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TDA7407D Datasheet, PDF (17/34 Pages) STMicroelectronics – ADVANCED CAR SIGNAL PROCESSOR | |||
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TDA7407D
6.5 FUNCTIONAL DESCRIPTION OF STEREODECODER
The stereodecoder part of the TDA7407D (see Fig. 19) contains all functions necessary to demodulate
the MPX signal like pilot tone dependent MONO/STEREO switching as well as "stereoblend" and "highcut"
functions.
6.5.1 Stereodecoder Mute
The TDA7407 has a fast and easy to control RDS mute function which is a combination of the audiopro-
cessor's softmute and the high-ohmic mute of the stereodecoder. If the stereodecoder is selected and a
softmute command is sent (or activated through the SM pin) the stereodecoder will be set automatically
to the high-ohmic mute condition after the audio signal has been softmuted.
Hence a checking of alternate frequencies could be performed. To release the system from the mute con-
dition simply the unmute command must be sent: the stereodecoder is unmuted immediately and the au-
dioprocessor is softly unmuted. Fig. 20 shows the output signal VO as well as the internal stereodecoder
) mute signal. This influence of Softmute on the stereodecoder mute can be switched off by setting bit 3 of
t(s the Softmute byte to "0". A stereodecoder mute command (bit 0, stereodecoder byte set to "1") will set the
stereodecoder in any case independently to the high-ohmic mute state.
duc Figure 19. Block Diagram of the Stereodecoder
soleteroPdruocdt(usc)t(-sO) -bsOoblestoelePteroPdruoct(s) Figure 20. Signals During Stereodecoder's Softmute
Ob te P SOFTMUTE
COMMAND
ole t
Obs STD MUTE
t
VO
D97AU638 t
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