WM8912
Production Data
DYNAMIC RANGE CONTROL (DRC)
The dynamic range controller (DRC) is a circuit which can be enabled in the digital DAC playback
path. 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, e.g. when recording from microphones built into a handheld
system. 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.
The DRC is enabled in the digital DAC playback path by setting DRC_ENA and DRC_DAC_PATH,
as shown in Table 1. Both bits must be set for DRC operation.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R40 (28h)
15
DRC_ENA
0
DRC enable
DRC Control 0
0 = disabled
1 = enabled
14
DRC_DAC_PAT
H
0
DRC path select
0 = Reserved
1 = DAC path
Table 1 DRC Enable
COMPRESSION/LIMITING CAPABILITIES
The DRC supports two different compression regions, separated by a “knee” at input amplitude T.
For signals above the knee, the compression slope DRC_HI_COMP applies; for signals 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 15.
DRC Output Amplitude (dB)
(Y0)
“knee”
DRC_KNEE_OP
0dB
DRC_KNEE_IP
DRC Input Amplitude (dB)
Figure 15 DRC Compression Characteristic
PD, Rev 4.0, September 2010
22
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
