Page 1
Low Power, 8.5 mW, 2.3 V to 5.5 V,
FEATURES
Digitally programmable frequency and phase
8.5 mW power consumption at 2.3 V
MCLK speed: 16 MHz (B grade), 5 MHz (A grade)
28-bit resolution: 0.06 Hz at 16 MHz reference clock
Sinusoidal, triangular, and square wave outputs
2.3 V to 5.5 V power supply
3-wire SPI interface
Extended temperature range: −40°C to +125°C
Power-down option
10-lead LFCSP
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
Time domain reflectometry (TDR) applications
Programmable Waveform Generator
AD9837
GENERAL DESCRIPTION
The AD9837 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 (TDR) applications.
The output frequency and phase are software programmable,
allowing easy tuning. The frequency registers are 28 bits wide:
with a 16 MHz clock rate, resolution of 0.06 Hz can be achieved;
with a 5 MHz clock rate, the AD9837 can be tuned to 0.02 Hz
resolution.
The AD9837 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 AD9837 has a power-down (sleep) function. Sections of the
device that are not being used can be powered down to minimize
the current consumption of the part. For example, the DAC can
be powered down when a clock output is being generated.
The AD9837 is available in a 10-lead LFCSP_WD package.
FUNCTIONAL BLOCK DIAGRAM
AGND
MCLK
28-BIT FREQ0 REG
28-BIT FREQ1 REG
Rev. 0
Informatio
n furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibi
lity is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of th
ird parties that may result from its use. Specifications subject to change without notice. No
license is g
ranted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademar
ks and registered trademarks are the property of their respective owners.
DGND
AVD D/
DVDD
MUX
12-BIT PHASE0 RE G
12-BIT PHASE1 REG
16-BIT CONTROL REGISTER
SERIAL INTERFACE
AND
CONTROL LO GIC
SCLK SDATAFSYNC
VDD
REGULATOR
ACCUMULATOR
2.5V
PHASE
(28-BIT)
CAP/2.5V
MUX
ON-BOARD
REFERENCE
FULL-SCAL E
CONTROL
12
Figure 1.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106,
Tel: 781.329.4700 www.analog
Fax: 781.461.3113 ©2011 Analog Devices, Inc. All rights re
DIVIDE
BY 2
SIN
ROM
MUX
AD9837
MUX
10-BIT DAC
MSB
200Ω
COMP
VOUT
R
9070-001
U.S.A.
.com
served.
Page 2
AD9837
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Timing Characteristics ................................................................ 4
Absolute Maximum Ratings ............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution .................................................................................. 5
Pin Configuration and Function Descriptions ............................. 6
Typical Performance Characteristics ............................................. 7
Test Circuit ........................................................................................ 9
Terminology .................................................................................... 10
Theory of Operation ...................................................................... 11
Circuit Description ......................................................................... 12
Numerically Controlled Oscillator Plus Phase Modulator ... 12
SIN ROM ..................................................................................... 12
Digital-to-Analog Converter (DAC) ....................................... 12
Regulator ...................................................................................... 12
REVISION HISTORY
4/11—Revision 0: Initial Version
Functional Description .................................................................. 13
Serial Interface ............................................................................ 13
Latency Period ............................................................................ 13
Control Register ......................................................................... 13
Frequency and Phase Registers ................................................ 15
Reset Function ............................................................................ 16
Sleep Function ............................................................................ 16
VOUT Pin ................................................................................... 16
Powering Up the AD9837 ......................................................... 16
Applications Information .............................................................. 19
Grounding and Layout .............................................................. 19
Interfacing to Microprocessors................................................. 19
Evaluation Board ............................................................................ 21
System Demonstration Platform .............................................. 21
AD9837 to SPORT Interface ..................................................... 21
Evaluation Kit ............................................................................. 21
Crystal Oscillator vs. External Clock ....................................... 21
Power Supply ............................................................................... 21
Evaluation Board Schematics ................................................... 22
Evaluation Board Layout ........................................................... 24
Outline Dimensions ....................................................................... 25
Ordering Guide .......................................................................... 25
Rev. 0 | Page 2 of 28
Page 3
AD9837
SPECIFICATIONS
VDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, TA = T
Table 1.
1
Parameter
Min Typ Max Unit Test Conditions/Comments
SIGNAL DAC SPECIFICATIONS
Resolution 10 Bits
Update Rate
A Grade 5 MSPS
B Grade 16 MSPS
V
Maximum 0.645 V
OUT
V
Minimum 37 mV
OUT
V
0.610 V
p-p
V
TC 200 ppm/°C
OUT
DC Accuracy
Integral Nonlinearity (INL) ±1.0 LSB
Differential Nonlinearity (DNL) ±0.5 LSB
DDS SPECIFICATIONS
Dynamic Specifications
Signal-to-Noise Ratio (SNR)
A Grade −64 dB f
B Grade −64 dB f
Total Harmonic Distortion (THD)
A Grade −68 dBc f
B Grade −68 dBc f
Spurious-Free Dynamic Range (SFDR)
Wideband (0 to Nyquist)
A Grade −65 dBc f
B Grade −65 dBc f
Narrow-Band (±200 kHz)
A Grade −94 dBc f
B Grade −97 dBc f
Clock Feedthrough −67 dBc
Wake-Up Time 1 ms
LOGIC INPUTS
Input High Voltage, V
1.7 V 2.3 V to 2.7 V power supply
INH
2.0 V 2.7 V to 3.6 V power supply
2.8 V 4.5 V to 5.5 V power supply
Input Low Voltage, V
0.5 V 2.3 V to 2.7 V power supply
INL
0.7 V 2.7 V to 3.6 V power supply
0.8 V 4.5 V to 5.5 V power supply
Input Current, I
10 mA
INH/IINL
Input Capacitance, CIN 3 pF
POWER SUPPLIES f
VDD 2.3 5.5 V
IDD
A Grade 3.7 5.0 mA IDD code dependent; see Figure 6
B Grade 4.5 5.5 mA IDD code dependent; see Figure 7
Low Power Sleep Mode 0.5 0.8 mA
1
Operating temperature range is −40°C to +125°C; typical specifications are at 25°C.
