Simultaneous Gate and Interconnect Sizing for Circuit-Level Delay Optimization

With delays due to the physical interconnect dominating the overall logic path delays, circuit-level delay optimization must take interconnect effects into account. Instead of sizing only the gates along the critical paths for delay reduction, the trade-off possible by simultaneously sizing gate and interconnect must also be considered. We show that for optimal gate and interconnect sizing, it is imperative that the interaction between the driver and the RC interconnect load be taken into account. We present an iterative sensitivity-based approach to simultaneous gate and interconnect sizing in terms of a gate delay model which captures this interaction. During each iteration, the path delay sensitivities are efficiently calculated and used to size the components along a path.