20 mW Power, 2.3 V to 5.5 V,
75 MHz Complete DDS
AD9834

Data SheetFEATURES

Capability for phase modulation and frequency modulation isprovided. The frequency registers are 28 bits; with a 75 MHz clock
rate, resolution of 0.28 Hz can be achieved. Similarly, with a 1 MHz
clock rate, the AD9834 can be tuned to 0.004 Hz resolution.
Frequency and phase modulation are affected by loading registers
through the serial interface and toggling the registers using
software or the FSELECT pin and PSELECT pin, respectively.

Narrow-band SFDR >72 dB
2.3 V to 5.5 V power supply
Output frequency up to 37.5 MHz
Sine output/triangular output
On-board comparator
3-wire SPI® interface
Extended temperature range: −40°C to +105°C
Power-down option
20 mW power consumption at 3 V
20-lead TSSOPThe AD9834 is written to using a 3-wire serial interface. This
serial interface operates at clock rates up to 40 MHz and iscompatible with DSP and microcontroller standards.
The device operates with a power supply from 2.3 V to 5.5 V.
The analog and digital sections are independent and can be runfrom different power supplies, for example, AVDD can equal
5 V with DVDD equal to 3 V.

APPLICATIONSFrequency stimulus/waveform generation
Frequency phase tuning and modulation
Low power RF/communications systems
Liquid and gas flow measurement
Sensory applications: proximity, motion, and defectdetection
Test and medical equipment

The AD9834 has a power-down pin (SLEEP) that allows
external control of the power-down mode. Sections of thedevice that are not being used can be powered down tominimize the current consumption. For example, the DAC canbe powered down when a clock output is being generated.

GENERAL DESCRIPTION

The part is available in a 20-lead TSSOP.

The AD9834 is a 75 MHz low power DDS device capable ofproducing high performance sine and triangular outputs. It also
has an on-board comparator that allows a square wave to be
produced for clock generation. Consuming only 20 mW of power
at 3 V makes the AD9834 an ideal candidate for power-sensitive
applications.

FUNCTIONAL BLOCK DIAGRAM
AVDD

AGND

DGND

DVDD

REFOUT

CAP/2.5V

ON-BOARD
REFERENCEREGULATOR
MCLK

VCC
2.5V

FULL-SCALECONTROLFSELECT
28-BIT FREQ0
REG

PHASE
ACCUMULATOR(28-BIT)

MUX
28-BIT FREQ1
REG

FS ADJUST

Σ

12

SIN
ROM

10-BIT
DAC

MUX

COMP

IOUT
IOUTB

MSB
12-BIT PHASE0 REG
12-BIT PHASE1 REG

MUX

MUX
DIVIDED
BY 2

16-BIT CONTROLREGISTERMUXSIGN BIT OUTSERIAL INTERFACEAND
CONTROL LOGICCOMPARATOR

VIN

FSYNC

SCLK

SDATA

PSELECTSLEEP RESET

02705-001

AD9834

Figure 1.
Rev. D

Document Feedback

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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or otherrights of third parties that may result from its use. Specifications subject to change without notice. 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 owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2003–2014 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com

AD9834

Data SheetTABLE OF CONTENTS
Features .............................................................................................. 1

Serial Interface ............................................................................ 18

Applications ....................................................................................... 1

Powering Up the AD9834 ......................................................... 18

General Description ......................................................................... 1

Latency ......................................................................................... 18

Functional Block Diagram .............................................................. 1

Control Register ......................................................................... 18

Revision History ............................................................................... 3

Frequency and Phase Registers ................................................ 20

Specifications..................................................................................... 4

Writing to a Frequency Register ............................................... 21

Timing Characteristics ................................................................ 6

Writing to a Phase Register ....................................................... 21

Absolute Maximum Ratings............................................................ 7

RESET Function ......................................................................... 21

ESD Caution .................................................................................. 7

SLEEP Function .......................................................................... 21

Pin Configuration and Function Descriptions ............................. 8

SIGN BIT OUT Pin.................................................................... 22

Typical Performance Characteristics ........................................... 10

The IOUT and IOUTB Pins...................................................... 22

Terminology .................................................................................... 14

Applications Information .............................................................. 23

Theory of Operation ...................................................................... 15

Grounding and Layout .................................................................. 26

Circuit Description ......................................................................... 16

Interfacing to Microprocessors ..................................................... 27

Numerically Controlled Oscillator Plus Phase Modulator ... 16

AD9834 to ADSP-21xx Interface ............................................. 27

SIN ROM ..................................................................................... 16

AD9834 to 68HC11/68L11 Interface ....................................... 27

Digital-to-Analog Converter (DAC) ....................................... 16

AD9834 to 80C51/80L51 Interface .......................................... 28

Comparator ................................................................................. 16

AD9834 to DSP56002 Interface ............................................... 28

Regulator...................................................................................... 17

Outline Dimensions ....................................................................... 29

Output Voltage Compliance...................................................... 17

Ordering Guide .......................................................................... 29

Functional Description .................................................................. 18

Rev. D | Page 2 of 32

Data Sheet

AD9834REVISION HISTORY
3/14—Rev. C to Rev. D
Changes to Table 3 ............................................................................ 7
Deleted Evaluation Board Section ................................................29
Changes to Ordering Guide ...........................................................35

4/10—Rev. A to Rev. B
Changes to Comparator Section ................................................... 15
Added Figure 28 .............................................................................. 16
Changes to Serial Interface Section .............................................. 17

2/11—Rev. B to Rev. C
Changes to IDD Parameter, Table 1 .................................................. 5
Changes to FS ADJUST Description, Table 4................................ 8
Added Output Voltage Compliance Section................................17
Changes to Figure 31 ......................................................................23
Changes to Figure 32 ......................................................................24
Deleted Using the AD9834 Evaluation Board Section and thePrototyping Area Section ...............................................................28
Added System Development Platform Section, AD9834 to
SPORT Interface Section, Figure 39, and Figure 40;
Renumbered Sequentially ..............................................................29
Changes to XO vs. External Clock Section and Power Supply
Section ..............................................................................................29
Deleted Bill of Materials, Table 19;
Renumbered Sequentially ..............................................................30
Added Evaluation Board Schematics Section and Figure 41 ....30
Added Figure 42 ..............................................................................31
Added Evaluation Board Layout Section and Figure 43 ............32
Added Figure 44 ..............................................................................33
Added Figure 45 ..............................................................................34
Changes to Ordering Guide ...........................................................35

8/06—Rev. 0 to Rev. A
Updated Format ................................................................. Universal
Changed to 75 MHz Complete DDS ............................... Universal
Changes to Features Section ............................................................ 1
Changes to Table 1 ............................................................................ 4
Changes to Table 2 ............................................................................ 6
Changes to Table 3 ............................................................................ 8
Added Figure 10, Figures Renumbered Sequentially ................... 9
Added Figure 16 and Figure 17, Figures Renumbered
Sequentially ...................................................................................... 10
Changes to Table 6 .......................................................................... 19
Changes to Writing a Frequency Register Section ..................... 20
Changes to Figure 29 ...................................................................... 21
Changes to Table 19 ........................................................................ 30
Changes to Figure 38 ...................................................................... 28
2/03—Revision 0: Initial Version

Rev. D | Page 3 of 32

AD9834

Data Sheet

SPECIFICATIONSVDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, TA = TMIN to TMAX, RSET = 6.8 kΩ, RLOAD = 200 Ω for IOUT and IOUTB, unless otherwise noted.
Table 1.
Parameter
SIGNAL DAC SPECIFICATIONSResolution
Update Rate
IOUT Full Scale 3
VOUT Max
VOUT Min
Output Compliance 4
DC Accuracy
Integral Nonlinearity
Differential Nonlinearity
DDS SPECIFICATIONS
Dynamic Specifications
Signal-to-Noise Ratio
Total Harmonic Distortion
Spurious-Free Dynamic Range (SFDR)
Wideband (0 to Nyquist)
Narrow Band (±200 kHz)B GradeC GradeClock FeedthroughWake-Up Time
COMPARATOR
Input Voltage Range
Input Capacitance
Input High-Pass Cutoff Frequency
Input DC Resistance
Input Leakage Current
OUTPUT BUFFER
Output Rise/Fall Time
Output Jitter
VOLTAGE REFERENCEInternal Reference
REFOUT Output Impedance 5
Reference Temperature Coefficient
LOGIC INPUTS
Input High Voltage, VINH
2

