TDA7406 datasheet(38/64 Pages) STMICROELECTRONICS

38 / 64 page

Functional Description of Stereodecoder

TDA7406

38/64

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

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).

TDA7406 数据表(PDF) 38 Page - STMicroelectronics