Hierarchical multi-dimensional table lookup for model compiler based circuit simulation

In this paper, a systematic method for automatically generating hierarchical multi-dimensional table lookup models for compact device and behavioral models with any number of terminals is presented. The method is based on an Abstract Syntax Tree representation of analytic equations. Expensive part of the computations represented by abstract syntax trees are identified and replaced by two-dimensional table lookup models. An error-control based optimization algorithm is developed to generate table lookup models with the minimal amount of table data for a given accuracy requirement. The proposed method has been implemented in the model compiler MCAST and the circuit simulator SPICE3. Experimental results show that, compared to non-optimized compilation based simulation, the simulation using the proposed table lookup optimization method is about 40 times faster and achieves sufficiently accurate results with error less than 1-2%.