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TPS62130 shorting

Keaton Andersen
Prodigy 30 points

I'm having problems with the following circuit:


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I'm getting a nice +/- 90% efficient drop from VIN of 3.3 or 5 to 17V down to 3.3V or 5V depending on the state of SJ1.  Runs nice, etc, and then the IC fries...  Power to ground short.

The second one I fried was hooked to some power resistors and a medium quality bench supply.  The resistors were drawing about 1.5A.  I was happily running just under 17V for a while. I turned the input voltage down from 17V to 12V and as I was dialing in the exact voltage on the knob my meters measuring the output voltage and current showed zeros.  Any ideas?  Thanks.
  • 0
    TI__Guru*** 142860 points
    It looks like your figure didn't come through. Can you please repost it? As well, can you send the PCB layout?

    You can always test the EVM instead of building your own PCB.
  • 0 in reply to Chris Glaser
    Prodigy 30 points

    Chris - Thanks for the quick reply. Do these help?

  • 0 in reply to Keaton Andersen
    TI__Guru*** 142860 points
    Wow, if that's all you have on your board, just use our EVM.

    Your layout looks good except for 1 key item. The VOS pin breaks the PGND connection to Cin/Cout. The PGND should have priority in the routing there. This creates excessive parasitic inductance which stresses the IC. You can try shorting the GNDs together with a wire over the VOS trace and see if it works any better.

    But you may have another issue, if you just have the single 10uF ceramic input cap. Are you hot-plugging the input source? Do you turn on the input power supply and then attach it to the PCB? Does the input power supply overshoot on startup? With the small amount of capacitance on the PCB, there could easily be an overvoltage on Vin. Look for such an overvoltage with a scope when you are doing your testing.