WM8961
Pre-Production
DAC SOFT MUTE AND SOFT UN-MUTE
The WM8961 also has a soft mute function, which, when enabled, gradually attenuates the volume of
the digital signal to zero. 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 DACSMM register
bit.
The DAC is soft-muted by default. To play back an audio signal, this function must first be disabled by
setting the DACMU bit to zero.
DACSMM would typically be enabled when using soft mute during playback of audio data so that
when soft mute is then 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).
DACSMM would typically be disabled when un-muting at the start of a digital music file, so 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 LDACVOL and
RDACVOL.
DAC muting and un-muting using soft
mute bit DACMU.
Soft un-mute not enabled (DACSMM
= 0).
DAC muting and un-muting using soft
mute bit DACMU.
Soft un-mute enabled (DACSMM =
1).
Figure 17 DAC Mute Control
The volume ramp rate during soft mute and un-mute is controlled by the DACMR bit. Ramp rates of
fs/32 and fs/2 are selectable as shown in Table 20 (fs = DAC sample rate).
REGISTER
ADDRESS
BIT
LABEL
DACMU
DEFAULT
DESCRIPTION
Digital Soft Mute
R5 (05h)
1
3
ADC and DAC
Control (1)
1 = Mute
0 = No mute (signal active)
R6 (06h)
DACSMM
0
DAC Soft Mute Mode
3
ADC and DAC
Control (2)
0 = Disabling soft-mute (DACMU=0)
will cause the volume to change
immediately to the LDACVOL /
RDACVOL settings
1 = Disabling soft-mute (DACMU=0)
will cause the volume to ramp up
gradually to the LDACVOL /
RDACVOL settings
DACMR
0
DAC Soft Mute Ramp Rate
2
0 = Fast ramp (fs/2 at fs=48k,
providing maximum delay of 10.7ms)
1 = Slow ramp (fs/32 at fs=48k,
providing maximum delay of
171ms)DAC Soft Mute Ramp Rate
Table 20 DAC Soft-Mute Control
PP, August 2009, Rev 3.1
w
38
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
