AK5701_07 Datasheet, PDF (35/64 Pages) Asahi Kasei Microsystems – 16-Bit ΔΣ Stereo ADC with PLL & MIC-AMP

[AK5701]
■ ALC Operation
The ALC (Automatic Level Control) is done by ALC block when ALC bit is “1”.
1. ALC Limiter Operation
During the ALC limiter operation, when either Lch or Rch exceeds the ALC limiter detection level (Table 22), the IVL
and IVR values (same value) are attenuated automatically by the amount defined by the ALC limiter ATT step (Table 23).
When ZELMN bit = “0” (zero cross detection is enabled), the IVL and IVR values are changed by ALC 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 ALC limiter and recovery operation (Table 24).
When ZELMN bit = “1” (zero cross detection is disabled), IVL and IVR values are immediately (period: 1/fs) changed by
ALC limiter operation. Attenuation step is fixed to 1 step regardless of the setting of LMAT1-0 bits.
The attenuation operation is executed continuously until the input signal level becomes ALC limiter detection level
(Table 22) or less. After completing the attenuation operation, unless ALC bit is changed to “0”, the operation repeats
when the input signal level exceeds LMTH1-0 bits.
LMTH1
0
0
1
1
LMTH0 ALC Limier Detection Level ALC Recovery Waiting Counter Reset Level
0
ALC Output ≥ −2.5dBFS
−2.5dBFS > ALC Output ≥ −4.1dBFS
1
ALC Output ≥ −4.1dBFS
−4.1dBFS > ALC Output ≥ −6.0dBFS
0
ALC Output ≥ −6.0dBFS
−6.0dBFS > ALC Output ≥ −8.5dBFS
1
ALC Output ≥ −8.5dBFS
−8.5dBFS > ALC Output ≥ −12dBFS
Table 22. ALC Limiter Detection Level / Recovery Counter Reset Level
(default)
ZELMN
0
1
LMAT1 LMAT0
ALC 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
1step
0.375dB
Table 23. ALC Limiter ATT Step
(default)
ZTM1
0
0
1
1
ZTM0
0
1
0
1
Zero Crossing Timeout Period
8kHz
16kHz
44.1kHz
128/fs
16ms
8ms
2.9ms
256/fs
32ms
16ms
5.8ms
512/fs
64ms
32ms
11.6ms
1024/fs
128ms
64ms
23.2ms
Table 24. ALC Zero Crossing Timeout Period
(default)
MS0404-E-02
- 35 -
2007/08