wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 36

• Manufacturer Part Number: wm9081
• Description: Mono Dac With 2.6w Class Ab/d Speaker Driver, Dynamic Range Controller And Retune Mobile Parametric Equalizer
• Manufacturer: Wolfson Microelectronics plc

WM9081
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Table 14 DRC Time Constants
ANTI-CLIP CONTROL
The DRC includes an Anti-Clip feature to avoid signal clipping when the input amplitude rises very
quickly. This feature uses a feed-forward technique for early detection of a rising signal level. Signal
clipping is avoided by dynamically increasing the gain attack rate when required. The Anti-Clip
feature is enabled using the DRC_ANTICLIP bit.
Note that the feed-forward processing increases the latency in the input signal path. For low-latency
applications (e.g. telephony), it may be desirable to reduce the delay, although this will also reduce
the effectiveness of the anti-clip feature. The latency is determined by the DRC_FF_DLY bit. If
necessary, the latency can be minimised by disabling the anti-clip feature altogether.
The DRC Anti-Clip control bits are described in Table 15.
Table 15 DRC Anti-Clip Control
R33 (21h)
DRC 2
R32 (20h)
DRC 1
REGISTER
REGISTER
ADDRESS
ADDRESS
15:12
BIT
11:8
BIT
5
1
DRC_FF_DLY
DRC_ANTICLIP
DRC_ATK[3:0]
DRC_DCY[3:0]
LABEL
LABEL
DEFAULT
DEFAULT
0000
0000
1
1
Gain attack rate (seconds/6dB)
Gain decay rate (seconds/6dB)
0000 = Reserved (181us)
0001 = 181us
0010 = 363us
0011 = 726us
0100 = 1.45ms (default)
0101 = 2.9ms
0110 = 5.8ms
0111 = 11.6ms
1000 = 23.2ms
1001 = 46.4ms
1010 = 92.8ms
1011 = 185.6ms
1100-1111 = Reserved
0000 = 186ms
0001 = 372ms
0010 = 743ms (default)
0011 = 1.49s
0100 = 2.97s
0101 = 5.94s
0110 = 11.89s
0111 = 23.78s
1000 = 47.56s
1001-1111 = Reserved
Feed-forward delay for anti-clip
feature
0 = 5 samples
1 = 9 samples
Time delay can be calculated as
5/f
rate.
Anti-clip enable
0 = Disabled
1 = Enabled
s
or 9/ f
s
DESCRIPTION
DESCRIPTION
, where f
PP, Rev 3.0, April 2009
s
is the sample
Pre-Production
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