AK4665A Datasheet, PDF (18/52 Pages) Asahi Kasei Microsystems – 20-Bit Stereo CODEC with MIC/HP-AMP

ASAHI KASEI
[AK4665A]
„ ALC1 Operation (MIC-ALC)
The ALC1 (Automatic Level Control) is done by ALC1 block when ALC1 bit is “1”.
1. ALC1 Limiter Operation
During the ALC1 limiter operation, when either Lch or Rch exceeds the ALC1 limiter detection level (LMTH1-0 bits:
Table 9), the IVOL value (same value for Lch and Rch) is attenuated automatically by the ALC1 limiter ATT step
(LMAT1-0 bits: Table 10).
When ZELMN bit is “0” (zero crossing detection is enabled), the IVOL value is changed by the ALC1 limiter operation
at the individual zero crossing points of Lch and Rch or at the zero crossing timeout. ZTM1-0 bits set the zero crossing
timeout period of both the ALC1 limiter and recovery operation (Table 11).
When ZELMN bit is “1” (zero crossing detection is disabled), the IVOL value is immediately (period: 1/fs) changed by
the ALC1 limiter operation. Attenuation step is fixed to 1 step regardless as the setting of LMAT1-0 bits.
After completing the attenuation operation, unless ALC1 bit is changed to “0”, the operation repeats when the input signal
level exceeds ALC1 limiter detection level.
LMTH1
0
0
1
1
LMTH0 ALC1 Limier Detection Level ALC1 Recovery Waiting Counter Reset Level
0
ALC1 Output ≥ −4.1dBFS
−4.1dBFS > ALC1 Output ≥ −6.0dBFS
1
ALC1 Output ≥ −6.0dBFS
−6.0dBFS > ALC1 Output ≥ −8.5dBFS
0
ALC1 Output ≥ −8.5dBFS
−8.5dBFS > ALC1 Output ≥ −12dBFS
1
ALC1 Output ≥ −10.1dBFS
−10.1dBFS > ALC1 Output ≥ −14.5dBFS
Table 9. ALC1 Limiter Detection Level / Recovery Waiting Counter Reset Level
Default
ZELMN
0
1
LMAT1 LMAT0
ALC1 Limiter ATT Step
0
0
1 step
0.375dB
0
1
2 step
0.750dB
1
0
4 step
1.500dB
1
1
8 step
3.000dB
x
x
1 step
0.375dB
Table 10. ALC1 Limiter ATT Step (x: Don’t care)
Default
FS3 FS2 FS1 FS0
0000
0001
0010
1000
1001
1010
1100
1101
1110
Others
ALC1 Zero Cross Timeout
ZTM=00
ZTM=01
ZTM=10
(Default)
384/fs (8.7ms) 768/fs (17.4ms) 1536/fs (34.8ms)
256/fs (8.0ms) 512/fs (16.0ms) 1024/fs (32.0ms)
384/fs (8.0ms) 768/fs (16.0ms) 1536/fs (32.0ms)
192/fs (8.7ms) 384/fs (17.4ms) 768/fs (34.8ms)
128/fs (8.0ms) 256/fs (16.0ms) 512/fs (32.0ms)
192/fs (8.0ms) 384/fs (16.0ms) 768/fs (32.0ms)
96/fs (8.7ms) 192/fs (17.4ms) 384/fs (34.8ms)
64/fs (8.0ms) 128/fs (16.0ms) 256/fs (32.0ms)
96/fs (8.0ms) 192/fs (16.0ms) 384/fs (32.0ms)
N/A
Table 11. ALC1 Zero Crossing Timeout Period
ZTM=11
3072/fs (69.7ms)
2048/fs (64.0ms)
3072/fs (64.0ms)
1536/fs (69.7ms)
1024/fs (64.0ms)
1536/fs (64.0ms)
768/fs (69.7ms)
512/fs (64.0ms)
768/fs (64.0ms)
Default
MS0440-E-01
- 18 -
2006/05