Cyclone II intenral supply voltage short after programming

Hi,

the project is in production for about three years w/o problems until last month. No changes have been made on the design, thus I cannot explain the problem occurring now. I think if it is something with the design itself, the failure would have occured much earlier.

Regarding the programming procedure I killed a FPGA myself on the lab-bench by plugging the USB Blaster with system being powered already - the FPGA worked until I plugged the USB Blaster, no programming occurred (device not found) and - the FPGA did no longer configure. But in this case, the defect was limited to the configuration Pins, the 3V3 and internal core voltage were not shorted at all. (I would assume JTAG configuration may still have been possible - no interface to test on card)

In my humble opinion, there must have been an overvoltage condition killing the FPGA completely. An overload to either pin seems more likely to kill the pin's output structure rather than the complete IC)

Does an overload the 3V3 also cause short on the core voltage or did both be overloaded?

Sincerely,

Carlhermann