WM8994ECSSLASHR datasheet(110/363 Pages) CIRRUS

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WM8994

110

Rev 4.6

DAC SOFT MUTE AND SOFT UN-MUTE

The WM8994 has a soft mute function which ensures that a gradual attenuation is applied to the DAC

outputs when the mute is asserted. The soft mute rate can be selected using the DAC_MUTERATE

bit.

When a mute bit 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_SOFTMUTEMODE register bit. If the

gradual un-mute ramp is selected (DAC_SOFTMUTEMODE = 1), then the un-mute rate is determined

by the DAC_MUTERATE bit.

Note that each DAC is soft-muted by default. To play back an audio signal, the mute must first be

disabled by setting the applicable mute control to 0 (see Table 50).

Soft Mute Mode would typically be enabled (DAC_SOFTMUTEMODE = 1) when using mute during

playback of audio data so that when the mute is subsequently disabled, the 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_SOFTMUTEMODE = 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).

The DAC soft-mute function is illustrated in Figure 30 for DAC1L and DAC1R. The same function is

applicable to DAC2L and DAC2R also.

= 00000000

= [non-zero]

DAC1L_MUTE = 0

DAC1R_MUTE = 0

DAC1L_MUTE = 1

DAC1R_MUTE = 1

DAC1L_MUTE = 0

DAC1R_MUTE = 0

DAC1L_MUTE = 0

DAC1R_MUTE = 0

DAC1L_MUTE = 1

DAC1R_MUTE = 1

DAC1L_MUTE = 0

DAC1R_MUTE = 0

DAC1L_VOL or DAC1R_VOL = [non-zero]

DAC_SOFTMUTEMODE = 0

DAC_SOFTMUTEMODE = 1

DAC muting and un-muting using volume control bits

DAC1L_VOL and DAC1R_VOL

DAC muting and un-muting using soft mute bits

DAC1L_MUTE or DAC1R_MUTE

Soft mute mode not enabled (DAC_SOFTMUTEMODE = 0).

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

Soft mute mode enabled (DAC_SOFTMUTEMODE = 1).

Figure 30 DAC Soft Mute Control

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