AD9943 Analog Devices, AD9943 Datasheet - Page 19

• Manufacturer Part Number: AD9943
• Description: Complete 10-Bit and 12-Bit/ 25 MHz CCD Signal Processors
• Manufacturer: Analog Devices

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
OUTPUTS
DATA
12
NC = NO CONNECT
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
Figure 18. AD9944 Recommended Circuit Configuration for CCD Mode
SUPPLY
DRIVER
1
2
3
4
5
6
7
8
INTERFACE
3V
32 31 30 29 28 27 26 25
9 10
SERIAL
0.1µF
PIN 1
IDENTIFIER
11
(Not to Scale)
TOP VIEW
AD9944
12 13 14 15 16
Rev. B | Page 19 of 20
3
0.1µF
3V
ANALOG
SUPPLY
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.
24
23
22
21
20
19
18
17
REFB
REFT
CCDIN
AVSS
AVDD
SHD
SHP
CLPOB
0.1µF
1.0µF
1.0µF
5
CLOCK
INPUTS
0.1µF
3V
ANALOG
SUPPLY
CCDIN
AD9943/AD9944