MIN
to T
, unless otherwise noted.
MAX
= 5 MHz, f
MCLK
= 16 MHz, f
MCLK
= 5 MHz, f
MCLK
= 16 MHz, f
MCLK
= 5 MHz, f
MCLK
= 16 MHz, f
MCLK
= 5 MHz, f
MCLK
= 16 MHz, f
MCLK
= 16 MHz, f
MCLK
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
= f
= f
= f
= f
= f
= f
= f
= f
= f
MCLK
MCLK
MCLK
MCLK
MCLK
MCLK
MCLK
MCLK
MCLK
/4096
/4096
/4096
/4096
/50
/50
/50
/50
/4096
DAC powered down (SLEEP1 and
SLEEP12 bits = 11; see Table 15)
Rev. 0 | Page 3 of 28
Page 4
AD9837
TIMING CHARACTERISTICS
VDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, unless otherwise noted.
Table 2.
1
Parameter
t1 62.5 ns min MCLK period (f
t2 25 ns min MCLK high duration (f
t3 25 ns min MCLK low duration (f
Limit at T
MIN
to T
Unit Description
MAX
= 16 MHz)
MCLK
= 16 MHz)
MCLK
= 16 MHz)
MCLK
t4 25 ns min SCLK period
t5 10 ns min SCLK high duration
t6 10 ns min SCLK low duration
t7 5 ns min FSYNC to SCLK falling edge setup time
t8 10 ns min SCLK falling edge to FSYNC rising edge time
t
− 5 ns max
4
t9 5 ns min Data setup time
t10 3 ns min Data hold time
t11 5 ns min SCLK high to FSYNC falling edge setup time
1
Guaranteed by design; not production tested.
Timing Diagrams
t
1
MCLK
t
2
t
3
9070-003
Figure 2. Master Clock
SCLK
FSYNC
t
11
t
7
t
5
t
6
t
4
t
8
t
10
t
9
SDATA
D15
41D51DD0D1D2D14
09070-004
Figure 3. Serial Timing
Rev. 0 | Page 4 of 28
Page 5
AD9837
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 3.
Parameter Rating
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/2.5V 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 +125°C
Storage Temperature Range −65°C to +150°C
Maximum Junction Temperature 150°C
Lead Temperature, Soldering (10 sec) 300°C
IR Reflow, Peak Temperature 220°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 4. Thermal Resistance
Package Type θJA θ
10-Lead LFCSP_WD (CP-10-9) 206 44 °C/W
Unit
JC
ESD CAUTION
Rev. 0 | Page 5 of 28
Page 6
AD9837
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1
COMP
VDD
2
CAP/2.5V
DGND
MCLK
NOTES
1. CONNECT EXP OSED PAD
TO GROUND.
AD9837
3
TOP VIEW
(Not to Scale)
4
5
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin No. Mnemonic Description
1 COMP DAC Bias Pin. This pin is used for decoupling the DAC bias voltage.
2 VDD
Positive Power Supply for the Analog and 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 μF and a 10 μF decoupling capacitor should
be connected between VDD and AGND.
3 CAP/2.5V
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 100 nF typical, which is
connected from CAP/2.5V to DGND. If VDD is less than or equal to 2.7 V, CAP/2.5V should be tied directly to
VDD to bypass the on-board regulator.
4 DGND Digital Ground.
5 MCLK
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.
6 SDATA Serial Data Input. The 16-bit serial data-word is applied to this input.
7 SCLK Serial Clock Input. Data is clocked into the AD9837 on each falling edge of SCLK.
8 FSYNC
Active Low Control Input. FSYNC 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.
9 AGND Analog Ground.
10 VOUT
Voltage Output. The analog and digital output from the AD9837 is available at this pin. An external load
resistor is not required because the device has a 200 Ω resistor on board.
EP Exposed Pad. Connect the exposed pad to ground.
