AK4950 Datasheet, PDF (49/106 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP & mini DSP

[AK4950]
2. ALC Recovery Operation
ALC recovery operation waits for the time set by WTM1-0 bits (Table 29) after completing ALC limiter operation. If the
input signal does not exceed “ALC recovery waiting counter reset level” (Table 27) during the wait time, ALC recovery
operation is executed. The VOL value is automatically incremented by the amount set by RGAIN2-0 bits (Table 30) up to
the set reference level (Table 31) in every one sampling. When the VOL value exceeds the reference level (REF7-0), the
VOL values are not increased.
When
“ALC recovery waiting counter reset level (LMTH1-0) ≤ Output Signal < ALC limiter detection level (LMTH1-0)”
during the ALC recovery operation, the waiting timer of ALC recovery operation is reset. When
“ALC recovery waiting counter reset level (LMTH1-0) > Output Signal”,
the waiting timer of ALC recovery operation starts.
ALC operations correspond to the impulse noise. When the impulse noise is input, the ALC recovery operation becomes
faster than a normal recovery operation. When large noise is input to a microphone instantaneously, the quality of small
level in the large noise can be improved by this fast recovery operation. The speed of fast recovery operation is set by
RFST1-0 bits (Table 33).
WTM1 bit WTM0 bit Recovery Wait Time
0
0
128/fs
0
1
256/fs
1
0
512/fs
1
1
1024/fs
Table 29. ALC Recovery Operation Waiting Period
RGAIN2 bit
0
0
0
0
1
1
1
1
RGAIN1 bit RGAIN0 bit GAIN Amount [dB]
0
0
0.0042
0
1
0.0021
1
0
0.0011
1
1
0.0005
0
0
0.0003
0
1
0.0001
1
0
0.00007
1
1
0.00003
Table 30. ALC Recovery GAIN Amount
(default)
MS1320-E-00
- 49 -
2011/10