WM8985
Pre-Production
REGISTER
ADDRESS
BIT
LABEL
ALCSEL
DEFAULT
00
DESCRIPTION
ALC function select:
REFER TO
32 (20h)
8:7
Input Limiter/
Automatic
Level Control
(ALC)
00=ALC off
01=ALC right only
10=ALC left only
11=ALC both on
Reserved. Initialise to 0
Set Maximum Gain of PGA
111=+35.25dB
6
0
5:3
ALCMAXGAIN
111
Input Limiter/
Automatic
Level Control
(ALC)
110=+29.25dB
101=+23.25dB
100=+17.25dB
011=+11.25dB
010=+5.25dB
001=-0.75dB
000=-6.75dB
2:0
ALCMINGAIN
000
Set minimum gain of PGA
000=-12dB
Input Limiter/
Automatic
Level Control
(ALC)
001=-6dB
010=0dB
011=+6dB
100=+12dB
101=+18dB
110=+24dB
111=+30dB
33 (21h)
7:4
3:0
ALCHLD
ALCLVL
0000
1011
ALC hold time before gain is increased.
0000 = 0ms
Input Limiter/
Automatic
Level Control
(ALC)
0001 = 2.67ms
0010 = 5.33ms
… (time doubles with every step)
1111 = 43.691s
ALC target – sets signal level at ADC input
Input Limiter/
Automatic
Level Control
(ALC)
1111 : -1.5dBFS
1110 : -1.5dBFS
1101 : -3dBFS
1100 : -4.5dBFS
...... (-1.5dB steps)
0001 : -21dBFS
0000 : -22.5dBFS
34 (22h)
8
ALCMODE
0
Determines the ALC mode of operation:
0=ALC mode
Input Limiter/
Automatic
Level Control
(ALC)
1=Limiter mode
7:4
ALCDCY
[3:0]
0011
Decay (gain ramp-up) time
(ALCMODE ==0)
Input Limiter/
Automatic
Level Control
(ALC)
Per step
410us
Per 6dB
3.3ms
90% of range
24ms
0000
0001
0010
820us
6.6ms
48ms
1.64ms
13.1ms
192ms
… (time doubles with every step)
1010
or
420ms
3.36s
24.576s
higher
0011
Decay (gain ramp-up) time
(ALCMODE ==1)
PP, Rev 3.4, October 2006
100
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
