
REV. 0
AD9846A
–21–
Internal Power-On Reset Circuitry
After power-on, the AD9846A will automatically reset all inter-
nal 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 will be ignored until the internal reset
operation is completed. Pin 43 (formerly RSTB on the AD984x
non-A products) is no longer used for the reset operation.
Toggling Pin 43 in the AD9846A will have no effect.
Grounding and Decoupling Recommendations
As shown in Figure 33, a single ground plane is recommended
for the AD9846A. This ground plane should be as continuous
as possible, particularly around Pins 25 through 39. This will
ensure 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 AD9846A, but
a separate digital driver supply may be used for DRVDD (Pin
13). DRVDD should always be decoupled to DRVSS (Pin 14),
which should be connected to the analog ground plane. Advan-
tages of using a separate digital driver supply include using a lower
voltage (2.7 V) to match levels with a 2.7 V ASIC, reducing digital
power dissipation, and reducing potential noise coupling. If the
digital outputs (Pins 3–12) must drive a load larger than 20 pF,
buffering is recommended to reduce digital code transition noise.
Alternatively, placing series resistors close to the digital out-
put pins may also help reduce noise.
36
35
34
33
32
31
30
29
28
27
26
25
13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
10
11
12
37
48 47 46 45 44
39 38
43 42 41 40
PIN 1
IDENTIFIER
TOP VIEW
(Not to Scale)
AUX1IN
AVSS
AUX2IN
AVDD2
BYP4
NC
CCDIN
BYP2
BYP1
AVDD1
AVSS
D0
D1
D2
D3
D4
D5
D6
D7
D8
NC
(MSB) D9
AD9846A
SCK
SDATA
SL
NC
STBY
NC
THREE-STATE
DVSS
DVDD2
VRB
VRT
CML
DRVDD
DRVSS
DVSS
DATACLK
DVDD1
HD
PBLK
CLPOB
SHP
SHD
CLPDM
VD
0.1 F
3V
ANALOG SUPPLY
CCD SIGNAL
3V
ANALOG SUPPLY
12
DATA
OUTPUTS
3
SERIAL
INTERFACE
0.1 F
1.0 F
0.1 F
3V
ANALOG SUPPLY
8
CLOCK
INPUTS
0.1 F
3V
ANALOG SUPPLY
3V
DRIVER
SUPPLY
NC = NO CONNECT
Figure 33. Recommended Circuit Configuration for CCD-Mode