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TPS54360B-Q1: Burning-Up Components in Regulator Circuitry

Nicholas Tomasello
Intellectual 420 points
Part Number: TPS54360B-Q1

To Whom it May Concern, 

I use the TPS54360B-Q1 to provide 5V to a couple of different components in a circuit. The design for this regulator was pretty close to the design based on the datasheet for a 5V 3.5A load. I am having trouble with the two input ceramic capacitors at the VIN pin of the regulator. After an 8 hour run, the circuit seems to work fine. Only a couple of boards that I send out seem to have a burn out with these two capacitors and I do not know why they seem to fail. Only these two capacitors burn up and nothing else. After they burn out, if I remove them from the board the circuit starts to work correctly again. Very strange behavior. If someone could provide insight into why this is happening that would be great. Attached are two pictures of input capacitor burns and one picture of a good board with no burn. Also attached is a schematic of the circuit and the reference circuit from the datasheet. 

Best regards, 

Nicholas Tomasello

  • 0
    TI__Mastermind 28020 points

    Hi Nicholas,

    Is it possible that you are applying a voltage greater than the voltage rating of the caps?

    My biggest suspicion is the strap across the inductor. How does it get  mounted to the board?

    Was is possible that these caps were flexed or pressure was applied during the mounting of the strap?

    Here is a product page of a ceramic cap manufacturer describing possible issues with shorted caps:

    Regards, Jason

  • 0 in reply to J Arrigo
    Intellectual 420 points

    Hi Jason, 

    The strap is only hot glue. We apply that after the boards are fabricated and received in order to keep them from moving in the field. It is a extremely high vibration and temperature fluctuating use case. The ceramic capacitors are rated for 100V and we generally only apply up to 60V to the regulator Vin pin. We believe it to be a mechanical failure but wanted an outside opinion to make sure that the electrical parameters are not the issue. 

    Thanks for your response. 

    Nicholas

  • 0 in reply to Nicholas Tomasello
    TI__Mastermind 28020 points

    Hi Nicholas,

    Thanks for the update. It sounds like a mechanical failure to me as well. It doesn't sound like you are exceeding the electrical specs of the capacitors.

    Regards, Jason