High-Speed Area-Efficient VLSI Architecture of Three-Operand Binary Adder

Three-operand binary adder is the basic functional unit to perform the modular arithmetic in various cryptography and pseudorandom bit generator (PRBG) algorithms. Carrysave adder (CS3A) is the widely used technique to perform the three-operand addition. However, the ripple-carry stage in the CS3A leads to a high propagation delay of O(n). Moreover, a parallel prefix two-operand adder such as Han-Carlson (HCA) can also be used for three-operand addition that significantly reduces the critical path delay at the cost of additional hardware. Hence, a new high-speed and area-efficient adder architecture is proposed using pre-compute bitwise addition followed by carryprefix computation logic to perform the three-operand binary addition that consumes substantially less area, low power and drastically reduces the adder delay to O(log2 n). The proposed architecture is implemented on the FPGA device for functional validation and also synthesized with the commercially available 32nm CMOS technology library. The post-synthesis results of the proposed adder reported 3.12, 5.31 and 9.28 times faster than the CS3A for 32-, 64- and 128- bit architecture respectively. Moreover, it has a lesser area, lower power dissipation and smaller delay than the HC3A adder. Also, the proposed adder achieves the lowest ADP and PDP than the existing three-operand adder techniques.