AK2347B Datasheet, PDF (28/34 Pages) Asahi Kasei Microsystems – Two-way Radio Audio & Sub-Audio Processor

ASAHI KASEI
[AK2347B]
16. Recommended External Application Circuits
1) TXA1 amplifier
This circuit can be used as the TX microphone amplifier. Set the gain to 30dB or less. If there
is a possibility that a high frequency noise component over 100kHz is input, form a first or second
order anti-aliasing filter. The following gives a sample configuration of a second order LPF with a
gain of 30dB and cut-off frequency of 10kHz:
_
+
TXA1
3 TXINO
C2
R3
R1 C1
4 TXIN _R2
C3
2 _AGND
C1=0.47uF
C2=33pF
C3=2200pF
R1=R2=10kΩ
R3=330kΩ
LSI
2) TXA2 amplifier
This amplifier is used for adjusting the gain of the tone signal. Set the gain to 0dB or less.
For high frequency noise over 100kHz, form an anti-aliasing filter. The following gives a sample
configuration of a second order LPF with a gain of 0dB and cut-off frequency of 13kHz:
_
+
TXA2
6 EXTINO
C2
R3
R1 C1
5 EXTIN _R2
C3
2 _AGND
LSI
C1=0.47uF
C2=100pF
C3=470pF
R1=R2=R3=51kΩ
MS1419-E-00
- 28 -
2012/05