WM1811A datasheet(90/328 Pages) WOLFSON

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WM1811A

Production Data

PD, November 2013, Rev 4.1

AIF1 - INPUT PATH SOFT MUTE CONTROL

The WM1811A provides a soft mute function for the AIF1 input paths. When the mute function is

selected, the WM1811A gradually attenuates the associated signal paths until the path is entirely

muted.

When the mute function is de-selected, the gain will either return instantly to the digital gain setting, or

will gradually ramp back to the digital gain setting, depending on the AIF1DAC1_UNMUTE_RAMP

The mute and un-mute ramp rate is selectable between two different rates.

The AIF1 input paths are soft-muted by default. To play back an audio signal, the soft-mute must first

be de-selected by setting AIF1DAC1_MUTE = 0.

The soft un-mute would typically be used during playback of audio data so that when the Mute is

subsequently disabled, a smooth transition is scheduled to the previous volume level and pop noise is

avoided. This is desirable when resuming playback after pausing during a track.

The soft un-mute would typically not be required when un-muting at the start of a music file, in order

that the first part of the music track is not attenuated. The instant un-mute behaviour is desirable in

this case, when starting playback of a new track. See “Digital Volume Soft Mute and Soft Un-Mute”

(Figure 19) for an illustration of the soft mute function.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1056 (0420h)

AIF1 DAC1

Filters (1)

AIF1DAC1_

MUTE

AIF1DAC input path Soft Mute Control

0 = Un-mute

1 = Mute

AIF1DAC1_

MUTERAT

AIF1DAC input path Soft Mute Ramp Rate

0 = Fast ramp (fs/2, maximum ramp time is

10.7ms at fs=48k)

1 = Slow ramp (fs/32, maximum ramp time is

171ms at fs=48k)

(Note: ramp rate scales with sample rate.)

AIF1DAC1_

UNMUTE_

RAMP

AIF1DAC input path Unmute Ramp select

0 = Unmuting the AIF1DAC path

(AIF1DAC1_MUTE=0) will immediately apply

the AIF1DAC1L_VOL and AIF1DAC1R_VOL

settings.

1 = Unmuting the AIF1DAC path

(AIF1DAC1_MUTE=0) will cause a gradual

volume ramp up to the AIF1DAC1L_VOL and

AIF1DAC1R_VOL settings.

Table 41 AIF1 Input Path Soft Mute Control

AIF1 - INPUT PATH NOISE GATE CONTROL

The WM1811A provides a digital noise gate function for the AIF1 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 AIF1 input path noise gate is enabled using the AIF1DAC1_NG_ENA register.

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

AIF1DAC1_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 AIF1DAC1_NG_HLD register.

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