Wolfson WM8978, Manual, Page: 41 / 119

Production Data
WM8978
w
PD, Rev 4.5, October 2011
41
LIMITER MODE
ALCMODE = 1 (Limiter Mode)
ALCATK
t
ATKLIM
t
ATKLIM6dB
t
ATKLIM90%
0000 22.7µs 182µs 1.31ms
0001 45.4µS 363µs 2.62ms
0010 90.8µS 726µs 5.23ms
0011 182µS 1.45ms 10.5ms
0100 363µS 2.91ms 20.9ms
0101 726µS 5.81ms 41.8ms
0110 1.45ms 11.6ms 83.7ms
0111 2.9ms 23.2ms 167ms
1000 5.81ms 46.5ms 335ms
1001 11.6ms 93ms 669ms
1010 23.2ms 186ms 1.34s
Attack Time (s)
ALCMODE = 1 (Limiter Mode)
ALCDCY
t
DCYLIM
t
DCYLIM6dB
t
DCYLIM90%
0000 90.8µs 726µs 5.23ms
0001 182µS 1.45ms 10.5ms
0010 363µS 2.91ms 20.9ms
0011 726µS 5.81ms 41.8ms
0100 1.45ms 11.6ms 83.7ms
0101 2.91ms 23.2ms 167ms
0110 5.81ms 46.5ms 335ms
0111 11.6ms 93ms 669ms
1000 23.2ms 186ms 1.34s
1001 46.5ms 372ms 2.68s
1010 93ms 744ms 5.36s
Attack Time (s)
Table 19 ALC Limiter Mode (Attack and Decay times)
MINIMUM AND MAXIMUM GAIN
The ALCMIN and ALCMAX register bits set the minimum/maximum gain value that the PGA can be
set to whilst under the control of the ALC. This has no effect on the PGA when ALC is not enabled.
REGISTER
ADDRESS
BIT LABEL DEFAULT DESCRIPTION
R32
ALC Control
1 5:3 ALCMAX 111 Set Maximum Gain of PGA
2:0 ALCMIN 000 Set minimum gain of PGA
Table 20 ALC Max/Min Gain
In normal mode, ALCMAX sets the maximum boost which can be applied to the signal. In limiter
mode, ALCMAX will normally have no effect (assuming the starting gain value is less than the
maximum gain specified by ALCMAX) because the maximum gain is set at the starting gain level.
ALCMIN sets the minimum gain value which can be applied to the signal.