TDA7406 Datasheet, PDF (38/64 Pages) STMicroelectronics – Car radio signal processor

Functional Description of Stereodecoder
TDA7406
between 0dB and the maximum separation. Internally 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.26, 27).
To adjust the external LEVEL-voltage to the internal range two values must be defined: the
LEVEL gain LG and VSBL (see Figure 27). 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 26. Internal stereoblend characteristics
The gain can be programmed through 4 bits in the “Stereodecoder-Adjustment”-byte. All
necessary internal reference voltages like REF5V are derived from a bandgap circuit.
Therefore they have a temperature coefficient near zero.
Figure 27. Relation between internal and external LEVEL-voltages for setup of
Stereoblend
70
20
8.9
Highcut Control
The highcut control set-up is similar to the stereoblend control set-up: the starting point
VHCH can be set with 2 bits to be 42, 50, 58 or 66% of REF5V whereas the range can be
set to be 17, 22, 28 or 33% of VHCH (see Figure 28).
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