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DRV10866 About FG waveform

masahiko shimizu
Guru 11235 points
Other Parts Discussed in Thread: DRV10866EVM, DRV10866

Hi

My customer is using DRV10866EVM.
He uses motor whose pole pairs is 4.

He has a issue.
When motor speed is high, FG waveform is missing teeth.
I think it exceeds RPM spec on which DRV10866 can drive.

Could you advice me the cause of this event?

Best regards
Shimizu

  • 0
    TI__Mastermind 26065 points

    Hi Shimizu,

    Could you explain more on missing teeth you mentioned? No FG output But still running?

    Best regards,

  • 0 in reply to Wilson Zuo
    Guru 11235 points

    Hi Wilson

    Thank you for your support.

    I send waveform of this event.
    Please see the attached file.
    It is FG and UVWoutput waveform.
    FG is light blue.
    FG is 750Hz from this waveform.

    This situation is "Spd_Adj is full range " and "VCC=4.75V" on EVM

    Is the cause that FG frequency value is larger than max FG frequency of DRV10866?
    or
    Is the cause that customer motor parameter doesn't match DRV10866?

    If parameter is cause, Could you tell me that "parameter value which is matched DRV10866" and "How to measure parameter of motor"

    Thanks
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 26065 points

    Hi Shimizu,

    750Hz FG will be out of the speed range DRV10866 can support. We should lower the speed of the motor. We can use PWM duty input control to lower down the speed of the motor. 

    If we want to change the parameters of the motor to get lower natural speed, we can increase the turns of the phase coil, increasing the Kt level.

    Also I think this is a multi-pole motor with high pole number, maybe 8pole or 12pole motor. If we can reduce the pole number to 4 or 6, the motor's FG will be much lower even at the same RPM.

    Best regards,

  • 0 in reply to Wilson Zuo
    Guru 11235 points
    Hi Wilson

    Thank you for your support.
    I understood.

    Thanks
    Shimizu
  • 0 in reply to masahiko shimizu
    Guru 11235 points
    Hi Wilson

    I'm sorry. I add a question.
    Could you let me know why supported FG max frequency is 750Hz, please?

    Is the reason DRV10866's control speed include feedback of current or BEMF ?

    Thanks
    Shimizu