TDA7402 datasheet(48/71 Pages) STMICROELECTRONICS

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Functional description of the multipath detector

TDA7402

48/71

8.2

Testmode

During the testmode, which can be activated by setting bit D0 and bit D1 of the stereo

decoder testing byte, several internal signals are available at the FD2R+ pin. During this

mode the input resistance of 100kOhm is disconnected from the pin. The internal signals

available are shown in the Data byte specification.

8.3

Dual MPX usage

8.3.1

Feature description

The A619 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 3 (Please note that the thresholds have a hysteresis of 500mV).

In this mode the stereo decoder high ohmic-mute mutes both inputs in parallel.

Figure 36.

Dual MPX input diagram

8.3.2

Configuration

The Dual MPX mode can be easily configured by setting bit 3 of subaddress 30 to LOW (see

Byte 30 description and application diagram of

Figure 38).

CONTROL

CIRCUITRY

INGAIN

100K

40K

100K

3.5...11dB

step 2.5dB

MPX/

MPX1

D00AU1167

MD2G/

MPX2

MD2/

CONTROL

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