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High-current failure in KL26

Question asked by Brian Bezanson on Oct 19, 2015
Latest reply on Oct 20, 2015 by xiangjun.rong

I've got a couple devices using MKL26Z128VFM4s that have failed in a way that causes the uC to repeatably draw very large (>1A, given enough power supply) currents as soon as power is supplied.  I don't know what events might have preceded the initial failure (they were out of my hands at the time), but I had two suspicions: floating inputs and a weak overvoltage on an input pin.  The input overvoltage was limited to VCC+0.9V and could only have supplied about 50uA, and applying the same conditions to other devices for extended durations has not replicated the failure.  There are also a couple unused pins, and I don't know what could have been going on with those.  When the first one happened, I suspected ESD, but then a second one came back to my bench with similar symptoms so I expect it's something more deterministic.

 

Does anybody know what sort of conditions might damage a chip like that?  I did find that if I supply enough power, in the brief moment before it gets dangerously hot, at least one of the KL26s still executes its code and responds to SWD.

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