Second Order Function Approximation with a Single Small Multiplication

This paper presents a new scheme for the hardware evaluation of elementary functions, based on a piecewise second order minimax approximation. The novelty is that this evaluation requires only one small rectangular multiplication. Therefore the resulting architecture combines a small table size, thanks to second-order evaluation, with a short critical path: Consisting of one table lookup, the rectangular multiplication, and one addition, the critical path is shorter than that of a plain first-order evaluation. Synthesis results for several functions show that this method outperforms all the previously published methods in both area and speed for precisions ranging from 12 to 24 bits.