E-TDA7406 STMicroelectronics, E-TDA7406 Datasheet - Page 35

• Manufacturer Part Number: E-TDA7406
• Description: Audio DSPs CAR RADIO SIGNAL
• Manufacturer: STMicroelectronics

Specifications of E-TDA7406

• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFP-44
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TDA7406
8
Figure 23. Block diagram of the stereodecoder
8.1
Functional Description of Stereodecoder
The stereodecoder-part of the TDA7406 (see Fig. 25) contains all functions necessary to
demodulate the MPX-signal like pilot tone-dependent MONO/STEREO-switching as well as
“stereoblend” and “highcut”. Adaptations like programmable input gain, roll-off
compensation, selectable de-emphasis time constant and a programmable field strength
input allow to use different IF-devices.
Stereodecoder-Mute
The TDA7406 has a fast and easy to control RDS-Mute function which is a combination of
the audioprocessor'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 soft muted. Hence a checking of alternate frequencies could be
performed. Additionally the PLL can be set to “Hold”-mode, which disables the PLL input
during the mute time. To release the system from the mute condition simply the unmute-
command must be sent: the stereodecoder is unmuted immediately and the audioprocessor
is softly unmuted.
stereodecoder mute signal. This influence of SoftMute on the stereodecoder mute can be
switched off by setting bit 3 of 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.
If any other source than the stereodecoder is selected the decoder remains muted and the
MPX-pin is connected to V
leakage currents. No further mute command should be applied.
Figure 28
ref
shows the output-signal V
to avoid any discharge of the coupling capacitor through
Functional Description of Stereodecoder
O
as well as the internal
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