wm8961 Wolfson Microelectronics plc, wm8961 Datasheet - Page 30

• Manufacturer Part Number: wm8961
• Description: Ultra-low Power Stereo Codec With 1w Stereo Class D Speaker Drivers And Ground Referenced Headphone Drivers
• Manufacturer: Wolfson Microelectronics plc

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WM8961
ADC DIGITAL FILTERS
The ADC filters perform true 24-bit signal processing to convert the raw multi-bit over-sampled data
from the ADC to the correct sampling frequency to be output on the digital audio interface.
ADC HIGH PASS FILTER
A digital high pass filter is applied by default to the ADC path to remove DC offsets. This filter can also
be programmed to remove low frequency noise in voice applications (e.g. wind noise or mechanical
vibration).
This filter can be disabled using the ADCHPD register bit. The cut-off frequency of the filter is
controlled by ADC_HPF_CUT.
In hi-fi mode the high pass filter is optimised for removing DC offsets without degrading the bass
response and has a cut-off frequency of 3.7Hz at fs=44.1kHz.
In voice mode the high pass filter is optimised for voice communication and it is recommended to
program
ADC_HPF_CUT=10 at fs=16kHz)
Table 13 ADC High Pass Filter
Table 14 ADC High Pass Filter Cut-Off Frequencies
The high pass filter characteristics are shown in the “Digital Filter Characteristics” section.
FREQUENCY
R5 (05h)
ADC and DAC
Control (1)
ADC & DAC
Control 2
REGISTER
SAMPLE
ADDRESS
R6 (06h)
11.025
16.000
22.050
24.000
32.000
44.100
48.000
(KHZ)
8.000
the
cut-off
ADC_HPF_CUT
0
8:7
BIT
=00
0.7
0.9
1.3
1.9
2.0
2.7
3.7
4.0
frequency
ADCHPD
ADC_HPF_CUT[
1:0]
LABEL
below
ADC_HPF_CUT
CUT-OFF FREQUENCY (HZ)
127
175
190
253
348
379
=01
300Hz
64
88
0
00
DEFAULT
(e.g.
ADC_HPF_CUT
0 = Enable high pass filter on left and
right channels
1 = Disable high pass filter on left and
right channels
00: Hi-fi mode (fc=4Hz at fs=48kHz)
01: Voice mode 1 (fc=127 at
fs=16kHz)
10: Voice mode 2 (fc=130 at
fs=8kHz)
11: Voice mode 3 (fc=267Hz at
fs=8kHz)
(Note: fc scales with sample rate.
See Table 14 for cut-off frequencies
at all supported sample rates)
ADC High Pass Filter Disable
ADC High Pass Filter Cutoff
ADC_HPF_CUT=11
130
178
258
354
386
514
707
770
=10
DESCRIPTION
PP, August 2009, Rev 3.1
ADC_HPF_CUT
at
1063
1464
1594
267
367
532
733
798
=11
Pre-Production
fs=8kHz
30
or