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lgi000
Visitor II
May 19, 2021
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What are the transfer functions of LPF1 and LPF2 for LSM6DSOX?

  • May 19, 2021
  • 1 reply
  • 1458 views

I am interested in calibrating precisely the delay introduced by the filter chain (LPF1 and/or LPF2) of the LSMDSOX (or DSO/DSM - I presume they are the same). I have found the settling times in Table 13 of App Note AN-5272, which is a good start, but is there more information available on the actual transfer functions of LPF1 and LPF2?

Can the self-test be used as a clean step function on the input, as a way to characterize the overall transfer function? The AN-5272 App Note suggests to wait 100 ms for a stable output, but it is not clear whether this is due to the settling time of the filters, or if it is imposed by some other stabilization of the self-test circuitry itself.

Thanks in advance,

Best regards,

Laurent

    This topic has been closed for replies.
    Best answer by Eleon BORLINI

    Hi Laurent @lgi000​ ,

    we -as ST- cannot disclose the detailed transfer functions of the internal filters, but I can point you a similar frequency response.

    Consider the IIS3DWB datasheet, p. 20: here the transfer function (frequency response) of the filter is the following one:

    0693W00000AQ3D0QAL.pngThere are 2 main parameters of this filter that you can adjust: the frequency pole, which is determined by ODR/2 (which is fixed at 13.33kHz for the IIS3DWB but can vary for the LSM6DSOX), and the slope of the filter, which is determined by the (adjustable) cut-off frequency (the -3dB frequency), that can be ODR/4, ODR/10 and ODR/20 for the IIS3DWB, and as described in the Table 72. (at p.63 of the datasheet) for the LSM6DSOX:

    0693W00000AQ3MCQA1.pngIf 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

    1 reply

    E
    Eleon BORLINIAnswer
    ST Employee
    May 27, 2021

    Hi Laurent @lgi000​ ,

    we -as ST- cannot disclose the detailed transfer functions of the internal filters, but I can point you a similar frequency response.

    Consider the IIS3DWB datasheet, p. 20: here the transfer function (frequency response) of the filter is the following one:

    0693W00000AQ3D0QAL.pngThere are 2 main parameters of this filter that you can adjust: the frequency pole, which is determined by ODR/2 (which is fixed at 13.33kHz for the IIS3DWB but can vary for the LSM6DSOX), and the slope of the filter, which is determined by the (adjustable) cut-off frequency (the -3dB frequency), that can be ODR/4, ODR/10 and ODR/20 for the IIS3DWB, and as described in the Table 72. (at p.63 of the datasheet) for the LSM6DSOX:

    0693W00000AQ3MCQA1.pngIf 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

    T
    tlifschitz
    Explorer
    June 29, 2023

    Hi Eleon

    Is it possible to have the frequency response plots of all the cutoff configurations? As you mentioned, on the datasheet only the first three curves are shown.

    Thank you

    Tobías

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