AK4538 Datasheet, PDF (26/70 Pages) Asahi Kasei Microsystems – 16Bit DS CODEC with MIC/HP/SPK-AMP

ASAHI KASEI
[AK4538]
n MIC Gain Amplifier
AK4538 has a Gain Amplifier for Microphone input. This gain is 0dB or +20dB, selected by the MGAIN bit. The typical
input impedance is 30kΩ.
n MIC Power
MGAIN bit
Input Gain
0
0dB
1
+20dB
Table 16. Input Gain
Default
The MPI and MPE pins supply power for the Microphone. These output voltages are 0.75 x AVDD (typ) and the maximum
output current is 1.25mA. MPWRI/MPWRE bit can control output from MPI and MPE pin.
MPE ^{“MPWRE” bit}
MPI
“MPWRI” bit
INT
EXT
MDT
“DTMIC” bit
500k _{0.075 x AVDD}
n MIC Detection Function
Figure 20. Microphone Power Supply
The AK4538 includes the detection function of microphone.
Example of the detection of external microphone.
(1) MPWRE= “1”.
(2) MPE drives external microphone.
(3) DTMIC bit is set by Table 17.
Input Level of DTM
DTMIC
External microphone
≥0.075 x AVDD
1
Connect
< 0.050 x AVDD
0
Disconnect
Table 17. Microphone detection result
MS0198-E-01
- 26 -
2003/5