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DRV8301: DRV8301

Robert Walsh
Prodigy 120 points
Part Number: DRV8301

Hello, so I have just been trying to get a better understanding of how the DRV8301 controls a PMSM by taking an Oscilloscope to the three leads and observing the waveform as I run the motor. However when I increase the speed of the motor, the width of the PWM gets bigger which is not what we expected. Could someone please explain what causes this? I have attached a video of what the scope outputs over the three leads when I increase the speed from 100-4000 RPMs. 

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    TI__Genius 14487 points
    Hi Robert,

    Are you using our DRV8301EVM to evaluate this condition? What surprises you about the PWM duty cycle?

    Usually when PWM signals control a motor, longer duty cycles make the motor drive faster. Effectively, a long duty cycle corresponds to a higher voltage across the motor terminals because the motor effectively averages the PWM signal. This is true with both brushed and brushless motors.

    Does that answer your question?