wm8974gefl-v Wolfson Microelectronics plc, wm8974gefl-v Datasheet - Page 20

• Manufacturer Part Number: wm8974gefl-v
• Description: Mono Codec With Speaker Driver
• Manufacturer: Wolfson Microelectronics plc

WM8974
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Table 9 ADC Oversample Rate Select
SELECTABLE HIGH PASS FILTER
Table 10 ADC Filter Select
Table 11 High Pass Filter Cut-off Frequencies (HPFAPP=1)
The polarity of the output signal can also be changed under software control using the ADCPOL
register bit.
With ADCOSR=0 the oversample rate is 64x which gives lowest power operation and when
ADCOSR=1 the oversample rate is 128x which gives best performance.
A selectable high pass filter is provided. To disable this filter set HPFEN=0. The filter has two
modes controlled by HPFAPP. In Audio Mode (HPFAPP=0) the filter is first order, with a cut-off
frequency of 3.7Hz. In Application Mode (HPFAPP=1) the filter is second order, with a cut-off
frequency selectable via the HPFCUT register. The cut-off frequencies when HPFAPP=1 are shown
in Table 11.
Note that the High Pass filter values (when HPFAPP=1) work on the basis that the SR register bits
are set correctly for the actual sample rate as shown in Table 11.
HPFCUT
000
001
010
011
100
101
110
111
R14
ADC Control
R14
ADC Control
REGISTER
ADDRESS
REGISTER
ADDRESS
The oversampling rate of the ADC can be adjusted using the ADCOSR register bit.
102
131
163
204
261
327
408
82
8
8
7
6:4
SR=101/100
3
0
BIT
BIT
11.025
113
141
180
225
281
360
450
563
ADCOSR
ADCPOL
HPFEN
HPFAPP
HPFCUT
LABEL
LABEL
122
153
196
245
306
392
490
612
12
102
131
163
204
261
327
408
16
82
1
0
000
DEFAULT
SR=011/010
0
0
FS (KHZ)
DEFAULT
22.05
113
141
180
225
281
360
450
563
High Pass Filter Enable
0=disabled
1=enabled
Select audio mode or application mode
0=Audio mode (1
1=Application mode (2
Application mode cut-off frequency
See Table 11 for details.
122
153
196
245
306
392
490
612
24
ADC oversample rate select:
0=64x (lower power)
1=128x (best performance)
0=normal
1=inverted
102
131
163
204
261
327
408
32
82
PD, Rev 4.5, September 2008
DESCRIPTION
DESCRIPTION
SR=001/000
st
order, fc = ~3.7Hz)
44.1
113
141
180
225
281
360
450
563
nd
order, fc = HPFCUT)
Production Data
122
153
196
245
306
392
490
612
48
20