AK4635 AKM [Asahi Kasei Microsystems], AK4635 Datasheet - Page 46

• Manufacturer Part Number: AK4635
• Description: 16-Bit Mono CODEC with ALC & MIC/SPK/Video-AMP
• Manufacturer: AKM [Asahi Kasei Microsystems]

2. ALC Recovery Operation
The ALC recovery operation waits for the WTM2-0 bits
If the input signal does not exceed “ALC recovery waiting counter reset level”
recovery operation is executed. The VOL value is automatically incremented by RGAIN1-0 bits
reference level
The ALC recovery operation is executed in a period set by WTM2-0 bits.
For example, when the current VOL value is 30H and RGAIN1-0 bits are set to “01”(2 steps), VOL is changed to 32H by
the auto limiter operation and then the input signal level is gained by 0.75dB (=0.375dB x 2). When the VOL value
exceeds the reference level (IREF7-0 or OREF5-0), the VOL values are not increased.
When
during the ALC recovery operation, the waiting timer of ALC recovery operation is reset. When
the waiting timer of ALC recovery operation starts.
The ALC operation corresponds 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 microphone instantaneously, the quality of
small level in the large noise can be improved by this fast recovery operation. The speed of first recovery operation is set
by RFST1-0 bits
Rev. 0.6
“ALC recovery waiting counter reset level (LMTH1-0) ≤ Output Signal < ALC limiter detection level (LMTH1-0)”
“ALC recovery waiting counter reset level (LMTH1-0) > Output Signal”,
WTM2
0
0
0
0
1
1
1
1
(Table
(Table
WTM1
0
0
1
1
0
0
1
1
30,
32).
Table
RGAIN1
WTM0
0
0
1
1
31) with zero crossing detection which timeout period is set by ZTM1-0 bits
Table 28. ALC Recovery Operation Waiting Period
0
1
0
1
0
1
0
1
RGAIN0
Table 29. ALC Recovery GAIN Step
16384/fs
1024/fs
2048/fs
4096/fs
8192/fs
128/fs
256/fs
512/fs
0
1
0
1
(Table
- 46 -
ALC Recovery Operation Waiting Period
1024ms
2048ms
128ms
256ms
512ms
1
2
3
4
8kHz
16ms
32ms
64ms
GAIN STEP
28) to be set after completing the ALC limiter operation.
0.375dB
0.750dB
1.125dB
1.500dB
1024ms
16kHz
128ms
256ms
512ms
16ms
32ms
64ms
8ms
(Table
(default)
25) during the wait time, the ALC
44.1kHz
185.8ms
371.5ms
11.6ms
23.2ms
46.4ms
92.9ms
2.9ms
5.8ms
(Table
29) up to the set
(default)
(Table
[AK4635]
2007/10
27).