Application of redundant gates as approach to synthesis of high reliable digital device is considered. Specific structure of self-timed digital device result in fact that traditional synthesis method of fault-tolerant digital device, such as triplicating, can not show good results. At the same time application of redundant gates allows in some cases achieve high reliability of the design with lower complexity than it can be in triplicated style. Earlier researches that could answer the question «Which redundant structure is better?» wasn't carried out. In this research different redundant structures is analyzed. A recommendation which structure is better in different situation is given. Complex index is proposed it allow comparing different fault-tolerant circuits.

Self-timed circuits (ST), reliability, fault-tolerance, redundant gates, functionally-full tolerant gate.