OTTER: Optimal Termination of Transmission lines Excluding Radiation

The design automation of high-speed digital system interconnects is a challenging problem which requires controlling reflections from discontinuities and noise due to crosstalk. On-chip interconnect design automation is well defined since the objective is to minimize R and C to minimize delay. In contrast, for boards and packaging interconnect, the design objective is much more difficult to specify in terms of a metric. This paper presents a generalized approach for RLC interconnect design automation. A new metric is defined that specifies the optimal design as a function of input signal rise-time, loading conditions on the line, parasitic resistance in the circuit and discontinuities in the interconnect. The approach is based on the recognition of the relation between moments of the responses and critical damping of the circuit. The metric is evaluated without any time-domain simulations to obtain the optimal termination. No simplifying assumptions are required for combinations of lumped and distributed lossy lines, with nonideal terminations.