Thermal verification on FPGAs

Thermal verification of complex ICs can help the designer to detect if a particular block is working beyond specifications. A simple method is to extract the output frequencies of an array of ring-oscillators previously distributed in the die. The main advantage is that neither external transducers nor analog parts are necessary. Other possibility is to bias one of the clamping diodes usually present in the pads, and measure its junction forward voltage. In both cases, the measurement of temperature can be done in actual working conditions; that is, with the chip inside the case with its heat sink and fan.