TDA7718B Datasheet, PDF (23/40 Pages) STMicroelectronics – 3 band car audio processor

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.
Chip Addr Sub Addr 0xxxxxxx
| Soft-step start here
Chip Addr Sub Addr 1xxxxxxx 1xxxxxxx ......
0xxxxxxx
| Soft-step
start here for all
DocID18305 Rev 3
23/40