AK4649 Datasheet, PDF (48/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
Register Name
LMTH1-0
ZELMN
ZTM1-0
WTM2-0
OREF5-0
OVL7-0,
OVR7-0
LMAT1-0
LFST
RGAIN1-0
RFST1-0
ALC2
Comment
fs=8kHz
Data
Operation
Limiter detection Level
01
−4.1dBFS
Limiter zero crossing detection
0
Enable
Zero crossing timeout period
01
32ms
Recovery waiting period
*WTM2-0 bits must be the same value 001
32ms
or larger value than ZTM1-0 bits
Maximum gain at recovery operation 28H
+6dB
Gain of VOL
91H
0dB
Limiter ATT step
00
1 step
Fast Limiter Operation
1
ON
Recovery GAIN step
00
1 step
Fast Recovery Speed
00
4 times
ALC enable
1
Enable
Table 35. Example of the ALC Setting (Playback)
fs=44.1kHz
Data
Operation
01
−4.1dBFS
0
Enable
11
23.2ms
100
46.4ms
28H
+6dB
91H
0dB
00
1 step
1
ON
00
1 step
00
4 times
1
Enable
5. Noise Suppression
The Noise Suppression is enabled when NSCE bit (Noise suppression enable bit) = “1” during ALC operation (ALC1 bit
= “1”). This function attenuates output signal level automatically when minute amount of the signal is input.
NSCE bit: Noise Suppression Enable
0: Disable (default)
1: Enable
(1) Noise Level Suppressing Operation
The output signal (Note 40) is suppressed when the input peak level is lower than “Noise Suppression Threshold Low
Level” set by NSTHL3-0 bits (Table 36) during the waiting time set by WTM2-0 bits (Table 28).
VOL value is changed by this noise suppressing operation only at the individual zero crossing points of Lch and Rch or at
the zero crossing timeout. Noise level suppressing operation has common zero cross timeout period to ALC recovery
operation which is set by ZTM1-0 bits. (Table 27)
This operation sets the volume automatically to the reference level (Table 40) with zero cross detection in the period
which is set by ZTM1-0 bits (Table 27). It is executed in the cycle of WTM2-0 bits settings.
Note 40. When the input signal volume is smaller than the value set by NSREF7-0 bits, normal ALC recovery operation
is executed.
MS1023-E-01
- 48 -
2010/08