CXA1742Q
Description of Operation
A 45 MHz IF signal is input to Pin 22. This input signal is amplified at the RF AMP and then mixed with the
local oscillation signals from the oscillator at the mixer to change the signal frequency to 60 kHz. When a
crystal or the other resonator circuit is connected to Pins 19 and 20, the oscillator can be self-executed by
composing a Colpitts-type oscillation circuit. It can be also used with an external local oscillation signal applied
to Pin 20.
The internal BPF eliminates any interference from the converted 60 kHz signal, which is then output to Pin 3.
The resulting signal is fed to Pins 4 and 5 to connect to the limiter and RSSI circuits.
The limiter eliminates an amplitude component from the signal. The resulting signal is then detected at the
quadrature FM detector circuit, and Pin 6 outputs an audio signal.
The RSSI circuit detects the RF AMP input signal voltage and generates from Pin 7 the DC voltage where
the detected voltage value is logarithmically compressed.
The resulting signal is fed to Pins 4 and 5 to connect to the limiter and RSSI circuits.
45MHz
IN
IFIN
30
29
28
27
26
25
24
23
22
21
XTALIN
20
19
18
17
16
15
14
13
12
11
31
32
33
34
35
36
37
38
39
40
Crystal
Oscillator
Circuit
RF AMP
PSN
PSN
XTALOUT
MIXER
1/2
OSC
BPF0
BPF1
AGC
RSSI
BIAS
LIM
DET
10
1
2
3
4
5
6
7
8
9
RSSI
OUT
AUDIO
OUT
AUDIO RSSI
output output
Signal Flow
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SONY [ SONY CORPORATION ]
