TDA7407D Datasheet, PDF (13/34 Pages) STMicroelectronics – ADVANCED CAR SIGNAL PROCESSOR

TDA7407D
tion even with those CD players.
The output of the Cd stage is permanently available of the Cd out-pins
6.1.3 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 before the volume-block to eliminate all offsets generated by the Stereodecoder, the
Input Stage and the In-Gain (Please notice that externally generated offsets, e.g. generated through the
leakage current of the coupling capacitors, are not cancelled).
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 audioprocessor is muted before the volume stage during this time.
t(s _{6.1.4 AutoZero Remain}
uc ^{In some cases, for example if the µP is executing a refresh cycle of the I2C bus programming, it is not}
d useful to start a new AutoZero action because no new source is selected and an undesired mute would
ro ^{) appear at the outputs. For such applications the TDA7407D could be switched in the "Auto Zero Remain}
P _t(s ^{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.
lete ^{uc 6.1.5 Multiplexer Output}
so ^{rod The output signal of the Input Multiplexer is available at separate pins (please see the Blockdiagram). This}
signal represents the input signal amplifier by the In Gain stage and is also going into the Mixer stage.
- ^{Ob te P 6.1.6 Softmute}
) ^{le The digitally controlled softmute stage allows muting/demuting the signal with a I2C bus programmable}
t(s ^{o slope. The mute process can either be activated by the softmute pin or by the I2C bus. The slope is real-}
s _{ized in a special S shaped curve to mute slow in the critical regions (see figure 9).}
uc Ob _{Figure 8. Input Stages}
Prodt(s) - CD+
100K
lete duc _CD-
so ^ro100K
s^{Ooblete P}_PHONE-
Ob ^CASSETTE
15K
15K
1
+
-
15K
15K
1
27K
27K
28K
+
-
28K
IN GAIN
100K
AM
MPX
100K
100K
STEREODECODER
D98AU854D
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