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Virtual Symmetry Axes for the Layout of Analog IC's
Abstract:
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.
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