Min

Grade B, Grade C 1
Typ
Max
10
75
3.0
0.6
30
0.8
±1
±0.5

55

Bits
MSPS
mA
V
mV
V

60
−66

−56

dB
dBc

fMCLK = 75 MHz, fOUT = fMCLK/4096
fMCLK = 75 MHz, fOUT = fMCLK/4096

−60

−56

dBc

fMCLK = 75 MHz, fOUT = fMCLK/75

−78
−74
−50
1

−67
−65

dBc
dBc
dBc
ms

fMCLK = 50 MHz, fOUT = fMCLK/50
fMCLK = 75 MHz, fOUT = fMCLK/75

1

V p-p
pF
MHz
MΩ
μA

AC-coupled internallyns
ps rmsUsing a 15 pF load
3 MHz sine wave, 0.6 V p-p

10
12
120
1.18
1
100

1.24

1.7
2.0
2.8

Input Low Voltage, VINL

Input Current, IINH/IINL
Input Capacitance, CIN

Test Conditions/Comments

LSB
LSB

10
4
5

1.12

Unit

0.6
0.7
0.8
10
3

Rev. D | Page 4 of 32VkΩ
ppm/°C
V
V
V
V
V
V
µA
pF

2.3 V to 2.7 V power supply
2.7 V to 3.6 V power supply
4.5 V to 5.5 V power supply
2.3 V to 2.7 V power supply
2.7 V to 3.6 V power supply
4.5 V to 5.5 V power supply

Data Sheet

AD9834

Parameter
POWER SUPPLIES
AVDD
DVDD
IAA 6
IDD6
B GradeC GradeIAA + IDD6
B GradeC GradeLow Power Sleep Mode
B GradeC GradeMin

2

Grade B, Grade C 1
Typ
Max

Unit

Test Conditions/Comments

V
V
mA

fMCLK = 75 MHz, fOUT = fMCLK/4096

3.8

5.5
5.5
5

2.0
2.7

3
3.7

mA
mA

IDD code dependent (see Figure 8)
IDD code dependent (see Figure 8)

5.8
6.5

8
8.7

mA
mA

2.3
2.3

0.5
0.6

mA
mA

DAC powered down, MCLK running
DAC powered down, MCLK running

B grade: MCLK = 50 MHz; C grade: MCLK = 75 MHz. For specifications that do not specify a grade, the value applies to both grades.
Operating temperature range is as follows: B, C versions: −40°C to +105°C, typical specifications are at 25°C.
3
For compliance, with specified load of 200 Ω, IOUT full scale should not exceed 4 mA.
4Guaranteed by design.
5
Applies when REFOUT is sourcing current. The impedance is higher when REFOUT is sinking current.
6
Measured with the digital inputs static and equal to 0 V or DVDD.
1
2

RSET
6.8kΩ

10nF

CAP/2.5V
REGULATORREFOUT
ON-BOARD
REFERENCE

12

AD9834SIN
ROM

FS ADJUSTFULL-SCALECONTROL

10-BIT DAC

AVDD
10nF

COMP

IOUT
RLOAD
200Ω

Figure 2. Test Circuit Used to Test the Specifications

Rev. D | Page 5 of 32

20pF

02705-002

100nF

AD9834

Data Sheet

TIMING CHARACTERISTICS
DVDD = 2.3 V to 5.5 V, AGND = DGND = 0 V, unless otherwise noted.
Table 2.
Parameter 1
t1
t2
t3
t4
t5
t6
t7
t8 MINt8 MAX
t9
t10
t11
t11A
t12
1

Limit at TMIN to TMAX
20/13.33
8/6
8/6
25
10
10
5
10
t4 − 5
5
3
8
8
5

Unit
ns minns minns minns minns minns minns minns minns maxns minns minns minns minns minTest Conditions/Comments
MCLK period: 50 MHz/75 MHz
MCLK high duration: 50 MHz/75 MHz
MCLK low duration: 50 MHz/75 MHz
SCLK period
SCLK high duration
SCLK low duration
FSYNC-to-SCLK falling edge setup time
FSYNC-to-SCLK hold time
Data setup time
Data hold time
FSELECT, PSELECT setup time before MCLK rising edge
FSELECT, PSELECT setup time after MCLK rising edge
SCLK high to FSYNC falling edge setup time

Guaranteed by design, not production tested.

Timing Diagrams
t1
02705-003

MCLK

t2
t3

Figure 3. Master ClockMCLK

VALID DATAVALID DATAVALID DATA

02705-004

t11A

t11
FSELECT,
PSELECT

Figure 4. Control Timing

t5

t12

t4

SCLK

t7

t8

t6

FSYNC

t10
SDATA

D15

D14

D2

D1

Figure 5. Serial Timing

Rev. D | Page 6 of 32

D0

D15

D14

02705-005

t9

Data Sheet

AD9834

ABSOLUTE MAXIMUM RATINGSTA = 25°C, unless otherwise noted.
Table 3.
Parameter
AVDD to AGND
DVDD to DGND
AGND to DGND
CAP/2.5V
Digital I/O Voltage to DGND
Analog I/O Voltage to AGND
Operating Temperature Range
Industrial (B Version)
Storage Temperature Range
Maximum Junction Temperature
TSSOP Package
θJA Thermal ImpedanceθJC Thermal Impedance
Lead Temperature, Soldering (10 sec)
IR Reflow, Peak Temperature
Reflow Soldering (Pb-Free)
Peak Temperature
Time at Peak Temperature

Ratings−0.3 V to +6 V
−0.3 V to +6 V
−0.3 V to +0.3 V
2.75 V−0.3 V to DVDD + 0.3 V−0.3 V to AVDD + 0.3 V

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stressrating 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 affectdevice reliability.

ESD CAUTION−40°C to +105°C−65°C to +150°C
150°C
143°C/W
45°C/W
300°C
220°C
260°C (+0/–5)
10 sec to 40 sec

