WM8985GEFLSLASHR datasheet(41/121 Pages) WOLFSON

41 / 121 page

Production Data

WM8985

PD, Rev 4.6, July 2009

PROGRAMMABLE NOTCH FILTER

A programmable notch filter is provided. This filter has a variable centre frequency and bandwidth,

programmable via two coefficients, a0 and a1. These coefficients should be converted to 2’s

complement numbers to determine the register values. A0 and a1 are represented by the register

bits NFA0[13:0] and NFA1[13:0]. Because these coefficient values require four register writes to

setup there is an NFU (Notch Filter Update) flag which should be set only when all four registers are

setup.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R27 (1Bh)

Notch Filter 1

6:0

NFA0[13:7]

Notch Filter a0 coefficient, bits [13:7]

NFEN

Notch filter enable:

0 = Disabled

1 = Enabled

NFU

Notch filter update. The notch filter

values used internally only update

when one of the NFU bits is set high.

R28 (1Ch)

Notch Filter 2

6:0

NFA0[6:0]

Notch Filter a0 coefficient, bits [6:0]

NFU

Notch filter update. The notch filter

values used internally only update

when one of the NFU bits is set high.

R29 (1Dh)

Notch Filter 3

6:0

NFA1[13:7]

Notch Filter a1 coefficient, bits [13:7]

NFU

Notch filter update. The notch filter

values used internally only update

when one of the NFU bits is set high.

R30 (1Eh)

Notch Filter 4

0-6

NFA1[6:0]

Notch Filter a1 coefficient, bits [6:0]

NFU

Notch filter update. The notch filter

values used internally only update

when one of the NFU bits is set high.

Table 17 Notch Filter Function

The coefficients are calculated as follows:

)

tan(

)

tan(

−

)

cos(

)

(

−

Where:

fc = centre frequency in Hz, fb = -3dB bandwidth in Hz, fs = sample frequency in Hz

The coefficients are calculated as follows:

NFA0 = -a0 x 213

NFA1 = -a1 x 212

These values are then converted to 2’s complement notation to determine the register values.

WM8985GEFL/R датащи(PDF) 41 Page - Wolfson Microelectronics plc

WM8985GEFL/R датащи(HTML) 41 Page - Wolfson Microelectronics plc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL