Sensors

22

Freescale Semiconductor, Inc.

MMA16xxKW

3.5.3.2

Low-Pass Filter

Data from the Sinc filter is processed by an infinite impulse response (IIR) low-pass filter.

The device provides the option for one of three low-pass filters. The filter is selected with the LPF[1:0] bits in the TYPE register.

The filter selection options are listed in Section 3.1.2.1, Table 8. Response parameters for the low-pass filter are specified in

Section 2.8. Filter characteristics are illustrated in the figures below.

Note: Low-Pass Filter Figures do not include g-cell frequency response.

Table 8. Low-Pass Filter Coefficients

Description

Filter Coefficients

Group Delay

180 Hz LPF

0.000534069200512

0.25

1

0.499999985098839

0.25

1

0

0

400 Hz LPF

0.003135988372378

0.000999420881271

1.0

0.001998946070671

0.000999405980110

0.89558845758438

0.250004753470421

1.0

0.499986037611961

0.250009194016457

800 Hz LPF

0.011904109735042

0.003841564059258

1.0

0.007683292031288

0.003841534256935

0.250001862645149

1.0

0.499994158744812

0.250003993511200

Hz

()

a

0

n

11

z0

⋅

()

n

12

z 1

–

⋅

()

n

13

z 2

–

⋅

()

++

d

11

z0

⋅

()

d

12

z 1

–

⋅

()

d

13

z 2

–

⋅

()

++

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n

21

z0

⋅

()

n

22

z 1

–

⋅

()

n

23

z 2

–

⋅

()

++

d

11

z0

⋅

()

d

22

z 1

–

⋅

()

d

23

z 2

–

⋅

()

++

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⋅⋅

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