AD9837

Data Sheet

Rev. A | Page 6 of 28

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

COMP

1

VDD

2

CAP/2.5V

3

DGND

4

MCLK

5

VOUT

10

AGND

9

FSYNC

8

SCLK

7

SDATA

6

AD9837

TOP VIEW

(Not to Scale)

NOTES

1. CONNECT EXPOSED PAD

TO GROUND.

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.