ACORN is a system for the physical design of cascode voltage switch (CVS) macros which utilizes tree placement and tree customization to improve macro wirability. The results obtained by designing a 43-tree differential (DCVS) macro on a masterslice chip image are presented to illustrate the design improvements. In this example, tree placement reduces wire length and via count by 12 percent relative to a transistor-pair placement design. Tree customization increases this improvement to 25 percent, and increases the porosity of the wired macro to vertical global wires from 8 percent for tree placement alone to 15 percent.
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