Explicit delay metric for interconnect optimization

Interconnect optimization relies heavily on delay metrics which have to be simple yet accurate. This is hard to achieve when the delay is at a point close to the source. We present an explicit metric in which the response at a node is approximated by order reduction to a two-pole circuit using the first 3 moments of the impulse response. The core of the metric is an accurate two-pole, one-zero model which yields the delay. Tests on RC wires and trees demonstrate that our metric is more accurate than the recently published implicit metric WED which uses a statistical interpretation of delay.