ADV7181BBCPZ datasheet(30/96 Pages) AD

30 / 96 page

ADV7181B

Rev. 0 | Page 30 of 96

Table 31. AGC Modes

Input Video Type

Luma Gain

Chroma Gain

Any

Manual gain luma.

Manual gain chroma.

Dependent on color burst amplitude.

Dependent on horizontal sync depth.

Taken from luma path.

Dependent on color burst amplitude.

CVBS

Peak White.

Taken from luma path.

Dependent on color burst amplitude.

Dependent on horizontal sync depth.

Taken from luma path.

Dependent on color burst amplitude.

Y/C

Peak White.

Taken from luma path.

YPrPb

Dependent on horizontal sync depth.

Taken from luma path.

Luma Gain

LAGC[2:0] Luma Automatic Gain Control, Address 0x30 [7:0]

The luma automatic gain control mode bits select the mode of

operation for the gain control in the luma path.

There are ADI internal parameters to customize the peak white

gain control. Contact ADI for more information.

Table 32. LAGC Function

LAGC[2:0]

Description

000

Manual fixed gain (use LMG[11:0]).

001

AGC (blank level to sync tip). No override through

peak white.

010(default)

AGC (blank level to sync tip). Automatic override

through peak white.

011

Reserved.

100

Reserved.

101

Reserved.

110

Reserved.

111

Freeze gain.

LAGT[1:0] Luma Automatic Gain Timing, Address 0x2F [7:6]

The luma automatic gain timing register allows the user to

influence the tracking speed of the luminance automatic gain

control. Note that this register only has an effect if the

LAGC[2:0] register is set to 001, 010, 011, or 100 (automatic

gain control modes).

If peak white AGC is enabled and active (see the

STATUS_1[7:0] Address 0x10 [7:0] section), the actual gain

update speed is dictated by the peak white AGC loop and, as a

result, the LAGT settings have no effect. As soon as the part

leaves peak white AGC, LAGT becomes relevant again.

The update speed for the peak white algorithm can be

customized by the use of internal parameters. Contact ADI for

more information.

Table 33. LAGT Function

LAGT[1:0]

Description

Slow (TC = 2 sec)

Medium (TC = 1 sec)

Fast (TC = 0.2 sec)

11 (default)

Adaptive

LG[11:0] Luma Gain, Address 0x2F [3:0];

Address 0x30 [7:0]; LMG[11:0] Luma Manual Gain,

Address 0x2F [3:0]; Address 0x30 [7:0]

Luma gain [11:0] is a dual-function register. If written to, a

desired manual luma gain can be programmed. This gain

becomes active if the LAGC[2:0] mode is switched to manual

fixed gain. Equation 1 shows how to calculate a desired gain.

If read back, this register returns the current gain value.

Depending on the setting in the LAGC[2:0] bits, this is one of

the following values:

•

Luma manual gain value (LAGC[2:0] set to luma manual

gain mode)

•

Luma automatic gain value (LAGC[2:0] set to any of the

automatic modes)

Table 34. LG/LMG Function

LG[11:0]/LMG[11:0]

Read/Write

Description

LMG[11:0] = X

Write

Manual gain for luma

path.

LG[11:0]

Read

Actually used gain.

(

)

...

2048

4095

≤

Gain

Luma

(1)

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