10
9
8
7
6
VOUT
AGND
FSYNC
SCLK
SDATA
09070-005
Rev. 0 | Page 6 of 28
Page 7
AD9837
–
–
TYPICAL PERFORMANCE CHARACTERISTICS
5.0
4.8
4.6
4.4
4.2
4.0
(mA)
DD
I
3.8
3.6
3.4
3.2
3.0
0 2 4 6 8 1012141618
VDD = 5V
VDD = 3V
MCLK FREQUENCY ( MHz)
Figure 5. Typical Current Consumption (IDD) vs. MCLK Frequency
= MCLK/10
for f
OUT
6
09070-00
98
–99
–100
–101
SFDR (dB)
–102
–103
–104
02468 1816141210
MCLK FREQUENCY ( MHz)
Figure 8. Narrow-Band SFDR vs. MCLK Frequency,
= MCLK/50 to ±200 kHz
f
OUT
09070-009
4.5
4.4
4.3
4.2
(mA)
DD
4.1
I
4.0
3.9
3.8
1 10 100 1000
OUTPUT FREQUENCY (kHz)
Figure 6. Typical IDD vs. Output Frequency for f
4.9
4.8
4.7
4.6
4.5
(mA)
4.4
DD
I
4.3
4.2
4.1
4.0
1 10 100 1k 10k
OUTPUT FREQUENCY (kHz)
Figure 7. Typical IDD vs. Output Frequency for f
VDD = 5V
VDD = 3V
MCLK
VDD = 5V
VDD = 3V
MCLK
= 5 MHz
= 16 MHz
50
–55
MCLK/7
–60
SFDR (dB)
–65
MCLK/50
–70
1 3 5 7 9 11 13 15
09070-007
MCLK FREQUENCY (MHz)
09070-010
Figure 9. Wideband SFDR vs. MCLK Frequency
–56
–58
–60
–62
SNR (dB)
–64
–66
–68
–70
0 2 4 6 8 1012141618
09070-008
MCLK FREQUENCY ( MHz)
09070-011
Figure 10. SNR vs. MCLK Frequency
Rev. 0 | Page 7 of 2
8
Page 8
AD9837
1000
900
800
700
600
WAKE-UP TI ME (µs)
500
400
–40 –20 0 20 40 60 80 140120100
VDD = 5.5V
TEMPERATURE (°C)
Figure 11. Wake-Up Time vs. Temperature
VDD = 2.3V
09070-012
0
–10
–20
–30
–40
–50
–60
POWER (dB)
–70
–80
–90
–100
0 1009010 20 30 40 50 60 70 80
Figure 14. Power vs. Frequency, f
FREQUENCY (kHz)
= 16 MHz, f
MCLK
Frequency Word = 0x1F81A
= 7.692 kHz,
OUT
09070-015
1.180
1.178
1.176
1.174
(V)
1.172
REF
V
1.170
1.168
1.166
1.164
–40 –20 0 20 40 60 80 100 140120
0
–10
–20
–30
–40
–50
–60
POWER (dB)
–70
–80
–90
–100
0 1009010 20 30 40 50 60 70 80
Figure 13. Power vs. Frequency, f
VDD = 2.7V
Figure 12. V
VDD = 5.0V
TEMPERATURE ( °C)
vs. Temperature
REF
FREQUENCY (kHz)
= 5 MHz, f
MCLK
Frequency Word = 0x1F751
= 2.4 kHz,
OUT
0
–10
–20
–30
–40
–50
–60
POWER (dB)
–70
–80
–90
–100
09070-013
02.50.5 1.0 1.5 2.0
Figure 15. Power vs. Frequency, f
FREQUENCY (MHz)
= 5 MHz, f
MCLK
= 0.714285 MHz = f
OUT
MCLK
09070-016
/7,
Frequency Word = 0x2492492
0
–10
–20
–30
–40
–50
–60
POWER (dB)
–70
–80
–90
–100
04123
09070-014
Figure 16. Power vs. Frequency, f
FREQUENCY (MHz)
= 16 MHz, f
MCLK
= 2.285714 MHz = f
OUT
MCLK
7
09070-01
/7,
Frequency Word = 0x2492492
Rev. 0 | Page 8 of 2
8
Page 9
AD9837
TEST CIRCUIT
100nF
CAP/2.5V
REGULATOR
COMP
12
SIN
ROM
10-BIT DAC
10nF
VDD
VOUT
20pF
AD9837
09070-002
Figure 17. Test Circuit Used to Test Specifications
Rev. 0 | Page 9 of 28
Page 10
AD9837
TERMINOLOGY
Integral Nonlinearity (INL) Total Harmonic Distortion (THD)
INL is the maximum deviation of any code from a straight line
passing through the endpoints of the transfer function. The
endpoints 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 (DNL)
DNL is the difference between the measured and ideal 1 LSB
change between two adjacent codes in the DAC. A specified
DNL of ±1 LSB maximum ensures monotonicity.
Output Compliance
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 compliance are generated, the AD9837 may not meet the specifications
listed in the data sheet.
Spurious-Free Dynamic Range (SFDR)
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 spur or harmonic 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 (THD) is the ratio of the rms sum of
harmonics to the rms value of the fundamental. For the AD9837,
THD is defined as
2
THD
=
2
log20
4
3
V
1
VVVVV
++++
6
5
2
2
2
2
where:
V
is the rms amplitude of the fundamental.
1
V
, V3, V4, V5, and V6 are the rms amplitudes of the second
2
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 is 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
output spectrum of the AD9837.
Rev. 0 | Page 10 of 28
Page 11
AD9837
2
THEORY OF OPERATION
Sine waves are typically thought of in terms of their magnitude
form: a(t) = sin(ωt). However, sine waves 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
MAGNITUDE
2π
2π
f.
PHASE
4π
4π
6π
6π
23
9070-0
by the traditional rate of ω = 2π
+
1
0
–1
28
0
Figure 18. 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 as follows:
ΔPhase = ωΔt (1)
Solving for ω,
ω = ΔPhase/Δt = 2πf (2)
Solving for f and substituting the reference clock frequency for
the reference period (1/f
f = ΔPhase × f
MCLK
= Δt),
MCLK
∕2π (3)
The AD9837 builds the output based on this simple equation. A
simple DDS chip can implement this equation with three major
subcircuits: numerically controlled oscillator (NCO) plus phase
modulator, SIN ROM, and digital-to-analog converter (DAC).
Each subcircuit is described in the Circuit Description section.
The AD9837 provides a sampled signal with its output following
the Nyquist sampling theorem. Specifically, its output spectrum
contains the fundamental plus aliased signals (images) that occur
at multiples of the reference clock frequency and the selected
output frequency. A graphical representation of the sampled
spectrum with aliased images is shown in Figure 19.
The prominence of the aliased images depends on the ratio of
to MCLK. If the ratio is small, the aliased images are very
f
OUT
prominent and of a relatively high energy level as determined by
the sin(x)/x roll-off of the quantized DAC output. In fact, depending on the f
/reference clock ratio, the first aliased image can
OUT
be on the order of −3 dB below the fundamental.
