Modeling The RC-interconnect Effects In A Hierarchical Timing Analyzer

Abstract

An approach for accurately modeling the RC-interconnect delay and gate-loading effects in a hierarchical timing analyzer is presented. The change in gate-loading due to interconnect resistance is considered by an "effective capacitance" approximation. The RC-interconnect path delays are precharacterized in terms of an interpolating polynomial function.

Improved effective capacitance computations for use in logic and layout optimization

“…Pileggi and coauthors propose an effective capacitance calculation that approximates the output waveform for single stage gates by using a two piece output waveform [15,12]. This approach calculates an effective capacitance by equating (i) the current at the gate output with driving-point admittance as the load, and (ii) the current at the gate output with a single effective capacitor as the load.…”

“…In these contexts, accurate estimation of gate delay and rise time depends on having an accurate model for the driving point admittance of a load interconnect tree at the output of a gate. Various approaches have been proposed to address the resulting effective capacitance problem [7,15,12,6,13].…”

Calculating the effective capacitance for the RC interconnect in VDSM technologies

“…These papers are simulationbased [6,7,9] or rely on analytical derivations [1,11]. Similarly and more recently, a number of research results have been published that focus on the loading effect of the RC wires on the gate propagation delay [8,9,12,13].…”

“…However, this is very costly in terms of storage and computational requirements. Therefore, the "effective capacitance" approach was proposed in [4,8].…”

Interconnect parasitic extraction in the digital IC design methodology

“…The Standard Parasitic Exchange Format (SPEF), recently approved as an IEEE standard, contains a representation of this model as its "reduced" form. Because driver characterizations are typically still based on a lumped-C load model, an effective-C (C eff ) [6] becomes common to leverage existing characterizations even with more complex load models [7].…”