ak4141 AKM Semiconductor, Inc., ak4141 Datasheet - Page 27

• Manufacturer Part Number: ak4141
• Description: Nicam/a2/eia-j Digital Stereo Decoder
• Manufacturer: AKM Semiconductor, Inc.

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
IVL and IVR are set to the same value for both channels. The ALC recovery operation is executed at a period set by
WTM2-0 bits. When zero cross is detected at both channels during the wait period set by WTM2-0 bits, the ALC recovery
operation waits until WTM2-0 period and the next recovery operation is executed.
For example, when the current VOL value is 30H and RGAIN1-0 bits are set to “01”, VOL is changed to 32H in 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 (REF7-0), 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 signal level in the large noise can be improved by this fast recovery operation. The speed of first recovery operation
is set by RFST1-0
MS0952-E-00
“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
bits(Table
WTM1
0
0
1
1
0
0
1
1
16) with zero crossing detection which timeout period is set by ZTM1-0 bits
RGAIN1
17).
WTM0
0
0
1
1
Table 14. ALC Recovery Operation Waiting Period
0
1
0
1
0
1
0
1
Table 15. ALC Recovery GAIN Step
RGAIN0
16384/fs
1024/fs
2048/fs
4096/fs
8192/fs
128/fs
256/fs
512/fs
0
1
0
1
(Table
- 27 -
1 step
2 step
3 step
4 step
ALC Recovery Operation Waiting Period
128.0ms
256.0ms
512.0ms
16.0ms
32.0ms
64.0ms
32kHz
4.0ms
8.0ms
GAIN STEP
14) to be set after completing the ALC limiter operation.
0.375dB
0.750dB
1.125dB
1.500dB
44.1kHz
185.8ms
371.5ms
11.6ms
23.2ms
46.4ms
92.9ms
2.9ms
5.8ms
(Table
(default)
11) during the wait time, the ALC
170.7ms
341.3ms
10.7ms
21.3ms
42.7ms
85.3ms
48kHz
2.7ms
5.3ms
(Table
(Table
15) up to the set
(default)
13). Then the
[AK4141]
2008/05