ATR4258 Datasheet, PDF (17/38 Pages) ATMEL Corporation – AM/FM RECEIVER IC

Deviation Sensor
ATR4258
Table 28. 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 29. Signals Available at Digital Output Pin 21
Bit 88
0
0
Bit 92
0 (AM)
1 (FM/WB)
INT (Pin 21)
1
NOT MPINT
Note:
1
0 (AM)
NOT STOP
1
1 (FM/WB)
NOT (STOP AND NOT MPINT)
MPINT = Multipath interrupt, Stop and MPINT signal are active low
Pin 35 (IFAGCH) is carried along with pin 36 (IFAGCL) to avoid crackles during a
change of the search stop mode to the AM reception mode.
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 low-pass-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
Pin 31
25k
17
4838A–AUDR–10/04