AREA ROUTING FOR ANALOG LAYOUT

An area router specifically tailored for the layout of analog circuits is presented. It is based on the A* algorithm, which combines the flexibility of maze routing with computational efficiency. Parasitics are controlled by means of a programmable cost function based on a set of user-defined weights. The weights can be automatically defined based on high-level electrical performance specifications and determine the net scheduling. An algorithm for symmetric routing preserves symmetries in differential architectures. Different current paths can be dealt with in each wire by means of a net partitioning procedure driven by information on the current driven by terminals. Shields can be built between critically coupled wires, in order to guarantee an effective limitation of cross-coupling. The weight-driven programmable cost function makes this router particularly suitable for a performance-driven approach to analog routing. Automatic weight definition also makes the use of the tool independent of the user's expertise. The implemented algorithms are described and results are illustrated proving the effectiveness of this approach.