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DRV8818: Back EMF when driver is not powered.

Part Number: DRV8818

Hello.

There has been a lot of discussion on one of the CNC forums concerning rotating stepper motors with no power applied to the DRV8818.

The controversy is whether or not you can damage the DRV8818 by spinning the stepper motor when no power is supplied to the chip.

So my question is Can the DRV8818 be damaged in this way.

Thanks for your help.

Larry

  • Hi Larry,

    The answer depends on how the device is connected when spinning the motor, how fast the motor spins, and long the motor spins.

    Assuming the exposure of the device is constrained within the absolute maximum ratings, the device should not be damaged.

    The overall concern is spinning the motor for long periods could overheat the device, or generate voltages outside the absolute maximum ratings.
    As the motor spins any current through the body diodes can heat the device. With no power to the device, the protection circuitry is not active. The device could fail due to overtemperature conditions.
  • Thanks for the reply. Since the stepper motor turns slowly and for a brief time I'm going to assume that the driver will be ok.

  • "The answer depends on how the device is connected when spinning the motor, how fast the motor spins, and long the motor spins."

    Regarding the speed and length of time for movement, would it be correct to say that a quick movement for say, 2 seconds, could in fact damage the driver chip?
  • Hi Micro CNC,

    Two seconds would probably not damage the driver. This assumes the device temperature is well below abs max when the 2 second operation occurs, and none of the voltage abs max ratings are violated.