TDA7460NDTR(2009) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TDA7460NDTR
(Rev.:2009)

Car radio signal processor

STMicroelectronics 

Stereo decoder part

TDA7460ND

The gain can be programmed through 4 bits in the "Stereo decoder-Adjustment" byte.

The mono voltage VMO (0 dB channel separation) can be chosen selecting 33, 42, 50 or

58 % of REF5V.All necessary internal reference voltages like REF5V are derived from a

bandgap circuit. Therefore they have a temperature coefficient near zero. This is useful if the

fieldstrength signal is also temperature compensated.

But most if devices apply a level voltage with a TC of 3300 ppm. The TDA7460ND offers this

TC for the reference voltages, too. The TC is selectable with bit D7 of the "stereo decoder

adjustment" byte.

Figure 24. Relation between internal and external LEVEL voltage and setup of stereo

blend

uct(s) - Obsolete Product(s) 5.5.9

INTERNAL

VOLTAGES

REF 5V

VSBL

SETUP OF VST

LEVEL INTERN

INTERNAL

VOLTAGES

REF 5V

LEVEL

VSBL

58%

50%

42%

33%

SETUP OF VMO

LEVEL INTERN

VMO

VST

t

FIELDSTRENGHT VOLTAGE

D97AU639

VMO

t

VST

FIELDSTRENGHT VOLTAGE

High cut control

The high cut control setup is similar to the stereo blend control setup: the starting point

VHCH can be set with 2 bits to be 42, 50, 58 or 66% of REF5 V whereas the range can be

set to be 17 or 33% of VHCH (see Figure 25.).

Figure 25. High cut characteristics

LOWPASS

TIME CONSTANT

3•τDeemp

Obsolete Prod τDeemp

VHCL

D97AU640

VHCH FIELDSTRENGHT

5.6

Functional description of the noise blanker

In the automotive environment the MPX signal is disturbed by spikes produced by the

ignition and for example the wiper motor. The aim of the noise blanker part is to cancel the

audible influence of the spikes. Therefore the output of the stereo decoder is held at the

actual voltage for 40 μs.

In a first stage the spikes must be detected but to avoid a wrong triggering on high

frequency (white) noise a complex trigger control is implemented. Behind the trigger stage a

pulse former generates the "blanking" pulse. To avoid any crosstalk to the signal path the

noise blanker is supplied by his own biasing circuit.

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