An Energy and Area Efficient Carry Select Adder with Dual Carry Adder Cell

In this paper, an energy and area efficient carry select adder (CSLA) is proposed. To minimize the redundant logic operation of a regular CSLA, a dual carry adder cell is proposed. The proposed dual carry adder is composed of an XOR/XNOR cell and two pairs of sum-carry cells. Both CMOS logic and a transmission gate were applied to the dual carry adder cell to achieve fast and energy efficient operation. Eight-bit, 16b, and 32b square-root (SQRT) CSLAs based on the proposed dual carry adder were developed. The post-layout simulation based on a SMIC 55 nm process demonstrated that the proposed CSLAs reduced power consumption by 68.4–72.2% with a slight delay increase for different bit widths. As the dual carry adder had much fewer transistors than the two regular full adders, the area of the proposed CSLAs was reduced by 45.8–51.1%. The area-power-delay product of the proposed CSLA improved 5.1×–6.73× compared with the regular CSLA.