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LMP8645HV: LMP8645HV destroy

Part Number: LMP8645HV
Other Parts Discussed in Thread: INA181

I wanted to experiment the LMP8645HV with a current measurement on a 48V power supply (the LMP8645HV is powered by +12V).  When I vary the load the function is correct. However, when I disconnect and reconnect the live load, the LMP8645HV no longer works and is destroyed. Why?

  • Hi Bernard,

    eventually you get a dangerous ringing caused by inductive kick back when diconnecting and reconnecting the load. What is your load? Is it complex? Also, your 48V power supply voltage might show excessive ringing during the abrupt load changes. Have you done any measurements of the input voltages of LMP8645HV? Can you show some scope plots?

    By the way, I would always protect the inputs of such a chip by the help of TVS.


  • Hello Bernard,

    We always appreciate addressing questions on the forum.

    I would have to agree with Kai that probing the input lines (+IN/-IN) of the LMP8645HV while you are disconnecting and conecting the load would provide insight on what is happening. There is a possibility that when you connect the live load, there is an instantaneous short from source to ground at the inputs and this is creating a quick enough common-mode (VCM) transient at the inputs which could cause a latch-up internally and destroy internal ESD structures.

    Could you provide a schematic? Is the 12V supply separate from the 48V supply? Are there capacitors connected to the inputs of LMP8645HV? Is your load inductive or capacitive? How are defining "destroyed"?

    You can try debugging the system by placing 10-Ω resistors in series with +IN and -IN pins to see if this provides some protection in terms of limiting the current into the device. After this you could also place 80V clamping TVS diodes from +IN/-IN to the device GND. See the figure from the INA181 datasheet as an example schematic on doing this. Although, these TVS diodes will only provide protection if the VCM exceed 80V. In the scenario I explained above, it is actually the speed (dVCM/dT) which is possibly causing the damage.


    Peter Iliya

    Current Sensing Applications

  • Hello Bernard,

    It's been several days since your last post, so hopefully your issue has been resolved. I will close the thread for now. If you need more help, please reply to re-open the thread or ask a new question in a new thread.

    Best regards,

    Ian Williams
    Applications Manager
    Current & Magnetic Sensing

  • Hello Kai and Peter,

     Thank you for your advice. The problem was indeed due to the resistive load which had an inductive effect. The TVS diodes have solved the problem.

     Best regards


  • Hi Bernard,

    thanks for your feedback.

    Good luck!