Rev. D | Page 7 of 32

AD9834

Data SheetFS ADJUST

1

20

IOUTB

REFOUT 2

19

IOUT

COMP 3

18

AGND

17

VIN

16

SIGN BIT OUT

CAP/2.5V 6

15

FSYNC

DGND 714SCLK

MCLK 813SDATA

FSELECT 9

12

SLEEP

PSELECT 10

11

RESET

AVDD 4DVDD 5

AD9834TOP VIEW(Not to Scale)02705-006

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

Figure 6. Pin Configuration

Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
ANALOG SIGNAL AND REFERENCE
1
FS ADJUST Full-Scale Adjust Control. A resistor (RSET) is connected between this pin and AGND. This determines the magnitudeof the full-scale DAC current. The relationship between RSET and the full-scale current is as follows:
IOUT FULL SCALE = 18 × FSADJUST/RSETFSADJUST = 1.15 V nominal, RSET = 6.8 kΩ typical.
2
REFOUT
Voltage Reference Output. The AD9834 has an internal 1.20 V reference that is made available at this pin.
3
COMP
DAC Bias Pin. This pin is used for decoupling the DAC bias voltage.
17
VIN
Input to Comparator. The comparator can be used to generate a square wave from the sinusoidal DAC output. The
DAC output should be filtered appropriately before being applied to the comparator to improve jitter. When Bit
OPBITEN and Bit SIGN/PIB in the control register are set to 1, the comparator input is connected to VIN.
19, 20IOUT,
Current Output. This is a high impedance current source. A load resistor of nominally 200 Ω should be connected
IOUTB
between IOUT and AGND. IOUTB should preferably be tied through an external load resistor of 200 Ω to AGND, but
it can be tied directly to AGND. A 20 pF capacitor to AGND is also recommended to prevent clock feedthrough.
POWER SUPPLY
4
AVDD
Positive Power Supply for the Analog Section. AVDD can have a value from 2.3 V to 5.5 V. A 0.1 μF decoupling
capacitor should be connected between AVDD and AGND.
5
DVDD
Positive Power Supply for the Digital Section. DVDD can have a value from 2.3 V to 5.5 V. A 0.1 μF decoupling
capacitor should be connected between DVDD and DGND.
6
CAP/2.5V
The digital circuitry operates from a 2.5 V power supply. This 2.5 V is generated from DVDD using an on-board
regulator (when DVDD exceeds 2.7 V). The regulator requires a decoupling capacitor of typically 100 nF that isconnected from CAP/2.5 V to DGND. If DVDD is equal to or less than 2.7 V, CAP/2.5 V should be shorted to DVDD.
7
DGND
Digital Ground.
18
AGND
Analog Ground.
DIGITAL INTERFACE AND CONTROL8MCLKDigital 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.
9
FSELECT
Frequency Select Input. FSELECT controls which frequency register, FREQ0 or FREQ1, is used in the phaseaccumulator. The frequency register to be used can be selected using Pin FSELECT or Bit FSEL. When Bit FSEL isused to select the frequency register, the FSELECT pin should be tied to CMOS high or low.
10
PSELECT
Phase Select Input. PSELECT controls which phase register, PHASE0 or PHASE1, is added to the phase accumulator
output. The phase register to be used can be selected using Pin PSELECT or Bit PSEL. When the phase registers arebeing controlled by Bit PSEL, the PSELECT pin should be tied to CMOS high or low.
11
RESET
Active High Digital Input. RESET resets appropriate internal registers to zero; this corresponds to an analog outputof midscale. RESET does not affect any of the addressable registers.
12
SLEEP
Active High Digital Input. When this pin is high, the DAC is powered down. This pin has the same function asControl Bit SLEEP12.

Rev. D | Page 8 of 32

Data Sheet
Pin No.
13
14
15

Mnemonic
SDATA
SCLK
FSYNC

16

SIGN BITOUT

AD9834
Description
Serial Data Input. The 16-bit serial data-word is applied to this input.
Serial Clock Input. Data is clocked into the AD9834 on each falling SCLK edge.
Active Low Control Input. This is the frame synchronization signal for the input data. When FSYNC is taken low, theinternal logic is informed that a new word is being loaded into the device.
Logic Output. The comparator output is available on this pin or, alternatively, the MSB from the NCO can be output
on this pin. Setting Bit OPBITEN in the control register to 1 enables this output pin. Bit SIGN/PIB determines
whether the comparator output or the MSB from the NCO is output on the pin.

Rev. D | Page 9 of 32

AD9834

Data Sheet

TYPICAL PERFORMANCE CHARACTERISTICS
4.0

0
AVDD = DVDD = 3V
TA = 25°C

TA = 25°C
3.5

–10

3.0

–20

SFDR (dBc)

5V
2.0
3V
1.5

–30
–40
–50

1.0

–60

0.5

–70

0

15

30
45
MCLK FREQUENCY (MHz)75

60

fOUT = 1MHz

–80

02705-007

0

SFDR dB MCLK/7

0

10

20

30
40
50
MCLK FREQUENCY (MHz)60

02705-010

IDD (mA)

2.5

70

Figure 10. Wideband SFDR vs. MCLK Frequency

Figure 7. Typical Current Consumption (IDD) vs. MCLK Frequency
4.00

TA = 25°C

5V

3.5

–10

3.0

AVDD = DVDD = 3V
TA = 25°C–203V

SFDR (dBc)

IDD (mA)

2.5
2.0
1.5

–30
50MHz CLOCK
–40
–50
–60

0.5

–70

1k

10k

100k
fOUT (Hz)

1M

10M

100M

–80
0.001

02705-008

0
100

10

100

Figure 11. Wideband SFDR vs. fOUT/fMCLK for Various MCLK Frequencies

Figure 8. Typical IDD vs. fOUT for fMCLK = 50 MHz
–60

–40

AVDD = DVDD = 3V
TA = 25°C
–45

–70

–50

SNR (dB)–65–75
SFDR dB MCLK/50–80

TA = 25°C
AVDD = DVDD = 3V
fOUT = MCLK/4096

–55

–60

–85

–65

–90
0

15

30
45
MCLK FREQUENCY (MHz)

60

75

–70
1.0

5.0
10.0
12.5
MCLK FREQUENCY (MHz)Figure 12. SNR vs. MCLK Frequency

Figure 9. Narrow-Band SFDR vs. MCLK Frequency

Rev. D | Page 10 of 32

25.0

50.0

02705-012

SFDR dB MCLK/7
02705-009

SFDR (dBc)

1.0
0.1
fOUT/fMCLK

0.01

02705-011

30MHz CLOCK

1.0

Data Sheet

AD9834
0.20

950

0.18

900

0.16

DVDD = 3.3V
DVDD = 2.3V

DVDD = 5.5V

800

0.12

5.5V

700

0.10
0.08

650

0.06

600

0.04

550

0.02

500
–40

105

25
TEMPERATURE (°C)

0–40Figure 13. Wake-Up Time vs. Temperature

–20

0

60
40
20
TEMPERATURE (°C)

80

100

02705-037

750

DVDD (V)0.1402705-013

WAKE-UP TIME (µs)

2.3V
850

100

02705-038

1000

Figure 16. SIGN BIT OUT Low Level, ISINK = 1 mA
5.5

1.250

DVDD = 5.5V
5.0

1.225
4.5

DVDD = 4.5V

UPPER RANGE
4.0

DVDD (V)V(REFOUT) (V)

1.200

1.175
LOWER RANGE

3.5
DVDD = 3.3V
3.0

1.150

DVDD = 2.7V
2.5

1.125

DVDD = 2.3V

2.0

25
TEMPERATURE (°C)

105

1.5
–40

02705-014

1.100
–40

–20

0

60
40
20
TEMPERATURE (°C)

80

Figure 17. SIGN BIT OUT High Level, ISINK = 1 mA

Figure 14. VREFOUT vs. Temperature
0–100
AVDD = DVDD = 5V
TA = 25°C

–10

–110

–20
–30

(dB)

–40

–130

–50
–60
–70

–140

–80

–150

–100

1k

10k
FREQUENCY (Hz)100k 200k

Figure 15. Output Phase Noise, fOUT = 2 MHz, MCLK = 50 MHz

0RWB 100

VWB 30FREQUENCY (Hz)100k
ST 100 SEC

02705-016

–160
100

–90

02705-015(dBc/Hz)–120

Figure 18. fMCLK = 10 MHz; fOUT = 2.4 kHz, Frequency Word = 000FBA9Rev. D | Page 11 of 32

AD9834

Data Sheet

0

0

–10

–10

–20

–20

–30

–30

–60

–60

–70

–70

–80

–80

–90

–90

VWB 300
FREQUENCY (Hz)5M
ST 50 SEC

–100

0

–10

–10

–20

–20

–30

–30

–40

–40

(dB)

0

–50

–60

–70

–70

–80

–80

–90

–90
0
RWB 1kVWB 300
FREQUENCY (Hz)5M
ST 50 SEC

1.6M
ST 200 SEC

–50

–60

–100

VWB 300
FREQUENCY (Hz)Figure 22. fMCLK = 50 MHz; fOUT = 120 kHz, Frequency Word = 009D496–100
02705-018(dB)

Figure 19. fMCLK = 10 MHz; fOUT = 1.43 MHz = fMCLK/7,
Frequency Word = 2492492

0
RWB 100

Figure 20. fMCLK = 10 MHz; fOUT = 3.33 MHz = fMCLK/3,
Frequency Word = 5555555

0
RWB 1kVWB 300
FREQUENCY (Hz)25M
ST 200 SEC

02705-021

0
RWB 1kFigure 23. fMCLK = 50 MHz; fOUT = 1.2 MHz, Frequency Word = 0624DD3
0

0
–10

–10

–20

–20
–30

–40

–40

(dB)

–30

–50

–50
–60

–60
–70

–70

–80

–80
–90

–100

–100

0
RWB 100

VWB 30FREQUENCY (Hz)160k
ST 200 SEC

02705-019–90

Figure 21. fMCLK = 50 MHz; fOUT = 12 kHz, Frequency Word = 000FBA90RWB 1kVWB 300
FREQUENCY (Hz)25M
ST 200 SEC

02705-022

–100

(dB)

