CM6533DH datasheet(23/60 Pages) CMEDIA

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CM6533,CM6533N,CM6533X1,CM6533DH

USB Audio Chip

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Rev.1.6

6.2 Recording Equalizer

CM6533/CM6533N/CM6533X1/CM6533DH also provide five (5)-band equalizer for the input. It can be used to

compensate the frequency response of microphone unit. Clients could fully customize all EQ coefficients (center

frequency, gain values, and bandwidth) through embedded FLASH.

6.3 Recording AGC

Automatic Gain Control (AGC) is an automatically controlled method to adjust with respect to the intensity of

signal; AGC closes the return circuit which is by the negative response system too.

AGC is by way of compressing volume, will increase Gain first when AGC is started to set up the upper and lower

limits of the signal. Then, it will compress the dynamic range of sound. It usually uses the occasion of AGC, should

there be recording and producing and speaking sound, or volume is being changed under little environment. If the

lasting low voice of volume, AGC will enlarge volume then volume is sustained loudly while AGC will reduce volume.

Features

Programmable AGC Parameters

Selectable Gain from –12 dB to 45 dB in 1-dB Steps

Selectable Attack, Release and Hold Times

AGC Enable/Disable Function

Limiter Enable/Disable Function

Pre-Detect Limiter Level Function

Two-Channel AGC Independent

Under input source types, to set AGC gain max/min limit

Dig mic

+20 ~ -16DB

0xf9= 0x24 (max)+fix gain(9db) =0x2d

0xfA= 0x00(min)

Analog mic

+30 ~ 0DB

0xf9=0x0F+fix gain(9db) inv -> 0x39(max)

0xfA=0x2D

inv -> 0x12(min)

AGC variable description

Fixed Gain:

The normal gain of the device when the AGC is inactive

Limiter Level: The value that sets the maximum allowed output amplitude

Attack Time:

The minimum time between two gain decrements

Release Time: The minimum time between two gain increments

Hold Time:

The time it takes for the very first gain increment after the input signal amplitude decreases

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