Towards PVT-Tolerant Glitch-Free Operation in FPGAs

Glitches are unnecessary transitions on logic signals that needlessly consume dynamic power. Glitches arise from imbalances in the combinational path delays to a signal, which may cause the signal to toggle multiple times in a given clock cycle before settling to its final value. In this paper, we propose a low-cost circuit structure that is able to eliminate a majority of glitches. The structure, which is incorporated into the output buffers of FPGA logic elements, suppresses pulses on buffer outputs whose duration is shorter than a configurable time window (set at the time of FPGA configuration). Glitches are thereby eliminated "at the source" ensuring they do not propagate into the high-capacitance FPGA interconnect, saving power. An experimental study, using Altera commercial tools for power analysis, demonstrates that the proposed technique reduces 70% of glitches, at a cost of 1% reduction in speed performance.