Methods for calculating coupling noise in early design: a comparative analysis

In this paper we compare different methods for calculating coupling noise, specially for use in the early design phase of a high performance custom design when all the detailed physical design information is not available. This analysis can be important in the design of functional blocks such as data paths in microprocessors, where if noise avoidance is included in the design planning phase, later changes in the design may be avoided. Thus, reducing the number of design iterations and overall design time. The ideal noise calculation technique should be very fast and reasonably accurate so as to account for all significant parameters that will affect the noise. We consider three different techniques and compare them with an exact analysis using a circuit simulator. It is shown that a lumped model is quite accurate for predicting noise on a variety of wire geometries up to 3 mm in length. We also propose a technique to extend this model to the practically important case when bus wires overlap only partially with neighbors.