WaveMin: A fine-grained clock buffer polarity assignment combined with buffer sizing

The clock buffer polarity assignment is one of the effective design schemes to mitigate the power/ground noise caused by the clock signal propagation. This work overcomes two fundamental limitations of the conventional clock buffer polarity assignment methods, which are (1) the unawareness of the signal delay (i.e., arrival time) differences to the leaf buffering elements and (2) the ignorance of the effect of the current fluctuation of non-leaf buffering elements on the total peak current waveform. Clearly, not addressing (1) and (2) in polarity assignment may cause a severe inaccuracy on the peak current estimation, which results in unnecessarily high peak current. To overcome the limitations, we propose a completely new fine-grained approach to the clock buffer polarity assignment combined with buffer sizing, formulating the problem into a multi-objective shortest path problem and solving it effectively. The experimental results show that the proposed method is able to produce designs with 17% lower peak current and 20% lower power noise on average compared the results produced by the best ever known method.