AD9943/AD9944

Rev. B | Page 19 of 20

24

REFB

23

REFT

22

CCDIN

21

AVSS

D2

1

D3

2

D0

D1

D4

3

20

AVDD

19

SHD

18

SHP

17

CLPOB

D5

4

D6

5

D7

6

D8

7

D9

8

DATA

OUTPUTS

12

910

3V

DRIVER

SUPPLY

3V

ANALOG

SUPPLY

3V

ANALOG

SUPPLY

12 13 14 15 16

5

CLOCK

INPUTS

3

SERIAL

INTERFACE

CCDIN

AD9944

(Not to Scale)

TOP VIEW

1.0

µF

1.0

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

NC = NO CONNECT

PIN 1

IDENTIFIER

32 31 30 29 28 27 26 25

11

Figure 18. AD9944 Recommended Circuit Configuration for CCD Mode

INTERNAL POWER-ON RESET CIRCUITRY

After power-on, the AD9943/AD9944 automatically reset all

internal registers and perform internal calibration procedures.

This takes approximately 1 ms to complete. During this time,

normal clock signals and serial write operations may occur.

However, serial register writes are ignored until the internal

reset operation is completed.

GROUNDING AND DECOUPLING

RECOMMENDATIONS

As shown in Figure 17 and Figure 18, a single ground plane is

recommended for the AD9943/AD9944. This ground plane

should be as continuous as possible. This ensures that all analog

decoupling capacitors provide the lowest possible impedance

path between the power and bypass pins and their respective

ground pins. All decoupling capacitors should be located as

close as possible to the package pins. A single clean power

supply is recommended for the AD9943 and AD9944, but a

separate digital driver supply may be used for DRVDD (Pin 11).

DRVDD should always be decoupled to DRVSS (Pin 12), which

should be connected to the analog ground plane. Advantages of

using a separate digital driver supply include using a lower

voltage (2.7 V) to match levels with a 2.7 V ASIC, and reducing

digital power dissipation and potential noise coupling. If the

digital outputs must drive a load larger than 20 pF, buffering

is the recommended method to reduce digital code transition

noise. Alternatively, placing series resistors close to the digital

output pins may also help reduce noise.

Note: The exposed pad on the bottom of the AD9943/AD9944

should be soldered to the GND plane of the printed circuit

board.