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TDA7405

11.6 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 36 (Please note that the thresholds have a hysteresis of 500mV). In this mode

the stereodecoder highohmic-mute mutes both inputs in parallel.

Figure 37. Blockdiagram Dual MPX

Table 10. Pin-Configuration DMPX-/WSM-Mode

11.7 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 29 and 30 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.

Dual MPX

Weak-Signal

Mute

AMIF(12)

DMPXC(25)

MPX2(26)

MD2(43)

MD2G(44)

off

AMIF-In

not used

MD2-In

MD2-Gnd

off

WSM-TC

WSM-In

WSM-Out

MD2-In

MD2-Gnd

off

AMIF-In

DMPC-Cntrl

MPX2

MD2-In

MD2-Gnd

WSM-TC

WSM-In

WSM-Out

DMPC-Cntrl

MPX2

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