AK4950 Datasheet, PDF (48/106 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP & mini DSP

[AK4950]
■ ALC Operation
The ALC (Automatic Level Control) is operated by ALC block when ALC bit is “1”. When ADCPF bit is “1”, the ALC
circuit operates for recording path. When ADCPF bit is “0”, the ALC circuit operates for playback path. ALC bit controls
ON/OFF of ALC operation.
Note 38. In this section, VOL means IVL and IVR for recording path, OVL and OVR for playback path.
Note 39. In this section, REF means IREF for recording path, OREF for playback path.
1. ALC Limiter Operation
During ALC limiter operation, when either L or R channel output level exceeds the ALC limiter detection level (Table
27), the VOL value (L/R in common) is attenuated automatically to the level under ALC recovery counter reset level. The
attenuate amount is depends on output level (Table 28). The volume is attenuated by the amount (L/R in common) shown
in Table 28 in every one sampling. (When ALC limiter operation is executed, this attenuate operation is repeated for 16
times.)
After completing the attenuate operation, unless ALC bit is changed to “0”, the operation repeats when the input signal
level exceeds ALC limiter detection level.
LMTH1 bit
0
0
1
1
LMTH0 bit ALC Limiter Detection Level
ALC Recovery Counter
(LM LEVEL)
Reset Level
0
–2.5dBFS
–4.1dBFS
1
–4.1dBFS
–6.0dBFS
0
–6.0dBFS
–8.5dBFS
1
–8.5dBFS
–12dBFS
Table 27. ALC Limiter Detection Level / Recovery Counter Reset Level
(default)
Output level
ATT Amount [dB]
Output Level (*) >= +0.53dBFS
0.38142
–1.16dBFS < Output Level < +0.53dBFS
0.06812
LM LEVEL < Output Level < –1.16dBFS
0.02548
(*) Compare with the next output data
Table 28. ALC Limiter ATT Amount
MS1320-E-00
- 48 -
2011/10