AN2989

High-pass filter

Doc ID 15761 Rev 1

17/28

4.1.1

Normal mode

In this configuration the high-pass filter can be reset reading the HP_FILTER_RESET

register, instantly matching the output data to the input acceleration.

Figure 6.

HP_FILTER_RESET readings

4.1.2

Reference mode

In Reference mode configuration the output data is calculated as the difference between the

input acceleration and the content of the REFERENCE register. This register is in 2’s

complement representation and the value of 1LSB of these 7-bit registers depends on the

selected full scale (Table 14).

Table 13.

High-pass filter cut-off frequency configuration

HPcoeff2,1

Data rate = 50 Hz

Data rate = 100 Hz

Data rate = 400 Hz

00

1

2

8

01

0.5

1

4

10

0.25

0.5

2

11

0.125

0.25

1

Table 14.

Reference mode LSB value

Full scale

Reference mode LSB value (mg)

2~16

4~31

8~63