TDA7405 Datasheet, PDF (37/56 Pages) STMicroelectronics – EQUALIZER CARRADIO SIGNAL PROCESSOR

TDA7405
5.6 Dual-MPX Mode
The TDA7405 is able to support a twin tuner concept via the Dual-MPX-Mode. In this configuration the MPX-pin
and the MD2G-pin are acting as MPX1 and MPX2 inputs. The DC-Voltage at the MD2-pin controls whether one
or both MPX-signals are used to decode the stereo FM-signal. It is designed as a window-comparator with the
characteristic shown in Figure 33 (Please note that the thresholds have a hysteresis of 500mV). In this mode
the stereodecoder highohmic-mute mutes both inputs in parallel.
Figure 33. Blockdiagram Dual MPX
Table 6. Pin-Configuration DMPX-/WSM-Mode
Dual MPX
Weak-Signal
Mute
AMIF(12)
DMPXC(25)
off
off
AMIF-In
not used
off
on
WSM-TC
WSM-In
on
off
AMIF-In
DMPC-Cntrl
on
on
WSM-TC
WSM-In
MPX2(26)
not used
WSM-Out
MPX2
WSM-Out
MD2(43)
MD2-In
MD2-In
MD2-In
DMPC-Cntrl
MD2G(44)
MD2-Gnd
MD2-Gnd
MD2-Gnd
MPX2
5.7 Weak-Signal Mute
For use with front-ends which do not support a weak-signal-mute function the TDA7405 offers this feature as
well. If this mode is enabled the pins 26 and 27 are used as an AC-coupling behind the Mute-Stage (see block-
diagram). In parallel pin 12 (AMIF) is switched internally to realize a mute time-constant with fast attack- and
slow decay-time.
37/56