wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 60

• Manufacturer Part Number: wm8918
• Description: Ultra Low Power Dac For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8918
Figure 36 DAC Mute Control
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DAC SOFT MUTE AND SOFT UN-MUTE
The WM8918 has a soft mute function. When enabled, this 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_UNMUTE_RAMP
register bit.
To mute the DAC, this function must be enabled by setting DAC_MUTE to 1.
Soft Mute Mode would typically be enabled (DAC_UNMUTE_RAMP = 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_UNMUTE_RAMP = 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 volume ramp rate during soft mute and un-mute is controlled by the DAC_MUTERATE bit.
Ramp rates of fs/32 and fs/2 can be selected, as shown in Table 33. The ramp rate determines the
rate at which the volume is increased or decreased. The actual ramp time depends on the extent of
the difference between the muted and un-muted volume settings.
DAC muting and un-muting using volume control bits
DACL_VOL and DACR_VOL.
DAC muting and un-muting using the DAC_MUTE bit.
If soft Mute Mode is not enabled (DAC_UNMUTE_RAMP = 0):
Setting the DAC_MUTE bit causes the volume to ramp down
at a rate controlled by DAC_MUTERATE.
Clearing the DAC_MUTE bit causes the volume to return to
the un-muted level immediately.
DAC muting and un-muting using the DAC_MUTE bit.
If soft Mute Mode is enabled (DAC_UNMUTE_RAMP = 1):
Setting the DAC_MUTE bit causes the volume to ramp down.
Clearing the DAC_MUTE bit causes the volume to ramp up to
the un-muted level at a rate controlled by DAC_MUTERATE.
PD, Rev 4.0, September 2010
Production Data
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