Datasheet
AD9822
Rev. B | Page 17 of 20
APPLICATIONS
CIRCUIT AND LAYOUT RECOMMENDATIONS
Figure 16 shows the recommended circuit configuration for
3-channel CDS mode operation. The recommended input
coupling capacitor value is 0.1 µF (see the Circuit Operation
section). A single ground plane is recommended for the
AD9822. A separate power supply may be used for DRVDD,
the digital driver supply, but this supply pin should still be
decoupled to the same ground plane as the rest of the AD9822.
The loading of the digital outputs should be minimized, either
by using short traces to the digital ASIC or by using external
digital buffers. To minimize the effect of digital transients
during major output code transitions, the falling edge of
CDSCLK2 should occur coincident with or before the rising
edge of ADCCLK (see Figure 3 through Figure 6 for timing).
All 0.1 µF decoupling capacitors should be located as close as
possible to the AD9822 pins. When operating in single-channel
mode, the unused analog inputs should be grounded.
Figure 17 shows the recommended circuit configuration for
3-channel SHA mode. All of the above considerations also apply
for this configuration, except that the analog input signals are
directly connected to the AD9822 without the use of coupling
capacitors. The analog input signals must already be dc-biased
between 0 V and 2 V (see the Circuit Operation section).
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
AD9822
CDSCLK1 AVDD
CDSCLK2
ADCCLK
OEB
DRVDD
DRVSS
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0 (LSB)
AVSS
VINR
OFFSET
VING
CML
VINB
CAPT
CAPB
AVSS
AVDD
SLOAD
SCLK
SDATA
3
CLOCK INPUTS
8
DATA OUTPUT
S
0.1µF
3
SERIAL INTERFACE
0.1µF
5V/3V
5V
0.1µF
0.1
µ
F
0.1µF
0.1µF
RED INPUT
GREEN INPUT
BLUE INPUT
0.1µF
0.1µF 1.0µF
0.1µF
0.1µF
+
10µF
5V
0.1µF
00623-017
Figure 16. Recommended Circuit Configuration, 3-Channel CDS Mode
00623-018
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27
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25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
AD9822
CDSCLK1 AVDD
CDSCLK2
ADCCLK
OEB
DRVDD
DRVSS
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0 (LSB)
AVSS
VINR
OFFSET
VING
CML
VINB
CAPT
CAPB
AVSS
AVDD
SLOAD
SCLK
SDATA
3
CLOCK INPUTS
8
DATA OUTPUT
S
0.1µF
3
SERIAL INTERFACE
0.1µF
5V/3V
5V
0.1µF
RED INPUT
GREEN INPUT
BLUE INPUT
0.1µF
0.1µF
0.1µF
+
10µF
5V
0.1µF
Figure 17. Recommended Circuit Configuration, 3-Channel SHA Mode (Analog Inputs Sampled with Respect to Ground)