AK4649 Datasheet, PDF (50/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
(3) Noise Suppression → Normal ALC Operation
During noise suppressing operation, if the input signal level exceeds Noise Suppression High Level, the operation
switches to normal ALC operation from noise suppressing or noise level hold operation. In this case, recovery speed is
faster than the normal recovery (Table 39).
However, when normal ALC operation is changed to noise suppressing operation and the internal volume is lower than
the reference value at Noise Suppression (NSREF7-0 bits), the recovery speed is the same as the ALC recovery speed
during the operation switches to normal ALC operation from noise suppressing.
NSGAIN1 bit
NSGAIN0 bit
Recovery Speed
0
0
8 step
0
1
12 step
(default)
1
0
16 step
1
1
28 step
Table 39. Fast Recovery Speed Setting from Noise Suppression to ALC Operation
NSREF7-0 bits GAIN[dB]
Step
F1H
+36.0
F0H
+35.625
EFH
+35.25
:
:
C5H
+19.5
:
:
0.375dB
92H
+0.375
91H
0.0
(default)
90H
−0.375
:
:
2H
−53.625
1H
−54.0
0H
MUTE
Table 40. Reference Value Setting when Noise Suppression is ON
MS1023-E-01
- 50 -
2010/08