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Running a BL-DC motor using DRV10963

Zahed Kabir
Prodigy 50 points
Other Parts Discussed in Thread: DRV10963, DRV10866

I tried to run a BL-DC motor from MAXON P/N: 455020 using DRV10963, I applied a 4kHz PWM signal to the PWM input, I am using 3.3V as Vcc. When the power is applied the motor runs for about 1.5sec and stalls little more than 5 seconds and run again for same amount of time. Datasheet of the motor says no load current at 6V nominal voltage is 38.6mA, the current draw is about 260mA running from 3.3V supply when the motor runs which is lower than the current limit of the iC. I have captured the pulse output from FG pin when the motor runs there are exactly 59 for each run cycle separated by ~5.8sec ..see the two plots below. 

  

Any idea why it is doing like that.

Thanks,

Zahed Kabir

  • 0
    TI__Guru** 114905 points
    Hi Zahed,

    Our experts on this device have been contacted. They should reply soon.
  • 0 in reply to Rick Duncan
    TI__Prodigy 355 points

    Hi Zahed,

         Could you help capture the phase U current waveform?

        It is better to have one overview and another one with zoom in view(10ms/div) just before motor stop.

     

  • 0 in reply to Yisong Lu
    Prodigy 50 points

    Hi Yisong, I do not have a current probe to capture the phase-U current as you have requested but captured the voltage at phase-U with respect to GND see the attached plots, the 1st plot is zoomed in towards end of run cycle. Thanks, Zahed

  • 0 in reply to Zahed Kabir
    TI__Prodigy 355 points
    Hi Zahed,
    By looking at the voltage waveform, the VCC is about 2.5V instead of 3.3V. is it true?
    The motor stops when it is transfering from open loop to closed loop. DRV10963 control logic has a short period of time coasting the motor between open loop and closed loop. We expect the motor to do coasting for 2~3 cycles before handing it over to closed loop. The coasting relies on the motor inertial. If the inertial is not big enough and the friction load is big, motor will stop in this gap.
    Your case seems like this condition. If that is the case, DRV10963 may not be a good fit in your application.
  • 0 in reply to Yisong Lu
    Prodigy 50 points

    Yisong,

    I am supplying 3.3V to Vcc line but apparently the phase voltage as seen by the winding drops to 2.5V with respect to GND

    I am trying to understand the motor behavior between open loop to closed loop transition, is there any measurement you can think off which will tell us the scenario? 

    On the other hand is there other integrated FAT motor drivers available which can do the job, my limitation is I have only 3.3V available and most other driver without internal FETs require ~5V or above to run those ICs! 

    Thanks,

    Zahed

  • 0 in reply to Zahed Kabir
    TI__Prodigy 355 points

    Zahed,

     Please try DRV10866. It works down to 1.8V.

     

  • 0 in reply to Yisong Lu
    Prodigy 50 points
    Yisong,
    I looked into DRV10866 before it has a limitation it can only drive in one direction without reversing capability also it has COMM pin which needs to be tied to neutral of the 3-phase motor, in my case I don't have neutral brought out. Is there any other BLDC driver available not necessarily with integrated FETs which can run from 3.3V supply??
    Thx, Zahed
  • 0 in reply to Zahed Kabir
    TI__Prodigy 355 points
    Zahed,
    COM pin is not a problem. You can just star connect U,V,W with 1k~10k resistor to generate the COM terminal. DRV10866 doesn't have the direction control function.