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DRV8308EVM circuitry speed control open-loop PWM

Aleksei Sporyagin
Prodigy 200 points
Other Parts Discussed in Thread: DRV8308EVM, DRV8308

1. I want to control brushless DC motor with help Kits DRV8308EVM from extern microcontroller(terminal CLKIN,GND). Is it necessary galvanic isolation microcontroller from terminal CLKIN,GND?

2. Configuration systems: control from computer GUI, DRV8308EVM, brushless DC motor Maxon 118889(no-load speed 11000 ob/min, number of pair poles = 2), open-loop PWM, 120° Commutation, MOD120 = 2048, no load. If PWM Duty Cycle<13% motor don’t spin. Because? What to do to the motor is rotated at PWM Duty Cycle<13%?When PWM Duty Cycle is changed in range 14-20% motor is pulled(example: PWM Duty Cycle=15%, motor rotates with constant speed, set PWM Duty Cycle=18%, motor is pulled and front new constant speed). Because? What to do to the motor is slipped on one speed on other speed? Also same was with motor from Kits DRV8308EVM.

  • 0
    TI__Mastermind 20985 points

    Aleksei,

    It's not necessary to add isolation between the MCU and DRV8308, but both devices should share the same GND.

    It is normal for motors to only spin if the applied duty cycle is large enough.  The starting friction needs to be overcome.  I think using a lower PWM frequency on the MOSFETs will allow lower duty cycles; the DRV8308 allows 25kHz to 200kHz.

    Let me know if you still have questions!

    Best regards,
    RE