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TPS55340 damage after a few hour

Frederic Lambercy
Prodigy 30 points
Other Parts Discussed in Thread: TPS55340

Hi,

I'm using a TPS55340PWP as step-up to convert 24VDC voltage to a 25.8V to 36V output.

The output voltage is set by a potentiometer to define the level needed on the load.


It works pretty well during approximately 10h, but suddently, during the middle of a test, the TPS55340 has burn. In fact, the SW pin (both pin 1 & 2) are short-circuited to the ground (measured after unsoldering it with a multimeter).


During the test, the output voltage was set to 32V, with approximately 2A on the Load.


Before that, I've monitor the temperature of the IC (with thermal camera) many times and the TPS55340 wasn't hot at all (not more than 50°C). The only component quite hot was the Diode (approx 70°C).

Does anyone ever experiment this kind of problem?

We will mount a new IC and redo the test, but I'm afraid that will happend again. This converter is supposed to be protected against short circuit, thermal and has a built-in current limitation, so I didn't understand how it can burn.

here's my schematics, all value were selected using webench simulation:

Thank you

  • 0
    TI__Guru**** 191445 points

    Usually that type of damage is caused by over voltage condition.

  • 0 in reply to JohnTucker
    Prodigy 30 points

    Hi,


    it can't be possible as the input voltage is a stable 24VDC external power supply.  During the test, I'm using a laboratory power supply which can't outptut more than 32V (which is actually the maximum input range of the TPS55340). But we don't modify the input voltage, it was always set at 24V.

    The only interrogation is about the feedback. I have added a MOS P to cut completely the output, and I have placed the feedback after it (to ensure a stable voltage even after the dropout in the MOS). But when I'm shutting down the DC/DC, I disable first the DC/DC, then turn off the MOS. Maybe the time between these action are too short?

    Or maybe the feedback must be obligatory before the MOS?

    Here's the actual schematics:

    Thanks