Design of Ultra-Low Power Consumption Approximate 4–2 Compressors Based on the Compensation Characteristic

Abstract

Approximate computing is tentatively applied in some digital signal processing applications which have an inherent tolerance for erroneous computing results. The approximate arithmetic blocks are utilized in them to improve the electrical performance of these circuits. Multiplier is one of the fundamental units in computer arithmetic blocks. Moreover, the 4-2 compressors are widely employed in the parallel multipliers to accelerate the compression process of partial products. In this brief, three novel approximate 4-2 compressors are proposed and utilized in 8-bit multipliers. Meanwhile, an error-correcting module (ECM) is presented to promote the error performance of approximate multiplier with the proposed 4-2 compressors. In this brief, the number of the approximate 4-2 compressor's outputs is innovatively reduced to one, which brings further improvements in the energy-efficiency. Compared with the exact 4-2 compressors, the simulation results indicate that the proposed approximate compressors UCAC1, UCAC2, UCAC3 achieve 24.76%, 51.43%, and 66.67% reduction in delay, 71.76%, 83.06%, and 93.28% reduction in power and 54.02%, 79.32%, and 93.10% reduction in area, respectively. And the utilization of these proposed compressors in 8-bit multipliers brings 49.29% reduction of power consumption on average.