TDA7411 Datasheet, PDF (9/43 Pages) STMicroelectronics – ADVANCED CAR SIGNAL PROCESSOR

TDA7411
Input stages
In the basic configuration one full differential, one quasi-differential, two single ended stereo, one mono-
differential and two tuner (AM and MPX) inputs are available. In addition the ac coupling input Acin0 can
be used as single ended input for the input multiplexer.
The full-differential input can be switched into quasi-differential mode (see Fig. 2) and the MD single ended
input can be used as mono-differential input (see Fig.1).
Figure 2. Full differential input
AutoZero
In order to reduce the number of pins there is no AC coupling between the In-Gain and the following stage,
so that any offset generated by or before the In-Gain-stage would be transferred or even amplified to the
output. To avoid that effect a special Offset-cancellation-stage called AutoZero is implemented. This stage
is located after the In-Gain-stage to eliminate all offsets generated by the stereo decoder, the Input-Stages
and the In-Gain (Please notice that externally generated offsets, e.g. generated through the leakage cur-
rent of the coupling capacitors, are not canceled).
The auto-zeroing is started every time the DATA-BYTE 0 is selected and takes a time of max. 0.3ms. To
avoid audible clicks the audio processor is muted before the tone control stage during this time.
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 TDA7411 could be switched in the AutoZero-Remain-
Mode (Bit 6 of the sub address byte). If this bit is set to high, the DATABYTE 0 could be loaded without
invoking the AutoZero and the old adjustment-value remains.
Sub Channel Multiplexer
All input stages are available as source in the sub channel multiplexer. The selected source is buffered
and available at the pins SubR, SubL.
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