ak4651 AKM Semiconductor, Inc., ak4651 Datasheet - Page 28

• Manufacturer Part Number: ak4651
• Description: 16bit ?? Codec With Mic/hp/spk-amp
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
(2) ALC1 Recovery Operation
The ALC1 recovery refers to the amount of time that the AK4651 will allow a signal to exceed a predetermined limiting
value prior to enabling the limiting function. The ALC1 recovery operation uses the WTM1-0 bits to define the wait
period used after completing an ALC1 limiter operation (Table 19). If the input signal does not exceed the “ALC1
Recovery Waiting Counter Reset Level” (LMTH: Table 15), the ALC1 recovery operation starts. The IPGA value
increases automatically by the recovery gain step (RGAIN bit: Table 20) with zero crossing operation (timeout is set by
ZTM1-0: Table 18) during this operation up to the reference level (REF5-0 bit: Table 21). The ALC1 recovery operation
is done at a period set by the WTM1-0 bits. Zero crossing is detected during WTM1-0 period, the ALC1 recovery
operation waits WTM1-0 period and the next recovery operation starts.
During the ALC1 recovery operation, when input signal level exceeds the ALC1 limiter detection level (LMTH), the
ALC1 recovery operation changes immediately into an ALC1 limiter operation.
In the case of
during the ALC1 recovery operation, the wait timer for the ALC1 recovery operation is reset. Therefore, in the case of
the wait timer for the ALC1 recovery operation starts.
The ALC1 operation corresponds to the impulse noise. When the impulse noise is input, the ALC1 recovery operation
becomes faster than a normal recovery operation.
MS0503-E-00
(Recovery waiting counter reset level) ≤ (IPGA Output Level) < (Limiter detection level)
(Recovery waiting counter reset level) > (IPGA Output Level),
WTM1
0
0
1
1
WTM0
Table 21. Setting Reference Value at ALC1 Recovery Operation
0
1
0
1
REF5-0
Table 19. ALC1 Recovery Operation Waiting Period
3DH
2DH
3CH
05H
04H
03H
02H
01H
00H
:
:
:
Table 20. ALC1 Recovery Gain Step Setting
1024/fs
128/fs
256/fs
512/fs
RGAIN
0
1
ALC1 Recovery Operation Waiting Period
GAIN (dB)
+26.5
+26.0
+19.0
+0.5
+0.0
−1.0
−2.0
−7.0
−8.0
128ms
8kHz
16ms
32ms
64ms
GAIN STEP
:
:
:
- 28 -
0.5dB
1.0dB
16kHz
STEP
0.5dB
1.0dB
16ms
32ms
64ms
8ms
Default
Default
44.1kHz
11.6ms
23.2ms
2.9ms
5.8ms
Default
[AK4651]
2006/04