Noise Immunity Investigation of Low Power Design Schemes

In modern CMOS digital design, the noise immunity has come to have an almost equal importance to the power consumption. In the last decade, many low power design schemes have been presented. However, no one can simply judge which one is the best from the noise immunity point of view. In this paper, we investigate the noise immunity of the static CMOS low power design schemes in terms of logic and delay errors caused by different kinds of noise existing in the static CMOS digital circuits. To fulfill the aims of the paper, first a model representing the different sources of noise in deep submicron design is presented. Then the model is applied to the most famous low power design schemes to find out the most robust one with regard to noise. Our results show the advantages of the dual threshold voltage scheme over other schemes from the noise immunity point of view. Moreover, it indicates that noise should be carefully taken into account when designing low power circuits; otherwise circuit performance would be unexpected. The study is carried out on three circuits; each is designed in five different schemes. The analysis is done using HSPICE, assuming 0.18 μm CMOS technology. key words: noise immunity, low power, power supply noise, digital design