TDA7501_07 Datasheet, PDF (11/29 Pages) STMicroelectronics – Line driver for digital car radio Signal processor (DSPLD)

TDA7501
Description of the input part
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.
HIZ-MUTE
MPX2
(AM+)
1
50K
CTRL
(TUNER-)
(D5/5)
1
50K
HIZ-MUTE
MPX1
(FM+)
1
50K
15K
15K
-
+
15K
15K
+
-
15K
15K
WINDOW-
COMPARATOR
& LOGIC
(D4/5)
AM
FM
D00AU1202
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
15K
15K
NAVI-/QDIFF1-
1
100K
-
+
NAVI+/COM+
15K
15K
1
100K
33K
D3/4
AMLEVEL/QDIFF2-
68K
+
D3/4
-
1
15K
15K
NAVI/QDIFF1
LEVEL/QDIFF2
D00AU1203
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