TDA7406 datasheet(18/64 Pages) STMICROELECTRONICS

18 / 64 page

Description of the audioprocessor part

TDA7406

18/64

The root cause of this procedure is, that after muting the stereodecoder (Step 1), the

internal stereodecoder filters have to settle in order to perform a proper offset-cancellation.

4.2.2

AutoZero-Remain

In some cases, for example if the µP is executing a refresh cycle of the IIC-Bus-

programming, it is not useful to start a new AutoZero-action because no new source is

selected and an undesired mute would appear at the outputs. For such applications the

TDA7406 could be switched in the AutoZero-Remain-Mode (Bit 6 of the subaddress-byte).

If this bit is set to high, the DATABYTE 0 could be loaded without invoking the AutoZero and

the old adjustment-value remains.

4.2.3

PAUSE Detector

A pause detector stage with programmable threshold (40/80/160mV) is provided (see data

Byte 14).

The pause detector info is available at the PAUSE pin; a capacitor must be connected

between this pin and GND.

When the incoming signal is detected to be outside the selected window, the external

capacitor is discharged. When the signal is inside the window, the capacitor is integrating

up.

The pause status can be detected in two ways:

reading directly the PAUSE pin level

Pause Off = level low (<3.0V)

Pause On = level high (>3.0V)

by reading the I2C transmitted byte, bit P

P = 1 pause active

P = 0 no pause detected

The external capacitor value fixes the time constant. The pull up current is 25

μA typical.

4.3

Loudness

There are four parameters programmable in the loudness stage:

●

Attenuation: 0 to -19dB attenuation in 1dB steps vs. frequency (see the response at fP

= 400Hz in Figure 4).

●

Peak Frequency: Four programmable peak frequencies: 200,400,600 and 800Hz (see

Figure 5).

●

Filter Order: First or second order frequency response (see Figure 6).

●

Flat mode: Selectable flat-mode. In flat mode the loudness stage works as a 0dB to -

19dB attenuator.

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