A pre-search assisted ILP approach to analog integrated circuit routing

The routing of analog integrated circuits (IC) has long been a challenge due to numerous constraints (such as symmetry and topology-matching) that matter for overall circuit performance. Existing automatic analog IC routing algorithms can be broadly categorized into two approaches: sequential approach that heuristically routes one net after another and constructive ILP (Integer Linear Programming). The former approach is usually fast but may miss opportunities of finding good solutions. The constructive ILP provides optimal solutions but can be very time consuming. We propose a simple yet efficient method that combines the advantages of both existing approaches. First, sequential routing is performed to obtain a set of candidate routing paths for each net. Then, an ILP is applied to commit each net to only one of its candidate routes. Experiments on two op-amp designs show that the post-layout performance (such as gain and phase margin) from our method is close to that of manual design. Our method also outperforms a previous work of automated analog IC routing.