A layout improvement method based on constraint propagation for analog LSI's
Masato Mogaki, Naoki Kato, Naomi Shimada, Yuriko Yamada · 1991
proposes a flexible layout improvement LSIs based on constraint urouagation. The - _method performs rerouting and compaction for a given initial layout pattern by considering design rules and layout constraints. First, it extracts topological relationship between cells and routing wires. Then, it makes a constraint graph according to design rules and various layout constraints which ensure circuit functionality. This algorithm modifies the layout by propagating constraints on the graph according to layout improvement rule requirements. The algorithm enables layout modification while routing and ensures 100% routing like a channel router. It can also be used as a twodimensional compactor.We extended the line expansion algorithm for multi-layer routing. We implemented the basic features of the layout improvement method and tested them. Experimental results show that the proposed method rout 3/4 of the unconnected wires with a 16% area increase. Better performance is expected with full implementation.