A fast method for MOS model evaluation in VLSI simulation with controllable error

Abstract

The authors present a tree-based model approximation (TBMA) MOSFET table model. With the method, the function domain of interest is partitioned recursively. Compared with an even partition strategy in a conventional table look-up, the partition size of a region inside the domain is large when the function is less nonlinear in that region and it is smaller if the function is more nonlinear. To reduce the dimension of the table, the gate-offset-voltage concept is used to shrink the three dimensional MOSFET model to a two dimensional model, maintaining the overall accuracy within a few percent. If smaller error is required, a TBMA correction table can be imposed to reduce the evaluation error to a specified value. Also, a new algorithm for constructing continuity partitions in the TBMA table is proposed.<>