Power consumption in CMOS combinational logic blocks at high frequencies

Abstract

A new model for estimating dynamic power dissipation in CMOS combinational circuits at differing voltages is presented. The proposed model deals with power dissipation of circuits at saturation frequencies, where the output voltage does not reach 100% of the supply voltage and the output voltage waveform is almost a triangular waveform. We show that the dynamic power consumption at saturation frequencies is only dependent on the supply voltage, and is independent of load capacitance and switching speed. This model shows that when a circuit is working in the saturation frequency range, as the frequency is increased, the performance/power ratio is increased. However, this increase in performance/power ratio is at the expense of noise margin. The model is theoretically and empirically shown to be correct. This model can be used to design a system where the differing combinational logic blocks are supplied with differing voltages. Such a system would consume lower power than if the system was supplied by a single voltage rail.