TDA7406 Datasheet, PDF (20/64 Pages) STMicroelectronics – Car radio signal processor

Description of the audioprocessor part
TDA7406
4.4
Soft Mute
The digitally controlled Soft Mute stage allows signal muting/demutingwith a programmable
slope. The Mute time is selectable among 4 values: 0.48, 0.96, 123 and 324ms. The mute
process can either be activated by the Soft Mute pin or via 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 I²C-bus output register (Bit0 = SM read bit) is set to 1 from the start
of muting until the end of de-muting.
Figure 7. Soft Mute-Timing
Note:
4.5
4.5.1
4.5.2
Please notice that a started Mute-action is always terminated and could not be interrupted
by a change of the mute -signal.
Volume Control
Gain/Attenuation Control
The volume control can range from a gain of 32dB up to an attenuation of 79dB; however it
is not recommended to use a gain higher than 20dB for performance reasons.
Soft Step Volume
When the speaker-level is changed, audible clicks could appear at the output. The root
cause of those clicks could either be a DC offset before the speaker-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 with four different values: 320μs, 1.28ms, 5.12ms and 20.4ms.
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