AK4637 Datasheet, PDF (56/96 Pages) Asahi Kasei Microsystems – 24bit Mono CODEC with MIC - SPK-AMP

[AK4637]
■ Input Digital Volume (Manual Mode)
The input digital volume becomes manual mode when ALC bit is set to “0” while ADCPF bit is “1”. This
mode is used in the cases shown below.
1. After exiting reset state, when setting up the registers for ALC operation (LMTH and etc.)
2. When the registers for ALC operation (Limiter period, Recovery period and etc.) are changed.
For example; when the sampling frequency is changed.
3. When IVOL is used as a manual volume control.
IVOL7-0 bits set the gain of the volume control (Table 39).
This volume has a soft transition function. Therefore no switching noise occurs during the transition. IVTM
bit set the transition time (Table 40). When IVTM bit = “1”, it takes 944/fs (19.7ms@fs=48kHz) from F1H
(+36dB) to 05H (-52.5dB). The volume is muted after transitioned to -72dB in the period set by IVTM bit
when changing the volume from 05H (-52.5dB) to 00H (MUTE).
IVOL7-0 bits
GAIN (dB)
Step
F1H
+36.0
F0H
+35.625
EFH
+35.25
:
:
E2H
+30.375
E1H
+30.0
E0H
+29.625
:
:
0.375dB
92H
+0.375
91H
0.0
90H
0.375
:
:
06H
52.125
05H
52.5
04H~00H
MUTE
Table 39. Input Digital Volume Setting
(default)
IVTM bit
0
1
Transition Time of Input Digital Volume
IVOL7-0 bits = “F1H” → “05H”
Setting Value
fs=8kHz
fs=48kHz
236/fs
29.5ms
4.9ms
944/fs
118ms
19.7ms
Table 40. Transition Time of Input Digital Volume
(default)
If IVOL7-0 bits are written during PMPFIL bit = “0”, IVOL operation starts with the written values after
PMPFIL bit is changed to “1”.
015010680-E-00
- 56 -
2015/09