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Author Topic: Short on the Due board?  (Read 136 times)
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I've been working on a project using the Due for a while now, and suddenly there is a problem. Whenever I apply power to the Due board through any of the usual means (USB, external supply to the Vin pin), the SAM3X gets extremely hot and the board is drawing huge currents. This is without anything beyond power being plugged into the board.

12V to Vin -> 400 mA drawn
7V to Vin -> 700 mA drawn

The only thing that may have physically gone wrong with my project is more than 3.3V being applied to one of the analog input pins. This wouldn't have been more than 5V if it did occur, however. I had a gauge pressure sensor attached to A8 that supplies 1V to 5V linearly based on a measured pressure of 0 kPa to 101 kPa above atmostpheric. The pressure should not at any point have caused the sensor to output more than 3V, but it remains a possibility.

Would an overvoltage applied to an analog input pin cause this problem of drawing so much current with nothing connected?

Thanks,
Taylor
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The only thing that may have physically gone wrong with my project is more than 3.3V being applied to one of the analog input pins.

That's definitely enough to destroy the chip through latch-up.  One reason you must
never exceed Vcc+0.3V or go below -0.3V is to prevent CMOS latch-up.  Wikipedia
will explain this.

Modern CMOS chips are fairly resistant to latchup and usually require high fault
currents to trigger it (100mA or so), but if you put the 5V rail on a pin that's more
than enough current to destroy any chip.  Even fairly small value resistors on the inputs
can provide a lot of robustness against this kind of issue.
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