摘要：Digital circuits operating in the sub-threshold regime consume the least energy. the strict energy constraints are desired in the applications which work at the lowest possible supply voltage. On the other hand, the conventional design flow utilizes the technology library provided by the foundry with a fixed voltage boundary, which causes problems when the supply scales down to the sub-threshold regime. In this paper, we present a design methodology to characterize the existing cell library with Liberty NCX to facilitate the standard design flow. It is demonstrated in 0.13 μm complementary metal-oxide-semiconductor （CMOs） technology with the supply voltage of 300 mV.