External filtering is required if the aliased image is within the
output band of interest.
f
OUT
SIGNAL AMPLITUDE
0Hz FIRST
sin(x)/x ENVELOPE
x = π (
f/f
)
C
f
–
f
C
OUT
f
C
IMAGE
SYSTEM CLOCK
f
+
f
C
OUT
SECOND
IMAGE
2
f
–
f
C
OUT
2
THIRD
IMAGE
FREQUENCY (Hz)
f
C
2
f
+
C
FOURTH
IMAGE
f
OUT
3
f
–
f
C
OUT
FIFTH
IMAGE
3
f
+
f
C
3
OUT
f
C
SIXTH
IMAGE
09070-040
Figure 19. DAC Output Spectrum
Rev. 0 | Page 11 of 28
Page 12
AD9837
CIRCUIT DESCRIPTION
The AD9837 is a fully integrated direct digital synthesis (DDS)
chip. The chip requires a reference clock and decoupling capacitors to provide digitally created sine waves up to 8 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 AD9837 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.
NUMERICALLY CONTROLLED OSCILLATOR PLUS PHASE MODULATOR
The AD9837 consists of two frequency select registers, a phase
accumulator, 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 2π. 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 AD9837
is implemented with 28 bits. Therefore, in the AD9837, 2π = 2
Likewise, the ΔPhase term is scaled into this range of numbers:
ΔPhase < 2
0 <
28
− 1
With these substitutions, Equation 3 becomes
f = ΔPhase × f
where 0 < Δ
Phase < 2
∕228 (4)
MCLK
28
− 1.
The input to the phase accumulator can be selected from either
the FREQ0 register or the FREQ1 register and is controlled by
the FSEL bit in the control register. 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 MSBs of the NCO. The
AD9837 has two phase registers; their resolution is 2π/4096.
28
.
SIN ROM
To make the output from the NCO useful, it must be converted
from phase information into a sinusoidal value. Because phase
information maps directly to amplitude, the SIN ROM uses the
digital phase information as an address to a lookup 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 because
28
a lookup table of 2
entries would be required. It is only necessary
to have sufficient phase resolution such that the errors due to
truncation are smaller than the resolution of the 10-bit DAC.
Therefore, the SIN ROM must have two bits of phase resolution
more than the 10-bit DAC.
The SIN ROM is enabled using the MODE bit (Bit D1) in the
control register (see Ta ble 1 6).
DIGITAL-TO-ANALOG CONVERTER (DAC)
The AD9837 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 because the device has an on-board
200 Ω resistor. The DAC generates an output voltage of 0.6 V p-p
typical.
REGULATOR
VDD provides the power supply required for the analog section
and the digital section of the AD9837. This supply can have a
value of 2.3 V to 5.5 V.
The internal digital section of the AD9837 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 AD9837
is less than or equal to 2.7 V, the CAP/2.5V and VDD pins should
be tied together to bypass the on-board regulator.
Rev. 0 | Page 12 of 28
Page 13
AD9837
FUNCTIONAL DESCRIPTION
SERIAL INTERFACE
The AD9837 has a standard 3-wire serial interface that is
compatible with the 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 operation is given in Figure 3.
FSYNC is a level triggered input that acts as a frame synchronization and chip enable input. 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
goes low, serial data is shifted into the input shift register of the
device on the falling edges of SCLK for 16 clock pulses. FSYNC
can be taken high after the 16th falling edge of SCLK, observing
the minimum SCLK falling edge to FSYNC rising edge time, t
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 goes high only after the 16th
SCLK falling edge of the last word loaded.
The SCLK can be continuous, or it can idle high or low between
write operations. In either case, it must be high when FSYNC
goes low (t
).
11
For an example of how to program the AD9837, see the AN-1070
Application Note on the Analog Devices, Inc., website. The
AD9837 has the same register settings as the AD9833/AD9834.
SLEEP12
SLEEP1
(see Tabl e 2). After FSYNC
7
8
.
LATENCY PERIOD
A latency period is associated with each asynchronous write
operation in the AD9837. If a selected frequency or phase
register is loaded with a new word, there is a delay of seven
or eight MCLK cycles before the analog output changes. The
delay can be seven or eight cycles, depending on the position
of the MCLK rising edge when the data is loaded into the
destination register.
CONTROL REGISTER
The AD9837 contains a 16-bit control register that allows the
user to configure the operation of the AD9837. All control bits
other than the MODE bit are sampled on the internal falling
edge of MCLK.
Figure 20 illustrates the functions of the control bits. Ta ble 7
describes the individual bits of the control register. The different
functions and the various output options of the AD9837 are
described in more detail in the following sections.
To inform the AD9837 that the contents of the control register
will be altered, Bit D15 and Bit D14 must be set to 0, as shown
in Tab l e 6.
Table 6. Control Register Bits
D15 D14 D13 to D0
0 0 Control bits
RESET
MODE + OPBI TEN
DIV2
OPBITEN
ACCUMULATOR
(28-BIT)
D150D140D13
PHASE
B28
D12
HLB
D11
FSEL
SIN
ROM
D10
PSELD90D8RESETD7SLEEP1D6SLEEP12D5OPBITEND40D3DIV2D20D1MODED00
0
MUX
1
DIVIDE
BY 2
Figure 20. Function of Control Bits
(LOW POWER)
10-BIT DAC
1
MUX
0
DIGITAL
OUTPUT
(ENABLE)
VOUT
09070-024
Rev. 0 | Page 13 of 28
Page 14
AD9837
Table 7. Control Register Bit Descriptions
Bit Bit Name Description
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 second write contains 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
consecutive writes. See Table 9 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 Tab le 10. Note, however, that consecutive 28-bit writes to the same frequency register are not allowed;
to execute consecutive 28-bit writes, you must alternate between the frequency registers.