–50

02705-020

(dB)

–40

–50

02705-017

(dB)

–40

Figure 24. fMCLK = 50 MHz; fOUT = 4.8 MHz, Frequency Word = 189374C

Rev. D | Page 12 of 32

AD9834
0

–10

–10

–20

–20

–30

–30

–40

–40

–50

–50

–60

–60

–70

–70

–80

–80

–90

–90

–100

0
RWB 1kVWB 300
FREQUENCY (Hz)25M
ST 200 SEC–100

Figure 25. fMCLK = 50 MHz; fOUT = 7.143 MHz = fMCLK/7,
Frequency Word = 2492492

0
RWB 1kVWB 300
FREQUENCY (Hz)25M
ST 200 SEC

Figure 26. fMCLK = 50 MHz; fOUT = 16.667 MHz = fMCLK/3,
Frequency Word = 5555555

Rev. D | Page 13 of 32

02705-024(dB)

002705-023(dB)

Data SheetAD9834

Data SheetTERMINOLOGY
Integral Nonlinearity (INL)
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 fullscale, 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 LSBchange between two adjacent codes in the DAC. A specified
DNL of ±1 LSB maximum ensures monotonicity.
Output Compliance
The output compliance refers to the maximum voltage that canbe generated at the output of the DAC to meet the specifications.
When voltages greater than that specified for the output compliance are generated, the AD9834 may not meet the
specifications listed in the data sheet.
Spurious-Free Dynamic Range (SFDR)
Along with the frequency of interest, harmonics of thefundamental frequency and images of these frequencies arepresent at the output of a DDS device. The SFDR refers to thelargest 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 inthe 0 to Nyquist bandwidth. The narrow-band SFDR gives theattenuation of the largest spur or harmonic in a bandwidth of±200 kHz about the fundamental frequency.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of harmonics to the rms valueof the fundamental. For the AD9834, THD is defined as

THD  20log

V2 2  V32  V4 2  V5 2  V6 2
V1

where V1 is the rms amplitude of the fundamental and V2, V3,
V4, V5, and V6 are the rms amplitudes of the second harmonic
through the sixth harmonic.
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 AD9834.

Rev. D | Page 14 of 32

Data Sheet

AD9834

THEORY OF OPERATION
Sine waves are typically thought of in terms of their magnitude
form a(t) = sin (ωt). However, these are nonlinear and not easy
to generate except through piecewise construction. On theother hand, the angular information is linear in nature, that is,
the phase angle rotates through a fixed angle for each unit oftime. The angular rate depends on the frequency of the signalby the traditional rate of ω = 2πf.

Knowing that the phase of a sine wave is linear and given areference interval (clock period), the phase rotation for that
period can be determined.
∆Phase = ω∆tSolving for ω,ω = ∆Phase/∆t = 2πf

MAGNITUDE+1

0

Solving for f and substituting the reference clock frequency forthe reference period (1/fMCLK = ∆t),

6π
4π

2π

f = ∆Phase × fMCLK/2π

–1
2π

PHASE

4π

6π
02705-025

2p

0Figure 27. Sine Wave

The AD9834 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 (DAC). Each of thesesubcircuits is discussed in the Circuit Description section.

Rev. D | Page 15 of 32

AD9834

Data Sheet

CIRCUIT DESCRIPTION
The AD9834 is a fully integrated direct digital synthesis (DDS)
chip. The chip requires one reference clock, one low precisionresistor, and eight decoupling capacitors to provide digitally createdsine waves up to 37.5 MHz. In addition to the generation of this RF
signal, the chip is fully capable of a broad range of simple andcomplex modulation schemes. These modulation schemes are
fully implemented in the digital domain, allowing accurate andsimple realization of complex modulation algorithms using DSP
techniques.
The internal circuitry of the AD9834 consists of the following
main sections: a numerically controlled oscillator (NCO),
frequency and phase modulators, SIN ROM, a DAC, acomparator, and a regulator.

NUMERICALLY CONTROLLED OSCILLATOR PLUS
PHASE MODULATORThis 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 π 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 AD9834 is
implemented with 28 bits. Therefore, in the AD9834, 2π = 228.
Likewise, the ∆Phase term is scaled into this range of numbers:
0 < ∆Phase < 228 − 1.
Making these substitutions into the previous equationf = ∆Phase × fMCLK/228
where 0 < ∆Phase < 228 − 1.
The input to the phase accumulator can be selected either fromthe FREQ0 register or FREQ1 register and is controlled by the
FSELECT pin or the FSEL 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 contentsof one of these phase registers is added to the MSBs of the NCO.
The AD9834 has two phase registers, the resolution of theseregisters being 2π/4096.

SIN ROM
To make the output from the NCO useful, it must be converted
from phase information into a sinusoidal value. Phase information maps directly into amplitude; therefore, 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, theoutput of the NCO is truncated to 12 bits. Using the full resolution of the phase accumulator is impractical and unnecessary
because it requires a look-up table of 228 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 the SIN ROM to have two bits of phase resolution
more than the 10-bit DAC.
The SIN ROM is enabled using the OPBITEN and MODE bitsin the control register. This is explained further in Table 18.

DIGITAL-TO-ANALOG CONVERTER (DAC)The AD9834 includes a high impedance current source 10-bit
DAC capable of driving a wide range of loads. The full-scale
output current can be adjusted for optimum power and externalload requirements using a single external resistor (RSET).
The DAC can be configured for either single-ended or differential
operation. IOUT and IOUTB can be connected through equal
external resistors to AGND to develop complementary output
voltages. The load resistors can be any value required, as long as
the full-scale voltage developed across it does not exceed thevoltage compliance range. Because full-scale current is
controlled by RSET, adjustments to RSET can balance changes
made to the load resistors.

COMPARATOR
The AD9834 can be used to generate synthesized digital clock
signals. This is accomplished by using the on-board self-biasing
comparator that converts the sinusoidal signal of the DAC to asquare wave. The output from the DAC can be filtered externally
before being applied to the comparator input. The comparator
reference voltage is the time average of the signal applied to VIN.
The comparator can accept signals in the range of approximately
100 mV p-p to 1 V p-p. As the comparator input is ac-coupled, tooperate correctly as a zero crossing detector, it requires a minimum
input frequency of typically 3 MHz. The comparator output is asquare wave with an amplitude from 0 V to DVDD.

Rev. D | Page 16 of 32

Data Sheet

AD9834The AD9834 is a sampled signal with its output following
Nyquist sampling theorem. Specifically, its output spectrum
contains the fundamental plus aliased signals (images) that
occur at multiples of the reference clock frequency and theselected output frequency. A graphical representation of thesampled spectrum, with aliased images, is shown in Figure 28.

REGULATORThe AD9834 has separate power supplies for the analog anddigital sections. AVDD provides the power supply required forthe analog section, and DVDD provides the power supply forthe digital section. Both of these supplies can have a value of
2.3 V to 5.5 V and are independent of each other. For example,
the analog section can be operated at 5 V, and the digital section
can be operated at 3 V, or vice versa.

The prominence of the aliased images is dependent on the ratioof fOUT to MCLK. If ratio is small, the aliased images are very
prominent and of a relatively high energy level as determinedby the sin(x)/x roll-off of the quantized DAC output. In fact,depending on the fOUT/reference clock relationship, the firstaliased image can be on the order of −3 dB below thefundamental.

The internal digital section of the AD9834 is operated at 2.5 V.
An on-board regulator steps down the voltage applied at DVDD
to 2.5 V. The digital interface (serial port) of the AD9834 also
operates from DVDD. These digital signals are level shifted
within the AD9834 to make them 2.5 V compatible.

A low-pass filter is generally placed between the output of the
DAC and the input of the comparator to further suppress theeffects of aliased images. Obviously, consideration must be
given to the relationship of the selected output frequency andthe reference clock frequency to avoid unwanted (and unexpected)
output anomalies. To apply the AD9834 as a clock generator,
limit the selected output frequency to <33% of reference clock
frequency, and thereby avoid generating aliased signals that fallwithin, or close to, the output band of interest (generally dcselected output frequency). This practice eases the complexity(and cost) of the external filter requirement for the clock
generator application. Refer to the AN-837 Application Note
for more information.

