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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.