TDA7406T datasheet(30/49 Pages) STMICROELECTRONICS

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TDA7406T

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4.8 Stereoblend Control

The stereoblend control block converts the internal LEVEL-voltage (LEVELSB) into an demodulator compatible

analog signal which is used to control the channel separation between 0dB and the maximum separation. Inter-

nally this control range has a fixed upper limit which is the internal reference voltage REF5V. The lower limit can

be programmed between 20 and 70% of REF5V in 3.3% steps (see figs.24, 25).

To adjust the external LEVEL-voltage to the internal range two values must be defined: the LEVEL gain LG and

VSBL (see fig. 25). At the point of full channel separation the external level signal has to be amplified so that

internally it becomes equal to REF5V. The second point (e.g. 10dB channel sep.) is then adjusted with the VSBL

voltage.

Figure 24. Internal stereoblend characteristics

The gain can be programmed through 4 bits in the “Stereodecoder-Adjustment”-byte. All necessary internal ref-

erence voltages like REF5V are derived from a bandgap circuit. Therefore they have a temperature coefficient

near zero.

Figure 25. Relation between internal and external LEVEL-voltages for setup of Stereoblend

TDA7406T 数据表(PDF) 30 Page - STMicroelectronics