Wire Load Oriented Analog Routing with Matching Constraints

As design complexity is increased exponentially, electronic design automation (EDA) tools are essential to reduce design efforts. However, the analog layout design has still been done manually for decades because it is a sensitive and error-prone task. Tool-generated layouts are still not well-accepted by analog designers due to the performance loss under non-ideal effects. Most previous works focus on adding more layout constraints on the analog placement. Routing the nets is thus considered as a trivial step that can be done by typical digital routing methodology, which is to use vias to connect every horizontal and vertical lines. Those extra vias will significantly increase the wire loads and degrade the circuit performance. Therefore, in this article, a wire load oriented analog routing methodology is proposed to reduce the number of layer changing of each routing net. Wire load is considered in the optimization goal as well as the wire length to keep the circuit performance after layout, while the analog layout constraints like symmetry and length matching are still satisfied during routing. As shown in the experimental results, this approach significantly reduces the wire load and performance loss after layout with little overhead on wire length.