WM8944BECSSLASHR datasheet(39/165 Pages) CIRRUS

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WM8944B

Rev 4.3

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R29 (1Dh)

DRC Control 1

DRC_ENA

DRC Enable

0 = Disabled

1 = Enabled

Table 15 DRC Enable

DRC COMPRESSION / EXPANSION / LIMITING

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 DRC also supports a noise gate region, where low-level input signals are heavily attenuated. This

function can be enabled or disabled according to the application requirements. The DRC response in

this region is defined by the expansion slope DRC_NG_EXP.

For additional attenuation of signals in the noise gate region, an additional “knee” can be defined

(shown as “Knee2” in Figure 16). When this knee is enabled, this introduces an infinitely steep drop-

off in the DRC response pattern between the DRC_LO_COMP and DRC_NG_EXP regions.

The overall DRC compression characteristic in “steady state” (i.e. where the input amplitude is near-

constant) is illustrated in Figure 16.

DRC_KNEE_IP

(Y0)

0dB

DRC

_HI_

COMP

DRC

_LO_

COMP

DRC Input Amplitude (dB)

DRC Output Amplitude (dB)

DRC_KNEE_OP

Knee1

Knee2

DRC_KNEE2_IP

DRC_KNEE2_OP

Figure 16 DRC Response Characteristic

The

slope

the

DRC

response

determined

by register

fields

DRC_HI_COMP

and

DRC_LO_COMP. A slope of 1 indicates constant gain in this region. A slope less than 1 represents

compression (i.e. a change in input amplitude produces only a smaller change in output amplitude). A

slope of 0 indicates that the target output amplitude is the same across a range of input amplitudes;

this is infinite compression.

When the noise gate is enabled, the DRC response in this region is determined by the DRC_NG_EXP

expansion (ie. a change in input amplitude produces a larger change in output amplitude).

When the DRC_KNEE2_OP knee is enabled (“Knee2” in Figure 16), this introduces the vertical line in

the response pattern illustrated, resulting in infinitely steep attenuation at this point in the response.

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