WM8775
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DIGITAL FILTER CHARACTERISTICS
PARAMETER
ADC Filter
Passband
TEST CONDITIONS
MIN
TYP
MAX
0.4535fs
0.01
UNIT
0.01 dB
-6dB
0
0.4892fs
Passband ripple
Stopband
dB
0.5465fs
-65
Stopband Attenuation
Group Delay
f > 0.5465fs
dB
fs
22
Table 14 Digital Filter Characteristics
ADC FILTER RESPONSES
0.02
0.015
0.01
0
-20
-40
-60
-80
0.005
0
-0.005
-0.01
-0.015
-0.02
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.5
1
1.5
2
2.5
3
Frequency (Fs)
Frequency (Fs)
Figure 23 ADC Digital Filter Ripple
Figure 22 ADC Digital Filter Frequency Response
ADC HIGH PASS FILTER
The WM8775 has a selectable digital highpass filter to remove DC offsets. The filter response is characterised by the
following polynomial.
1 - z-1
H(z) =
1 - 0.9995z-1
0
-5
-10
-15
0
0.0005
0.001
Frequency (Fs)
0.0015
0.002
Figure 24 ADC Highpass Filter Response
PP Rev 1.8, June 2004
32
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
