TDA7718B datasheet(23/40 Pages) STMICROELECTRONICS

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TDA7718B

Description of the audioprocessor

4.9

Soft-step control

In this device, the soft-step function is available for volume, speaker, loudness, treble,

middle and bass block. With soft-step function, the audible noise of DC offset or the sudden

change of signal can be avoided when adjusting gain setting of the block.

For each block, the soft-step function is controlled by soft-step soft-step on/off control bit in

the control table. The soft-step transient time selection (5 ms or 10 ms) is common for all

blocks and it is controlled by soft-step time control bit. The soft-step operation of all blocks

has a common centralized control. In this case, a new soft-step operation can not be started

before the completion previous soft-step.

There are two different modes to activate the soft-step operation. The soft-step operation

can be started right after I2C data sending, or the soft-step can be activated in parallel after

data sending of several different blocks. The two modes are controlled by the ‘act bit’ (it is

normally bit7 of the byte.) of each byte. When act bit is ‘0’, which means action, the soft-step

is activated right after the date byte is sent. When the act bit is ‘1’, which means wait, the

block goes to wait for soft-step status. In this case, the block will wait for some other block to

activate the operation. The soft-step operation of all blocks in wait status will be done

together with the block which activate the soft-step. With this mode, all specific blocks can

do the soft-step in parallel. This avoids waiting when the soft-step is operated one by one.

 Soft-step start here

 Soft-step

start here for all

Chip Addr

Sub Addr

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Chip Addr

Sub Addr

1xxxxxxx

......

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TDA7718B 数据表(PDF) 23 Page - STMicroelectronics