TDA7501

Description of the input part

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3.2

Dual MPX mode

The TDA7501 is able to support a twin tuner concept via the Dual MPX Mode. In this

configuration the FM pin and the AM-pin are acting as MPX1 and MPX2 inputs. The DC

Voltage at the TUNER pin controls whether MPX1, both MPX signals or MXX2 is used to

decode the stereo FM signal (see Figure 6 Please note that the thresholds have a

hysteresis of 500mV. During this mode the high ohmic mute acts on both inputs in parallel.

Furthermore, a background tuner on the internal AM path can be selected by software

aswtching to one of the two MPX inputs.

For the programming of the Dual MPX Mode see the programming section.

Figure 7.

Block diagram Dual MPX.

3.3

Additional quasi differential Input

The TDA7501 can be programmed to additional quasi-differential input by rearranging the

configuration of the navigation and AM level inputs. Since the AM level input becomes the

2nd differential input, the level shift function is not available.

For the programming of the navigation/AM level input configuration see the programming

section.

Figure 8.

Additional quasi differential input simplified

1

MPX2

(AM+)

HIZ-MUTE

HIZ-MUTE

MPX1

(FM+)

CTRL

(TUNER-)

50K

50K

50K

15K

15K

15K

1

15K

15K

15K

1

WINDOW-

COMPARATOR

& LOGIC

(D4/5)

(D5/5)

AM

FM

D00AU1202

-

+

-

+

1

NAVI-/QDIFF1-

AMLEVEL/QDIFF2-

NAVI+/COM+

100K

100K

68K

15K

15K

15K

1

15K

15K

15K

33K

1

D3/4

NAVI/QDIFF1

LEVEL/QDIFF2

D00AU1203

D3/4

-

+

-

+