WM8940CGEFLSLASHV datasheet(86/91 Pages) WOLFSON

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WM8940

Production Data

PD, Rev 4.3, November 2011

NOTCH FILTERS AND LOW PASS FILTER

The WM8940 supports four programmable notch filters. The fourth notch filter can be configured as a

low pass filter. The following illustrates three digital notch filters, followed by a single low pass filter in

the ADC filter path. Both the centre frequency and -3dB bandwidth are programmable for the notch

filters. The cut off frequency is programmable for the low pass filter. The following graphs show the

responses of 1) a single notch filter at three chosen centre frequencies, with three bandwidths for

each, 2) the low pass filter at three chosen cut off frequencies and 3) the cascade of three notch

filters followed by the low pass filter, each with a different centre / cut off frequency with three

bandwidths for each.

Figure 46 ADC Notch Filter Responses (48kHz); fc=100Hz, 1kHz, 10kHz; fb = 100Hz, 600Hz, 2kHz

Figure 47 ADC Low Pass Filter Responses (48kHz); fc= 1kHz, 5kHz, 10kHz

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

(dB)

20k

100

200

500

10k

Frequency (Hz)

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

(dB)

20k

100

200

500

10k

Frequency (Hz)

WM8940CGEFL/V Datasheet(PDF) 86 Page - Wolfson Microelectronics plc

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