Simultaneous Switching Noise Consideration for Power/Ground Network Optimization

With the rapid development of semiconductor technology, the working frequency of chips increases dramatically. Thus simultaneous switching noise (SSN) must be considered for robust power/ground (P/G) network design. In this paper, we mainly focus on the SSN effects for P/G network optimization. We first point out the drawbacks of the P/G optimization process without considering the SSN, by analyzing the optimized P/G grids. Then we propose a random walk based technique to consider SSN by adding decoupling capacitor (decap) prior to the nonlinear optimization process. This additional decap allocation phase constructs good current return path for the switching current caused by clock buffers and then reduces the dynamic voltage drop. Experiment results show that the proposed method achieves 2X speed up over the original approach without adding decaps in advance while the decap budget overhead is acceptable.