AK4560A Datasheet, PDF (39/47 Pages) Asahi Kasei Microsystems – 16bit CODEC with ALC and MIC/HP/SPK-Amps

ASAHI KASEI
[AK4560A]
n ALC1 Operation
1. ALC1 Limiter Operation
During the ALC1 limiter operation, when either Lch or Rch exceed ALC1 limiter detection level (LMTH), IPGA value is
attenuated by ALC1 limiter ATT step (LMAT1-0) automatically. Then the IPGA value is changed commonly for L/R
channels.
In case of ZELM = “1”, timeout period is set by LTM1-0 bits. The operation for attenuation is done continuously until the
input signal level becomes LMTH or less. After finishing the operation for attenuation, if ALC1 bit does not change into
“0”, the operation of attenuation repeats when the input signal level exceed LMTH. (Refer to Figure 30)
In case of ZELM = “0”, timeout period is set by ZTM1-0 bits. The IPGA value is attenuated by zero crossing detection
automatically. (Refer to Figure 31)
The ALC1 operation corresponds to the impulse noise in additional to the ALC operation of AK4516A. When the impulse
noise is input, the ALC1 recovery operation becomes the faster period than a normal recovery operation.
[Explanation for ALC1 operation]
Limiter starts
ATT level (LMAT1-0)
Limiter detection level(LMTH)
ATT level (LMAT1-0)
ATT level (LMAT1-0)
(1) 2dB
Recovery waiting counter
reset level (LMTH)
Limiter update period (LTM1-0)
Limiter finish
Figure 30. Disable ALC1 zero crossing detection (ZELM = “1”)
(1). When the signal is input between 2dB, the AK4560A does not operate the ALC1 limiter and recovery.
MS0028-E-00
- 39 -
2000/05