Pre-Production
WM8985
HIGHPASS FILTER
The WM8985 has a selectable digital highpass filter in the ADC filter path. This filter has two
modes, audio and applications. In audio mode the filter is a 1st order IIR with a cut-off of around
3.7Hz. In applications mode the filter is a 2nd order high pass filter with a selectable cut-off
frequency.
5
0
-5
-10
-15
-20
-25
-30
-35
-40
0
5
10
15
20
25
30
35
40
45
Frequency (Hz)
Figure 46 ADC Highpass Filter Response, HPFAPP=0
10
0
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-10
-20
-30
-40
-50
-60
0
200
400
600
800
1000
1200
0
200
400
600
800
1000
1200
Frequency (Hz)
Frequency (Hz)
Figure 47 ADC Highpass Filter Responses (48kHz),
HPFAPP=1, all cut-off settings shown
Figure 48 ADC Highpass Filter Responses (24kHz),
HPFAPP=1, all cut-off settings shown
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
0
200
400
600
800
1000
1200
Frequency (Hz)
Figure 49 ADC Highpass Filter Responses (12kHz),
HPFAPP=1, all cut-off settings shown
PP, Rev 3.4, October 2006
111
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
