Research Of Circuit Design Method Based On Standard Cell Extension

The frequency performance of circuits was decided by delay of critical path, which was bottleneck of performance improvement. Improving circuit performance by optimization of critical path has been one of the research hotspot. On one hand, because of intense competition of market and increasing complexity of chip scale, period of research and development was challenged and full custom design, which can achieve least critical-path delay, could not meet requirement of timing cost; on the other hand, in order to take both of performance and timing cost into account, half custom design method based on standard cell was often used. But shortest critical path delay could not be realized because of limited drive capacity and quantity of standard cell library,which could lead to insufficient optimization of critical path.Therefore, a semi-custom design technology which was based on standard cell extension was proposed. Critical pah was analyzed logical effort model and extended cell library with perfect driving capability was constructed according to analysis result. Critical path was optimized by logic effort algorithm and shortest time-delay could be achieved by equality of cell gate effort in path. The standard cell might be extended arbitrarily on design request, that is, design automation could be realized and the very method had advantageous portability for mainstream technology. Circuits for a certain process chip were designed and simulated by four kinds of TSMC technology respectively. It could be concluded from the practical experiment that the semi-custom design method based on extended standard cell library could shorten the critical path delay and improve circuit frequency effectively in mainstream technology design.