TDA7462 datasheet(10/25 Pages) STMICROELECTRONICS

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SoftMute

The digitally controlled SoftMute stage allows

muting/de-muting the signal with a I

2C bus pro-

grammable slope. The mute process can either

be activated by the SoftMute pin(SM) or by the

2C bus. This slope is realized in a special S-

shaped curve to mute slow in the critical regions

(see Figure 6).

For timing purposes the Bit 3 of the I

2C bus out-

put register is set to 1 from the start of muting un-

til the end of de-muting.

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 in

four steps.

-20.0

-15.0

-10.0

-5.0

0.0

10.0

100.0

1.0K

10.0K

Figure 3. Loudness Attenuation @ fc = 400Hz

(second order)

-20.0

-15.0

-10.0

-5.0

0.0

10.0

100.0

1.0K

10.0K

Figure 4. Loudness Center frequency @ Attn.

= 15dB (second order)

100

1,000

-20

-15

-10

-5

(dB)

D98AU844

Figure 5. Loudness @ Attn. = 15dB, fc = 400Hz

EXT.

MUTE

+SIGNAL

REF

-SIGNAL

2C BUS

OUT

Time

D97AU634

Figure 6. Softmute Timing

2dB

1dB

-1dB

-2dB

Time

D97AU635

VOUT

10ms

Figure 7. Soft Step Timing

Note: Please notice that a started Mute action is always terminated

and could not be interrupted by a change of the mute signal.

Note: For steps more than 1dB the softstep mode should be

deactivated because it could generate a 1dB error during the

blend-time

TDA7462

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