When the applied voltage at the DVDD pin of the AD9834 isequal to or less than 2.7 V, Pin CAP/2.5V and Pin DVDD should
be tied together, thus bypassing the on-board regulator.

OUTPUT VOLTAGE COMPLIANCE
The AD9834 has a maximum current density, set by the RSET,of 4 mA. The maximum output voltage from the AD9834 is
VDD − 1.5 V. This is to ensure that the output impedance of
the internal switch does not change, affecting the spectral
performance of the part. For a minimum supply of 2.3 V, themaximum output voltage is 0.8 V. Specifications in Table 1 areguaranteed with an RSET of 6.8 kΩ and an RLOAD of 200 Ω.

To enable the comparator, Bit SIGN/PIB and Bit OPBITEN in
the control resister are set to 1. This is explained further inTable 17.
fOUT

0Hz

fC – fOUT
2fC – fOUT

fC + fOUT

2fC + fOUT

fC

3fC – fOUT

2 fC
3fC

FIRST
IMAGE

SECOND
IMAGE

THIRD
IMAGE

FOURTHIMAGESYSTEM CLOCKFREQUENCY (Hz)Figure 28. The DAC Output Spectrum

Rev. D | Page 17 of 32

FIFTH
IMAGE

3fC + fOUT

SIXTH
IMAGE
02705-040

SIGNAL AMPLITUDE

sin x/x ENVELOPE
x = π (f/fC)

AD9834

Data Sheet

FUNCTIONAL DESCRIPTIONSERIAL INTERFACEThe AD9834 has a standard 3-wire serial interface that is compatible with SPI, QSPI™, MICROWIRE™, and DSP interface
standards.
Data is loaded into the device as a 16-bit word under thecontrol of a serial clock input (SCLK). The timing diagram
for this operation is given in Figure 5.
For a detailed example of programming the AD9833 andAD9834 devices, refer to the AN-1070 Application Note.
The FSYNC input is a level triggered input that acts as a frame
synchronization and chip enable. Data can only be transferred
into the device when FSYNC is low. To start the serial datatransfer, FSYNC should be taken low, observing the minimum
FSYNC-to-SCLK falling edge setup time (t7). After FSYNC goes
low, serial data is shifted into the input shift register of thedevice 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(t8). Alternatively, FSYNC can be kept low for a multiple of
16 SCLK pulses and then brought high at the end of the datatransfer. In this way, a continuous stream of 16-bit words can beloaded while FSYNC is held low, with FSYNC only going highafter the 16th SCLK falling edge of the last word is loaded.
The SCLK can be continuous, or alternatively, the SCLK canidle high or low between write operations but must be highwhen FSYNC goes low (t12).

POWERING UP THE AD9834
The flow chart in Figure 31 shows the operating routine for theAD9834. When the AD9834 is powered up, the part should bereset. This resets appropriate internal registers to 0 to provide
an analog output of midscale. To avoid spurious DAC outputs
during AD9834 initialization, the RESET bit/pin 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 contain invalid data, and, therefore, should be set to a
known value by the user. The RESET bit/pin should then be set

to 0 to begin generating an output. The data appears on the
DAC output eight MCLK cycles after RESET is set to 0.

LATENCY
Latency is associated with each operation. When Pin FSELECT
and Pin PSELECT change value, there is a pipeline delay before
control is transferred to the selected register. When the t11 andt11A timing specifications are met (see Figure 4), FSELECT and
PSELECT have latencies of eight MCLK cycles. When the t11 andt11A timing specifications are not met, the latency is increased by
one MCLK cycle.
Similarly, there is a latency associated with each asynchronous
write operation. If a selected frequency/phase register is loadedwith a new word, there is a delay of eight to nine MCLK cycles
before the analog output changes. There is an uncertainty of one
MCLK cycle because it depends on the position of the MCLK
rising edge when the data is loaded into the destination register.
The negative transition of the RESET and SLEEP functions are
sampled on the internal falling edge of MCLK. Therefore, theyalso have a latency associated with them.

CONTROL REGISTER
The AD9834 contains a 16-bit control register that sets up theAD9834 as the user wants to operate it. All control bits, except
MODE, are sampled on the internal negative edge of MCLK.
Table 6 describes the individual bits of the control register. The
different functions and the various output options from theAD9834 are described in more detail in the Frequency andPhase Registers section.
To inform the AD9834 that the contents of the control register
are to be altered, DB15 and DB14 must be set to 0 as shown in
Table 5.
Table 5. Control Register
DB15
0Rev. D | Page 18 of 32

DB14
0DB13 . . . DB0
CONTROL bits

Data Sheet

AD9834SLEEP12SLEEP1PHASE
ACCUMULATOR(28-BIT)

SIN
ROM

IOUT

0

(LOW POWER)
10-BIT DAC

MUX
1MODE + OPBITEN
0
MUX

IOUTB

MSB
COMPARATORDIVIDE
BY 2
1

1

MUX

SIGN BIT OUT
02705-026

0

DIGITALOUTPUT(ENABLE)

VIN

SIGN/PIBOPBITEN

Figure 29. Function of Control Bits

DB15
0

DB14
0

DB13
B28

DB12
HLB

DB11
FSEL

DB10
PSEL

DB9
PIN/SW

DB8
RESET

DB7
SLEEP1DB6SLEEP12DB5
OPBITEN

DB4
SIGN/PIB

DB3
DIV2

DB2
0

DB1
MODE

DB0
0

Table 6. Description of Bits in the Control Register
Bit
DB13

Name
B28

DB12

HLB

DB11

FSEL

DB10

PSEL

DB9

PIN/SW

DB8

RESET

DB7

SLEEP1DB6SLEEP12

Description
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 contains the 14 MSBs. The first two bits of each 16-bit
word define the frequency register the word is loaded to and should, therefore, be the same for both of the consecutive
writes. Refer to Table 10 for the appropriate addresses. The write to the frequency register occurs after both words havebeen loaded. An example of a complete 28-bit write is shown in Table 11. Note however, that consecutive 28-bit writes
to the same frequency register are not allowed, switch between frequency registers to do this type of function.
B28 = 0, the 28-bit frequency register operates as two 14-bit registers, one containing the 14 MSBs and the othercontaining 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 DB12 (HLB) informs the AD9834 whether the bits to be altered are the 14 MSBs or 14 LSBs.
This control bit allows the user to continuously load the MSBs or LSBs of a frequency register ignoring the remaining
14 bits. This is useful if the complete 28-bit resolution is not required. HLB is used in conjunction with DB13 (B28). This
control bit indicates whether the 14 bits being loaded are being transferred to the 14 MSBs or 14 LSBs of the addressedfrequency register. DB13 (B28) must be set to 0 to be able to change the MSBs and LSBs of a frequency word separately.
When DB13 (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.
The FSEL bit defines whether the FREQ0 register or the FREQ1 register is used in the phase accumulator. See Table 8 toselect a frequency register.
The PSEL bit defines whether the PHASE0 register data or the PHASE1 register data is added to the output of the phaseaccumulator. See Table 9 to select a phase register.
Functions that select frequency and phase registers, reset internal registers, and power down the DAC can be
implemented using either software or hardware. PIN/SW selects the source of control for these functions.
PIN/SW = 1 implies that the functions are being controlled using the appropriate control pins.
PIN/SW = 0 implies that the functions are being controlled using the appropriate control bits.
RESET = 1 resets internal registers to 0, this corresponds to an analog output of midscale.
RESET = 0 disables RESET. This function is explained in the RESET Function section.
SLEEP1 = 1, the internal MCLK is disabled. The DAC output remains at its present value as the NCO is no longer
accumulating.
SLEEP1 = 0, MCLK is enabled. This function is explained in the SLEEP Function section.
SLEEP12 = 1 powers down the on-chip DAC. This is useful when the AD9834 is used to output the MSB of the DAC data.
SLEEP12 = 0 implies that the DAC is active. This function is explained in the SLEEP Function section.

