Fast Voltage Transients on FPGAs: Impact and Mitigation Strategies

Abstract

As FPGAs grow in size and speed, so too does their power consumption. Power consumption on recent FPGAs has increased to the point that it is comparable to that of high-end CPUs. To mitigate this problem, power reduction techniques such as dynamic voltage scaling (DVS) and clock gating can potentially be applied to FPGAs. However, it is unclear whether they are safe in the presence of fast voltage transients. These fast voltage transients are caused by large changes in activity which we believe are common in most designs. Previous work has shown that it is these fast voltage transients that produce the largest variations in delay. In our work, we measure the impact transients have on applications and present a mitigation strategy to prevent them from causing timing failures. We create transient generators that are able to significantly reduce an application's measured Fmax, by up to 25. We also show that transients are very fast and produce immediate timing impact and hence transient mitigation must occur within the same clock cycle as the transient. We create a clock edge suppressor that is able to detect when a transient event is happening and delay the clock edge, thus preventing any timing failures. Using our clock edge suppressor, we show that we can run an application at full frequency in the presence of fast voltage transients, thereby enabling more aggressive DVS approaches and larger power savings.