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DRV8876EVM: DRV8876 IMODE Setting Problem

Part Number: DRV8876EVM
Other Parts Discussed in Thread: DRV8876-Q1, DRV8876

I use DRV8876-Q1 EVM to driver our motor. If we don’t make any change in EVM, it can work normally. Since I need a nFAULT status to control the motor revers. So I change the IMODE to 20k ohm. When I turn on the 5VDC source, the fault LED become bright immediately and motor can’t work normal. If I change the IMODE resistor to 0 ohm, then the motor can work normal. Do you have any idea to share? Thanks.

BR,

Gary

  • Hi Gary,

    I may need to see this for myself on the bench and get back to you. In the meantime, if you could take scope shots of VM, IPROPI, IN1, and IN2? What voltage is VREF, and what have you selected for PMODE?
  • Hi James Lockridge,

    Sorry I will take scope waveform for you tomorrow. I had saw the VREF is 2.5V and PMODE is pulled high. I had saw the nFAULT is always low after I turn on the 5VDC source. I guess whether the low status cause the MSP430 to turn off the driver? Thanks.

    BR,

    Gary

  • Gary,

    I wrote the firmware for that board, but I didn't make the MSP430 shut down the DRV8876 when the nFAULT is asserted. If you want to confirm that, you can see if the nSLEEP pin is still high and if the IN1 and IN2 inputs changed.
  • Hi James Lockridge,

    I fix the problem.

    I am working on the PWM control mode. The dual output is in reverse mode. I set the IMODE to 20k. I turn the IN1 PWM to completely counter clockwise and turn IN2 PWM to completely clockwise. Then the nFault is always low. When I turn a little back the IN2 PWM, then the motor can work normal. The waveform show in below. Thanks for your support.

     CH1: nFAULT, CH2: VREF, CH3: IPROPI

     CH1: nFAULT, CH2: OUT1, CH3: IPROPI, CH4: OUT2