Rev. D | Page 19 of 32

AD9834
Bit
DB5

Name
OPBITEN

DB4

SIGN/PIB

DB3

DIV2

DB2
DB1

Reserved
MODE

DB0

Reserved

Data Sheet
Description
The function of this bit is to control whether there is an output at the SIGN BIT OUT pin. This bit should remain at 0 if theuser is not using the SIGN BIT OUT pin.
OPBITEN = 1 enables the SIGN BIT OUT pin.
OPBITEN = 0, the SIGN BIT OUT output buffer is put into a high impedance state, therefore no output is available at the
SIGN BIT OUT pin.
The function of this bit is to control what is output at the SIGN BIT OUT pin.
SIGN/PIB = 1, the on-board comparator is connected to SIGN BIT OUT. After filtering the sinusoidal output from the
DAC, the waveform can be applied to the comparator to generate a square waveform. Refer to Table 17.
SIGN/PIB = 0, the MSB (or MSB/2) of the DAC data is connected to the SIGN BIT OUT pin. Bit DIV2 controls whether it is
the MSB or MSB/2 that is output.
DIV2 is used in association with SIGN/PIB and OPBITEN. Refer to Table 17.
DIV2 = 1, the digital output is passed directly to the SIGN BIT OUT pin.
DIV2 = 0, the digital output/2 is passed directly to the SIGN BIT OUT pin.
This bit must always be set to 0.
The function of this bit is to control what is output at the IOUT pin/IOUTB pin. This bit should be set to 0 if the Control
Bit OPBITEN = 1.
MODE = 1, the SIN ROM is bypassed, resulting in a triangle output from the DAC.
MODE = 0, the SIN ROM is used to convert the phase information into amplitude information, resulting in a sinusoidal
signal at the output. See Table 18.
This bit must always be set to 0.

FREQUENCY AND PHASE REGISTERS
The AD9834 contains two frequency registers and two phaseregisters. These are described in Table 7.
Table 7. Frequency/Phase Registers
Register
FREQ0

Size
28 bits

FREQ1

28 bits

PHASE012 bits

PHASE1

12 bits

Description
Frequency Register 0. When either the
FSEL bit or FSELECT pin = 0, this register
defines the output frequency as a fractionof the MCLK frequency.
Frequency Register 1. When either the
FSEL bit or FSELECT pin = 1, this register
defines the output frequency as a fractionof the MCLK frequency.
Phase Offset Register 0. When either the
PSEL bit or PSELECT pin = 0, the contentsof this register are added to the output ofthe phase accumulator.
Phase Offset Register 1. When either the
PSEL bit or PSELECT pin = 1, the contentsof this register are added to the output ofthe phase accumulator.

The analog output from the AD9834 is
fMCLK/228 × FREQREG
where FREQREG is the value loaded into the selected frequency
register. This signal is phase shifted by
2π/4096 × PHASEREG
where PHASEREG is the value contained in the selected phaseregister. Consideration must be given to the relationship of theselected output frequency and the reference clock frequency to
avoid unwanted output anomalies.

Access to the frequency and phase registers is controlled byboth the FSELECT and PSELECT pins, and the FSEL and PSEL
control bits. If the Control Bit PIN/SW = 1, the pins control thefunction; whereas, if PIN/SW = 0, the bits control the function.
This is outlined in Table 8 and Table 9. If the FSEL and PSEL
bits are used, the pins should be held at CMOS logic high or
low. Control of the frequency/phase registers is interchangeablefrom the pins to the bits.
Table 8. Selecting a Frequency Register
FSELECT
0
1
X
X

FSEL
X
X
0
1

PIN/SW1
1
0
0

Selected Register
FREQ0 REG
FREQ1 REG
FREQ0 REG
FREQ1 REG

Table 9. Selecting a Phase Register
PSELECT
0
1
X
X

PSEL
X
X
0
1

PIN/SW1
1
0
0

Selected Register
PHASE0 REG
PHASE1 REG
PHASE0 REG
PHASE1 REG

The FSELECT pin and PSELECT pin are sampled on the internalfalling edge of MCLK. It is recommended that the data on thesepins does not change within a time window of the falling edge of
MCLK (see Figure 4 for timing). If FSELECT or PSELECT changes
value when a falling edge occurs, there is an uncertainty of one
MCLK cycle because it pertains to when control is transferredto the other frequency/phase register.
The flow charts in Figure 32 and Figure 33 show the routine
for selecting and writing to the frequency and phase registersof the AD9834.

Rev. D | Page 20 of 32

Data Sheet

AD9834

WRITING TO A FREQUENCY REGISTER

Table 13. Writing 00FF to the 14 MSBs of FREQ0 REG

When writing to a frequency register, Bit DB15 and Bit DB14
give the address of the frequency register.

SDATA Input
0001 0000 0000 0000

Table 10. Frequency Register Bits
DB15
0
1

DB14
1
0

DB13 . . . DB0
14 FREQ0 REG BITS
14 FREQ1 REG BITS

0100 0000 1111 1111

If the user wants to alter 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, Control Bit B28(DB13) should be set to 1. An example of a 28-bit write isshown in Table 11.
Note however that continuous writes to the same frequency
register are not recommended. This results in intermediate
updates during the writes. If a frequency sweep, or somethingsimilar, is required, it is recommended that users alternate
between the two frequency registers.
Table 11. Writing FFFC000 to FREQ0 REG
SDATA Input
0010 0000 0000 0000
0100 0000 0000 0000
0111 1111 1111 1111

Result of Input Word
Control word write(DB15, DB14 = 00), B28 (DB13) = 1,
HLB (DB12) = X
FREQ0 REG write(DB15, DB14 = 01), 14 LSBs = 0000
FREQ0 REG write (DB15, DB14 = 01),
14 MSBs = 3FFF

In some applications, the user does not need to alter all 28 bitsof the frequency register. With coarse tuning, only the 14 MSBs
are altered; though with fine tuning only the 14 LSBs are altered.
By setting Control Bit B28 (DB13) 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 thatthe 14 MSBs of the frequency word can be altered independentof the 14 LSBs, and vice versa. Bit HLB (DB12) in the control
register identifies the 14 bits that are being altered. Examples ofthis are shown in Table 12 and Table 13.
Table 12. Writing 3FFF to the 14 LSBs of FREQ1 REG
SDATA Input
0000 0000 0000 0000
1011 1111 1111 1111

Result of Input Word
Control word write(DB15, DB14 = 00), B28 (DB13) = 0,
HLB (DB12) = 0, that is, LSBs
FREQ1 REG write(DB15, DB14 = 10), 14 LSBs = 3FFF

Result of Input Word
Control word write(DB15, DB14 = 00), B28 (DB13) = 0,
HLB (DB12) = 1, that is, MSBs
FREQ0 REG write(DB15, DB14 = 01), 14 MSBs = 00FF

WRITING TO A PHASE REGISTER
When writing to a phase register, Bit DB15 and Bit DB14 are set
to 11. Bit DB13 identifies which phase register is being loaded.
Table 14. Phase Register Bits
DB15
1
1

DB14
1
1

DB13
0
1

DB12
X
X

DB11
MSB 12 PHASE0 bits
MSB 12 PHASE1 bits

DB0
LSB
LSB

RESET FUNCTION
The RESET function resets appropriate internal registers to 0 to
provide an analog output of midscale. RESET does not reset thephase, frequency, or control registers.
When the AD9834 is powered up, the part should be reset. To
reset the AD9834, set the RESET pin/bit to 1. To take the partout of reset, set the pin/bit to 0. A signal appears at the DAC
output seven MCLK cycles after RESET is set to 0.
The RESET function is controlled by both the RESET pin andthe RESET control bit. If the Control Bit PIN/SW = 0, the
RESET bit controls the function, whereas if PIN/SW = 1, the
RESET pin controls the function.
Table 15. Applying RESETRESET Pin
0
1
X
X

RESET Bit
X
X
0
1

PIN/SW Bit
1
100

ResultNo reset applied
Internal registers reset
No reset applied
Internal registers reset

The effect of asserting the RESET pin is evident immediately atthe output, that is, the zero-to-one transition of this pin is not
sampled. However, the negative transition of RESET is sampled
on the internal falling edge of MCLK.

SLEEP FUNCTION
Sections of the AD9834 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 DAC can be powered
down through hardware or software. The pin/bits required for
the SLEEP function are outlined in Table 16.

