CS7622 datasheet(22/36 Pages) CIRRUS

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CS7622

DS322PP1

Black Level Control - Loop Gain, Clamp Length

Default = 2Ah; Read/Write (address 0Dh

)

Where:

K = 1/256*blk_gain

n = Black loop clamp length = blk_clp_l[5:0]

fu = update rate

Bit Number

765432

Bit Name

blk_gain1

blk_gain0

blk_clp_15

blk_clp_14

blk_clp_13

blk_clp_12

blk_clp_11

blk_clp_10

Default

001010

Bit

Mnemonic

Function

7:6

blk_gain1-0

Black Loop Gain Factor: can be set to 1x,2x,4x,or 8x and is simply a multiply-

ing constant to effect the weight of each black pixel before it is accumulated.

00 - defines a gain of 1x

01 - defines a gain of 2x

10 - defines a gain of 4x

11 - defines a gain of 8x

5:0

blk_clp_15-10

Black Loop Clamp Length: The black clamp length effects the loop time con-

stant and also acts to average out noise in the black level. The larger this value

the more pixels that are summed before the loop is updated which causes

greater averaging and a smaller settling time constant.

The table below shows the black loop time constant for various settings of Off-

set Range (register 04h, bit 0) and Fixed Gain Settings (register 14h, bits 5-3).

(See Table 5)

Fixed Gain

(Register 16h)

Offset Range = 1

Offset Range = 0

not fixed

-1/(ln(1-nK))(1/fu)

-1/(ln(1-nK/2))(1/fu)

-1/(ln(1-nK/8))(1/fu)

-1/(ln(1-nK/16))(1/fu)

-1/(ln(1-nK/4))(1/fu)

-1/(ln(1-nK/8))(1/fu)

-1/(ln(1-nK/2))(1/fu)

-1/(ln(1-nK/4))(1/fu)

-1/(ln(1-nK))(1/fu)

-1/(ln(1-nK/2))(1/fu)

Table 6.

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