WM8608 ETC-unknow, WM8608 Datasheet - Page 37

• 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

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DYNAMIC PEAK COMPRESSOR
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An auto-mute function is provided that automatically mutes the output stage when a digital silence
period is detected. Digital silence is defined as a consecutive period of 1024 zero input samples at
the output of the volume control. Auto-mute will be removed as soon as the volume control output
becomes non-zero. (Please note that on the sub channel the noise level is greatly reduced, rather
than complete digital silence.)
To achieve digital silence, you can do one of the following:
The auto-mute operates independently across all channel pairs, and can be enabled or disabled on
individual channel pairs.
The mute features maximize the SNR of the PWM amplifier system. Soft-mute will only maximize the
SNR of channel pairs that have auto-mute enabled.
Table 35 Mute
The WM8608 includes a Dynamic Peak Compressor for each channel, which prevents the
occurrence of digital clipping when gains in excess of 0dB are applied. The compressor automatically
adjusts the signal amplitude to allow headroom for the LFE boost, sub-woofer mixing, tone controls,
loudspeaker equalisation and digital volume control. The compressor has a programmable limit
threshold, programmable attack and decay time-constants, a frequency-dependent decay mode, and
built-in zero-cross detect. The compressor can be configured either to operate independently on all
channels (DUAL MONO), or on linked channel-pairs (STEREO), e.g. Table 36. The following
channels are paired together: Front-Left and Front-Right, Surround-Left and Surround-Right, Front-
Centre and Rear-Centre.
COMPRESSOR THRESHOLD
The compressor has a digital peak detector which tracks the maximum input signal level at the
output of the volume control. With reference to Figure 22, if this signal is below the threshold set by
control bit THRESH, the compressor operates transparently with no change to the signal level.
However, if peak signal rises above the threshold, the gain through the compressor is modified so
that the upper part of the curve is followed. This ensures that the output signal does not exceed 0dB.
R12 (0Ch)
Mute
REGISTER
ADDRESS
Turn on auto-mute and set the volume control to zero.
Turn on auto-mute and input zero data on the serial data input pins with the bass
management filters disabled. (Page 29)
Turn on auto-mute and soft mute.
1
2
3
4
BIT
0
SMUTE
AMUTEF
AMUTES
AMUTEC
AMUTESB
LABEL
DEFAULT
0
1
1
1
1
0 = disable (signal active)
1= enable
Front Auto-mute
0 = disable
1 = enable
Surround Auto-mute
0 = disable
1 = enable
mute
0 = disable
1 = enable
Subwoofer Auto-mute
0 = disable
1 = enable
Digital Soft Mute
Front Centre and Rear Centre Auto-
DESCRIPTION
PP Rev 1.5 March 2004
WM8608
37