WM8980_12 Datasheet, PDF (39/123 Pages) Wolfson Microelectronics plc – Stereo CODEC with Speaker Driver and Video Buffer

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WM8980
ATTACK AND DECAY TIMES
The attack and decay times set the update times for the PGA gain. The attack time is the time
constant used when the gain is reducing. The decay time is the time constant used when the gain is
increasing. In limiter mode, the time constants are faster than in ALC mode. The time constants are
shown below in terms of a single gain step, a change of 6dB and a change of 90% of the PGAs gain
range.
Note that, these times will vary slightly depending on the sample rate used (specified by the SR
register).
NORMAL MODE
ALCMODE = 0 (Normal Mode)
ALCATK
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
t_ATK
104µs
208µs
416µs
832µs
1.66ms
3.33ms
6.66ms
13.3ms
26.6ms
53.2ms
106ms
Attack Time (s)
t_ATK6dB
832µs
1.66ms
3.33ms
6.66ms
13.3ms
26.6ms
53.2ms
106ms
213.2ms
426ms
852ms
t_ATK90%
6ms
12ms
24ms
48ms
96ms
192ms
384ms
767ms
1.53s
3.07s
6.13s
ALCMODE = 0 (Normal Mode)
ALCDCY
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
t_DCY
410µs
820µs
1.64ms
3.28ms
6.56ms
13.1ms
26.2ms
52.5ms
105ms
210ms
420ms
Decay Time (s)
t_DCY6dB
3.28ms
6.56ms
13.1ms
26.2ms
52.5ms
105ms
210ms
420ms
840ms
1.68s
3.36s
t_DCY90%
23.6ms
47.2ms
94.5ms
189ms
378ms
756ms
1.51s
3.02s
6.05s
12.1s
24.2s
Table 19 ALC Normal Mode (Attack and Decay times)
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PP, Rev 3.8, May 2012
39