An FPGA with power-gated switch blocks

Static power consumption is an important component of the total power consumption in FPGAs built using 90nm and smaller technology nodes. A previous study proposed powering down regions of logic blocks in an FPGA when idle to reduce the static power dissipation. This previous work did not consider powering down the switch blocks (SBs). However, the static power of SBs constitute more than 50% of an FPGA's static power. In this paper, we present an architecture that enables selectively powering down SBs along with the logic blocks during their idle periods. The potential power savings from this architecture depends on the proportion of SBs that can be powered down. We present modifications to our CAD flow to maximize the number of such SBs, and we experimentally estimate their proportion using a set of synthetic benchmark circuits. Our estimation results show that 53% to 83% of the SBs can be powered down in a functional module of size 24×24 tiles and an architecture power gating regions of size 4×4 tiles, leading to overall static power reductions of 70% to 84% compared to an architecture that does not support power gating.