MT9P006

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22

offset of between –2048 and 2047 is added. The resulting

The analog offset applied is determined automatically by

the black level calibration algorithm, which attempts to shift

the output of the analog signal chain so that black is at a

particular level. The digital offset is a fine-tuning of the

analog offset.

Pixel

Voltage

Digital

Gain

Analog

Gain

Digital Datapath

X

+

Analog Signal Chain

X

+

Digital

Offset

Correction

Black

Level

Calibration

ADC

Analog

Offset

Gain

There are two types of gain supported: analog gain and

digital gain. Combined, gains of between 1 and 128 are

possible. The recommended gain settings are shown in

Table 15.

Table 15. GAIN INCREMENT SETTINGS

Gain Range

Increments

Digital Gain

Analog Multipier

Analog Gain

1– 4

0.125

0

0

8–32

4.25–8

0.25

0

1

17–32

9–128

1

1–120

1

32

1. Analog gain should be maximized before applying digital gain.

2. The recommended minimum gain is 1.38 (0x000B)

3. For optimal sensor performance, when using gain settings <= 4.0, also set reserved register R0x3E = 0x0080 and for gain settings >4.0,

set register R0x003E=0x00C0.

The combined gain for a color C is given by:

Table 16. ISO GAIN SETTINGS

ISO Level

Register Address

Register Value

Gain Value

(with Col_sum=0)

(with Col_sum=1)

(with Col_sum=0)

(with Col_sum=1)

ISO 142 (min)

0x35

0x000B

0x0006

1.38

0.75

ISO 200

0x35

0x0010

0x0008

2.00

1.00

ISO 400

0x35

0x0020

0x0010

4.00

2.00

ISO 800

0x35

0x0060

0x0020

8.00

4.00

ISO 1600

0x35

0x0860

0x0060

16.00

8.00

1. The minimum ISO level is ISO 142.

Analog Gain

The analog gain is specified independently for each color

channel. There are two components, the gain and the

multiplier. The gain is specified by Green1_Analog_Gain,

Red_Analog_Gain, Blue_Analog_Gain, and

Green2_Analog_Gain in steps of 0.125. The analog

multiplier is specified by Green1_Analog_Multiplier,

Red_Analog_Multiplier, Blue_Analog_Multiplier, and

Green2_Analog_Multiplier. These combine to form the

analog gain for a given color C as shown in this equation:

8)

The gain component can range from 0 to 7.875 in steps of

0.125, and the multiplier component can be either 0 or 1

(resulting in a multiplier of 1 or 2). However, it is best to keep

the “gain” component between 1 and 4 for the best noise