[AK4675]
■ MIC Detection
The AK4675 has a detect function of microphone inputs.
The followings show the example of external microphone detection sequence:
(1) PMMP bit should be set to “1” after CPU detects the jack insertion of microphone or headphone.
(2) The MPWR pin drives external microphone.
(3) The GPO2 pin (at GPOM2 bit = “1”) and DTMIC bit are set as Table 21. In case of Headset (with Mic), the input
voltage of the MDT pin is higher than 0.075 x AVDD because of the relationship between the bias resistance at the
MPWR pin (typ. 2.2kΩ) and the microphone impedance. In case of Headphone (No Mic), the input voltage of the
MDT pin is 0V because the pin of headphone jack is connected to the MDT pin is assigned as ground.
Input Level of MDT pin
GPO2 pin
DTMIC bit
Result
H
L
1
0
Mic (Headset)
No Mic (Headphone)
≥ 0.075 x AVDD
< 0.050 x AVDD
Table 21. Microphone Detection Result
PMMP bit
MPWR
AK4675
LIN1
LIN2
MDT
G
M
R
R
L
L
Headset
DTMIC bit
typ.
500k
or
0.075 x AVDD
G
Headphone
Figure 55. Microphone Power Supply and Mic Detection
MS0963-E-00
2008/05
- 69 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
