AK4665A Datasheet, PDF (28/52 Pages) Asahi Kasei Microsystems – 20-Bit Stereo CODEC with MIC/HP-AMP

ASAHI KASEI
[AK4665A]
„ ALC2 Operation (LOUT, ROUT pins)
The ALC2 (Automatic Level Control) of stereo line out is done by ALC2 block when ALC2 bit is “1”. The gain of ALC2
block is fixed to 0dB when ALC2 bit is “0”.
(1) ALC2 Limiter Operation
During the ALC2 limiter operation, when the ALC2 output level exceeds the ALC2 limiter detection level (LMTHP bit:
Table 23), the volume value of ALC2 is attenuated automatically by the amount defined by the ALC2 limiter ATT step
(LMATP1-0 bits: Table 24). The volume value is changed without zero crossing detection. LTMP1-0 bits (Table 25) set
the ALC2 limiter operation period.
LMTHP ALC2 Limiter Detection Level ALC2 Recovery Waiting Counter Reset Level
0
ALC2 Output ≥ −7.5dBV
−7.5dBV > ALC2 Output ≥ −9.5dBV
1
ALC2 Output ≥ −11.5dBV
−11.5dBV > ALC2 Output ≥ −13.5dBV
Table 23. ALC2 Limiter Detection Level / Recovery Waiting Counter Reset Level
Default
LMATP1
0
0
1
1
LMATP0
ATT STEP
0
1 step
0.5dB
1
2 step
1.0dB
0
3 step
1.5dB
1
4 step
2.0dB
Table 24. ALC2 Limiter ATT step
Default
FS3 FS2 FS1 FS0
0000
0001
0010
1000
1001
1010
1100
1101
1110
Others
ALC2 Limiter Time
LTMP=00
LTMP=01
LTMP=10
(Default)
6/fs (136µs)
12/fs (272µs)
24/fs (544µs)
4/fs (125µs)
8/fs (250µs)
16/fs (500µs)
6/fs (125µs)
12/fs (250µs)
24/fs (500µs)
3/fs (136µs)
6/fs (272µs)
12/fs (544µs)
2/fs (125µs)
4/fs (250µs)
8/fs (500µs)
3/fs (125µs)
6/fs (250µs)
12/fs (500µs)
1.5/fs (136µs)
3/fs (272µs)
6/fs (544µs)
1/fs (125µs)
2/fs (250µs)
4/fs (500µs)
1.5/fs (125µs)
3/fs (250µs)
6/fs (500µs)
N/A
Table 25. ALC2 Limiter Operation Period
LTMP=11
48/fs (1088µs)
32/fs (1000µs)
48/fs (1000µs)
24/fs (1088µs)
16/fs (1000µs)
24/fs (1000µs)
12/fs (1088µs)
8/fs (1000µs)
12/fs (1000µs)
Default
(2) ALC2 Recovery Operation
The ALC2 recovery operation waits for WTMP1-0 bits (Table 26) to be set after completing the ALC2 limiter operation.
If the input signal does not exceed “ALC2 recovery waiting counter reset level” (LMTHP bit) during the wait time, the
ALC2 recovery operation is done. The ALC2 value is automatically incremented by RGAINP bit (Table 27) up to the set
reference level (REFP5-0 bits: Table 28). The ALC2 recovery operation is done at a period set by WTMP1-0 bits. When
zero cross is detected at both channels during the wait period set by WTM1-0 bits, the ALC recovery operation waits until
WTM1-0 period and the next recovery operation is done. The setting period of WTM1-0 bits should be the same as
ZTM1-0 bits or longer time. When MOFF9 bit is “0”, the volume value is incremented with soft transition. The soft
transition time is set by PTS1-0 bits (Table 39). The WTMP1-0 bits should be set to the same period as PTS1-0 bits or
longer. When MOFF9 bit is “1”, the volume increase immediately.
During the ALC2 recovery operation, the ALC2 limiter operation starts immediately as soon as the ALC2 output level
exceeds the ALC2 limiter detection level (LMTHP bit).
MS0440-E-01
- 28 -
2006/05