Design and analysis of asynchronous adders

An asynchronous adder can take advantage of the shorter carry propagation chains that occur in practice and exhibit a data-dependent computation delay. Basically, an asynchronous adder has a mechanism to announce early completion by detecting when it is done. Such an adder is extremely useful in asynchronous implementation of computing structures. In this paper we evaluate the designs tradeoffs of well-known asynchronous adder configurations based on ripple-carry and carry lookahead topologies. We show that, using complex gates, carry lookahead asynchronous adders can be realised that outperform ripple-carry asynchronous adders, both in average-case delay and worst-case delay without increasing the area and power consumption. The underlying timing assumptions and applications of the adder in asynchronous pipelines (micropipelines) are also discussed