U4255BM-M Datasheet, PDF (13/32 Pages) ATMEL Corporation – AM / FM RECEIVER IC

Deviation Sensor
U4255BM-M
Table 23. Search Stop Detector Measurement Time
Time Window for Stop Signal Bit 78 Bit 77 Bit 76
1 ´ 3.1969 ms
0
0
0
.....
63 ´ 3.1969 ms
1
1
1
Bit 75
0
1
Bit 74
0
1
Bit 73
1
1
Table 24. Search Stop Window
Search Stop Window
± 0.5 kHz
± 1.1 kHz
± 2.3 kHz
± 4.8 kHz
± 10 kHz
± 20 kHz
± 40 kHz
± 80 kHz
Bit 87
0
0
0
0
1
1
1
1
Bit 86
0
0
1
1
0
0
1
1
Bit 85
0
1
0
1
0
1
0
1
Table 25. Signals Available at Digital Output Pin 21
Bit 88
Bit 92
INT (Pin 21)
0
0 (AM)
1
0
1 (FM/WB)
NOT MPINT
1
0 (AM)
NOT STOP
1
1 (FM/WB)
NOT (STOP AND NOT MPINT)
The deviation sensor is active in AM and FM/WB mode and measures the modulation of
the signal. It is implemented as a peak detector of the lowpass-filtered MPX signal (see
Figure 7). The output voltage at Pin 31 is proportional to the frequency deviation in
FM/WB or the modulation depth in AM respectively.
Figure 7. Deviation Sensor
+
MPX
4k
25k
Pin 31
13
4519C–AUDR–07/02