TDA7460NDTR(2009) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TDA7460NDTR
(Rev.:2009)

Car radio signal processor

STMicroelectronics 

Stereo decoder part

TDA7460ND

5.5.2

Input stages

The In gain stage allows to adjust the MPX signal to a magnitude of about 1Vrms internally

which is the recommended value. The 4.th order input filter has a corner frequency of 80kHz

and is used to attenuate spikes and noise and acts as an anti-aliasing filter for the following

switch capacitor filters.

5.5.3 Demodulator

In the demodulator block the left and the right channel are separated from the MPX signal.

In this stage also the 19 kHz pilot tone is cancelled. For reaching a high channel separation

the TDA7460ND offers an I2C bus programmable roll-off adjustment which is able to

compensate the lowpass behavior of the tuner section. If the tuner attenuation at 38kHz is in

a range from 20.2% to 31% the TDA7460ND needs no external network before the MPX pin.

) Within this range an adjustment to obtain at least 40d B channel separation is possible.

t(s The bits for this adjustment are located together with the fieldstrength adjustment in one

c byte. This gives the possibility to perform an optimization step during the production of the

du car radio where the channel separation and the fieldstrength control are trimmed.

ro Figure 22. Signals during stereo decoder's soft mute

te P SOFTMUTE

le COMMAND

so t

b STD MUTE

t(s) - O t

uc VO

Obsolete Prod 5.5.4

D97AU638

t

De-emphasis and high cut

The lowpass filter for the de-emphasis allows to choose between a time constant of 50ms

and 75ms (bit D7, Stereo decoder byte).

The high cut control range will be in both cases tHC = 2 · tDeemp. Inside the high cut control

range (between VHCH and VHCL) the LEVEL signal is converted into a 5 bit word which

controls the lowpass time constant between tDeemp...3 · tDeemp. There by the resolution will

remain always 5 bits independently of the absolute voltage range between the VHCH and

VHCL values.

The high cut function can be switched off by I2C bus (bit D7, Fieldstrength byte set to "0").

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