AK4695 Datasheet, PDF (39/107 Pages) Asahi Kasei Microsystems – 24bit 4ch CODEC with MIC/HP/SPK/LINE-AMP

[ ALCEQ: First order zero pole high pass filter ]
Gain
[dB]
0dB
[AK4695]
-3.5dB
100Hz
(fc₂)
150Hz
(fc₁)
Frequency
[Hz]
Figure 30. ALCEQ Frequency Response (fs = 48kHz)
1. ALC Limiter Operation
During ALC limiter operation, when either L or R channel output level exceeds the ALC limiter detection level (Table 22),
the VOL value (same value for both L and R) is attenuated automatically according to the output level (Table 23). The
volume is attenuated by the step amount shown in Table 23 at every sampling. (This attenuation is repeated for sixteen
times once ALC limiter operation is executed.)
After completing the attenuate operation, unless ALC0/1/2/3 bit is changed to “0”, the operation repeats when the input
signal level exceeds ALC limiter detection level.
When ATTLMT bit = “1”, VOL value is attenuated to 0dB if the volume is over ALC limiter detection level. In this case,
attenuation under 0dB is not executed. The reference level must be set to a plus value or mute. When ATTLMT bit = “0”
(default values), normal attenuation is executed without volume limitation.
LMTH1 bit
0
0
1
1
LMTH0 bit
ALC Limiter Detection Level
(LM-LEVEL)
ALC Recovery Waiting Counter
Reset Level
0
–2.5dBFS
–4.1dBFS
1
–4.1dBFS
–6.0dBFS
0
–6.0dBFS
–8.5dBFS
1
–8.5dBFS
–12dBFS
Table 22. ALC Limiter Detection Level / Recovery Counter Reset Level
(default)
Output Level
+0.53dBFS  Output Level (Level Detection 1)
–1.16dBFS  EQ Output Level (Level Detection 2) < +0.53dBFS
LM-LEVEL  EQ Output Level (Level Detection 2) < –1.16dBFS
Table 23. ALC Limiter ATT Amount
ATT Step [dB]
0.38148
0.06812
0.02548
MS1463-E-01
- 39 -
2014/12