TDA7402 Datasheet, PDF (33/59 Pages) STMicroelectronics – CARRADIO SIGNAL PROCESSOR

Figure 26. Signals during stereodecoder’s SoftMute
TDA7402
Figure 27. Signal-Control via SoftMute-Pin
3.2 InGain + Infilter
The InGain stage allows to adjust the MPX-signal to a magnitude of about 1V_rms internally which is the recom-
mended value. The 4.th order input filter has a corner frequency of 80kHz and is used to attenuate spikes and
noise and acts as an anti-aliasing filter for the following switch capacitor filters.
3.3 Demodulator
In the demodulator block the left and the right channel are separated from the MPX-signal. In this stage also the
19-kHz pilottone is cancelled. For reaching a high channel separation the A619 offers an I²C-bus programmable
roll-off adjustment which is able to compensate the lowpass behavior of the tuner section. If the tuner’s attenu-
ation at 38kHz is in a range from 7.2% to 31.0% the A619 needs no external network in front of the MPX-pin.
Within this range an adjustment to obtain at least 40dB channel separation is possible. The bits for this adjust-
ment are located together with the fieldstrength adjustment in one byte. This gives the possibility to perform an
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