REV. B
AD9845B
–21–
Internal Power-On Reset Circuitry
After power-on, the AD9845B 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 opera-
tion is completed.
Grounding and Decoupling Recommendations
As shown in Figure 33, a single ground plane is recommended
for the AD9845B. This ground plane should be as continuous
as possible, particularly around Pins 25–39. 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 AD9845B, 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. 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 (Pins 1–12) must drive a load larger than 20 pF, buff-
ering is recommended to reduce digital code transition noise.
Alternatively, placing series resistors close to the digital out-
put pins may also help reduce noise.
Pin 37 on the AD9845A was called CML and required a 0.1 mF
bypass capacitor to ground. Pin 37 is not internally connected
on the AD9845B, and so the older AD9845A bypass capacitor
may be left in place. All NC pins are not internally connected on
the AD9845B and may be left floating or tied to ground.
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
3748 47 46 45 44 39 3843 42 41 40
PIN 1
IDENTIFIER
TOP VIEW
(Not to Scale)
AUX1IN
AVSS
AUX2IN
AVDD2
BYP3
NC
CCDIN
BYP2
BYP1
AVDD1
AVSS
AVSS
D0
D1
D2
D3
D4
D5
D6
D7
D8
(MSB) D11
AD9845B
NC
NC
SCK
SDATA
SL
STBY
DVSS
DVDD2
VRB
VRT
NC
DRVDD
DRVSS
DVSS
DATACLK
DVDD1
HD
PBLK
CLPOB
SHP
SHD
CLPDM
VD
3V
ANALOG SUPPLY
CCD SIGNAL
3V
ANALOG SUPPLY
12
DATA
OUTPUTS
3
SERIAL
INTERFACE
3V
ANALOG SUPPLY
8
CLOCK
INPUTS
3V
ANALOG SUPPLY
3V
DRIVER
SUPPLY
NC = INTERNALLY NOT CONNECTED
D9
D10
NC
0.1 F
1.0 F
1.0 F
0.1 F
0.1 F
0.1 F
0.1 F
0.1 F
0.1 F
0.1 F
0.1 F
Figure 33. Recommended Circuit Configuration for CCD-Mode
