TDA7407 datasheet(20/30 Pages) STMICROELECTRONICS

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AF Search Control

The TDA7407 is supplied with several functional-

ity to support AF-checks using the stereodecoder.

As mentioned already before the highohmic-mute

feature avoids any clicks during the jump condi-

tion. It is possible a the same time to evaluate the

noise- and multipath-content of the alternate fre-

quency by using the Quality detector output.

Therefore the multipath-detector is switched auto-

matically to a small time-constant.

One additional pin (AFS) is implemented in order

separate

the

audioprocessor-mute

and

stereodecoder AF-functions. In Figure 22 the

blockdiagram and control-functions of the com-

plete AFS-functionality is shown (please note that

the pins AFS and SM are active low as well as all

control-bits indicated by an overbar).

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 resistor of 100kOhm is

disconnected from the pin. The internal signals

available are shown in the software specification.

Figure 22. Mute Control Logic

TDA7407

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