AK4649 Datasheet, PDF (49/96 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK-AMP

[AK4649]
NSTHL3 bit
0
0
0
0
0
0
0
0
1
1
1
NSTHL2 bit
NSTHL1 bit
NSTHL0 bit
Noise Suppression
Threshold Low Level
0
0
0
−81dB
(default)
0
0
1
−78dB
0
1
0
−75dB
0
1
1
−72dB
1
0
0
−69dB
1
0
1
−66dB
1
1
0
−63dB
1
1
1
−60dB
0
0
0
−57dB
0
0
1
−54dB
0
1
0
−51dB
Table 36. Noise Suppression Threshold Low Level
NATT1 bit NATT0 bit ATT STEP
0
0
1/4 (Note 41)
0
1
1/2 (Note 42)
1
0
1
1
1
2
Note 41. 1step attenuated in 4 x “WTM cycles”.
Note 42. 1step attenuated in 2 x “WTM cycles”.
Table 37. Noise ATT Settings
(default)
ZTM1 bit
0
0
1
1
ZTM0 bit
Zero Cross Timeout Period
8kHz
16kHz
44.1kHz
0
128/fs
16ms
8ms
2.9ms
1
256/fs
32ms
16ms
5.8ms
0
512/fs
64ms
32ms
11.6ms
1
1024/fs
128ms
64ms
23.2ms
Table 27. ALC Zero Cross Timeout Period Settings
(default)
(2) Noise Level Hold
During the waiting time set by WTM2-0 bits (Table 28), VOL values are kept when the input signal peak level is in
between the set value of NSTHH1-0 (Note 43) and Noise Suppression Threshold Low Level (Noise Suppression High
Level >input signal level ≥ Noise Suppression Threshold Low Level) therefore the output signal level does not change.
NSTHH1 bit NSTHH0 bit Noise Suppression High Level (Note 43)
0
0
NSTHL3-0bits + 3dB
0
1
NSTHL3-0bits + 6dB
(default)
1
0
NSTHL3-0bits + 9dB
1
1
NSTHL3-0bits + 12dB
Note 43. Noise Suppression Threshold Low Level (NSTHL3-0 bits) + Gain (NSTHH1-0 bits) = Noise Suppression High
Level
Table 38. Noise Suppression High Level Settings
MS1023-E-01
- 49 -
2010/08