WM8904
Pre-Production
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.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R33 (21h)
DAC Digital 1
Selects DAC filter characteristics
0 = Normal mode
11
DAC_SB_FILT
0
1 = Sloping stopband mode
(recommended when fs 24kHz
Table 38 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.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R33 (21h)
DAC Oversample Rate Select
0 = Low power (normal OSR)
1 = High performance (double OSR)
6
DAC_OSR128
0
DAC Digital 1
Table 39 DAC Oversampling Control
PP, Rev 3.3, September 2012
70
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