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Original question:

LM5116

LM5116: LM5116

Anushree N
Prodigy 130 points
Part Number: LM5116

Hi,

I have designed a 20A DC DC Converter using LM5116 IC for an output of 14.5V. I performed short circuit test for my board (an input of around 70V was provided) . But the IC failed after short circuit protection test. Should i add any protection circuit at the output to protect it from damaging the unit (in the field, since my application is an automotive one).

  • 0
    TI__Mastermind 25590 points
    Anushree,

    LM5116 should reduce duty cycle in the event of a short, then go into hiccup. This should protect the device in a short circuit condition.

    How exactly did the IC fail?
    Did you see the reduced duty cycle and/or hiccup?
    Can you monitor the VIN pin to make sure the short doesn't create an overshoot on VIN?

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 130 points
    Hi,
    We were unable to monitor the vin pin, but we shall do it today and let you know. But one thing that we observed was that, there was an instant drop of output voltage to zero. We were not able to capture the exact waveform due to the sudden change.
  • 0 in reply to Anushree N
    TI__Mastermind 25590 points
    Anushree,

    Can you give me more details on the failure? Does it stop working during the short? Does it recover after the short is removed?

    Let me know what you find on VIN.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 130 points

    Hi Sam,

    We provided an input voltage of 75V, and shorted the output. But there was an immediate drop of output voltage to zero. Then, we checked the output again after removing from short circuit. But the device didnt recover from the short circuit test. We later found that the IC's pins were shorted. (HO and SW pins)
    Regarding the VIN pin, we found the voltage oscillating during the short circuit, but seems to be normal immediately after removing the short circuit.
    What should we proceed with?

    - Anushree

  • 0 in reply to Anushree N
    TI__Mastermind 25590 points
    Anushree,

    It sounds like an overvoltage condition caused by the high VIN and the short circuit. Please try this test again but monitor VIN, SW, HO, and others to make sure they are not going above the absolute max rated voltage from the datasheet.

    -Sam