TDA7404D Datasheet, PDF (8/26 Pages) STMicroelectronics – CARRADIO-SIGNAL-PROCESSOR

TDA7404D
1.0 DESCRIPTION OF FUNCTIONALITY
1.1 Input stages
Most of the input stages have remained the same as in preceding ST-Audioprocessors with exception of the
CD-inputs (see Figure 1). In the meantime there are some CD-players in the market which have a significant
high source-impedance which effects strongly the common-mode-rejection of the normal differential input stage.
The additional buffer of the TDA7404D Diff
-input avoids this drawback and offers the full common-mode-rejection even with those CD-players.
Figure 1. Input-stages
Diffin+
/(SE4)
100k
Diffgnd
100k
Mono+
28k
28k
Mono -
SE1
100k
28k
28k
Ingain
SE2
100k
SE3
100k
Note. It is possible that the Differential input is switched a single ended input (SE4) like SE1.. 3.
1.2 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
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