Datasheet

Description of the audio processor TDA7419
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Figure 3. Input stage
4.3 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.
4.3.1 AutoZero remain
In some cases, for example if the µP is executing a refresh cycle of the I
2
C 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.
4.4 Loudness
There are four parameters programmable in the loudness stage:
4.4.1 Attenuation
Figure 4 shows the attenuation as a function of frequency at f
P
= 400 Hz
Output Stage
QD
QD_L
QD_R
QD_G
SE3
SE2
SE2_L
SE2_R
QD
SE1
SE2
SE3
Main
Source
Second
Source
In Gain
SE1
SE1_L
SE1_R
AC2IN_L/SE3L
AC2IN_R/SE3R
SE4