ASAHI KASEI
[AK4644]
MIC Gain Amplifier
The AK4644 has a gain amplifier for microphone input. The gain of MIC-Amp is selected by the MGAIN1-0 bits (see
Table 23). The typical input impedance is 60kΩ(typ)@MGAIN1-0 bits = “00” or 30kΩ(typ)@MGAIN1-0 bits = “01”,
“10” or “11”.
MGAIN1 bit MGAIN0 bit
Input Gain
0dB
+20dB
+26dB
+32dB
0
0
1
1
0
1
0
1
Default
Table 23. Mic Input Gain
MIC Power
When PMMP bit = “1”, the MPWR pin supplies power for the microphone. This output voltage is typically 0.75 x AVDD
and the load resistance is minimum 0.5kΩ. In case of using two sets of stereo mic, the load resistance is minimum 2kΩ for
each channel. No capacitor must not be connected directly to MPWR pin (see Figure 34).
PMMP bit
MPWR pin
Hi-Z
Output
0
1
Default
Table 24. MIC Power
MIC Power
MPWR pin
Microphone
Microphone
Microphone
Microphone
LIN1 pin
RIN1 pin
LIN2 pin
RIN2 pin
Figure 34. MIC Block Circuit
MS0477-E-01
2006/10
- 38 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