B28 = 0 configures the 28-bit frequency register to operate as two 14-bit registers, one containing the 14 MSBs and
the other containing the 14 LSBs. In this way, the 14 MSBs of the frequency word can be altered independently 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. Bit D12 (HLB) informs the AD9837 whether the bits to be altered are the 14 MSBs or the 14 LSBs.
D12 HLB
D11 FSEL The FSEL bit defines whether the FREQ0 register or the FREQ1 register is used in the phase accumulator (see Table 8).
D10 PSEL
D9 Reserved This bit should be set to 0.
D8 RESET This bit controls the reset function.
D7 SLEEP1 This bit enables or disables the internal MCLK.
D6 SLEEP12 This bit powers down the on-chip DAC.
D5 OPBITEN This bit, in association with the MODE bit (Bit D1), controls the output at the VOUT pin (see Tab le 16).
D4 Reserved This bit must be set to 0.
D3 DIV2 DIV2 is used in association with Bit D5 (OPBITEN). See Table 16.
D2 Reserved This bit must be set to 0.
D1 MODE
D0 Reserved This bit must be set to 0.
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. The HLB bit is used in conjunction
with the B28 bit (Bit D13). The HLB bit indicates whether the 14 bits to be loaded are transferred to the 14 MSBs or
the 14 LSBs of the addressed frequency register. Bit D13 (B28) must be set to 0 to change the MSBs or LSBs of a
frequency word separately. When Bit D13 (B28) is set to 1, the HLB 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.
The PSEL bit defines whether the PHASE0 register data or the PHASE1 register data is added to the output of the
phase accumulator (see Table 8).
RESET = 1 resets internal registers to 0, which corresponds to an analog output of midscale.
RESET = 0 disables the reset function (see the Reset Function section).
SLEEP1 = 1 disables the internal MCLK. The DAC output remains at its present value because the NCO is no longer
accumulating.
SLEEP1 = 0 enables the internal MCLK (see the Sleep Function section).
SLEEP12 = 1 powers down the on-chip DAC. This is useful when the AD9837 is used to output the MSB of the DAC data.
SLEEP12 = 0 implies that the DAC is active (see the Sleep Function section).
OPBITEN = 1 causes the output of the DAC to no longer be available at the VOUT pin. Instead, the MSB (or MSB/2) of
the DAC data is connected to the VOUT pin. This output is useful as a coarse clock source. The DIV2 bit (Bit D3)
controls whether the VOUT pin outputs the MSB or the MSB/2.
OPBITEN = 0 connects the output of the DAC to VOUT. The MODE bit (Bit D1) determines whether the output is
sinusoidal or triangular.
DIV2 = 1 causes the MSB of the DAC data to be output at the VOUT pin.
DIV2 = 0 causes the MSB/2 of the DAC data to be output at the VOUT pin.
This bit, in association with the OPBITEN bit (Bit D5), controls the output at the VOUT pin when the on-chip DAC is
connected to VOUT. This bit should be set to 0 if the OPBITEN bit is set to 1 (see Table 16).
MODE = 1 bypasses the SIN ROM, resulting in a triangle output from the DAC.
MODE = 0 uses the SIN ROM to convert the phase information into amplitude information, resulting in a sinusoidal
signal at the output. (The OPBITEN bit (Bit D5) must also be set to 0 for sinusoidal output.)
Rev. 0 | Page 14 of 28
Page 15
AD9837
FREQUENCY AND PHASE REGISTERS
The AD9837 contains two frequency registers and two phase
registers, which are described in Ta b le 8 .
Table 8. Frequency and Phase Registers
Register Size Description
FREQ0 28 bits
FREQ1 28 bits
PHASE0 12 bits
PHASE1 12 bits
The analog output from the AD9837 is
f
/228 × FREQREG
MCLK
where FREQREG is the value loaded into the selected frequency
register.
This signal is phase shifted by
2π/4096 ×
PHASEREG is the value contained in the selected phase
where
PHASEREG
register.
The relationship of the selected output frequency and the reference clock frequency must be considered to avoid unwanted
output anomalies.
The flowchart in Figure 24 shows the routine for writing to the
frequency and phase registers of the AD9837.
Writing to a Frequency Register
When writing to a frequency register, Bit D15 and Bit D14 of
the control register give the address of the frequency register
(see Tabl e 9).
Table 9. Frequency Register Bits
D15 D14 D13 to D0
0 1 14 FREQ0 register bits
1 0 14 FREQ1 register bits
To change the entire contents of a frequency register, two consecutive writes to the same address must be performed because the
frequency registers are 28 bits wide. The first write contains the
14 LSBs, and the second write contains the 14 MSBs. For this
mode of operation, the B28 control bit (Bit D13) must be set
to 1. An example of a 28-bit write is shown in Tabl e 10.
Frequency Register 0.
When the FSEL bit = 0, the FREQ0
register defines the output frequency
as a fraction of the MCLK frequency.
Frequency Register 1.
When the FSEL bit = 1, the FREQ1
register defines the output frequency
as a fraction of the MCLK frequency.
Phase Offset Register 0.
When the PSEL bit = 0, the contents of
the PHASE0 register are added to the
output of the phase accumulator.
Phase Offset Register 1.
When the PSEL bit = 1, the contents of
the PHASE1 register are added to the
output of the phase accumulator.
Table 10. Writing 0xFFFC000 to the FREQ0 Register
SDATA Input Result of Input Word
0010 0000 0000 0000
0100 0000 0000 0000
0111 1111 1111 1111
Control word write
(D15, D14 = 00), B28 (D13) = 1,
HLB (D12) = X
FREQ0 register write
(D15, D14 = 01), 14 LSBs = 0x0000
FREQ0 register write
(D15, D14 = 01), 14 MSBs = 0x3FFF
Note, however, that continuous writes to the same frequency
register may result in intermediate updates during the writes. If
a frequency sweep, or something similar, is required, it is recommended that users alternate between the two frequency registers.
