AK4601VQ Datasheet, PDF (76/111 Pages) Asahi Kasei Microsystems – Audio HUB CODEC with Digital Mixer

[AK4601]
■ Analog Input Blcok
1. Microphone Input Gain
The AK4601 has gain amplifiers for microphone input. The gain of L and R channels can be
independently selected by MGNL[3:0] and MGNR[3:0] bits (Table 40). The input impedance is typ.
20k@ADC1VL/R bit = “0” and typ. 25k@ADC1VL/R bit = “1”. This gain amplifier executes zero
crossing detection when changing the gain by setting MICLZCE bit = “1” / MICRZCE bit = “1”. Zero
crossing detection is executed independently for L and R channels. Zero crossing timeout period is
16ms@fs=48kHz. When MICLZCE bit = “0”/ MICRZCE bit = “0”, the volume is changed immediately by
register settings.
When writing to MGNL/R[3:0] bits continuously, take an interval of zero crossing timeout period or more.
If the MGNL/R[3:0] bits are changed before zero crossing, the volume of Lch and Rch may differ. When
the volume level that is same as the present volume is set, the zero crossing counter is not reset and
time outs according to the previous writing timing. Therefore, in this case, writing to MGNL/R [3:0] bits
continuously is possible with a shorter interval of the zero crossing timeout period.
1-1. Microphone Input Selector
Mode
MGNL[3]
MGNR[3]
MGNL[2]
MGNR[2]
MGNL[1]
MGNR[1]
MGNL[0]
MGNR[0]
Input Gain
0
0
0
0
0
0dB
1
0
0
0
1
2dB
2
0
0
1
0
4dB
3
0
0
1
1
6dB
4
0
1
0
0
8dB
5
0
1
0
1
10dB
6
0
1
1
0
12dB
7
0
1
1
1
14dB
8
1
0
0
0
16dB
9
1
0
0
1
18dB
A
1
0
1
0
21dB
B
1
0
1
1
24dB
C
1
1
0
0
27dB
D
1
1
0
1
30dB
E
1
1
1
0
33dB
F
1
1
1
1
36dB
Table 40. Microphone Input Gain
(default)
1-2. Zero Crossing Timeout
The microphone gain is changed independently on the timing of zero crossing detection or zero crossing
timeout.
PLL_MCLK Zero Crossing Timeout Period
48kHz base 122.880MHz
16.0ms
44.1kHz base 112.986MHz
17.4ms
Table 41. Zero Crossing Timeout Period
1-3. Start-up Time of MIC Input Pin
The AK4601 starts to charge a DC cut capacitor when the PDN pin is set to “H” from “L”. Since the input
impedance is 25kΩ, the time constant will be 25ms if the DC cut capacitor is 1µF. A wait time of about
100ms should be taken before power up the ADC to charge the DC cut capacitor sufficiently. A click
noise may occur just after the ADC is powered up if this wait time is not enough.
016000391-E-01
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2016/12