SA2104/SA2104S
(Continued)
Pin
Pin voltage (Typ.) (V)
Symbol
Pin description
Internal circuit
No.
AM
FM
22
AM RF IN
AM RF input pin.
3.0
3.0
23
24
RF VCC
(VCC for FM OSC stage)
••
3.0
3.0
3.0
3.0
FM RF OUT FM RF output pin.
FUNCTION DESCRIPTION
Application note:
1. AM low•cut circuit
When pin3 is open, no AF signal can pass through the AMP stage because of the common mode.
When the value of C3 that connected to pin3 is over 1uF, all AF signal can pass through the AMP stage.
The cut•off frequency fL is determined by the internal resistance 22Wk (Typ.) and the external capacitor C3 as
below:
1
fL =
(Hz)
3
2 x ʌ x 22 x10 x C3
It is possible to reduce the recovered output level at AM mode, by additional resistance between the pin (3)
and GND line.
2. FM detection circuit
Recommended circuit and recommended coil are as follows. (Test frequency is 10.7M)
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
REV:2.0
2004.07.31
Http: www.silan.com.cn
Page 7 of 13
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