Active leakage power optimization for FPGAs

Active leakage power dissipation is considered in field-programmable gate arrays (FPGAs) and two "no cost" approaches for active leakage reduction are presented. It is well known that the leakage power consumed by a digital CMOS circuit depends strongly on the state of its inputs. The authors' first leakage reduction technique leverages a fundamental property of basic FPGA logic elements [look-up tables (LUTs)] that allows a logic signal in an FPGA design to be interchanged with its complemented form without any area or delay penalty. This property is applied to select polarities for logic signals so that FPGA hardware structures spend the majority of time in low-leakage states. In an experimental study, active leakage power is optimized in circuits mapped into a state-of-the-art 90-nm commercial FPGA. Results show that the proposed approach reduces active leakage by 25%, on average. The authors' second approach to leakage optimization consists of altering the routing step of the FPGA computer-aided design (CAD) flow to encourage more frequent use of routing resources that have low leakage power consumptions. Such "leakage-aware routing" allows active leakage to be further reduced, without compromising design performance. Combined, the two approaches offer a total active leakage power reduction of 30%, on average.