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DRV8412: The strange behavior at Fault* pin at the power-up sequency

Ted Xu
Expert 4620 points
Part Number: DRV8412

Hi BU team

DRV8412 was designed for the stepper motor application.  Monitored the Fault* pin timing during the powered-up and found an unsmooth rising edge. 

The issues were showed in two below screenshots.

Would you help check it and share your comments?

Thanks 

  • 0
    TI__Guru** 114905 points
    Hi Ted,

    The following is based on the assumption that VDD and GVDD are using the same supply. Please confirm this is correct.

    Is there an external pullup resistor? If so what is the resistor value and what voltage is the resistor connected?

    The behavior appears to be correct. As VDD increases to approximately 2V the internal circuitry awakens and asserts a GVDD undervoltage fault. The nFAULT voltage appears to be a little higher than expected, but is still a logic low.

    As GVDD reaches ~8.5V typical, the nFAULT is removed.
  • 0 in reply to Rick Duncan
    TI__Expert 4620 points

    Hi Rick

    Thanks for your prompt response. 

    No external pull-up resistor at nFault pin.