AK4951AEN Datasheet, PDF (37/105 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/HP/SPK-AMP

[AK4951A]
■ Microphone Gain Amplifier
The AK4951A has a gain amplifier for microphone input. It is powered-up by PMADL/R bit = “1”. The gain
of MIC-Amp is selected by the MGAIN3-0 bits. The typical input impedance is 30k. A click noise may
occur if the MIC-Amp gain is changed when both MIC-Amp and ADC (PMADL/R bits = “1”) are powered
up.
High frequency characteristics are attenuated when MIC-Amp = +30dB. The attenuation amount of when
MIC-Amp = +30dB is -0.5dB at 10kHz frequency and -1.5dB at 20kHz frequency comparing with when
MIC-Amp = +18dB.
Table 23. Input Gain
MGAIN3 bit MGAIN2 bit MGAIN1 bit MGAIN0 bit
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
Others
(N/A: Not available)
Input Gain
0dB
+3dB
+6dB
+9dB
+12dB
+15dB
+18dB
+21dB
+24dB
+27dB
+30dB
N/A
(default)
■ Microphone Power
When PMMP bit = “1”, the MPWR1 or MPWR2 pin supplies the power for microphones. This output
voltage is typically 2.4V @MICL bit =“0”, and typically 2.0V@MICL bit = “1”. The load resistance is
minimum 1.0k In case of using two sets of stereo microphones, the load resistance is minimum 2k for
each channel. Any capacitor must not be connected directly to the MPWR1 and MPWR2 pins (Figure 25).
Table 24. Microphone Power
PMMP bit MPSEL bit
MPWR1 pin
MPWR2 pin
0
x
Hi-Z
Hi-Z
1
0
Output
Pull-down (13kΩ)
1
Pull-down (13kΩ)
Output
(x: Do not care)
(default)
MIC Power
MPWR1 pin
MPSEL bit
MPWR2 pin
LIN1 pin
RIN1 pin
LIN2 pin
RIN2 pin
Figure 25. Microphone Block Circuit
Microphone
Microphone
Microphone
Microphone
016001936-E-00
- 37 -
2016/03