WM1811A datasheet(95/328 Pages) WOLFSON

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Production Data

WM1811A

PD, November 2013, Rev 4.1

AIF2 - INPUT PATH NOISE GATE CONTROL

The WM1811A provides a digital noise gate function for the AIF2 input paths. The noise gate ensures

best noise performance when the signal path is idle. When the noise gate is enabled, and the signal

level is below the noise gate threshold, then the noise gate is activated, causing the signal path to be

muted.

The AIF2 input path noise gate is enabled using the AIF2DAC_NG_ENA register.

The noise gate threshold (the signal level below which the noise gate is activated) is set using

AIF2DAC_NG_THR.

To prevent erroneous triggering, a time delay is applied before the gate is activated; the signal path is

only muted when the signal level stays below the threshold for longer than ‘hold time’, determined by

the AIF2DAC_NG_HLD register.

When the noise gate is activated, the WM1811A gradually attenuates the AIF2 input signal paths until

each is entirely muted. When the signal level increases, and the noise gate is de-activated, the gain

will return to the AIF2DACL_VOL and AIF2DACR_VOL digital gain settings. The un-mute behaviour

can be immediate or gradual; this is determined by the AIF2DAC_MUTERATE and

AIF2DAC_UNMUTE_RAMP registers described in Table 47.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1328 (0530h)

AIF2 DAC

Noise Gate

6:5

AIF2DAC_

NG_HLD

[1:0]

AIF2DAC input path Noise Gate Hold Time

(delay before noise gate is activated)

00 = 30ms

01 = 125ms

10 = 250ms

11 = 500ms

3:1

AIF2DAC_

NG_THR

[2:0]

100

AIF2DAC input path Noise Gate Threshold

000 = -60dB

001 = -66dB

010 = -72dB

011 = -78dB

100 = -84dB

101 = -90dB

110 = -96dB

111 = -102dB

AIF2DAC_

NG_ENA

AIF2DAC input path Noise Gate Enable

0 = Disabled

1 = Enabled

Table 48 AIF2 Input Path Noise Gate Control

AIF2- INPUT PATH MONO MIX CONTROL

A digital mono mix can be selected on theAIF2input channels. The mono mix is generated as the sum

of the Left and Right AIF channel data. When the mono mix function is enabled, the combined mono

signal is applied to the Left channel and the Right channel of the AIF2 signal processing and digital

mixing paths. To prevent clipping, 6dB attenuation is applied to the mono mix.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1312(0520h)

AIF2DAC

Filters (1)

AIF2DAC_

MONO

AIF2DAC input path Mono Mix Control

0 = Disabled

1 = Enabled

Table 49 AIF2 Input Path Mono Mix Control

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