WM8775

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PP Rev 1.8, June 2004

32

DIGITAL FILTER CHARACTERISTICS

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ADC Filter

±0.01 dB

0

0.4535fs

Passband

-6dB

0.4892fs

Passband ripple

±0.01

dB

Stopband

0.5465fs

Stopband Attenuation

f > 0.5465fs

-65

dB

Group Delay

22

fs

Table 14 Digital Filter Characteristics

ADC FILTER RESPONSES

-80

-60

-40

-20

0

0

0.5

1

1.5

2

2.5

3

Frequency (Fs)

Figure 22 ADC Digital Filter Frequency Response

-0.02

-0.015

-0.01

-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

Frequency (Fs)

Figure 23 ADC Digital Filter Ripple

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.

Figure 24 ADC Highpass Filter Response

H(z) =

-15

-10

-5

0

0

0.0005

0.001

0.0015

0.002

Frequency (Fs)