wm9714l Wolfson Microelectronics plc, wm9714l Datasheet - Page 36

• Manufacturer Part Number: wm9714l
• Description: Ac?97 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

WM9714L
w
When operating in stereo, the peak detector takes the maximum of left and right channel peak
values, and any new gain setting is applied to both left and right PGAs, so that the stereo image is
preserved. However, the ALC function can also be enabled on one channel only. In this case, only
one PGA is controlled by the ALC mechanism, while the other channel runs independently with its
PGA gain set through the control register.
When one ADC channel is unused, the peak detector disregards that channel. The ALC function can
also operate when the two ADC outputs are mixed to mono in the digital domain, but not if they are
mixed to mono in the analogue domain, before entering the ADCs.
Table 14 ALC Control
62h
ALC / Noise
Gate Control
60h
ALC Control
REGISTER
ADDRESS
15:14
13:11
10:9
15:12
11:8
7:4
3:0
BIT
ALCSEL
MAXGAIN
ZCTIMEOUT
ALCL
HLD
DCY
ATK
LABEL
00
(OFF)
111
(+30dB)
11
1011
(-12dB)
0000
(0ms)
0011
(192ms)
0010
(24ms)
DEFAULT
ALC function select
00 = ALC off (PGA gain set by register)
01 = Right channel only
10 = Left channel only
11 = Stereo (PGA registers unused)
PGA gain limit for ALC
111 = +30dB
110 = +24dB
….(6dB steps)
001 = -6dB
000 = -12dB
Programmable zero cross timeout (delay
for 12.288MHz BITCLK):
11: 2^17 * tbitclk (10.67 ms)
10: 2^16 * tbitclk (5.33 ms)
01: 2^15 * tbitclk (2.67 ms)
00: 2^14 * tbitclk (1.33 ms)
ALC target – sets signal level at ADC
input
0000 = -28.5dB FS
0001 = -27.0dB FS
… (1.5dB steps)
1110 = -7.5dB FS
1111 = -6dB FS
ALC hold time before gain is increased.
0000 = 0ms
0001 = 2.67ms
0010 = 5.33ms
… (time doubles with every step)
1111 = 43.691s
ALC decay (gain ramp-up) time
0000 = 24ms
0001 = 48ms
0010 = 96ms
… (time doubles with every step)
1010 or higher = 24.58s
ALC attack (gain ramp-down) time
0000 = 6ms
0001 = 12ms
0010 = 24ms
… (time doubles with every step)
1010 or higher = 6.14s
DESCRIPTION
PP, Rev 3.2, October 2008
Pre-Production
36