Fast substrate noise-aware floorplanning with preference directed graph for mixed-signal SOCs

In this paper, we introduce a novel substrate noise estimation technique during early floorplanning, based on the concept of Block Preference Directed Graph (BPDG) and the classic Sequence Pair (SP) floorplan representation. Given a set of analog and digital blocks, the BPDG is constructed based on their inherent noise characteristics to capture their preferred relative orders for substrate noise minimization. For each sequence pair generated during floorplanning evaluation, we can measure its violation against BPDG very efficiently. We observe that by simply counting the number of violations obtained in this manner, it correlates remarkably well with accurate but computation-intensive substrate noise modeling. Thus, our BPDG-based model has high fidelity to guide the substrate noise-aware floorplanning and layout optimization, which become a growing concern for mixed-signal/RF system on chips (SOC). Our experimental results show that the proposed approach is over 60x faster than conventional floorplanning with even very compact substrate noise models. We also obtain less area and total substrate noise than the conventional approach.