VS6663CD datasheet(46/64 Pages) STMICROELECTRONICS

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Video timing

VS6663CD

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Doc ID027033 Rev 2

6.3.2

Digital gain

To help compensate for the relatively coarse analogue gain steps, VS6663CD contains a

digital multiplier to “fill” in the missing steps. By mixing analogue and digital gain it is

possible to implement 3% gain steps across the full 1x to 16x gain range

The details of the digital gain implementation are listed below:

•

four individual 16-bit digital channel gains - one per Bayer channel

–

digital_gain_greenR (0x020E and 0x020F)

–

digital_gain_red (0x0210 and 0x0211)

–

digital_gain_blue (0x0212 and 0x0213)

–

digital_gain_greenB (0x0214 and 0x0215)

•

The digital gain range for each channel is 0.0039 to 1.996 in steps of 0.0039 (1/256)

–

digital_gain_min {0x1084:0x1085} = 0x0001 (0.0039)

–

digital_gain_max {0x1086:0x1087} = 0x01FF (1.996)

–

digital_gain_step {0x1088:0x1089} = 0x0001 (0.0039)

6.3.3

Integration and gain parameter retiming

The modification of exposure parameter (coarse integration time or gain) register values

does not take effect immediately.

The exact time at which changes to certain parameters take effect is controlled both to

ensure that each frame of image data produced has consistent settings and that changes in

groups of related parameters can be synchronized.

To eliminate the possibility of the sensor array seeing only part of the new exposure and

gain setting, if the serial interface communications extends over a frame boundary, the

internal retiming of exposure and gain data is disabled while writing data to the serial

interface register map. Therefore if the 4 bytes of exposure and gain data is sent as an auto-

0x0040

0100

2.5 dB (x1.33)

0x0050

0101

3.2 dB (x1.45)

0x0060

0110

4.1 dB (x1.60)

0x0070

0111

5.0 dB (x1.78)

0x0080

1000

6.0 dB(x2.00)

0x0090

1001

7.2 dB (x2.29)

0x00A0

1010

8.5 dB (x2.66)

0x00B0

1011

10.1 dB (x3.20)

0x00C0

1100

12.0 dB (x4.00)

0x00D0

1101

14.5 dB (x5.33)

0x00E0

1110

18.1 dB (x8.00)

0x00F0

1111

24.1 dB (x16.00)

Table 25. Analog gain control (continued)

Gain value (0x0204/0x0205)

Coarse gain code [A7:A4]

Coarse analog gain

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