WM8945ECSSLASHR datasheet(38/169 Pages) WOLFSON

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WM8945

Production Data

PD, May 2011, Rev 4.1

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” (shown as “Knee1” in

Figure 17) 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 17). 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 17.

Figure 17 DRC Response Characteristic

The slope of the DRC response is 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 register. A slope of 1 indicates constant gain in this region. A slope greater than 1

represents expansion (i.e. A change in input amplitude produces a larger change in output

amplitude).

When the DRC_KNEE2_OP knee is enabled (“Knee2” in Figure 17), this introduces the vertical line in

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

The DRC parameters are listed in Table 16.

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