WM8738
DIGITAL FILTER CHARACTERISTICS
PARAMETER
Passband
Stopband
Passband ripple
Stopband
Stopband Attenuation
Group Delay
Table 2 Digital Filter Characteristics
f > 0.5465fs
0.5465fs
-65
22
SYMBOL
TEST CONDITIONS
±0.01
dB
-6dB
MIN
0
0.5fs
±0.01
TYP
MAX
0.4535fs
Production Data
UNIT
dB
dB
dB
Samples
ADC FILTER RESPONSES
0.02
0
0.015
0.01
-20
Response (dB)
Response (dB)
0.005
0
-0.005
-0.01
-0.015
-0.02
-40
-60
-80
0
0.5
1
1.5
Frequency (Fs)
2
2.5
3
0
0.05
0.1
0.15
0.2
0.25
0.3
Frequency (Fs)
0.35
0.4
0.45
0.5
Figure 6 ADC Digital Filter Frequency Response
Figure 7 ADC Digital Filter Ripple
ADC HIGH PASS FILTER
The WM8738 has a selectable digital highpass filter to remove DC offsets. The filter response is characterised by the
following polynomial.
H(z) =
1 - z
-1
1 - 0.9995z
-1
0
Response (dB)
-5
-10
-15
0
0.0005
0.001
Frequency (Fs)
0.0015
0.002
Figure 8 ADC Highpass Filter Response
w
PD Rev 4.3 November 2004
12
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
