Title :
Constraint-based channel routing for analog and mixed analog/digital circuits
Author :
Choudhury, Umakanta ; Sangiovanni-Vincentelli, Alberto
Author_Institution :
California Univ., Berkeley, CA, USA
fDate :
4/1/1993 12:00:00 AM
Abstract :
A well-defined methodology for mapping the constraints on a set of critical coupling capacitances into constraints in the vertical-constraint (VC) graph of a channel is presented. The approach involves directing undirected edges, adding directed edges, and increasing the weights of edges in the VC graph in order to meet crossover constraints between orthogonal segments and adjacency constraints between parallel segments while attempting to cause minimum increase in the channel height due to the constraints. Use is made of shield nets when necessary. A formal description of the conditions under which the crossover and the adjacency constraints are satisfied is provided and used to construct the appropriate mapping algorithms. The problem of imposing matching constraints on the routing parasitics in a channel with lateral symmetry is addressed. It is observed that perfect matching is not possible for a matched pair of nets with intersecting horizontal spans. A technique to achieve almost perfect mirror symmetry is presented for such pairs of nets
Keywords :
circuit layout CAD; graph theory; integrated circuit technology; linear integrated circuits; mixed analogue-digital integrated circuits; network routing; CAD; adjacency constraints; channel routing; critical coupling capacitances; crossover constraints; lateral symmetry; mapping algorithms; matching constraints; mirror symmetry; mixed analog/digital circuits; orthogonal segments; routeing; routing parasitics; shield nets; vertical constraint graph; Algorithm design and analysis; Analog circuits; Circuit optimization; Cost function; Coupling circuits; Design automation; Digital circuits; Parasitic capacitance; Routing; Very large scale integration;
Journal_Title :
Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on