AD9822

Rev. B | Page 14 of 20

PGA Gain Registers

There are three PGA registers for individually programming the gain in the red, green, and blue channels. Bits D8, D7, and D6 in each

register must be set low, and Bits D5 through D0 control the gain range in 64 increments. See Figure 15 for the PGA gain vs. the PGA

register code. The coding for the PGA registers is straight binary, with an all 0s word corresponding to the minimum gain setting (1×)

and an all 1s word corresponding to the maximum gain setting (5.7×).

Table 9. PGA Gain Register Settings

D8

D7

D6

D5

D4

D3

D2

D1

D0

Set to 0

Set to 0

Set to 0

MSB

LSB

Gain (V/V)

Gain (dB)

0

0

0

0

0

0

0

0

01

1.0

0.0

0

0

0

0

0

0

0

0

1

1.013

0.12

•

•

•

•

•

•

•

•

•

0

0

0

1

1

1

1

1

0

5.4

14.6

0

0

0

1

1

1

1

1

1

5.7

15.1

Offset Registers

There are three PGA registers for individually programming the offset in the red, green, and blue channels. Bits D8 through D0 control

the offset range from −350 mV to +350 mV in 512 increments. The coding for the offset registers is sign magnitude, with D8 as the sign

bit. Table 10 shows the offset range as a function of the Bits D8 through D0.

Table 10. Offset Register Settings

D8 (MSB)

D7

D6

D5

D4

D3

D2

D1

D0 (LSB)

Offset (mV)

0

0

0

0

0

0

0

0

01

0

0

0

0

0

0

0

0

0

1

+1.2

•

•

•

•

•

•

0

1

1

1

1

1

1

1

1

+350

1

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

1

−1.2

•

•

•

•

•

•

1

1

1

1

1

1

1

1

1

−350