wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 33

• 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

Pre-Production
DYNAMIC RANGE CONTROLLER (DRC)
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The dynamic range controller (DRC) is a circuit which can be enabled in the digital data path of the
WM9081. The function of the DRC is to adjust the signal gain in conditions where the input amplitude
is unknown or varies over a wide range. The DRC can apply Compression and Automatic Level
Control to the signal path. It incorporates ‘anti-clip’ and ‘quick release’ features for handling transients
in order to improve intelligibility in the presence of loud impulsive noises.
Using the DRC to normalise the audio signal level can also provide protection from excessive output
power conditions, which can lead to battery droop, increased heat dissipation and over-temperature
system shutdown.
The DRC is enabled as shown in Table 10. Note that the DRC is not available in hardware control
mode.
Table 10 DRC Enable
COMPRESSION/LIMITING CAPABILITIES
The DRC supports two different compression regions, separated by a ’knee’ at a specific input
amplitude. In the region above the knee, the compression slope DRC_HI_COMP applies; in the
region below the knee, the compression slope DRC_LO_COMP applies.
The overall DRC compression characteristic in ’steady state’ (i.e. where the input amplitude is near-
constant) is illustrated in Figure 25.
Figure 25 DRC Compression Characteristic
R32 (20h)
DRC 1
REGISTER
ADDRESS
DRC Output Amplitude (dB)
DRC_KNEE_OP
(Y0)
BIT
15
DRC Compression Characteristic
DRC_ENA
LABEL
DRC_LO_COMP
DRC_KNEE_IP
“knee”
DEFAULT
0
DRC_HI_COMP
DRC enable
0 = Disabled
1 = Enabled
DRC Input Amplitude (dB)
0dB
DESCRIPTION
PP, Rev 3.0, April 2009
WM9081
33