (D13) = 0
HLB (D12) = 0/1
WRITE A 16-BIT WORD
(SEE TABLES VI AND VII
FOR EXAMPLES)
WRITE 14MSBs OR LSBs
TO A
FREQUENCY REGISTER?
WRITE TO PHASE
REGISTER?
(16-BIT WRITE)
D15, D14 = 11
D13 = 0/1 (CHOOSE THE
PHASE REGISTER)
D12 = X
D11 ... D0 = PHASE DATA
WRITE TO ANOTHER
PHASE REGISTER?
YES
WRITE ANOTHER FULL
28-BIT WORD TO A
FREQUENCY REGISTER?
WRITE TWO CONSECUTIVE
16-BIT WORDS
(SEE TABLE V FOR EXAMPLE)
(CONTROL REGISTER WRITE)
B28 (D13) = 1
WRITE A FULL 28-BIT WORD
TO A FREQUENCY REGISTER?
DATA WRITE
NO
YES
YES
NO
YES
NO NO
YES
YES
Figure 9. Data Writes
INTERFACING TO MICROPROCESSORS
The AD9833 has a standard serial interface that allows the part to
interface directly with several microprocessors. The device uses
an external serial clock to write the data/control information
into the device. The serial clock can have a frequency of 40 MHz
maximum. The serial clock can be continuous, or it can idle high
or low between write operations. When data/control information
is being written to the AD9833, FSYNC is taken low and is held
low while the 16 bits of data are being written into the AD9833.
The FSYNC signal frames the 16 bits of information being loaded
into the AD9833.
AD9833 to ADSP-21xx Interface
Figure 10 shows the serial interface between the AD9833 and
the ADSP-21xx. The ADSP-21xx should be set up to operate in
the SPORT transmit alternate framing mode (TFSW = 1). The
ADSP-21xx is programmed through the SPORT control register
and should be configured as follows:
•Internal clock operation (ISCLK = 1)
•Active low framing (INVTFS = 1)
•16-bit word length (SLEN = 15)
•Internal frame sync signal (ITFS = 1)
•Generate a frame sync for each write (TFSR = 1)
Transmission is initiated by writing a word to the Tx register
after the SPORT has been enabled. The data is clocked out on
each rising edge of the serial clock and clocked into the AD9833
on the SCLK falling edge.
*ADDITIONAL PINS OMITTED FOR CLARITY
AD9833*
FSYNC
SDATA
SCLK
ADSP-2101/
ADSP-2103*
TFS
DT
SCLK
Figure 10. ADSP-2101/ADSP-2103 to AD9833 Interface
AD9833 to 68HC11/68L11 Interface
Figure 11 shows the serial interface between the AD9833 and
the 68HC11/68L11 microcontroller. The microcontroller is
configured as the master by setting bit MSTR in the SPCR to 1.
This provides a serial clock on SCK while the MOSI output drives
the serial data line SDATA. Since the microcontroller does not
have a dedicated frame sync pin, the FSYNC signal is derived from
a port line (PC7). The setup conditions for correct operation of
the interface are as follows:
•SCK idles high between write operations (CPOL = 0)
•Data is valid on the SCK falling edge (CPHA = 1)
When data is being transmitted to the AD9833, the FSYNC line is
taken low (PC7). Serial data from the 68HC11/68L11 is transmit-
ted in 8-bit bytes with only eight falling clock edges occurring in
the transmit cycle. Data is transmitted MSB first. In order to load
data into the AD9833, PC7 is held low after the first 8 bits are
transferred, and a second serial write operation is performed to
the AD9833. Only after the second 8 bits have been transferred
should FSYNC be taken high again.
REV. A–16–
AD9833
*ADDITIONAL PINS OMITTED FOR CLARITY
AD9833*
FSYNC
SDATA
SCLK
68HC11/68L11*
PC7
MOSI
SCK
Figure 11. 68HC11/68L11 to AD9833 Interface
AD9833 to 80C51/80L51 Interface
Figure 12 shows the serial interface between the AD9833 and the
80C51/80L51 microcontroller. The microcontroller is operated
in mode 0 so that TxD of the 80C51/80L51 drives SCLK of the
AD9833, while RxD drives the serial data line SDATA. The
FSYNC signal is again derived from a bit programmable pin on
the port (P3.3 being used in the diagram). When data is to be trans-
mitted to the AD9833, P3.3 is taken low. The 80C51/80L51
transmits data in 8-bit bytes, thus only eight falling SCLK edges
occur in each cycle. To load the remaining 8 bits to the AD9833,
P3.3 is held low after the first 8 bits have been transmitted, and a
second write operation is initiated to transmit the second byte of
data. P3.3 is taken high following the completion of the second
write operation. SCLK should idle high between the two write
operations. The 80C51/80L51 outputs the serial data in a format
that has the LSB first. The AD9833 accepts the MSB first
(the 4 MSBs being the control information, the next 4 bits being
the address, while the 8 LSBs contain the data when writing to a
destination register). Therefore, the transmit routine of the
80C51/80L51 must take this into account and rearrange the bits
so that the MSB is output first.
