
[AK4645EZ] 
MS0605-E-00 
2007/06 
- 43 - 
■
 ALC Operation 
The ALC (Automatic Level Control) is operated by ALC block when ALC bit is “1”. When only DAC is powered-up, 
ALC circuit operates at playback path. When only ADC is powered-up or both ADC and DAC are powered-up, ALC 
circuit operates at recording path. 
PMADL bit, PMADR bit 
PMDAC bit 
LOOP bit
0 
x 
“00” 
1 
x 
0 
x 
0 
“01”, “10” or “11” 
1 
1 
Recording Monitor Playback
Table 27. ALC Setting (x: Don’t care) 
1.
ALC Limiter Operation 
During the ALC limiter operation, when either Lch or Rch exceeds the ALC limiter detection level (Table 28), the IVL 
and IVR values (same value) are attenuated automatically by the amount defined by the ALC limiter ATT step (Table 29). 
The IVL and IVR are then set to the same value for both channels. 
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 30). 
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 as the setting of LMAT1-0 bits. 
The attenuation operation is done continuously until the input signal level becomes ALC limiter detection level (Table 28) 
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 
LMTH0 ALC Limier Detection Level
ALC Recovery Waiting Counter Reset Level 
0 
0 
ALC Output 
≥
2.5dBFS 
0 
1 
ALC Output 
≥
4.1dBFS 
1 
0 
ALC Output 
≥
6.0dBFS 
1 
1 
ALC Output 
≥
8.5dBFS 
Table 28. ALC Limiter Detection Level / Recovery Counter Reset Level 
ZELMN 
LMAT1 
LMAT0 
0 
0 
0 
1 
1 
0 
1 
1 
1 
x 
x 
Table 29. ALC Limiter ATT Step (x: Don’t care) 
Zero Crossing Timeout Period 
ZTM1 
ZTM0 
8kHz 
0 
0 
128/fs 
16ms 
0 
1 
256/fs 
32ms 
1 
0 
512/fs 
64ms 
1 
1 
1024/fs 
128ms 
Table 30. ALC Zero Crossing Timeout Period 
Status 
Power-down 
Playback 
Recording 
Recording & Playback 
ALC 
Power-down 
Playback path 
Recording path 
Recording path 
Recording path 
Default
Default
2.5dBFS > ALC Output 
≥
4.1dBFS 
4.1dBFS > ALC Output 
≥
6.0dBFS 
6.0dBFS > ALC Output 
≥
8.5dBFS 
8.5dBFS > ALC Output 
≥
12dBFS 
ALC Limiter ATT Step 
1 step 
2 step 
4 step 
8 step 
1step 
Default 
0.375dB 
0.750dB 
1.500dB 
3.000dB 
0.375dB 
0 
Default 
16kHz 
8ms 
16ms 
32ms 
64ms 
44.1kHz 
2.9ms 
5.8ms 
11.6ms 
23.2ms