Rev. D | Page 21 of 32

AD9834

Data Sheetfrom the DAC, the waveform can be applied to the comparator
to generate a square waveform.

Table 16. Applying the SLEEP Function
SLEEP
Pin
0
1

SLEEP1Bit
X
X

SLEEP12Bit
X
X

PIN/SW
Bit
1
1

X
X

0
0

0
1

0
0

X

1

0

0

X

1

1

0

ResultNo power-down
DAC powered
down
No power-down
DAC powered
downInternal clock
disabled

MSB from the NCO

Both the DAC
powered down
and the internal
clock disabled

OPBITEN
Bit
0
1
1
1
1
1

DAC Powered Down
This is useful when the AD9834 is used to output the MSB of
the DAC data only. In this case, the DAC is not required andcan be powered down to reduce power consumption.

Internal Clock Disabled
When the internal clock of the AD9834 is disabled, the DAC
output remains at its present value because the NCO is nolonger accumulating. New frequency, phase, and control words
can be written to the part when the SLEEP1 control bit is active.
The synchronizing clock remains active, meaning that the
selected frequency and phase registers can also be changed
either at the pins or by using the control bits. Setting the
SLEEP1 bit to 0 enables the MCLK. Any changes made to theregisters when SLEEP1 is active are observed at the output after
a certain latency.
The effect of asserting the SLEEP pin is evident immediately atthe output, that is, the zero-to-one transition of this pin is not
sampled. However, the negative transition of SLEEP is sampled
on the internal falling edge of MCLK.

SIGN BIT OUT PIN
The AD9834 offers a variety of outputs from the chip. The
digital outputs are available from the SIGN BIT OUT pin. The
available outputs are the comparator output or the MSB of the
DAC data. The bits controlling the SIGN BIT OUT pin are
outlined in Table 17.
This pin must be enabled before use. The enabling/disabling of
this pin is controlled by the Bit OPBITEN (DB5) in the control
register. When OPBITEN = 1, this pin is enabled. Note that the
MODE bit (DB1) in the control register should be set to 0 if
OPBITEN = 1.

The MSB from the NCO can be output from the AD9834. By
setting the SIGN/PIB (DB4) control bit to 0, the MSB of the
DAC data is available at the SIGN BIT OUT pin. This is usefulas a coarse clock source. This square wave can also be divided
by two before being output. Bit DIV2 (DB3) in the control register
controls the frequency of this output from the SIGN BIT OUT pin.
Table 17. Various Outputs from SIGN BIT OUT
MODE
Bit
X
0
0
0
0
1

SIGN/PIB
Bit
X
0
0
1
1
X

DIV2
Bit
X
0
1
0
1
X

SIGN BIT OUT Pin
High impedance
DAC data MSB/2
DAC data MSB
Reserved
Comparator output
Reserved

THE IOUT AND IOUTB PINS
The analog outputs from the AD9834 are available from the
IOUT and IOUTB pins. The available outputs are a sinusoidal
output or a triangle output.

Sinusoidal Output
The SIN ROM converts the phase information from thefrequency and phase registers into amplitude information,
resulting in a sinusoidal signal at the output. To have asinusoidal output from the IOUT and IOUTB pins, set
Bit MODE (DB1) 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, theoutput is no longer sinusoidal. The DAC produces 10-bit linear
triangular function. To have a triangle output from the IOUT
and IOUTB pins, set Bit MODE (DB1) to 1.
Note that the SLEEP pin and SLEEP12 bit must be 0 (that is, theDAC is enabled) when using the IOUT and IOUTB pins.
Table 18. Various Outputs from IOUT and IOUTBOPBITEN Bit
00
1
1

MODE Bit
01
0
1

IOUT and IOUTB Pins
Sinusoid
Triangle
Sinusoid
Reserved

VOUT MAXThe AD9834 has an on-board comparator. To connect thiscomparator to the SIGN BIT OUT pin, the SIGN/PIB (DB4)control bit must be set to 1. After filtering the sinusoidal output

VOUT MIN

Rev. D | Page 22 of 32

3π/2

7π/2

Figure 30. Triangle Output

11π/2

02705-027

Comparator Output

Data Sheet

AD9834

APPLICATIONS INFORMATION
pin, causing the AD9834 to modulate the carrier frequency
between the two values.

Because of the various output options available from the part,the AD9834 can be configured to suit a wide variety of
applications.

The AD9834 has two phase registers, enabling the part toperform PSK. With phase shift keying, the carrier frequency isphase shifted, the phase being altered by an amount that is
related to the bit stream that is input to the modulator.

One of the areas where the AD9834 is suitable is in modulation
applications. The part can be used to perform simple modulationsuch as FSK. More complex modulation schemes such as GMSK
and QPSK can also be implemented using the AD9834.

The AD9834 is also suitable for signal generator applications.
With the on-board comparator, the device can be used togenerate a square wave.

In an FSK application, the two frequency registers of theAD9834 are loaded with different values. One frequency
represents the space frequency, and the other represents themark frequency. The digital data stream is fed to the FSELECT

With its low current consumption, the part is suitable forapplications where it is used as a local oscillator.

DATA WRITE
SEE FIGURE 33

SELECT DATASOURCESSEE FIGURE 34

WAIT 8/9 MCLKCYCLES
SEE TIMING DIAGRAMFIGURE 3

INITIALIZATIONSEE FIGURE 32

DAC OUTPUT
VOUT = VREFOUT × 18 × RLOAD/RSET × (1 + (SIN(2π(FREQREG × fMCLK × t/228 + PHASEREG/212))))YES
CHANGE PHASE?
NOCHANGE FSEL/FSELECT?

YES

NO
YES

CHANGE FREQUENCY?
NO

YES

NO
CHANGE PHASEREGISTER?
YESCHANGE DAC OUTPUTFROM SIN TO RAMP?

CHANGE FREQUENCYREGISTER?
YESNOCONTROLREGISTER
WRITE

YES

CHANGE OUTPUT AT
SIGN BIT OUT PIN?
NO

Figure 31. Flow Chart for Initialization and OperationRev. D | Page 23 of 32

02705-028

YES

CHANGE PSEL/
PSELECT?

AD9834

Data Sheet
INITIALIZATIONAPPLY RESETUSING PIN

USING CONTROLBIT(CONTROL REGISTER WRITE)(CONTROL REGISTER WRITE)RESET = 1
PIN/SW = 0

PIN/SW = 1

SET RESET PIN = 1

WRITE TO FREQUENCY AND PHASE REGISTERS
FREQ0 REG = fOUT0/fMCLK × 228
FREQ1 REG = fOUT1/fMCLK × 228
PHASE0 AND PHASE1 REG = (PHASESHIFT × 2 12)/2π(SEE FIGURE 33)(CONTROL REGISTER WRITE)RESET BIT = 0
FSEL = SELECTED FREQUENCY REGISTERPSEL = SELECTED PHASE REGISTERPIN/SW = 0

USING PIN(APPLY SIGNALS AT PINS)RESET PIN = 0
FSELECT = SELECTED FREQUENCY REGISTERPSELECT = SELECTED PHASE REGISTER

02705-029

USING CONTROLBITSET RESET = 0
SELECT FREQUENCY REGISTERS
SELECT PHASE REGISTERS

Figure 32. Initialization

DATA WRITE

WRITE A FULL 28-BIT WORD
TO A FREQUENCY REGISTER?
YESNOWRITE 14 MSBs OR LSBs
TO A FREQUENCY REGISTER?

NOWRITE TO PHASEREGISTER?

YES
YES(CONTROL REGISTER WRITE)
B28 (D13) = 1(CONTROL REGISTER WRITE)
B28 (D13) = 0
HLB (D12) = 0/1(16-BIT WRITE)(SEE TABLE 11 FOR EXAMPLE)YESWRITE ANOTHER FULL
28-BIT TO A
FREQUENCY REGISTER?
NO

D15, D14 = 11
D13 = 0/1 (CHOOSE THE
PHASE REGISTER)
D12 = X
D11 ... D0 = PHASE DATAWRITE A 16-BIT WORD
(SEE TABLES 12 AND 13
FOR EXAMPLES)WRITE 14 MSBs OR LSBs
TO A
FREQUENCY REGISTER?

