wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 62

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

WM8918
w
DAC SLOPING STOPBAND FILTER
Two DAC filter types are available, selected by the register bit DAC_SB_FILT. When operating at
sample rates <= 24kHz (eg. during voice communication) it is recommended that the sloping
stopband filter type is selected (DAC_SB_FILT=1) to reduce out-of-band noise which can be audible
at low DAC sample rates. See “Digital Filter Characteristics” for details of DAC filter characteristics.
Table 36 DAC Sloping Stopband Filter
DAC OVERSAMPLING RATIO (OSR)
The DAC oversampling rate is programmable to allow power consumption versus audio performance
trade-offs. The default oversampling rate is low for reduced power consumption; using the higher
OSR setting improves the DAC signal-to-noise performance.
Table 37 DAC Oversampling Control
R33 (21h)
DAC Digital 1
R33 (21h)
DAC Digital 1
REGISTER
REGISTER
ADDRESS
ADDRESS
BIT
BIT
11
6
DAC_OSR128
DAC_SB_FILT
LABEL
LABEL
DEFAULT
DEFAULT
0
0
DAC Oversample Rate Select
0 = Low power (normal OSR)
1 = High performance (double OSR)
Selects DAC filter characteristics
0 = Normal mode
1 = Sloping stopband mode
(recommended when fs <= 24kHz)
PD, Rev 4.0, September 2010
DESCRIPTION
DESCRIPTION
Production Data
62