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DRV10970EVM: Motor running at single speed, PWM control input has no influence

Andy Carlson
Prodigy 20 points
Part Number: DRV10970EVM
Other Parts Discussed in Thread: DRV10970

Hello,

 I am attempting to drive a blower motor (datasheet attached) using the DRV10970 evaluation board. From the blower datasheet, I have wired and configured the board to run in 30-deg sinusoidal mode with needing to invert the +/- hall signals. The motor will spin when powered, however, it only spins at one speed regardless of the position of the potentiometer. I've confirmed that the PWM signal is changing correctly, and the hall signals look clean. Would like to confirm this is the correct wiring and board configuration for this motor and figure out why the speed control is not working.

Thank you,

Andy

  • 0
    TI__Mastermind 21805 points

    Hello Andy,

    Can you take a screenshot of the PWM signal from TP3 with the potentiometer turned fully clockwise as well as fully counterclockwise?

    Have you adjusted the current limit by changing R16 (on the CS pin #17)? You could be current limiting with the default setting and preventing the speed from increasing further.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    Prodigy 20 points

    Matt,

     Thank you for pointing me to the resistor on the CS pin, there wasn't any documentation about it in the Evaluation Board manual, but the driver datasheet explained it. After putting a 0-Ohm in it's place, I was able to get the motor to react to the speed control. However, I am only able to get around 20% of the full range before the drive shuts down and stops the motor. The motor is rated at 0.9A and the drive is rated to 1.5A, so I'm not sure it's a current problem. Where's the next place to look to understand why the drive stops at higher speeds?

    Thank you,

    Andy

  • 0 in reply to Andy Carlson
    TI__Mastermind 21805 points

    Hi Andy,

    The power supply current is rated at 0.9A but the datasheet states a maximum coil current of 3.0A. The DRV10970 current rating is based on the motor current (coil current), not the supply current.

    You may want to measure the phase current during operation to see if it is exceeding the DRV10970 limit.

    Thanks,

    Matt