Optimal Gate Size Selection for Standard Cells in a Library

Standard cell libraries provide designers with a fixed set of well characterized logic blocks. As designs are pushed for high performance, low area and low power, it is essential to have a good standard cell library that can help achieve these goals. As gate sizing is crucial to timing, the number of gate sizes (drive strengths) available for each of the primitives is an important factor to be considered. While an infinite granularity of gate sizes is preferable to get the best entitlement, it is often impractical due to the huge cost associated with developing and maintaining libraries. It is therefore essential to find ways to achieve the best performance, power and area, with a reasonable library size. In this paper we focus on the problem of finding out the optimal ratio of gate sizes to be selected. 65nm libraries were used for validating the claims on a real design and the results are presented in this paper.