TDA7407 datasheet(15/30 Pages) STMICROELECTRONICS

15 / 30 page

structure and range like the Volume stage.

FUNCTIONAL DESCRIPTION OF STEREODE-

CODER

The stereodecoder part of the TDA7407 (see Fig.

15) contains all functions necessary to demodu-

late the MPX signal like pilot tone dependent

MONO/STEREO

switching

well

"stereoblend" and "highcut" functions.

Stereodecoder Mute

The TDA7407 has a fast and easy to control RDS

mute function which is a combination of the audio-

processor’s softmute and the high-ohmic mute of

the stereodecoder. If the stereodecoder is selected

and a softmute command is sent (or activated

through the SM pin) the stereodecoder will be set

automatically to the high-ohmic mute condition af-

ter the audio signal has been softmuted.

Hence a checking of alternate frequencies could

be performed. To release the system from the

mute condition simply the unmute command must

be sent: the stereodecoder is unmuted immedi-

ately and the audioprocessor is softly unmuted.

Fig. 16 shows the output signal VO as well as the

internal stereodecoder mute signal. This influ-

ence of Softmute on the stereodecoder mute can

be switched off by setting bit 3 of the Softmute

byte to "0". A stereodecoder mute command (bit

0, stereodecoder byte set to "1") will set the

stereodecoder in any case independently to the

high-ohmic mute state.

0.0

2.5

5.0

7.5

10.0

12.5

15.0

10.0

100.0

1.0K

10.0K

Figure 14. Treble Center Frequencies

@ Gain = 14dB

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

10.0

100.0

1.0K

10.0K

Figure 13. Treble Control @ fc = 17.5KHz

Figure 15. Block Diagram of the Stereodecoder

TDA7407

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