TDA7718N Datasheet, PDF (17/40 Pages) STMicroelectronics – 3 band car audio processor

TDA7718N
Description of the audioprocessor
4.3
SoftMute
The digitally controlled SoftMute stage allows muting/demuting the signal with a I²C bus
programmable slope. The mute process can either be activated by the SoftMute pin or by
the I²C bus. This slope is realized in a special S-shaped curve to mute slow in the critical
regions (see Figure 7).
For timing purposes the bit 0 of the I²C bus output register is set to 1 from the start of muting
until the end of demuting.
Figure 7. SoftMute timing
1
EXT.
MUTE
Note:
+SIGNAL
REF
-SIGNAL
1
I²C BUS
OUT
D97AU634
Time
Please notice that a started mute-action is always terminated and could not be interrupted
by a change of the mute –signal.
4.4
SoftStep volume
When the volume-level is changed audible clicks could appear at the output. The root cause
of those clicks could either be a DC-offset before the volume-stage or the sudden change of
the envelope of the audio signal. With the SoftStep-feature both kinds of clicks could be
reduced to a minimum and are no more audible. The blend-time from one step to the next is
programmable as 5 ms or 10 ms. The SoftStep control is described in detail in Chapter 4.9.
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