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; with fine tuning, only the 14 LSBs are altered. By
setting the B28 control bit (Bit 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. In this way, the
14 MSBs of the frequency word can be altered independently
of the 14 LSBs, and vice versa. The HLB bit (Bit D12) in the
control register identifies which 14 bits are being altered (see
Tabl e 11 and Ta ble 1 2 ).
Table 11. Writing 0x3FFF to the 14 LSBs of the FREQ1 Register
SDATA Input Result of Input Word
0000 0000 0000 0000
1011 1111 1111 1111
Control word write
(D15, D14 = 00), B28 (D13) = 0,
HLB (D12) = 0, that is, LSBs
FREQ1 register write
(D15, D14 = 10), 14 LSBs = 0x3FFF
Table 12. Writing 0x00FF to the 14 MSBs of the FREQ0 Register
SDATA Input Result of Input Word
0001 0000 0000 0000
0100 0000 1111 1111
Control word write
(D15, D14 = 00), B28 (D13) = 0,
HLB (D12) = 1, that is, MSBs
FREQ0 register write
(D15, D14 = 01), 14 MSBs = 0x00FF
Writing to a Phase Register
When writing to a phase register, Bit D15 and Bit D14 are set to
11. Bit D13 identifies the phase register that is being loaded.
Table 13. Phase Register Bits
D15 D14 D13 D12 D11 to D0
1 1 0 X 12 PHASE0 register bits
1 1 1 X 12 PHASE1 register bits
Rev. 0 | Page 15 of 28
Page 16
AD9837
V
RESET FUNCTION
The reset function resets the appropriate internal registers to 0
to provide an analog output of midscale. A reset does not reset
the phase, frequency, or control registers. When the AD9837 is
powered up, the part should be reset (see the Powering Up the
AD9837 section). To reset the AD9837, set the RESET bit to 1.
To take the part out of reset, set the bit to 0. A signal appears at
the DAC output seven or eight MCLK cycles after the RESET
bit is set to 0.
Table 14. Applying the Reset Function
RESET Bit Result
0 No reset applied
1 Internal registers reset
SLEEP FUNCTION
Sections of the AD9837 that are not in use can be powered
down to minimize power consumption by 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 shown in Tabl e 15 .
Table 15. Applying the Sleep Function
SLEEP1 Bit SLEEP12 Bit Result
0 0 No power-down
0 1 DAC powered down
1 0 Internal clock disabled
1 1
DAC powered down and
internal clock disabled
DAC Powered Down
When the AD9837 is used to output the MSB of the DAC data
only, the DAC is not required. The DAC can be powered down
using the SLEEP12 bit to reduce power consumption.
Internal Clock Disabled
When the internal clock of the AD9837 is disabled, the DAC
output remains at its present value because 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.
Because the synchronizing clock (FSYNC) remains active, 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 are
observed at the output after a latency period (see the Latency
Period section).
VOUT PIN
The AD9837 offers a variety of outputs from the chip, all of
which are available from the VOUT pin. The available outputs
are the MSB of the DAC data, a sinusoidal output, or a triangle
output.
The OPBITEN and MODE bits (Bit D5 and Bit D1 in the
control register) are used to determine the output that is
available from the AD9837 (see Tab l e 16 ).
Table 16. Outputs from the VOUT Pin
OPBITEN Bit MODE Bit DIV2 Bit VOUT Pin Output
0 0 X Sinusoid
0 1 X Triangle
1 0 0 DAC data MSB/2
1 0 1 DAC data MSB
1 1 X Reserved
MSB of the DAC Data
The MSB of the DAC data can be output from the AD9837. By
setting the OPBITEN bit (Bit D5) 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 2 before being
output. The DIV2 bit (Bit D3) in the control register controls
the frequency of this output from the VOUT pin.
Sinusoidal Output
The SIN ROM converts the phase information from the frequency
and phase registers into amplitude information, resulting in a
sinusoidal signal at the output. To obtain a sinusoidal output
from the VOUT pin, set the MODE bit (Bit D1) to 0 and the
OPBITEN bit (Bit D5) 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 produces a 10-bit linear triangular
function (see Figure 21). To obtain a triangle output from the
VOUT pin, set the MODE bit (Bit D1) to 1 and the OPBITEN
bit (Bit D5) to 0.
OUT MAX
V
OUT MIN
2π 4π
Figure 21. Triangle Output
6π
POWERING UP THE AD9837
The flowchart in Figure 22 shows the operating routine for the
AD9837. When the AD9837 is powered up, the part should be
reset. This resets the appropriate internal registers to 0 to provide
an analog output of midscale. To avoid spurious DAC outputs
during AD9837 initialization, the RESET bit should be set to 1
until the part is ready to begin generating an output.
A reset does not reset the phase, frequency, or control registers.
These registers will contain invalid data and, therefore, should
be set to known values by the user. The RESET bit should then
be set to 0 to begin generating an output. The data appears on
the DAC output seven or eight MCLK cycles after the RESET
bit is set to 0.
9070-025
Rev. 0 | Page 16 of 28
Page 17
AD9837
DATA WRITE
(SEE FIGURE 24)
SELECT DATA
SOURCES
INITIALIZATION
(SEE FIG URE 23)
CHANGE
PSEL BIT?
NO
CHANGE PHASE
REGISTER?
YES
YES
09070-026
YES
YES
CHANGE
FSEL BIT?
CHANGE FREQUENCY
REGISTER?
CONTROL REG ISTER
(SEE TABLE 7)
WRITE
NO
WAIT 7/ 8 MCLK
CHANGE PHASE?
