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DRV8840: can we drive resistive

Part Number: DRV8840
Other Parts Discussed in Thread: DRV8871

Dear reader,

On a existing PCB design I use the DRV8840. I would like to drive and regulate a thermal pad which is a pure resistive load (120ohms on 24V supplly).

My preliminary tries are failed. the Ichop set is >500mA and the duty cycle is not 100%. below


Is there a limitation explaining that result?

Thanks in advance for your support!

Regards

  • the load voltage signal is purlpe(=blue-red)
  • Hi Sebastien,

    The DRV8840 should be able to drive a purely resistive load with no issues. Usually when there is a problem driving a resistive load, we find there is some capacitance hidden somewhere.

    What are the blue and red signals?
    What are the inputs doing?
    If you are PWMing the inputs, what is your PWM frequency?

    If you have a current probe, please check the load current to determine if it exceeds the ITRIP value?

    If you do not have a current probe, please check the voltage across the sense resistor.

    If you provide these extra scope captures, it will help.

    For a 200mA load. Have you considered using the DRV8871 as an alternative? The DRV8871 is a smaller package and requires fewer external components.
  • Hi Sebastien,

    Have you been able to resolve your issue? If not, please provide the information requested.

    Thanks.
  • Hi Sebastien,

    We have not heard from you in some time, and are assuming your issue has been resolved. If it has not, please reply to this post or if the post is locked select "Ask a related question" at the top right of the window.