Energy-optimal voltage model supporting a wide range of nodal switching rates for early design-space exploration

Abstract

This paper explores the models of the energy-optimal voltage (VOPT) of near/sub-threshold digital VLSI circuits with a focus on the support for a wide range of nodal switching rates. The previous models can estimate the VOPT of the circuits having relatively high nodal switching rates (VOPT, H), but can become inaccurate in finding the VOPT of the circuits having low nodal switching rate. In this work, therefore, we develop the models for finding (i) the VOPT of the circuits having low nodal switching rates (VOPT, L) and (ii) the critical nodal switching rate point (αcrit) below which the VOPT, L should be used. The models are verified with inverter chains and sub-threshold 10-transistor SRAM arrays in SPICE-level simulation. The model takes only process technology parameters to estimate VOPTs, and can be suitable for early-stage design-space exploration.