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DRV8711: Motor is giving undervolt and predriver fault without any load.

vishal prajapati
Prodigy 10 points
Part Number: DRV8711

We are operating 2 stepper motor with single DRV8711 driver IC. Motor is taking 1.3 Ampere of current after making changes in parameters suitable with our requirement. But after rotating 2 or 3 round motor driving ic is giving undervoltage and predriver fault. Though we are moving motor without any load. Is there any specific parameters we have to set ?

  • 0
    Genius 3680 points

    Hi Vishal,

    I have never tried to operate 2 stepper motors with a single DRV8711 driver but I think it is not a very good idea unless:

    - these 2 motors were identical and had their shafts coupled directly and adjusted precisely so BEMFs of these 2 motors were in phase (in this case

    I think these 2 motors would behave as one bigger one)

    - in microstepping mode for very low speeds.

    DRV8711 and probably most of other stepper motor drivers use current regulation to dump motor oscillations and connecting 2 motors to a single driver probably will cause increased resonances of these 2 motors, loosing steps and stalls.

    It is hardly to say if your problems are caused by connecting 2 motors to a single driver or other factors.

    First, I would try to operate single motor with a driver, make sure the motor works well at  desired speeds, loads and during acceleration / deceleration phases.

    Then I would try to operate these 2 motors together slowly increasing speed from 0, once the problems arise I would try to play with DRV8711 parameters to see if it is possible to reduce these problems. I would also try to connect motor windings in parallel and in series.

    Operating DRV8711 with 2 motors may also increase a risk of damage to DRV8711 and Mosfets.

    Can you provide more information like electrical diagram if it is not evm board, VM voltage, DRV8711 registers values, is VM voltage stable when problem occurs (does power supply have enough current capacity)?

    Decay mode that works the best for me for single motors is "101: Use auto mixed decay at all times".

    Regards,

    Grzegorz

  • 0 in reply to Grzegorz Pelikan
    TI__Guru 56650 points

    Hi Vishal,

    I agree with Grzegorz's debugging process. First, I would try to operate single motor with the driver. And then, First, I would try to operate single motor with a driver.

    Also, what input capacitor do you have? Would you increase the input capacitor to make the input voltage stable and avoid the under voltage issue.

    Regards,

    Wang Li