TDA7418 Datasheet, PDF (12/29 Pages) STMicroelectronics – 3 Band car audio procesor

Description of the audioprocessor
4
Description of the audioprocessor
TDA7418
4.1
Input stages
In the basic configuration, one stereo pseudo differential (programmable as single-ended
input) and three single-ended stereo inputs are available.
Pseudo differential stereo input (PD/SE4)
The PD input is implemented as a buffered pseudo differential stereo stage with 100kΩ
input-impedance at each input. The attenuation is fixed to -3dB in order to adapt the
incoming signal level. It is also configurable as single-ended input.
Single-ended stereo input (SE1, SE2, SE3)
The input-impedance at each input is 100kΩ and the attenuation is fixed to -3dB for
incoming signals.
Figure 3. Input stage
QD_L/SE4_L
QD_G
QD_R/SE4_R
SE1_L
SE1_R
QD/SE4
QD/SE4
SE1
SE1
Input
Selector
In Gain
SE2_L
SE2_R
SE2
SE2
SE3_L
SE3_R
SE3
SE3
4.2
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. 0.6ms
for the alignment. To avoid audible clicks the Audio processor is muted before the loudness
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
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