Making visible the thermal behaviour of embedded microprocessors on FPGAs

This paper shows a method to verifying the thermal status of complex FPGA-based circuits like microprocessors. Thus, the designer can evaluate if a particular block is working beyond specifications. The idea is to extract the output frequencies of an array of ring-oscillators previously distributed in the die, taking full advantage of the configuration port capabilities in Xilinx technology. As a result, it is shown that the FPGA technology offers the designers of embedded systems the possibility of viewing a detailed thermal map of a circuit at a minimum cost. The verification can be done in actual working conditions; for example with heat sinks and fans attached to the chip, inside the system case, or even in an on-board satellite application. The main results of the work are unthinkable using other alternatives like IR cameras, external sensors, or embedded diodes.