ASAHI KASEI
[AK2346B]
16. 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 1st or 2nd order anti-aliasing filter. The following simplified schematic shows an
example of 2nd order anti-aliasing filter that has 30dB gain and 10kHz cut-off frequency.
C1=0.47uF
C2=33pF
4
TXINO
C2
R3
C3=2200pF
R1
C1
_
+
3
TXIN
R2
R1=R2=10k
C3
Ω
TXA1
R3=330k
Ω
AGND
LSI
2) EXTLIMIN pin configuration
To eliminate an external DC offset must be decoupled by capacitor to signal input.
6
EXTLIMIN
C=0.047uF
C
LSI
3) RXA1 Amplifier
This is an operational amplifier suitable for receive gain adjuster and anti-aliasing filter to
eliminate high frequency noise component over 100kHz The gain should be less than 20dB.
The following simplified schematic shows an example of 2nd order anti-aliasing filter that has
20dB gain and 39kHz cut-off frequency.
C1=0.47uF
C2=33pF
22
RXINO
C2
R3
R1
C1
C3=560pF
_
+
23 RXIN
R2
R1=10k
C3
Ω
RXA1
R2=9.1k
Ω
AGND
R3=100k
Ω
LSI
MS1409-E-00
2012/05
- 26 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
