WM8959 datasheet(54/155 Pages) WOLFSON

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WM8959

Pre-Production

PP, May 2008, Rev 3.1

DAC SOFT MUTE AND SOFT UN-MUTE

The WM8959 has a soft mute function which, when enabled, gradually attenuates the volume of the

DAC output. When soft mute is disabled, the gain will either gradually ramp back up to the digital

gain setting, or return instantly to the digital gain setting, depending on the DAC_MUTEMODE

The DAC is soft-muted by default (DAC_MUTE = 1). To play back an audio signal, this function must

first be disabled by setting DAC_MUTE to 0.

Soft Mute Mode would typically be enabled (DAC_MUTEMODE = 1) when using DAC_MUTE during

playback of audio data so that when DAC_MUTE is subsequently disabled, the sudden volume

increase will not create pop noise by jumping immediately to the previous volume level (e.g.

resuming playback after pausing during a track).

Soft Mute Mode would typically be disabled (DAC_MUTEMODE = 0) when un-muting at the start of a

music file, in order that the first part of the track is not attenuated (e.g. when starting playback of a

new track, or resuming playback after pausing between tracks).

DAC muting and un-muting using volume control bits

DACL_VOL and DACR_VOL.

DAC muting and un-muting using soft mute bit DAC_MUTE.

Soft Mute Mode not enabled (DAC_MUTEMODE = 0).

DAC muting and un-muting using soft mute bit DAC_MUTE.

Soft Mute Mode enabled (DAC_MUTEMODE = 1).

Figure 28 DAC Mute Control

The volume ramp rate during soft mute and un-mute is controlled by the DAC_MUTERATE bit.

Ramp rates of fs/32 and fs/2 are selectable as shown in Table 19. The ramp rate determines the rate

at which the volume will be increased or decreased. The actual ramp time depends on the extent of

the difference between the muted and un-muted volume settings.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

DAC_MUTERATE

DAC 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)

DAC_MUTEMODE

DAC Soft Mute Mode

0 = Disabling soft-mute

(DAC_MUTE=0) will cause the DAC

volume to change immediately to

DACL_VOL and DACR_VOL settings

1 = Disabling soft-mute

(DAC_MUTE=0) will cause the DAC

volume to ramp up gradually to the

DACL_VOL and DACR_VOL settings

R10 (0Ah)

DAC_MUTE

DAC Soft Mute Control

0 = DAC Un-mute

1 = DAC Mute

Table 19 DAC Soft-Mute Control

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