wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 79

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

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Pre-Production
DAC SOFT MUTE AND SOFT UN-MUTE
The WM8400 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).
Figure 32 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 44. 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.
Table 44 DAC Soft-Mute Control
R11 (0Bh)
REGISTER
ADDRESS
7
6
2
BIT
DAC_MUTERATE
DAC_MUTEMODE
DAC_MUTE
LABEL
0b
0b
1b
DEFAULT
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).
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)
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
0 = DAC Un-mute
1 = DAC Mute
DAC Soft Mute Mode
DAC Soft Mute Control
DESCRIPTION
PP, April 2009, Rev 3.0
WM8400
79