U4255BM-M Datasheet, PDF (9/32 Pages) ATMEL Corporation – AM / FM RECEIVER IC

U4255BM-M
Table 14. FM Band Filter Center Frequency Correction
IF Correction
Bit 17
Bit 16
- 0 kHz
0
0
- 6.25 kHz
0
0
- 12.50 kHz
0
0
- 18.75 kHz
0
0
- 25.00 kHz
0
1
- 31.25 kHz
0
1
- 37.50 kHz
0
1
- 43.75 kHz
0
1
+ 0 kHz (default)
1
0
+ 6.25 kHz
1
0
+ 12.50 kHz
1
0
+ 18.75 kHz
1
0
+ 25.00 kHz
1
1
+ 31.25 kHz
1
1
+ 37.50 kHz
1
1
+ 43.75 kHz
1
1
Bit 15
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 14
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Integrated FM Band Filter
For FM reception a band filter with variable bandwidth is integrated in front of the
demodulator to provide channel selectivity on the 2^nd IF. The bandwidth of this filter can
be adjusted by Bit 0 to 3 (see Table 15) to be suitable for the present receiving condi-
tion. In WB mode, the bandwidth of the integrated filter is shifted to lower bandwidth
values, while the necessary channel selectivity is achieved by an external ceramic filter.
The center frequency of the integrated FM band filter can be adjusted by means of
Bit 14 to 17 (Bit 4 set to 1). The field strength after the integrated FM band filter that is
available at Pin 20 (Bit55 = 1) can be used for this purpose.
Table 15. Bandwidth of the Integrated FM Band Filter.
IF Bandwidth
Bit 3
Bit 2
200 kHz
0
0
190 kHz
0
0
180 kHz
0
0
170 kHz
0
0
160 kHz
0
1
150 kHz
0
1
140 kHz
0
1
130 kHz
0
1
120 kHz
1
0
110 kHz
1
0
100 kHz
1
0
90 kHz
1
0
80 kHz
1
1
70 kHz
1
1
60 kHz
1
1
50 kHz
1
1
Bit 1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
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