CS7622 데이터 시트보기 (PDF) - Cirrus Logic

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CS7622

CCD Imager Analog Processor

Cirrus Logic 

CS7622

Black Level Control - Loop Gain, Clamp Length

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

Bit Number

Bit Name

Default

7

blk_gain1

0

6

blk_gain0

0

5

blk_clp_15

1

4

blk_clp_14

0

3

blk_clp_13

1

2

blk_clp_12

0

1

blk_clp_11

1

0

blk_clp_10

0

Bit

Mnemonic

Function

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

7:6

blk_gain1-0

01 - defines a gain of 2x

10 - defines a gain of 4x

11 - defines a gain of 8x

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

5:0

blk_clp_15-10 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)

not fixed

x1

x2

x4

x8

Offset Range = 1

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

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

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

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

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

Table 6.

Where:

K = 1/256*blk_gain

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

fu = update rate

Offset Range = 0

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

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

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

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

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

22

DS322PP1

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