WM8946ECSSLASHR datasheet(41/175 Pages) WOLFSON

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Production Data

WM8946

PD, July 2012, Rev 4.3

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 18), 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.

REF

PARAMETER

DESCRIPTION

DRC_KNEE_IP

Input level at Knee1 (dB)

DRC_KNEE_OP

Output level at Knee1 (dB)

DRC_HI_COMP

Compression ratio above Knee1

DRC_LO_COMP

Compression ratio below Knee1

DRC_KNEE2_IP

Input level at Knee2 (dB)

DRC_NG_EXP

Expansion ratio below Knee2

DRC_KNEE2_OP

Output level at Knee2 (dB)

Table 16 DRC Response Parameters

The noise gate is enabled when the DRC_NG_ENA register is set. When the noise gate is not

enabled, parameters 5, 6, 7 above are ignored, and the DRC_LO_COMP slope applies to all input

signal levels below Knee1.

The DRC_KNEE2_OP knee is enabled when the DRC_KNEE2_OP_ENA register is set. When this

bit is not set, then parameter 7 above is ignored, and the Knee2 position always coincides with the

low end of the DRC_LO_COMP region.

The “Knee1” point in Figure 18 is determined by register fields DRC_KNEE_IP and DRC_KNEE_OP.

Parameter Y0, the output level for a 0dB input, is not specified directly, but can be calculated from the

other parameters, using the equation:

The DRC Compression / Expansion / Limiting parameters are defined in Table 17.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R29 (1Dh)

DRC Control 1

DRC_NG_ENA

DRC Noise Gate Enable

0 = Disabled

1 = Enabled

R32 (20h)

DRC Control 4

12:8

DRC_KNEE2_IP

000000

Input signal level at the Noise Gate

threshold ‘Knee2’.

00000 = -36dB

00001 = -37.5dB

00010 = -39dB

… (-1.5dB steps)

11110 = -81dB

11111 = -82.5dB

Only applicable when

DRC_NG_ENA = 1.

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