[AK4634]
AK4634
MIC-Power
MIC-Amp
MPI pin
1k
1k
MICP pin
MICNpin
BICK pin
FCK pin
STDO pin
Audio
I/F
A/D HPF
Figure 33. MIC Differential Input Circuit
■ MIC Gain Amplifier
The AK4634 has a Gain Amplifier for Microphone input. These gains are selected by the MGAIN3-0 bit. The typical
input impedance is 30kΩ.
MGAIN3 bit
MGAIN2 bit
MGAIN1 bit
MGAIN0 bit
Input Gain
0dB
0
0
0
0
0
0
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
+20dB
+26dB
+32dB
+10dB
+17dB
+23dB
+29dB
+3dB
(default)
+6dB
Others
N/A
Table 20. Input Gain
■ MIC Power
The MPI pin supplies power for the Microphone. This output voltage is proportional to 0.8 x AVDD typically and the
load resistance is minimum 2kΩ. Any capacitor must not be connected to the MPI pin, directly. (Figure 34)
AK4634
MIC-Power
MPI pin
≥ 2k
Audio
I/F
MIC pin
BICK pin
FCK pin
STDO pin
A/D HPF
MIC-Amp
Figure 34. MIC Block Circuit
Rev. 0.5
2007/10
- 36 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
