Ultralow-Voltage Power Gating Structure Using Low Threshold Voltage

A novel power gating (PG) structure using only low-threshold-voltage metal-oxide-semiconductor field-effect transistors (MOSFETs) is proposed to extend the PG to an ultralow-voltage region ( ~ 0.3 V). The proposed structure deploys series-connected low-V _th footers with two virtual ground ports and selectively chooses the logic cells for connecting them to each virtual ground port according to the delay criticality. Furthermore, additional circuitry is designed to reduce not only the subthreshold leakage current but also the gate-tunneling leakage and to reduce the wake-up time and rush current compared to the conventional PG. The total PG switch size of the proposed PG structure including the additional circuits is less than the conventional one. The simulation results are compared to those of other well-known circuit schemes and show that, in the ultralow-voltage region, the other high-V _th-based PG schemes cannot be used due to the impractical delay increase and long wake-up time, whereas the proposed PG structure keeps the balance among the critical PG issues. The proposed PG is evaluated using inverter chains and ISCAS85 benchmark circuits at 0.6-V supply voltage, which are designed using 45-nm complementary metal-oxide-semiconductor predictive technology model.