WM8955L

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Product Preview Rev 0.4 May2003

38

DIGITAL FILTER CHARACTERISTICS

Depending on the MCLK frequencyand sample rate selected, 4 different types of digital filter can be

used in the DAC, called Type 0, 1, 2 and 3 (see “Master Clock and Audio Sample Rates”). The

performance of Types 0 and 1 is listed in the table below, the responses of all filters is shown in the

following pages.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

DAC Filter Type 0 (USB mode, 250fs operation)

+/- 0.03dB

0

0.416fs

Passband

-6dB

0.5fs

Passband Ripple

+/-0.03

dB

Stopband

0.584fs

Stopband Attenuation

f > 0.584fs

-50

dB

DAC Filter Type 1 (USB mode, 272fs or Normal mode operation)

+/- 0.03dB

0

0.4535fs

Passband

-6dB

0.5fs

Passband Ripple

+/- 0.03

dB

Stopband

0.5465fs

Stopband Attenuation

f > 0.5465fs

-50

dB

Table 29 Digital Filter Characteristics

TERMINOLOGY

1.

Stop Band Attenuation (dB) - the degree to which the frequencyspectrum is attenuated (outside audio band)

2.

Pass-band Ripple – anyvariation of the frequencyresponse in the pass-band region

DAC FILTER RESPONSES

-100

-80

-60

-40

-20

0

0

0.5

1

1.5

2

2.5

3

Frequency (Fs)

-0.06

-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

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 17 DAC Filter Frequency Response – Type 0

Figure 18 DAC Filter Ripple – Type 0