Pomiar czasu propagacji inwerterów implementowanych w układach programowalnych w temperaturze ciekłego azotu

摘要

W artykule przedstawiono wyniki eksperymentów, w których sprawdzono zdolność pracy wybranych układów reprogramowalnych w warunkach niskich temperatur, w szczególności w temperaturze ciekłego azotu 77 K (-196°C). Zaprezentowano wyniki pomiarów uśrednionego czasu propagacji inwerterów zrealizowanych w testowanych układach reprogramowalnych. Do badań wybrano struktury PLD oraz CPLD. Badano układy ATF16V8 (Atmel), GAL16V8 (Lattice) i XC2C32 (Xilinx). Przedstawiono wyniki pomiarów uzyskane w temperaturze pokojowej (300 K) oraz w warunkach niskich temperatur - w temperaturze ciekłego azotu (77 K).%In this paper the results of experiments with programmable devices in low temperatures are presented. For most CMOS devices, including programmable devices, low temperature, in particular the temperature of liquid nitrogen 77 K, is far below the typical range. The producers usually guarantee the proper work for their devices at 0°C for commercial devices or -40°C for industrial ones. Even for special military devices the lowest temperature used is -55°C. In the experiments performed by the authors the ability of proper working at the liquid nitrogen temperature (77 K) for some chosen PLD and CPLD devices were examined. The examined devices were immersed in a Dewar flask (Fig. 1). There was found that some of them worked properly in such low temperature, and also could be programmed. According to the theory of silicon semiconductors, in low temperatures the activity of carriers increases, so decrease in the propagation delay of the measured gates was expected. There was measured the average propagation time of the inverters implemented in programmable devices (Fig. 2 and Fig. 3). The results for GAL16V8, ATF16V8 and XC2C32 are given in Tabs. 1 and 3. The obtained results of the average propagation delay and the estimated maximum system frequency were compared with the datasheet information (Tabs. 2 and 4).