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The digital filter of three axis accelerometers(ADXL312)

Question asked by Mochi on Jul 6, 2017


I have a question about the digital filter of three axis accelerometers.
The data sheet of ADXL362 says "The internal low-pass filter pole is automatically set to ¼ or the selected ODR (based on the HALF_BW setting) to ensure the Nyquist sampling criterion is met and no aliasing occurs."
ADXL312, ADXL313, ADXL345, ADXL346, these three axis accelerometers are equipped with digital filters rather than analog.
I would like to know how steep the digital filter has characteristics.
Do these digital filters have much sharper characteristics than Butterworth filters?

My customers expect the digital filter to work better than the ADXL 362 analog filter set to 1/4 ODR.


Best regards




After that, I gathered information with EZ and found the keyword "IIR filter".
Unfortunately I am not accustomed to digital filters, so I can not intuitively feel this meaning.
I imagine in vagueness that "single pole IIR filter" is the same as a simple CR filter.
"The bandwidth of the ADDL 312, ADXL 313, ADXL 345, ADXL 346 depends on the output data rate (ODR) setting. The" -3 dB "bandwidth is always ½ the ODR."
Is this correct?

When I expect a sharp anti-alias filter, should I use an accelerometer equipped with an analog filter in the preceding stage?
It's very few, but ...


Best regards




I solved this problem on my own.
The following materials have helped me;
Practical Filter Design Challenges and Considerations for Precision ADCs     by Steven Xie