AK4635 AKM [Asahi Kasei Microsystems], AK4635 Datasheet - Page 45

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

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ALC Operation works in ALC block. When ADCPF bit = “1”, ALC operation is enable for recording path. When ADCPF
bit = “0”, ALC operation is enable for playback path. The ON/OFF of ALC operation for recording is controlled by ALC1
bit and the ON/OFF of ALC operation for playback is controlled by ALC2 bit.
1. ALC Limiter Operation
When the ALC limiter is enabled, and output exceeds the ALC limiter detection level
attenuated by the amount defined in LMAT1-0 bits
When the ZELMN bit = “0” (zero crossing detection valid), the VOL value is changed by ALC limiter operation at the
zero crossing point or zero crossing timeout. Zero crossing timeout period is set by ZTM1-0 bit that in common with ALC
recovery zero crossing timeout period’s setting
(period : 1/fs) when output Level is over FS(Digital Full Scale).
When the ZELMN bit = “1” (zero crossing detection invalid), VOL value has been changed immediately (period: 1/fs) by
ALC limiter operation. The attenuation for limiter operation is fixed to 1 step and not controlled by setting LMAT1-0 bits.
After finishing the attenuation operation, if ALC bit does not change to “0”, the operation repeats when the output signal
level exceeds the ALC limiter detection level.
Rev. 0.6
ALC Operation
LMTH1
0
0
1
1
ZTM1
LMAT1
LMTH0 ALC Limiter Detection Level
0
0
1
1
0
0
1
1
0
1
0
1
Table 25. ALC Limiter Detection Level / Recovery Waiting Counter Reset Level
ZTM0
LMAT0
ALC Output ≥ −2.5dBFS
ALC Output ≥ −4.1dBFS
ALC Output ≥ −6.0dBFS
ALC Output ≥ −8.5dBFS
0
1
0
1
0
1
0
1
Table 27. ALC Zero Crossing Timeout Period Setting
1024/fs
128/fs
256/fs
512/fs
Table 26. ALC Limiter ATT Step Setting
ALC1 Output
≥ LMTH
1
2
2
1
(Table
(Table
128ms
27).At LFST bit = “1”, VOL value is attenuated 1step immediately
8kHz
16ms
32ms
64ms
ALC1 Output
- 45 -
Zero Crossing Timeout Period
26) automatically.
ALC1 Limiter ATT Step
ALC Recovery Waiting Counter Reset Level
≥ FS
1
2
4
2
−2.5dBFS > ALC Output ≥ −4.1dBFS
−4.1dBFS > ALC Output ≥ −6.0dBFS
−6.0dBFS > ALC Output ≥ −8.5dBFS
−8.5dBFS > ALC Output ≥ −12dBFS
16kHz
16ms
32ms
64ms
8ms
ALC1 Output
≥ FS + 6dB
1
2
4
4
44.1kHz
23.2ms
11.6ms
(Table
2.9ms
5.8ms
ALC1 Output
≥ FS + 12dB
25), the volume value is
1
2
8
8
(default)
(default)
(default)
[AK4635]
2007/10