AK4563A Datasheet, PDF (31/39 Pages) Asahi Kasei Microsystems – Low Power 16bit 4ch ADC & 2ch DAC with ALC

ASAHI KASEI
[AK4563A]
2. ALC Recovery Operation
The ALC recovery operation waits until a time of setting WTM1-0 bits after completing the ALC limiter. If the input
signal does not exceed “ALC recovery waiting counter reset level (LMTH)”, the ALC recovery operation is done. The
IPGA value increases automatically by this operation up to the set reference level (REF6-0 bits). Then the IPGA value is
set for L/R commonly. The ALC recovery operation is done at a period set by WTM1-0 bits.
When L/R channels in IPGA0 and IPGA1 are detected by zero crossing operation during WTM1-0, the ALC recovery
operation waits until WTM1-0 period and the next recovery operation is done.
During the ALC recovery operation or the recovery waiting, when either input signal level of L/R channels in IPGA0 and
IPGA1 exceed the ALC limiter detection level (LNTH), the ALC recovery operation changes into the ALC limiter
operation immediately
In case of “ALC recovery waiting counter reset level (LMTH) ≤ Input Signal < ALC limiter detection level (LMTH)”
during the ALC recovery operation, the waiting timer of ALC recovery operation is reset. Therefore, in case of “ALC
recovery waiting counter reset level (LMTH) > Input Signal”, the waiting timer of ALC recovery operation starts.
If the impulse noise is supplied at FR = “0”, the ALC recovery operation becomes the faster period than a set of ZTM1-0
and WTM1-0 bits. When FR bit is “1”, the ALC operation in AK4561 is the same as AK4516A’s.
Limiter detection level (LMTH)
During recovery counter reset
WTM counter starts
(1)
Recovery waiting counter
reset level (LMTH)
Zero crossing detect
(2)
WTM counter starts
ZTM counter starts
(2)
WTM counter starts
ZTM counter starts
(2)
WTM counter starts
Figure 18. The transition from the limiter operation to the recovery operation
(1). When the input signal is below the ALC recovery waiting counter reset level, the ALC recovery operation waits the
time set by WTM1-0 bits. If the input signal does not exceed the ALC limiter detection level or the ALC recovery
waiting counter reset level, the ALC recovery operation is done only once.
(2). The IPGA value is changed by the zero crossing operation in ALC recovery operation, but the next counter of the
ALC recovery waiting timer is also starting.
Other:
When a channel of one side enters the limiter operation during the waiting zero crossing, the present ALC recovery
operation stops, according as the small value of IPGA (a channel of waiting zero crossing), the ALC limiter operation is
done.
When both channels are waiting for the next ALC recovery operation, the ALC limiter operation is done from the IPGA
value of a point in time.
MS0067-E-02
- 31 -
2004/12