Physical Design and Optimization

Abstract

In the previous chapter, we pointed out the lack of power distribution synthesis methods and summarized several shortcomings in previous power bus synthesis approaches. This chapter presents a new approach to synthesize power distribution and to alleviate many of these shortcomings. We describe our new optimization-based strategy which consists of physical design, optimization, electrical modeling, and electrical evaluation components. Specifically, this chapter formulates the physical design and optimization aspects of power distribution synthesis, but only incorporates high-level electrical modeling and electrical evaluation into this strategy. We postpone describing in detail the incorporation of all the electrical aspects until the next chapter. We begin by extending the work previously described in the macro-2D custom design style, and focus on creating new synthesis strategies to handle analog power distribution concerns. We discuss our design style selection and illustrate its generality. We discuss our design objectives and new formulations for power bus topology selection and sizing. We describe the algorithms to synthesize the power I/O cell assignment and power bus topology and sizing, all simultaneously. Next, we formulate the simultaneous power bus synthesis and power I/O cell assignment problem and describe why we chose simulated annealing optimization. We review simulated annealing and then describe our specific annealing formulation for the power distribution synthesis problem.