WM8978 Wolfson Microelectronics Ltd., WM8978 Datasheet - Page 91

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WM8978

Manufacturer Part Number
WM8978
Description
The WM8978 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
Manufacturer
Wolfson Microelectronics Ltd.
Datasheet

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Preliminary Technical Data
w
33 (21h)
34 (22h)
REGISTER
ADDRESS
2:0
7:4
3:0
8
7:4
3:0
BIT
ALCMINGAIN
ALCHLD
ALCLVL
ALCMODE
ALCDCY
[3:0]
ALCATK
LABEL
000
0000
1011
0
0011
0011
0010
DEFAULT
Set minimum gain of PGA
000=-12dB
001=-6dB
010=0dB
011=+6dB
100=+12dB
101=+18dB
110=+24dB
111=+30dB
ALC hold time before gain is increased.
0000 = 0ms
0001 = 2.67ms
0010 = 5.33ms
… (time doubles with every step)
1111 = 43.691s
ALC target – sets signal level at ADC input
1111 : -1.5dBFS
1110 : -1.5dBFS
1101 : -3dBFS
1100 : -4.5dBFS
...... (-1.5dB steps)
0001 : -21dBFS
0000 : -22.5dBFS
Determines the ALC mode of operation:
0=ALC mode
1=Limiter mode
Decay (gain ramp-up) time
(ALCMODE ==0)
0000
0001
0010
… (time doubles with every step)
1010
or
higher
Decay (gain ramp-up) time
(ALCMODE ==1)
0000
0001
0010
… (time doubles with every step)
1010
ALC attack (gain ramp-down) time
(ALCMODE == 0)
0000
0001
0010
… (time doubles with every step)
1010
or
higher
Per step
410us
820us
1.64ms
420ms
Per step
90.8us
181.6us
363.2us
93ms
Per step
104us
208us
416us
106ms
DESCRIPTION
Per 6dB
3.3ms
6.6ms
13.1ms
3.36s
Per 6dB
726.4us
1.453ms
2.905ms
744ms
Per 6dB
832us
1.664ms
3.328ms
852ms
90% of range
24ms
48ms
192ms
24.576s
90% of range
5.26ms
10.53ms
21.06ms
5.39s
90% of range
6ms
12ms
24.1ms
6.18s
PTD Rev 2.6 November 2005
Input Limiter/
Automatic
Level Control
(ALC)
Input Limiter/
Automatic
Level Control
(ALC)
Input Limiter/
Automatic
Level Control
(ALC)
Input Limiter/
Automatic
Level Control
(ALC)
Input Limiter/
Automatic
Level Control
(ALC)
Input Limiter/
Automatic
Level Control
(ALC)
REFER TO
WM8978
91