*ADDITIONAL PINS OMITTED FOR CLARITY
FSYNC
SDATA
SCLK
P3.3
RxD
TxD
AD9833*
80C51/80L51*
Figure 12. 80C51/80L51 to AD9833 Interface
AD9833 to DSP56002 Interface
Figure 13 shows the interface between the AD9833 and the
DSP56002. The DSP56002 is configured for normal mode
asynchronous operation with a gated internal clock (SYN = 0,
GCK = 1, SCKD = 1). The frame sync pin is generated internally
(SC2 = 1), the transfers are 16 bits wide (WL1 = 1, WL0 = 0),
and the frame sync signal will frame the 16 bits (FSL = 0).
The frame sync signal is available on pin SC2, but it needs to be
inverted before being applied to the AD9833. The interface to
the DSP56000/DSP56001 is similar to that of the DSP56002.
*ADDITIONAL PINS OMITTED FOR CLARITY
FSYNC
SDATA
SCLK
SC2
STD
SCK
AD9833*
DSP56002*
Figure 13. DSP56002 to AD9833 Interface
AD9833 EVALUATION BOARD
The AD9833 Evaluation Board allows designers to evaluate the
high performance AD9833 DDS modulator with a minimum
of effort.
To prove that this device will meet the user’s waveform synthesis
requirements, the user requires only a power supply, an IBM
®
compatible PC, and a spectrum analyzer along with the evalua-
tion board.
The DDS evaluation kit includes a populated, tested AD9833
printed circuit board. The evaluation board interfaces to the
parallel port of an IBM compatible PC. Software is available
with the evaluation board that allows the user to easily program
the AD9833. A schematic of the evaluation board is shown in
Figure 14. The software will run on any IBM compatible PC
that has Microsoft Windows
®
95
, Windows 98, Windows ME,
or Windows 2000 NT
®
installed.
Using the AD9833 Evaluation Board
The AD9833 evaluation kit is a test system designed to simplify
the evaluation of the AD9833. An application note is also avail-
able with the evaluation board and gives full information on
operating the evaluation board.
Prototyping Area
An area is available on the evaluation board for the user to add
additional circuits to the evaluation test set. Users may want to
build custom analog filters for the output or add buffers and
operational amplifiers to be used in the final application.
XO vs. External Clock
The AD9833 can operate with master clocks up to 25 MHz.
A25 MHz oscillator is included on the evaluation board. How-
ever, this oscillator can be removed and, if required, an external
CMOS clock connected to the part.
Power Supply
Power to the AD9833 evaluation board must be provided exter-
nally through pin connections. The power leads should be twisted
to reduce ground loops.
REV. A
AD9833
–17–
MCLK
R1
50⍀
DGND
DVDD
OUT
DVDD
C5
0.1␮F
LK2
U3
18
16
14
1
6
4
2
DVDD
C6
0.1␮F
U2
J1
SCLK
SDATA
FSYNC
DVDD
C6
0.1␮FC8
10␮F
C7
0.1␮F
C9
0.1␮F
C10
10␮F
J2 J3
DVDD VDD
VOUT
C4
VDD
C3
0.01␮F
C2
0.1␮F
VDD
C11
10␮F
C1
0.1␮F
LK1
2
VDDCAP
3
1
10
COMP
DGND AGND
49
5
8
6
7
MCLK
FSYNC
SDATA
SCLK
U1
AD9833
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
SCLK
FSYNC
SDATA
VOUT
Figure 14. Evaluation Board Layout
Integrated Circuits
U1 AD9833BRU
U2 74HCT244
U3 OSC XTAL 25 MHz
Capacitors
C1, C2 100 nF Ceramic Capacitor 0805
C3 10 nF Ceramic Capacitor
C4 Option for Extra Decoupling Capacitor
C5, C6, C7, C9 100 nF Ceramic Capacitor
C8, C10, C11 10 mF Tantalum Capacitor
Resistor
R1 50 W Resistor
Links
LK1, LK2 2-Pin Sil Header
Sockets
MCLK VOUT Subminiature BNC Connector
Connectors
J1 36-Pin Edge Connector
J2, J3 PCB Mounting Terminal Block
REV. A–18–
AD9833
OUTLINE DIMENSIONS
10-Lead Mini Small Outline Package [MSOP]
(RM-10)
Dimensions shown in millimeters
0.23
0.08 0.80
0.40
8ⴗ
0ⴗ
0.15
0
0.27
0.17
0.95
0.85
0.75
SEATING
PLANE
1.10 MAX
10 6
5
1
0.50 BSC
3.00 BSC
3.00 BSC
4.90 BSC
PIN 1
COMPLIANT TO JEDEC STANDARDS MO-187BA
COPLANARITY
0.10
REV. A
AD9833
–19–
Revision History
Location Page
6/03—Data Sheet changed from REV. 0 to REV. A.
Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
C02704–0–6/03(A)
–20–