TDA7406 Datasheet, PDF (18/64 Pages) STMicroelectronics – Car radio signal processor

Description of the audioprocessor part
TDA7406
4.2.2
4.2.3
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.
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.
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:
a) reading directly the PAUSE pin level
Pause Off = level low (<3.0V)
Pause On = level high (>3.0V)
b) 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 25μA 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 f_P
= 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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