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DRV8825: the discontinuity of the current with phase B

Ken Zhang
Expert 3575 points
Part Number: DRV8825

Tool/software:

hi,

a my account meet a abnormally stop rotating issue with DRV8825,the discontinuity of the current with phase B is captured. The schematic and waveforms are in the test report.

what are possible reasons to lead the discontinuity of the current with phase B ?

the discontinuity of the current with phase B .pptx

  • 0
    TI__Intellectual 2540 points

    Hi Ken, 

    Please answer the following questions to help me debug the issue:

    1. I noticed that there is a discontinuity in the step signal in the last slide graphs. Is that by design?
    2. Does it coincide with the current waveform discontinuity?
    3. Also, what is the voltage on the vref pins?
    4.  

    In this graph, I see that phase A is also missing some steps. Can you please plot the step signal along with this graph? 

    Regards,
    Karan

  • 0 in reply to Karan Doshi
    TI__Expert 3575 points

    Karan

    will update you after check with customer later

  • 0 in reply to Karan Doshi
    TI__Expert 3575 points

    Karan

    1. I noticed that there is a discontinuity in the step signal in the last slide graphs. Is that by design?-----Yes
    2. Does it coincide with the current waveform discontinuity?-----Yes
    3. Also, what is the voltage on the vref pins?

    -----Vref is from a 3.3V power supply by resister divider. There are a lot of noise  when motor is spinning. When current waveform discontinuity happens, no abnormal waveform on vref is captured.

    4.In this graph, I see that phase A is also missing some steps. Can you please plot the step signal along with this graph? 

    ----There is no step missing after customer double check it . the waveform in picture should be caused by oscilloscope's display performance. 

  • 0 in reply to Ken Zhang
    TI__Intellectual 2540 points

    Hi Ken, 

    Will get back to you on this in a day.

    Regards,
    Karan

  • 0 in reply to Karan Doshi
    TI__Intellectual 2540 points

    Hi Ken, 

    Appreciate your patience here. Can you share the zoomed in waveform where the current discontinuity happens? Please plot that alongside with step pulses. Right now it's difficult to make that part out. Let me know if I am missing something here. 

    Also, to verify, can you also plot the nHOME pin and make sure it happens every 128 steps? 

    Regards,
    Karan