TDA7461N datasheet(9/31 Pages) STMICROELECTRONICS

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Mixing Stage

This stage offers the possibility to mix the internal

beep or the phone signal to any other source.

Due to the fact that the mixing stage is also lo-

cated behind the In-Gain stage fine adjustments

of the main source level can be done in this way.

Loudness

There are four parameters programmable in the

loudness stage (see fig. 3, 4, 5):

- Attenuation

- Center Frequency

- Loudness Q

- Flat Mode: in this mode the loudness stage works

as a 0 - 15dB attenuator.

Softmute

The digitally controlled softmute stage allows

muting/demuting the signal with a I

2C bus pro-

grammable slope. The mute process can either

be activated by the softmute pin or by the I

bus. The slope is realized in a special S shaped

curve to mute slow in the critical regions (see fig-

ure 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 demuting.

15K

100K

CDGND

15K

PHONE

PH_GND

15K

D97AU633A

100K

STEREODECODER

IN GAIN

CASSETTE

MPX

Figure 2. Input stages

-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)

TDA7461N

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