YES
CHANGE FREQUENCY?
CHANGE DAC OUTPUT
FROM SIN TO TRIANGLE?
YES
YES
CHANGE OUTPUT TO
A DIGITAL SIGNAL?
CYCLES
YES
NO
NO
NO
NO
Figure 22. Flowchart for AD9837 Initialization and Operation
INITIALIZATION
APPLY RESET
(CONTROL REGISTER WRITE)
RESET = 1
WRITE TO FREQUENCY AND PHAS E REGISTE RS
FREQ0 REG =
PHASE0 AND PHASE1 REG = (P HASESHIFT × 212)/2π
FREQ1 REG =
SELECT FREQ UENCY REGIST ERS
SELECT PHASE REGISTERS
(CONTROL REGISTER WRITE)
FSEL = SELECTED FREQUENCY REGISTER
PSEL = SELECTED PHASE REGISTER
f
OUT0
f
OUT1
(SEE FIGURE 24)
SET RESET = 0
RESET BIT = 0
/
f
/
f
MCLK
MCLK
× 2
× 2
28
28
09070-027
Figure 23. Flowchart for Initialization
Rev. 0 | Page 17 of 28
Page 18
AD9837
DATA WRITE
WRITE A FULL 28-BIT WORD
TO A FREQUENCY REGISTER?
(CONTROL REGIST ER WRITE)
B28 (D13) = 1
WRITE T WO CONSECUT IVE
16-BIT WO RDS
(SEE TABLE 10 FOR EXAMPLE)
WRITE ANOT HER FULL
28-BIT WORD TO A
FREQUENCY REG ISTER?
YES
YES
NO
WRITE 14 MSBs OR LSBs
TO A FREQUENCY REGIST ER?
YES
(CONTROL REGISTER WRITE)
B28 (D13) = 0
HLB (D12) = 0/1
WRITE A 16-BIT WORD
(SEE TABLE 11 AND TABLE 12
FOR EXAMPLES)
WRITE 14 MSBs OR LSBs
FREQUENCY REGI STER?
TO A
NO
ONON
YES
WRITE TO PHASE
REGISTER?
YES
(16-BIT W RITE)
D15, D14 = 11
D13 = 0/1 (CHOOSE THE
PHASE REGISTER)
D12 = X
D11 ... D0 = PHASE DATA
WRITE TO ANOTHER
PHASE REGISTER?
NO
YES
09070-028
Figure 24. Flowchart for Data Writes
Rev. 0 | Page 18 of 28
Page 19
AD9837
APPLICATIONS INFORMATION
The various output options available from the AD9837 make
the part suitable for a wide variety of applications, including
modulation applications. The AD9837 can be used to perform
simple modulation, such as frequency shift keying (FSK). More
complex modulation schemes, such as Gaussian minimum shift
keying (GMSK) and quadrature phase shift keying (QPSK), can
also be implemented using the AD9837.
In an FSK application, the two frequency registers of the AD9837
are loaded with different values. One frequency represents the
space frequency, and the other represents the mark frequency.
Using the FSEL bit in the control register of the AD9837, the user
can modulate the carrier frequency between the two values.
The AD9837 has two phase registers, enabling the part to perform phase shift keying (PSK). With PSK, the carrier frequency
is phase shifted, that is, the phase is altered by an amount that
is related to the bit stream input to the modulator.
The AD9837 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 also suitable for
applications in which it can be used as a local oscillator.
GROUNDING AND LAYOUT
The printed circuit board that houses the AD9837 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 because it provides
the best shielding. Digital and analog ground planes should be
joined in one place only. If the AD9837 is the only device that
requires an AGND to DGND connection, the ground planes
should be connected at the AGND and DGND pins of the
AD9837. If the AD9837 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 AD9837.
Avoid running digital lines under the device; these lines couple
noise onto the die. The analog ground plane should be allowed
to run under the AD9837 to avoid noise coupling. The power
supply lines to the AD9837 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 to
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 and signals are placed
on the other side.
Good decoupling is important. The AD9837 should have supply
bypassing of 0.1 μF ceramic capacitors in parallel with 10 μF
tantalum capacitors. To achieve the best performance from the
decoupling capacitors, they should be placed as close as possible
to the device, ideally right up against the device.
INTERFACING TO MICROPROCESSORS
The AD9837 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 or 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 or control information is written to the AD9837, FSYNC is taken low and is held
low until the 16 bits of data are written into the AD9837. The
FSYNC signal frames the 16 bits of information that are loaded
into the AD9837.
AD9837 to 68HC11/68L11 Interface
Figure 25 shows the serial interface between the AD9837 and
the 68HC11/68L11 microcontroller. The microcontroller is configured as the master by setting the MSTR bit in the SPCR to 1.
This setting provides a serial clock on SCK; the MOSI output
drives the serial data line, SDATA. Because 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 to be transmitted to the AD9837, the FSYNC line
(PC7) is taken low. Serial data from the 68HC11/68L11 is transmitted in 8-bit bytes with only eight falling clock edges occurring
in the transmit cycle. Data is transmitted MSB first. To load data
into the AD9837, PC7 is held low after the first eight bits are
transferred, and a second serial write operation is performed to
the AD9837. Only after the second eight bits are transferred
should FSYNC be taken high again.
68HC11/68L11
PC7
MOSI
SCK
Figure 25. 68HC11/68L11 to AD9837 Interface
AD9837
FSYNC
SDATA
SCLK
09070-030
Rev. 0 | Page 19 of 28
Page 20
AD9837
AD9837 to 80C51/80L51 Interface
Figure 26 shows the serial interface between the AD9837 and
the 80C51/80L51 microcontroller. The microcontroller is operated in Mode 0 so that TxD of the 80C51/80L51 drives SCLK of
the AD9837, and RxD drives the serial data line, SDATA. The
FSYNC signal is derived from a bit programmable pin on the
port (P3.3 is shown in Figure 26).
