A transregional model for near-threshold circuits with application to minimum-energy operation

The most energy-efficient operating point for CMOS circuits is near the threshold voltage. Conventional models are difficult to use in this region because they are piecewise and/or discontinuous around threshold. This paper proposes a simple new model for I_on that is valid in the near-threshold region. Based on the ON-current, a propagation delay model is derived. The model is applied to determine the minimum energy point for inverter chains. The transregional model matches simulated data within 15 mV, while the conventional exponential subthreshold model underestimates the supply voltage by up to 80 mV.