TDA7402_07 STMICROELECTRONICS [STMicroelectronics], TDA7402_07 Datasheet - Page 18

• Manufacturer Part Number: TDA7402_07
• Description: Car radio signal processor
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Audioprocessor part
4.1.3
4.1.4
4.1.5
4.2
4.2.1
4.2.2
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Mono differential Input 1 (MD1)
The MD1 input is designed as a basic differential stage with 56kΩ input impedance. This
input is configurable as a single ended stereo input (see pin-out).
Mono differential Input 2 (MD2)
The MD2 input has the same topology as MD1, but without the possibility to configure it to
single ended.
Single ended stereo Input (SE1), single ended mono input (AM) and
FM-MPX input
All single ended inputs offer an input impedance of 100kΩ. The AM pin can be connected by
software to the input of the stereo-decoder in order to use the AM noiseblanker and AM High
Cut feature.
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 DATA-BYTE 0 is selected and needs max. 0.3ms
for the alignment. To avoid audible clicks the Audioprocessor is muted before the loudness
stage during this time. The AutoZero feature is only present in the main signal path.
AutoZero for stereo decoder selection
A special procedure is recommended for selecting the stereo decoder at the main input-
selector to guarantee an optimum offset cancellation:
1.
2.
3.
4.
5.
The root cause of this procedure is, that after muting the stereo decoder (Step 1), the
internal stereo decoder filters have to settle in order to perform a proper offset cancellation.
AutoZero remain
In some cases, for example if the µP is executing a refresh cycle of the I
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
A619 could be switched in the AutoZero Remain Mode (Bit 6 of the subaddress byte). If
this bit is set to high, the DATABYTE 0 could be loaded without invoking the AutoZero and
the old adjustment value remains.
SoftMute or Mute the signal-path
Temporary deselect the stereo decoder at all input selectors
Configure the stereo decoder via IIC-Bus
Wait 1ms
Select the stereo decoder at the main input selector first
2
C Bus
TDA7402