WM8608 ETC-unknow, WM8608 Datasheet - Page 38

• Manufacturer Part Number: WM8608
• Description: The Wm8608 Comprises A High Performance Multi-channel Pwm Digital Power Amplifier Controller. Simply By Adding Appropriate Power Output Stages A Multi-channel Power Amplifier May Be Built. Six Identical Full Audio Bandwidth Channels, Plus A Reduced B
• Manufacturer: ETC-unknow

WM8608
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ATTACK AND DECAY TIMES
The attack time-constant ATK controls how fast the gain is reduced when the signal goes above the
threshold. It is defined as the time taken for the gain to reduce by 6dB. Normally a short attack time-
constant is used to prevent the signal clipping when a high-amplitude transient occurs.
The decay time-constant DCY controls how fast the gain is increased when the signal begins to fall
again. It is defined as the time taken for the gain to increase by 6dB. Normally, the decay time-
constant is much longer than the attack time-constant, to prevent the input signal from entering
repeated limiting cycles.
The frequency-dependent decay feature automatically detects the input frequency and sets the
decay time to decay slower for low frequency signals. This reduces low-frequency signal distortion by
preserving the waveform of each input cycle, whilst allowing the compressor to respond quickly to
high frequency transients. This feature is enabled via the FDEP control bit.
ZERO-CROSS
The Dynamic Peak Compressor has a zero cross detector to prevent gain changes introducing clicks
in the signal. The ZC is controlled by the same register R25 used in the volume control.
Figure 22 Dynamic Peak Compressor Characteristics
Table 36 Front, Surround, Front Centre and Rear Centre Channel Dynamic Peak
Compressor (1)
R21 (15h)
Front,
Surround,
Front Centre
and Rear
Centre
Channel
Dynamic
Peak
Compressor
REGISTER
ADDRESS
THRESH
[dB]
Output Level
-30
-36
-24
-18
-12
0dB
(dB)
-36
-30
0
1
2
BIT
+12dB
-24
PLENF
PLENS
PLENC
+6dB
LABEL
0dB
-18
-6dB
-12
-12dB
Volume Control
Setting
typical
1
1
1
DEFAULT
-6
0
Front Channel Compressor Enable
0 = disable
1 = enable
Surround Channel Compressor
Enable
0 = disable
1 = enable
Channel Compressor Enable
0 = disable
1 = enable
Front Centre and Rear Centre
+6
Peak Input Level [dB]
+12
DESCRIPTION
PP Rev 1.5 March 2004
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