AK4637EN Datasheet, PDF (39/96 Pages) Asahi Kasei Microsystems – 24bit Mono CODEC with MIC/SPK-AMP

[AK4637]
■ MIC/LINE Input Selector
The AK4637 has an input selector. MDIF bit select single-ended input and differential input. When MDIF
bit = “0”, the AIN pin is an input pin. Single-ended signal to the MIC-Amp can be input via the AIN pin.
When MDIF bit = “1”, the IN+ pin and the IN- pin are input pins. Differential signal can be input to these
pins. At this time, the IN- pin cannot be used as the BEEP pin. When DMIC bit = “1”, digital microphone
input is selected regardless of MDIF bit.
DMIC bit MDIF bit
MIC Input
0
0
1
AIN pin
IN+/ pins
(default)
1
x
Digital MIC
Table 21. MIC/Line In Path Select (x: Do not care, N/A: Not available)
MPWR pin
1k
IN+ pin
IN- pin
1k
MIC-Power
AK4637
MIC-Amp
A/D HPF
Audio
I/F
BICK pin
FCK pin
STDO pin
Figure 34. Differential Input Block Circuit (MDIF bit = “1”)
■ Microphone Gain Amplifier
The AK4637 has a gain amplifier for microphone input. It is powered-up by PMADC bit = “1”. The gain of
MIC-Amp is selected by the MGAIN3-0 bits. When single-ended input, the typical input impedance is
30k. When differential input, the typical input impedances are IN+=20kΩ and IN-=57kΩ@MGAIN3-0
bits = “0000” (0dB), IN+=16kΩ and IN-=244kΩ@MGAIN3-0 bits = “0110” (+18dB). A click noise may
occur if the MIC-Amp gain is changed when both MIC-Amp and ADC (PMADC bit = “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.
MGAIN3 bit
0
0
0
0
0
0
0
0
1
1
1
MGAIN2 bit MGAIN1 bit MGAIN0 bit Input Gain
0
0
0
0dB
0
0
1
+3dB
0
1
0
+6dB
0
1
1
+9dB
1
0
0
+12dB
1
0
1
+15dB
1
1
0
+18dB
1
1
1
+21dB
0
0
0
+24dB
0
0
1
+27dB
0
1
0
+30dB
Others
N/A
Table 22. Input Gain (N/A: Not available)
(default)
015010680-E-00
- 39 -
2015/09