AK4641 Datasheet, PDF (23/51 Pages) Asahi Kasei Microsystems – 16 BIT CODEC WITH BLUETOOTH INTERFACE

ASAHI KASEI
[AK4641]
„ MIC Gain Amplifier
The AK4641 has a Gain Amplifier for Microphone input. This gain is 0dB or +20dB, selected by the MGAIN bit. The
typical input impedance is 30kΩ.
„ MIC Power
MGAIN bit
Input Gain
0
0dB
1
+20dB
Table 9. Input Gain
Default
The MPI and MPE pins supply power for the Microphone. These output voltages are 0.75 x AVDD (typ) and the load
resistance is 2kΩ(min). No capacitor must be connected directly to MPI and MPE pins. MPWRI/MPWRE bit can control
output from MPI and MPE pin.
MPE ^{MPWRE bit}
AK4641
Headset
Headphone
GMR L
or
G
RL
MPI
MPWRI bit
INT
EXT
MDT
DTMIC bit
500k _{0.075 x AVDD}
Figure 22. Microphone Power Supply and Mic Detection
„ MIC Detection Function
The AK4641 includes the detection function of microphone. The external circuit is showed in Figure 22.
The followings show the example of external microphone detection sequence:
(1) MPWRE bit = “1”.
(2) MPE drives external microphone.
(3) DTMIC bit is set as Table 10. In case of Headset, the input voltage of MDT pin is higher than 0.078 x AVDD because
of the relationship between the bias resistance at MPE pin (typ. 2.2kΩ) and the microphone impedance. In case of
Headphone, the input voltage of MDT pin is 0V because the pin of headphone jack connected to MDT pin is assigned
as ground.
Input Level of DTM
DTMIC
Result
≥ 0.078 x AVDD
1
Mic (Headset)
< 0.050 x AVDD
0
No Mic (Headphone)
Table 10. Microphone Detection Result
MS0301-E-00
- 23 -
2004/05