wm8742 Wolfson Microelectronics plc, wm8742 Datasheet - Page 32

• Manufacturer Part Number: wm8742
• Description: 24-bit 192khz Dac With Advanced Digital Filtering
• Manufacturer: Wolfson Microelectronics plc

WM8742
w
VOLUME RAMP MODE
There are two ways to change the volume in the WM8742, controlled by VOL_RAMP.
VOL_RAMP=0, the volume changes in a single step from the current volume setting to the new
volume when an update is applied to the gain control registers. When VOL_RAMP=1, the volume is
automatically ramped from the current volume setting to the new volume setting when an update is
applied to the volume control registers. The speed at which this happens is dependant on the sample
rate as shown in Table 27 below:
Table 27 Volume Ramp Rates
Table 28 Volume Ramp Control
ANTI-CLIPPING DIGITAL ATTENUATION MODE
Audio material is regularly recorded up to 0dB level and heavily compressed. This may cause
clipping and occasional distortion when the digital media is applied to a DAC. In order to prevent this
in the WM8742, an anti-clipping mode is provided, which attenuates the digital signal by 2dB as it is
processed through the digital filters.
Table 29 Anti-Clipping Digital Attenuation Control
DSD PLUS GAIN CONTROL
The gain in the DSD Plus data path can be adjusted. The default setting provides a 1.4Vrms
differential output level.
Table 30 DSD Plus Gain Control
SAMPLE RATE (kHz)
REGISTER ADDRESS
REGISTER ADDRESS
REGISTER ADDRESS
Volume Control
Volume Control
Mode Control 2
176.4
44.1
88.2
196
04h
04h
08h
32
48
96
R4
R4
R8
BIT
BIT
BIT
RAMP RATE (ms/dB)
0
1
6
ATT2DB
LABEL
LABEL
LABEL
RAMP
VOL_
DSD_
GAIN
1.000
0.726
0.667
0.726
0.667
0.726
0.667
DEFAULT
DEFAULT
DEFAULT
0
0
0
Volume ramp mode control:
0 = Apply volume change in a single
step.
1 = Ramp between current volume
setting and new volume setting.
Anti-clipping mode control:
0 = Off, 0dB attenuation
1 = On, 2dB attenuation applied
DSD Plus gain control:
0 = Low gain, 1.4Vrms differential
output level
1 = High gain, 2.0Vrms differential
output level
DESCRIPTION
DESCRIPTION
DESCRIPTION
PD, Rev 4.2,August 2009
Production Data
When
32