When data is to be transmitted to the AD9837, P3.3 is taken low.
The 80C51/80L51 transmits data in 8-bit bytes with only eight
falling SCLK edges occurring in each cycle. To load the remaining eight bits to the AD9837, P3.3 is held low after the first eight
bits are 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 AD9837 accepts the MSB first (the four MSBs are
the control information, the next four bits are the address, and
the eight 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.
80C51/80L51
AD9837
AD9837 to DSP56002 Interface
Figure 27 shows the interface between the AD9837 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 frames the 16 bits (FSL = 0). The frame sync signal is
available on the SC2 pin, but it must be inverted before it is applied
to the AD9837. The interface to the DSP56000/DSP56001 is
similar to that of the DSP56002.
DSP56002
SC2
STD
SCK
Figure 27. DSP56002 to AD9837 Interface
AD9837
FSYNC
SDATA
SCLK
9070-032
P3.3
RxD
TxD
Figure 26. 80C51/80L51 to AD9837 Interface
FSYNC
SDATA
SCLK
09070-031
Rev. 0 | Page 20 of 28
Page 21
AD9837
EVALUATION BOARD
The AD9837 evaluation board allows designers to evaluate the
high performance AD9837 DDS modulator with a minimum
of effort.
SYSTEM DEMONSTRATION PLATFORM
The system demonstration platform (SDP) is a hardware and
software evaluation tool for use in conjunction with product
evaluation boards. The SDP board is based on the Blackfin®
ADSP-BF527 processor with USB connectivity to the PC
through a USB 2.0 high speed port. For more information,
see the SDP board product page.
Note that the SDP board is sold separately from the AD9837
evaluation board.
AD9837 TO SPORT INTERFACE
The Analog Devices SDP board has a SPORT serial port that is
09070-037
used to control the serial inputs to the AD9837. The connections
are shown in Figure 28.
ADSP-BF527
SPORT_TFS
SPORT_TSCLK
SPORT_DT0
AD9837
FSYNC
SCLK
SDATA
Figure 29. AD9837 Evaluation Software Interface
CRYSTAL OSCILLATOR VS. EXTERNAL CLOCK
The AD9837 can operate with master clocks up to 16 MHz.
A 16 MHz oscillator is included on the evaluation board. This
oscillator can be removed and, if required, an external CMOS
clock can be connected to the part. Options for the general
oscillator include the following:
09070-033
Figure 28. SDP to AD9837 Interface
EVALUATION KIT
The DDS evaluation kit includes a populated, tested AD9837
printed circuit board (PCB). The schematics of the evaluation
board are shown in Figure 30 and Figure 31.
The software provided in the evaluation kit allows the user to
easily program the AD9837 (see Figure 29). The evaluation software runs on any IBM-compatible PC with Microsoft® Windows®
software installed (including Windows 7). The software is compatible with both 32-bit and 64-bit operating systems.
More information about the evaluation software is available on
the software CD and on the AD9837 product page.
• AEL 301-Series oscillators, AEL Crystals
• SG-310SCN oscillators, Epson Electronics
POWER SUPPLY
Power to the AD9837 evaluation board can be provided from
the USB connector or externally through pin connections. The
power leads should be twisted to reduce ground loops.
Rev. 0 | Page 21 of 28
Page 22
AD9837
EVALUATION BOARD SCHEMATICS
09070-034
Figure 30. Evaluation Board Schematic
Rev. 0 | Page 22 of 28
Page 23
AD9837
09070-038
Figure 31. SDP Connector Schematic
Rev. 0 | Page 23 of 28
Page 24
AD9837
EVALUATION BOARD LAYOUT
9070-039
Figure 32. Evaluation Board Layout
Rev. 0 | Page 24 of 28
Page 25
AD9837
OUTLINE DIMENSIONS
2.48
3.10
3.00 SQ
2.90
2.38
2.23
0.50 BSC
PIN 1 INDEX
AREA
0.80
0.75
0.70
SEATING
PLANE
TOP VIEW
0.30
0.25
0.20
0.50
0.40
0.30
0.05 MAX
0.02 NOM
0.20 REF
6
EXPOSED
PAD
5
BOTTOM VIEW
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
10
1.74
1.64
1.49
1
1
P
N
I
R
O
C
I
A
T
N
I
D
)
5
1
.
R
0
(
121009-A
Figure 33. 10-Lead Lead Frame Chip Scale Package [LFCSP_WD]
3 mm × 3 mm Body, Very Very Thin, Dual Lead
(CP-10-9)
Dimensions shown in millimeters
ORDERING GUIDE
Temperature
Range Max MCLK Package Description
Model
1, 2
AD9837BCPZ-RL −40°C to +125°C 16 MHz 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 DGH
AD9837BCPZ-RL7 −40°C to +125°C 16 MHz 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 DGH
AD9837ACPZ-RL −40°C to +125°C 5 MHz 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 DGG
AD9837ACPZ-RL7 −40°C to +125°C 5 MHz 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 DGG
EVAL-AD9837SDZ Evaluation Board
1
Z = RoHS Compliant Part.
2
The evaluation board for the AD9837 requires the system demonstration platform (SDP) board, which is sold separately.
Package
Option Branding
Rev. 0 | Page 25 of 28
Page 26
AD9837
NOTES
Rev. 0 | Page 26 of 28
Page 27
AD9837
NOTES
Rev. 0 | Page 27 of 28
Page 28
AD9837
NOTES
©2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09070-0-4/11(0)
Rev. 0 | Page 28 of 28
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