ACA-CSU: A Carry Selection Based Accuracy Configurable Approximate Adder Design

Approximate arithmetic circuits can be more effective if their accuracy can be controlled. In this paper, we propose a carry selection based accuracy configurable approximate adder. In the proposed design, longer carry chains provide better accuracy and CSU (Carry Select Unit) gives it better delay properties. The proposed design is generic so that multiple accuracy levels are possible at design time. Our experiments show that our design is considerably more accurate than the already proposed state of the art approximate adders. The latency of the proposed adder is also better than the state of the art adders.