TDA7719 datasheet(24/45 Pages) STMICROELECTRONICS

24 / 45 page

Description

TDA7719

24/45

4.10

Softstep control

In this device, the softstep function is available for volume, speaker, loudness, treble, middle

and bass block. With softstep 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 softstep function is controlled by softstep on/off control bit in the control

table. The softstep transient time selection (5ms or 10ms) is common for all blocks and it is

controlled by softstep time control bit. The softstep operation of all blocks has a common

centralized control. In this case, a new softstep operation can not be started before the

completion previous softstep.

There are two different modes to activate the softstep operation. The softstep operation can

be started right after I2C data sending, or the softstep 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 softstep

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

block goes to wait for softstep status. In this case, the block will wait for some other block to

activate the operation. The softstep operation of all blocks in wait status will be done

together with the block which activate the softstep. With this mode, all specific blocks can do

the softstep in parallel. This avoids waiting when the softstep is operated one by one.

↑ Softstep start here

↑ Softstep start

here for all

It is not allowed to cross 0dB with softstep directly. From plus gain to minus gain, it must

go to +0dB first, then destination. From minus gain to plus gain, it must go to -0dB first,

and then destination.

When one block is in ‘wait for softstep’ status, it is not allowed to send data to this block

again before its softstep is completed.

To know if there is a softstep in operation, it is possible to monitor the ‘busy’ signal by

I2C transmission mode (Section 5.1.2). When softstep is busy (busy=0), it is better to

wait before sending new data until it is free (busy=1).

Chip Addr

Sub Addr

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Chip Addr

Sub Addr

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