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christopher2
Visitor II
October 28, 2014
Question

LSM9DS1 Startup Power Sequencing. Problems inherit in not abiding.

  • October 28, 2014
  • 3 replies
  • 1201 views
Posted on October 28, 2014 at 19:50

I would like to know if bringing up both the Vdd_IO and Vdd lines at the same time on the LSM9DS1 is hazardous for the unit or problematic for its functioning. Why must the rails be brought up in sequence and what problems might I face if I bring them up at the same time?

I have a slew rate controlled switch, but my lines to Vdd_IO and Vdd are tied together. Before I do the board rework I was curious what problems I might see if I simply brought both lines up at the same time. 

Any insight is much appreciated.

#lsm9ds1
    This topic has been closed for replies.

    3 replies

    O
    oyvind2
    Visitor II
    March 5, 2015
    Posted on March 05, 2015 at 16:20

    Bump. I would like to know the same thing.

    H
    harri
    Visitor II
    August 5, 2016
    Posted on August 05, 2016 at 14:56

    Me too.

    M
    massimo239955_stm1
    Visitor II
    February 8, 2017
    Posted on February 08, 2017 at 11:12

    Hello all,

    I also had the same question.

    However looking at the schematics of the LSM9DS1 eval board (

    http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mems-motion-sensor-eval-boards/steval-mki159v1.html

    ) and the relative ST MEMS adapters motherboard (

    http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mems-motion-sensor-eval-boards/steval-mki109v2.html

    ) it's possible to see that the Vdd and Vdd_IO pins are connected toghether into the motherboard. This violates what is written in the datasheet. So what's wrong, the datasheet or the motherboard schematic?

    Thank you. Best regards,

    Massimo

    M
    Miroslav BATEK
    ST Employee
    February 9, 2017
    Posted on February 09, 2017 at 10:35

    If you use the same power supply for Vdd_IO and Vdd you can connect the pins together. It is common practice. From my experience, I don't remember any issue with this approach. In datasheet is recommended power-up sequence, it is mainly valid in case of Vdd_IO is not equal Vdd.

    M
    massimo239955_stm1
    Visitor II
    February 9, 2017
    Posted on February 09, 2017 at 10:45

    Hi Miroslav,

    it was not explicitly reported in the datasheet so I raised the issue. Thank you very much for your reply.

    Best regards,

    Massimo

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