TDA7541 Datasheet, PDF (30/76 Pages) STMicroelectronics – AM/FM car radio tuner IC with stereo decoder and intelligent selectivity system

Functional description
TDA7541
4.1.4
“0”: 120 kHz
The bit has only influence if bit BWENA is “1”, or if bit ISSON is “1”
WBON
Weather band enable
“1”: Weather band enable (FMmixer1 is disabled, Wbmixer1enabled, stereo decoder gain
26dB, ISS filter bandwidth 24 kHz,IF2Q=”00”)
“0”: Weather band disable
For weather band enable it is need to set ISSON = “1”
ISSM
ISS filter application mode
“0”: ISS filter application mode1
“1”: ISS filter application mode2
If BWENA is “1” the band width is always switched to ISSBW in case of ISS filter activated
BWDEF
Enable bit ISSBW for ISS filter band with control
“1”: ISS filter is internally controlled, but band width is defined by bit ISSBW
“0”: ISS filter is internally controlled, band width is defined by mode1/2 table
For the internal control two application modes are available (ISSM). The conditions and
settings are described in Table 10 and Table 11.
Block diagram quality detection principle
(without overdeviation correction)
Table 11. Internal ISS control signals
Signal
Low
Ac No adjacent channel
ac+ No strong adjacent channel
Sm
Field strength higher as weak signal mute
threshold
Dev Deviation lower as threshold DWTH
dev+ Deviation lower as threshold DTH*DWTH
Inton ISS filter off by logic (wide)
int80 ISS filter 120kHz (mid)
High
Adjacent channel present
Adjacent channel higher as ac
Field strength lower as weak signal mute
threshold
Deviation higher as threshold DWTH
Deviation higher as threshold DTH*DWTH
ISS filter on by logic
ISS filter 80kHz (narrow)
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