TDA7419_09 Datasheet, PDF (16/40 Pages) STMicroelectronics – 3 band car audio processor

Description of the audio processor
Figure 3. Input stage
QD_L
QD_G
QD_R
QD
QD
SE1_L
SE1_R
SE4
SE1
SE1
SE2_L
SE2_R
SE2
SE2
AC2IN_L/SE3L
AC2IN_R/SE3R
SE3
SE3
TDA7419
Main
Source
In Gain
Second
Source
Output Stage
4.3
4.3.1
4.4
4.4.1
AutoZero
The AutoZero allows a reduction of the number of pins as well as external components by
canceling any offset generated by or before the In-Gain-stage (Please notice that externally
generated offsets, e.g. generated through the leakage current of the coupling capacitors,
are not canceled).
The auto-zeroing is started every time the input source is changed and needs max. 0.3ms
for the alignment. To avoid audible clicks the Audio processor is muted before the loudness
stage during this time. The AutoZero feature is only present in the main signal-path.
AutoZero remain
In some cases, for example if the µP is executing a refresh cycle of the I²C 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, it can
be switched in the AutoZero remain mode (bit 6 of the subaddress byte). If this bit is set to
high, the AutoZero will not be invoked and the old adjustment-value remains.
Loudness
There are four parameters programmable in the loudness stage:
Attenuation
Figure 4 shows the attenuation as a function of frequency at f_P = 400 Hz
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