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LMR51610: VIN pin short to GND if 60VDC or more is applied on the input on startup

Pascal Courvoisier
Prodigy 10 points
Part Number: LMR51610

Tool/software:

We currently use the LMR51610 in our designs already, it's been working perfectly for 12, 24, and 48VDC input voltages. Recently we have had an application that requires the circuit to start from 60VDC, usually, we have tested the board with startup voltages from 0V to 52VDC with no issues even when we ramped the input voltage to past 62VDC after startup, again with no problem.

The new application has the board start from 60VDC, this instantaneously creates a short to ground within the IC and causes permanent damage.

My questions are:

  1. What is the startup voltage maximum
  2. If it is higher than 60VDC what could be the issue

This is a snippet of the power supply section of the cicuit

 

  • 0
    TI__Mastermind 20300 points

    Hi Pascal,

    Do you have any waveforms showcasing the failure? 

    1) The abs max of the device is 70V, but we recommend not exceeding 65V.

    2) There could be a few starting possibilities:

    1. I suspect it could be due to the slew rate of the input voltage. Does reducing the slew rate of the input voltage remove the failure?
    2. Maybe there is some overshoot of the input voltage source exceeding the limitations of the device. You can tell if this is possible by taking a waveform of the input voltage and output voltage at the working 52V startup.

    Thanks,

     Richard

  • 0 in reply to Richard Fu22
    Prodigy 10 points

    Hey Richard,

    Thank you for the quick reply, and the answers to my questions,

    i don't unfortunately have any waveforms of the failure itself, i do have some at the startup voltage of 52,

    it seems like a periodic input ringing, and the input voltage is scaled by 7.1 times in the image and is set to 53.25, the 5.7out is after the inductor

  • 0 in reply to Pascal Courvoisier
    TI__Mastermind 20300 points

    Hi Pascal,

    It looks like the VIN pin has a bit of noise. Maybe increasing thei nput capacitance can help? Let me know if any of the fixes resolve the issue. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Prodigy 10 points

    Hey Richard,

    Thank you for your input, increasing the capacitance seems to have done the trick, and startup for 62VDC on the input is now possible, I can not believe that's all it took, and doubling the capacitance directly on the input, amazing thank you.