WM8959
Pre-Production
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
register bit.
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.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R10 (0Ah)
7
DAC_MUTERATE
0b
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)
6
DAC_MUTEMODE 0b
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
2
DAC_MUTE
1b
DAC Soft Mute Control
0 = DAC Un-mute
1 = DAC Mute
Table 19 DAC Soft-Mute Control
PP, May 2008, Rev 3.1
54
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
