I am trying to design a board with ATSAMD21G17 with QFN package... and after 4 months, I have received my board correctly assembled. Anyway When I try to use the SWD connector to burn it or just to supply 3.3V , My chip samd21G become really hot and I can not never obtain 3.3V ... then big problem!, I think I make an error in the design (because I have more than 50 boards with this problem!) but after reading manual of the chip, check my design I do not manage to find the solution... Maybe if there is an expert he will see the problem very fastly (I assume a supply problem ... I have also an other board with ATSAMD21G18 and no problem with them...
thanks for your help , I can send you also the layout
the die pad (pin 49) is to GND but I am not sure , maybe problem is from that?