SHort on 3.3V...

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SHort on 3.3V...

Postby rew » 07 Jul 2016, 05:57

I'm bringing up a new board. A few new things on that board so I tried to be careful. This paid off because one of the low side mosfets had a short. Power supply current limit was set to 100 mA and increased to 230mA for a very short time to check if the powersupply startup was too slow.

On the other hand, I seem to have a "semiconductor short" on the 3.3V line. The 3.3V regulator has been removed and I sitll measure a short at 0.5V when the lab powersupply directly powers the 3.3V.

That more-or-less leaves just the CPU, right? (I don't have a DRV on this design. The DRV has been replaced by a 12V stepdown, a 7805 for the 5V, two dual opamps for the current amplification (absent on this specific board) and LM5109's to drive the gates....)

If I remember correctly I was able to flash the chip before adding the power stage.

Anybody have an idea as to how a shorted lowside mosfet (just a soldering short: phase to GND the gate was "free") can blow up my CPU?

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