AK4213 Datasheet, PDF (18/38 Pages) Asahi Kasei Microsystems – Mono Class-D SPK-Amp with Stereo Cap-less HP-Amp

[AK4213]
(2) ALC Recovery Operation
The ALC recovery operation waits for the WTM2-0 bits to be set after completing the ALC limiter operation. If the input
signal does not exceed “ALC recovery waiting counter reset level” during wait time, the ALC recovery operation is
executed. The SPGA value is automatically incremented by RGAIN1-0 bits up to the set reference level (REF5-0 bits)
with zero crossing detection which timeout period is set by ZTM1-0 bits. The ALC recovery operation period is set by
WTM2-0 bits. When zero cross is detected during the wait period set by WTM2-0 bits, the ALC recovery operation waits
until WTM2-0 period and the next recovery operation is executed. The setting period of WTM2-0 bits should be same as
ZTM1-0 bits or longer period.
When RGAIN 1-0 bits are set to “10”, the ALC recovery operation is not executed even the ALC limiter
operation is executed.
During the ALC recovery operation, when the ALC output level exceeds ALC limiter detection level (LMTH bit), the
ALC limiter operation is executed immediately. When
“ALC recovery waiting counter reset level ≤ ALC Output Signal < ALC limiter detection level (LMTH1-0)”
during the ALC recovery operation, the waiting timer of ALC recovery operation is reset. When
“ALC recovery waiting counter reset level > ALC Output Signal”,
the waiting timer of ALC recovery operation starts.
The ALC operation corresponds to the impulse noise. When the impulse noise is input, the ALC recovery operation
becomes faster than a normal recovery operation. When large noise is input to microphone instantaneously, the quality of
small singal level in the large noise can be improved by this fast recovery operation.
WTM2 bit
0
0
0
0
1
1
1
1
WTM1 bit WTM0 bit
Recovery Waiting Timer
typ.
max
0
0
16.4ms
26.3ms
0
1
32.8ms
51.5ms
1
0
65.6ms
105.0ms
1
1
131.2ms
210.0ms
0
0
262.4ms
419.9ms
0
1
524.8ms
839.7ms
1
0
1049.6ms
1679.4ms
1
1
2099.2ms
3358.8ms
Table 8. ALC Recovery Waiting Timer Period
(default)
RGAIN1 RGAIN0
GAIN STEP
0
0
1 step
0.5dB
0
1
2 step
1.0dB
1
0
0 step
0dB
1
1
Reserved
Table 9. ALC Recovery GAIN Step
(default)
(Only limiter operation)
REF5-0
GAIN (dB)
Step
3FH
+19.5
3EH
+19.0
3DH
+18.5
3CH
+18.0
(default)
:
:
19H
+0.5
0.5dB
18H
0.0
17H
−0.5
:
:
02H
−11.0
01H
−11.5
00H
−12.0
Table 10. Reference Level at ALC Recovery Operation
MS0949-E-01
- 18 -
2008/07