CONSTRAINT-BASED CHANNEL ROUTING FOR ANALOG AND MIXED ANALOG-DIGITAL CIRCUITS

The goal of routing in analog and mixed analog/digital circuits is not simply to achieve the required connections in minimum area, but also to satisfy a set of constraints on parasitics which affect circuit performance. For many mixed analog/digital circuits designed today there is a need to develop channel routing algorithms for channels containing analog nets. In this paper, algorithms for mapping a set of bounding constraints on critical coupling capacitances into constraints in the vertical-constraint graph of the channel are presented. When the channel height is then minimized, the minimization is automatically subjected to the coupling constraints. For differential circuits, it may be necessary to match specific pairs of interconnect parasitics. A technique is presented which tries to match the parasitics for pairs of nets having intersecting horizontal spans in the channel. The concepts presented in this paper can be used for high-performance digital VLSI also.