AK2346A Datasheet, PDF (33/37 Pages) Asahi Kasei Microsystems – Two-way Radio Audio Processor

ASAHI KASEI
[AK2346A]
18. Recommended External Application Circuits
1) TXA1 Amplifier
This is an operational amplifier required for typical transmit microphone. The gain should be less
than 30dB. To eliminate high frequency noise component over than 100kHz from input signal,
please compose 1^st or 2^nd order anti-aliasing filter. The following simplified schematic shows an
example of 2^nd order anti-aliasing filter that has 30dB gain and 10kHz cut-off frequency.
_
+
TXA1
20 TXINO
C2
19
R3
R1 C1
TXIN _R2
C3
LSI
C1=0.47uF
C2=33pF
C3=2200pF
R1=R2=10kΩ
R3=330kΩ
2) TXA2 amplifier
This amplifier is used for adjusting the gain of the external tone signal. The gain should be less
than 30dB. To eliminate high frequency noise component over than 100kHz from input signal,
please compose 1^st or 2^nd order anti-aliasing filter. The following simplified schematic shows an
example of 2^nd order anti-aliasing filter that has 30dB gain and 10kHz cut-off frequency.
_
+
TXA2
17 EXTINO
C2
R3
R1 C1
16 EXTIN1 _R2
C3
AGND
C4
21
EXTIN2
C1=0.47uF
C2=33pF
C3=2200pF
R1=R2=10kΩ
R3=330kΩ
C4=0.047uF
LSI
MS1289-E-02
- 33 -
2012/06