NO

Figure 33. Data Write

Rev. D | Page 24 of 32

WRITE TO ANOTHER
PHASE REGISTER?

YES
NO

YES
02705-030

WRITE TWO CONSECUTIVE
16-BIT WORDS

Data Sheet

AD9834
SELECT DATA SOURCESFSELECT AND PSELECTPINS BEING USED?

YESSET FSELECT
AND PSELECTNO(CONTROL REGISTER WRITE)(CONTROL REGISTER WRITE)PIN/SW = 1
02705-031

PIN/SW = 0
SET FSEL BIT
SET PSEL BIT

Figure 34. Selecting Data Sources

Rev. D | Page 25 of 32

AD9834

Data Sheet

GROUNDING AND LAYOUT
The printed circuit board (PCB) that houses the AD9834 should
be designed so that the analog and digital sections are separated
and confined to certain areas of the board. This facilitates theuse of ground planes that can easily be separated. A minimum
etch technique is generally best for ground planes because it
gives the best shielding. Digital and analog ground planes
should only be joined in one place. If the AD9834 is the only
device requiring an AGND-to-DGND connection, the groundplanes should be connected at the AGND and DGND pins of
the AD9834. If the AD9834 is in a system where multiple devices
require AGND-to-DGND connections, the connection should
be made at one point only, establishing a star ground point as
close as possible to the AD9834.
Avoid running digital lines under the device because these
couple noise onto the die. The analog ground plane should beallowed to run under the AD9834 to avoid noise coupling. The
power supply lines to the AD9834 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, suchas 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 it 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 analog and digital supplies
to the AD9834 are independent and separately pinned out tominimize coupling between analog and digital sections of thedevice. All analog and digital supplies should be decoupled to
AGND and DGND, respectively, with 0.1 μF ceramic capacitors
in parallel with 10 μF tantalum capacitors. To achieve the best
performance from the decoupling capacitors, they should beplaced as close as possible to the device, ideally right up against
the device. In systems where a common supply is used to drive
both the AVDD and DVDD of the AD9834, it is recommended
that the system’s AVDD supply be used. This supply should havethe recommended analog supply decoupling between the AVDD
pins of the AD9834 and AGND, and the recommended digital
supply decoupling capacitors between the DVDD pins and DGND.
Proper operation of the comparator requires good layout strategy.
The strategy must minimize the parasitic capacitance between
VIN and the SIGN BIT OUT pin by adding isolation using aground plane. For example, in a multilayered board, the VIN
signal could be connected to the top layer, and the SIGN BIT OUT
could be connected to the bottom layer so that isolation isprovided by the power and ground planes between them.

Rev. D | Page 26 of 32

Data Sheet

AD9834INTERFACING TO MICROPROCESSORSThe AD9834 has a standard serial interface that allows the partto 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 highor low between write operations. When data/control information is
being written to the AD9834, FSYNC is taken low and is held
low until the 16 bits of data are written into the AD9834. The
FSYNC signal frames the 16 bits of information being loaded
into the AD9834.

AD9834 TO 68HC11/68L11 INTERFACE
Figure 36 shows the serial interface between the AD9834 andthe 68HC11/68L11 microcontroller. The microcontroller isconfigured as the master by setting Bit MSTR in the SPCR to 1,
providing a serial clock on SCK while 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)

Figure 35 shows the serial interface between the AD9834 andthe 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 registerand should be configured as follows: Internal clock operation (ISCLK = 1)
 Active low framing (INVTFS = 1)
 16-bit word length (SLEN = 15)

 Data is valid on the SCK falling edge (CPHA = 1)
When data is being transmitted to the AD9834, the FSYNC line istaken low (PC7). Serial data from the 68HC11/68L11 is transmitted
in 8-bit bytes with only eight falling clock edges occurring in thetransmit cycle. Data is transmitted MSB first. To load data into
the AD9834, PC7 is held low after the first eight bits are transferred
and a second serial write operation is performed to the AD9834.
Only after the second eight bits have been transferred should
FSYNC be taken high again.
68HC11/68L111

 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 oneach rising edge of the serial clock and clocked into the AD9834
on the SCLK falling edge.

TFS

FSYNC

DT

SDATA

SCLK

PC7

FSYNC

MOSI

SDATA

SCK

SCLK

1ADDITIONAL PINS OMITTED FOR CLARITY.

Figure 36. 68HC11/68L11 to AD9834 Interface

AD98341SCLK

1ADDITIONAL PINS OMITTED FOR CLARITY.

02705-032

ADSP-21xx1

AD98341

Figure 35. ADSP-21xx to AD9834 Interface

Rev. D | Page 27 of 32

02705-033

AD9834 TO ADSP-21xx INTERFACEAD9834

Data Sheet

AD9834 TO 80C51/80L51 INTERFACE

AD9834 TO DSP56002 INTERFACE

Figure 37 shows the serial interface between the AD9834 andthe 80C51/80L51 microcontroller. The microcontroller isoperated in Mode 0 so that TXD of the 80C51/80L51 drives SCLKof the AD9834, 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 the diagram). When data is to be transmitted to
the AD9834, P3.3 is taken low. The 80C51/80L51 transmits datain 8-bit bytes, thus only eight falling SCLK edges occur in eachcycle. To load the remaining eight bits to the AD9834, P3.3 isheld low after the first eight bits have been transmitted, and asecond write operation is initiated to transmit the second byte ofdata. 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 an LSBfirst format. The AD9834 accepts the MSB first (the four MSBs
being the control information, the next four bits being theaddress, and the eight LSBs containing the data when writing
to a destination register). Therefore, the transmit routine of the
80C51/80L51 must take this into account and rearrange the bitsso that the MSB is output first.

Figure 38 shows the interface between the AD9834 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), andthe frame sync signal frames the 16 bits (FSL = 0). The frame sync
signal is available on Pin SC2, but needs to be inverted before
being applied to the AD9834. The interface to the DSP56000/
DSP56001 is similar to that of the DSP56002.

AD98341

P3.3

FSYNC

RXD

SDATA

TXD

SCLK

1ADDITIONAL PINS OMITTED FOR CLARITY.

02705-034

80C51/80L511

Figure 37. 80C51/80L51 to AD9834 Interface

Rev. D | Page 28 of 32

AD98341

SC2

FSYNC

STD

SDATA

SCK

SCLK

1ADDITIONAL PINS OMITTED FOR CLARITY.

Figure 38. DSP56002 to AD9834 Interface

02705-035

DSP560021

Data Sheet

AD9834OUTLINE DIMENSIONS
6.60
6.50
6.40

20

11

4.50
4.40
4.30
6.40 BSC
1

10

PIN 1
0.65
BSC
1.20 MAX

0.15
0.05
COPLANARITY
0.10

0.30
0.19

0.20
0.09
8°
0°

SEATING
PLANE

0.75
0.60
0.45

COMPLIANT TO JEDEC STANDARDS MO-153-AC

Figure 39. 20-Lead Thin Shrink Small Outline Package [TSSOP](RU-20)Dimensions shown in millimeters

ORDERING GUIDE
Model 1
AD9834BRU
AD9834BRU-REEL
AD9834BRU-REEL7
AD9834BRUZ
AD9834BRUZ-REEL
AD9834BRUZ-REEL7
AD9834CRUZ
AD9834CRUZ-REEL7
1

Maximum MCLK (MHz)
50
50
50
50
50
50
75
75

Temperature Range−40°C to +105°C−40°C to +105°C−40°C to +105°C−40°C to +105°C−40°C to +105°C−40°C to +105°C−40°C to +105°C−40°C to +105°C

Package Description
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]
20-Lead Thin Shrink Small Outline Package [TSSOP]

Z = RoHS Compliant Part.

Rev. D | Page 29 of 32

Package
Option
RU-20
RU-20
RU-20
RU-20
RU-20
RU-20
RU-20
RU-20

AD9834

Data SheetNOTES

Rev. D | Page 30 of 32

Data Sheet

AD9834

NOTES

Rev. D | Page 31 of 32

AD9834

Data Sheet

NOTES©2003–2014 Analog Devices, Inc. All rights reserved. Trademarks andregistered trademarks are the property of their respective owners.
D02705-0-3/14(A)Rev. D | Page 32 of 32