TDA7461 Ver la hoja de datos (PDF) - STMicroelectronics

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TDA7461

Car radio signal processor

STMicroelectronics 

TDA7461

Description of the audio processor part

Figure 7.

Loudness attenuation = 15 dB @ fc = 400 Hz

(dB)

D98AU844

-5

-10

-15

3.3.2

-20

10

100

1,000

Hz

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. The slope is realized in a special S shaped curve to mute slow in the critical regions

(see Figure 8). For timing purposes the Bit 3 of the I2C bus output register is set to 1 from

the start of muting until the end of demuting.

Figure 8. Softmute timing

3.3.3

1

EXT.

MUTE

+SIGNAL

REF

-SIGNAL

1

I2C BUS

OUT

D97AU634

Time

1. Please notice that a started Mute action is always terminated and could not be interrupted by a change of

the mute signal.

Soft step volume

When volume level is changed often an audible click appears at the output. The root cause

of those clicks could be either a DC offset before the volume stage or the sudden change of

the envelope of the audio signal. With the Soft step feature both kinds of clicks could be

reduced to a minimum and are no more audible (see Figure 9).

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