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High-pass path: BW_FILT setting

user1
Associate

When BW_FILT[1:0] = 00, it's different between AN5201 AND DATASHEET. Which one is real?

in AN5201:0693W00000FBx7wQAD.pngIn Datasheet(DocID031788):

0693W00000FBx8BQAT.png

1 ACCEPTED SOLUTION

Accepted Solutions
Eleon BORLINI
ST Employee

Hi @user1​ ,

Please consider that the two should refer to different signal paths, as shown in the below picture:

0693W00000FC7QFQA1.pngIn particular, in the "application note" case, the HP filter path is considered: this means that when you select this path, and when you consider the BW_FILT[1:0] bit values (00 and 01), the band will be defined by the range [HP_filter_cutoff, ODR/4], and the upper value of this range will be always ODR/4.

In the "datasheet" case on the other side, you are considering the Low pass filter 2, or "LPF2" signal path, and in this case, if you select BW_FILT = 00bin, the resulting high frequency limit will be ODR/2, which is basically the maximum frequency according to the Nyquist theorem.

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster.

-Eleon

View solution in original post

1 REPLY 1
Eleon BORLINI
ST Employee

Hi @user1​ ,

Please consider that the two should refer to different signal paths, as shown in the below picture:

0693W00000FC7QFQA1.pngIn particular, in the "application note" case, the HP filter path is considered: this means that when you select this path, and when you consider the BW_FILT[1:0] bit values (00 and 01), the band will be defined by the range [HP_filter_cutoff, ODR/4], and the upper value of this range will be always ODR/4.

In the "datasheet" case on the other side, you are considering the Low pass filter 2, or "LPF2" signal path, and in this case, if you select BW_FILT = 00bin, the resulting high frequency limit will be ODR/2, which is basically the maximum frequency according to the Nyquist theorem.

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster.

-Eleon