TDA7501 Datasheet TDA7501 | P10-P12

Description of the input part TDA7501

10/29

3.1 Input Stages

The device offers several input stages for the different signals which have to be handled by

the system. A quasi differential input (see Figure 4) can be used for (external) CD changer.

The two mono differential inputs allow the connection of phone & navigation (see Figure 5)

or it could be used as fully differential stereo input. Additionally a single-ended stereo input

is available for Cassette applications. The lower part of the input section is dedicated to the

tuner signals. Another quasi differential input (see Figure 6) is used to connect AM and FM

referred to the tuner reference (Tuner). This concept supports also double tuner systems.

Also two seperate level inputs are present which are followed by level-shifters to allow the

use of the TDA7500's ADCs. For AM noise blanking an envelope detector driven by the AM

IF is also available.

Figure 4. Quasi differential input-stage.

Figure 5. Mono differential input-stage.

Figure 6. Differential input-stage for AM/FM.

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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

MPX2

(AM+)

HIZ-MUTE

MPX1

(FM+)

CTRL

(TUNER-)

50K

15K

15K 15K

15K

WINDOW-

COMPARATOR

& LOGIC

(D4/5)

(D5/5)

D00AU1202

1NAVI-/QDIFF1-

AMLEVEL/QDIFF2-

NAVI+/COM+

100K

68K

15K

15K 15K

15K

33K

D3/4

NAVI/QDIFF1

LEVEL/QDIFF2

D00AU1203

D3/4

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Description of the input part TDA7501

12/29

3.4 Transfer function of the AM/FM level inputs

In the TDA7501 two level shift stages convert a tuner level (DC) signal to a unipolar output

signal with respect to the Codec Interface reference, that is 1.65V.

The FM level input can be programmed to a signal range of either 0 to 5V (Lo range) which

is the default, or 0 to 6V (Hi range). The AM level input is fixed to the lower 0 to 5V input

range.

For the programming of the FM level input range see the programming section.

Figure 9. AM/FM level inputs transfer function (DC)

10 2345Vin(V)

1.65

1.90

2.15

2.30

2.65

Vout

(V)

LO RANGE

HI RANGE

D00AU1204

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P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P29

TDA7501

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