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TPS54260: TPS54260 continue blow in Inverting Power Supply

Michael Schmid
Prodigy 30 points
Part Number: TPS54260
Other Parts Discussed in Thread: TPS54360

Tool/software:

Dear TI experts,

we have in a TPS54260 inverting psu following the TI app note www.ti.com/.../slva317b.pdf

 

This schematic works until around 250mA of current drawn, then the chip burn, and is short between Vin(pin2) and PH(10). We have it in 2 schematics,

one for +24V to -8V and

one for +24V to -18V.

Both show the same behavior. The chip should have a internal over-current protection, but that did not work. We have killed 4 pcs already. We like to take up to 1A from each negative rail. The inductor values might not be perfect, and we may have to use the TPS54360 (allows a higher switching current), but in any case the over current protection should prevent any damage.

Any explanation, why the over-current protection of the IC is not working?

Best regards,

Michael

  • 0
    TI__Expert 5490 points

    Hi Michael,

    Looks like the issue is due to either VIN pin or the PH pin crossing the abs.max of the TPS54360 device. can you please share VIN, PH and Vout waveforms when issue is happening?.

    Thanks,

    Nitya

  • 0 in reply to Nityanand Hegde
    Prodigy 30 points

    Hi Nitya,

    thanks for the quick reply. I dont know, how to trigger a scope recording in the moment, the device burn. Thats a millisecond, i guess.

    But your hint brought on the right track. We had a mistake in the layout on the PCB, so a copper trace was cut and a wire soldered to correct it. By making the wire shorter, the waveforms look better. So the problem was not overcurrent, but overvoltage on the switching node, because of the bad layout.

    I guess, this solves the problem, we will make a new layout anyway.

    Thanks for your help,