Skew-aware polarity assignment in clock tree

ABSTRACT

In modern sequential VLSI designs, clock tree plays an important role in synchronizing different components in a chip. To reduce peak current and power/ground noises caused by clock network, assigning different signal polarities to clock buffers is proposed in previous work. Although peak current and power/ground noises are minimized by signal polarities assignment, an assignment without timing information may increase the clock skew significantly. As a result, a timing-aware signal polarities assigning technique is necessary. In this article, we propose a novel signal polarities assigning technique which can not only reduce peak current and power/ground noises simultaneously but also render the clock skew in control. The experimental result shows that the clock skew produced by our algorithm is 94% of original clock skew in average while the clock skews produced by three algorithms (Partition, MST, Matching) in the absence of post clock tuning steps in the previous work are 235%, 272%, and 283%, respectively. Moreover, our algorithm is as efficient as the three algorithms of the previous work in reducing peak current and power/ground noises.

REFERENCES

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INDEX TERMS

Primary Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.2 Design Aids

General Terms:
Design

Keywords:
Clock skew, clock tree, peak current, polarity assignment, power/ground noise