TDA7402_07 datasheet(21/71 Pages) STMICROELECTRONICS

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TDA7402

Audioprocessor part

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4.4

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 Bit0 of the I2C bus output register is set to 1 from the start of muting

until the end of de-muting.

Figure 7.

Softmute timing

Note:

Please notice that a started mute action is always terminated and could not be interrupted

by a change of the mute -signal.

4.5

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 audiosignal. 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 in four steps.

Figure 8.

SoftStep timing

EXT.

MUTE

+SIGNAL

REF

-SIGNAL

2C BUS

OUT

Time

D97AU634

1dB

0.5dB

-0.5dB

-1dB

Time

D00AU1170

VOUT

SS Time

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