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TPS54336A: Latch-up issue, internal short

Yoshwa
Expert 4050 points
Part Number: TPS54336A

Hi team,

Customer inquired following latch-up issue

 I am experiencing what appears to be a latch-up issue with your TPS54336 regulator.  When I power-up my circuit (under no-load conditions) at 22V, it works fine.  When I do this at 24V, however, the chip instantaneously acts as a dead short about 50% of the time.  (The part has an Abs Max rating of 30V.)  If I try to re-power it at a lower voltage, the part remains shorted.  (In other words, it appears to be permanently damaged.)  Though I have not yet proved it to be the case, I have strong anecdotal evidence that these "shorted" units heal themselves when left un-powered overnight.  Any thoughts on what could cause these bizarre symptoms?

We will appreciate your help.

  • 0
    TI__Expert 6425 points
    Hi Yoshwa,
    would you like to upload schematic and waveform?
    Because now it's Chinese new year, response will be slow.
    BRs,
    Edwin.
  • 0
    Prodigy 140 points

    Thank you, but I've solved my problem.

    First, there was no latch-up condition.  Parts that were shorted remained permanently shorted.

    The issue arose from having too little input capacitance.  Even though the Web Bench program said 10uF was enough, the input voltage waveform would over-shoot by 5V or more on power-up before settling out at the applied value.  Since our supply voltage is 24V, this was often enough to kill the part.  By increasing the capacitance to 47uF, I was able to critically damp the ringing and prevent the problem.