Production Data

WM8786

w

PD Rev 4.2 February 2007

11

DIGITAL FILTER CHARACTERISTICS

The WM8786 digital filter characteristics scale with sample rate.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

ADC Sample Rate (Single Rate - 48Hz typically)

+/- 0.005dB

0

0.454fs

Passband

-6dB

0.5fs

Passband Ripple

+/- 0.005

dB

Stopband

0.546fs

Stopband Attenuation

f > 0.546fs

-85

dB

Group Delay

32/fs

s

ADC Sample Rate (Dual Rate - 96kHz typically)

+/- 0.005dB

0

0.454fs

Passband

-6dB

0.5fs

Passband Ripple

+/- 0.005

dB

Stopband

0.546fs

Stopband Attenuation

f > 0.546fs

-85

dB

Group Delay

32/fs

s

ADC Sample Rate (Quad Rate - 192kHz typically)

+/- 0.005dB

0

0.25fs

-3dB

0.45fs

Passband

-6dB

0.5fs

Passband Ripple

+/- 0.005

dB

Stopband

0.75fs

Stopband Attenuation

f > 0.75fs

-85

dB

Group Delay

10/fs

s

ADC High Pass Filter

-3dB

3.7

-0.5dB

10.4

Corner Frequency

-0.1dB

21.6

Hz

Table 1 Digital Filter Characteristics

TERMINOLOGY

1.

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

2.

Pass-band Ripple – any variation of the frequency response in the pass-band region

HIGH PASS FILTER TRANSFER CHARACTERISTIC

The high pass filter response is defined by the following polynomial:

1

-

-1

)z

-

(1

-

1

z

-

1

H(z)

α

=

where α = 2