WM8912 datasheet(22/128 Pages) WOLFSON

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WM8912

Production Data

PD, Rev 4.0, September 2010

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R40 (28h)

DRC Control 0

DRC_ENA

DRC enable

0 = disabled

1 = enabled

DRC_DAC_PAT

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_KNEE_IP

(Y0)

0dB

DRC_

HI_C

OMP

DRC Input Amplitude (dB)

DRC Output Amplitude (dB)

DRC_KNEE_OP

“knee”

Figure 15 DRC Compression Characteristic

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