Asynchronous Early Output Block Carry Lookahead Adder with Improved Quality of Results

Abstract: A new asynchronous early output block carry lookahead adder (BCLA) incorporating redundant carries is proposed. Compared to the best of existing semi-custom asynchronous carry lookahead adders (CLAs) employing delay-insensitive data encoding and following a 4-phase handshaking, the proposed BCLA with redundant carries achieves 13% reduction in forward latency and 14.8% reduction in cycle time compared to the best of the existing CLAs featuring redundant carries with no area or power penalty. A hybrid variant involving a ripple carry adder (RCA) in the least significant stages i.e. BCLA-RCA is also considered that achieves a further 4% reduction in the forward latency and a 2.4% reduction in the cycle time compared to the proposed BCLA featuring redundant carries without area or power penalties.