TDA7460ND(2009) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TDA7460ND
(Rev.:2009)

Car radio signal processor

STMicroelectronics 

Stereo decoder part

TDA7460ND

5.6.4

Over deviation detector

If the system is tuned to stations with a high deviation the noise blanker can trigger on the

higher frequencies of the modulation. To avoid this wrong behavior, which causes noise in

the output signal, the noise blanker offers a deviation dependent threshold adjustment.

By rectifying the MPX signal a further signal representing the actual deviation is obtained. It

is used to increase the PEAK voltage. Offset and gain of this circuit are programmable in 3

steps with the bits D6 and D7 of the stereo decoder byte (the first step turns off the detector,

see Figure 18.).

5.7

Functional description of the multipath detector

Obsolete Product(s) - Obsolete Product(s) 5.8

Using the internal detector the audible effects of a multipath condition can be minimized. A

multipath condition is detected by rectifying the 19 kHz spectrum in the fieldstrength signal.

Selecting the "internal influence" in the configuration byte, the channel separation is

automatically reduced during a multipath condition according to the voltage appearing at the

MPOUT pin.

To obtain a optimal performance an adaptation is necessary. Therefore the gain of the

19 kHz bandpass is programmable in four steps as well as the rectifier gain. The attack and

decay times can be set by the external capacitor value.

Test mode

During the test mode which can be activated by setting bit D0 of the testing byte and bit D5

of the subaddress byte to "1" several internal signals are available at the CASSR pin. During

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

signals available are shown in the software specification.

Figure 27. Block diagram of the multipath detector

LEVEL

MPIN

MP ENABLE

BANDPASS

19KHz

VDD

DC=1μ

RECTIFIER

to SB

-

int. INFLUENCE

15K

GAIN

2 BITS

GAIN

2 BITS

TO PHONE_GND - APR

D98AU862

MPOUT

220nF

32/49

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