I recently built a custom development board based on ATmega2560. I tried to power the board via VIN port. At 4v, the current draw increases steadily from 20mA to 40mA and then goes on increasing exponentially to 1.2A quickly, tripping the power supply (Set at 1.2A max).
I have also tested for short circuits, but there aren't any short circuits on the board.
Neither the Atmega2560, nor the CH340C were mounted during this test. Just USB circuit and power supply circuit components.
I have attached the power supply circuit of my board. Can anyone kindly tell me what is causing this current draw surge and how to fix it?
They open fine for me - it's something on your system for those
But yeah, if it's pulling 1.2A, something is getting hot, and very quickly (I would be suspicious of a near-short at that current - like, a short through really thin wire can pull as little as 1.2A); you can find out where the failure is with your hands.
Where my father worked, they would get really-pushing-the-envelope boards (in terms of layers, fine pitch, etc - they were doing this a while back, when the top of the line wasn't as fancy as now, but since they made test equipment for the next generation of semiconductors, their testers were balls-to-the-wall pushing technical limits), like, the bare boards cost a tens of thousands IIRC, and they would pay for quick turn on the prototypes because they were racing the competition and needed the new products ready ASAP so customers could bring their next generation to market sooner, and part of the deal was they'd get them faster if they accepted that they weren't tested by the board house. And when they had shorts (often between the power/ground planes through a via), they would put power on them, and photograph it with a fancy-pants (particularly for the time) thermal camera to find the short, then have the rework people drill out the short and patch it up.
