Virtual Symmetry Axes for the Layout of Analog IC'sAbstract:A new approach to the layout of integrated circuits with multiple symmetry axes is presented in this paper. When more than one symmetry is present, the usual approach to placement and compaction makes extensive use of hierarchy, which requires fixed positions for symmetry axes. As a result, wiring and area optimizations are poor. The position of a virtual symmetry axis is variable, and dynamically defined by the center of a group of symmetric modules and area called cluster. Virtual symmetry axes have been implemented in a placement tool using the Simulated Annealing algorithm and in a compaction tool based on the constraint-graph longest-path algorithm. Results are proving the suitability of this approach.Download a Compressed PostScript version of this paper.
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