Modeling unbuffered latches for timing analysis

  • Authors:
  • C. S. Amin;F. Dartu;Y. I. Ismail

  • Affiliations:
  • Dept. of ECE, Northwestern Univ., Evanston, IL, USA;Dept. of ECE, Northwestern Univ., Evanston, IL, USA;Dept. of ECE, Northwestern Univ., Evanston, IL, USA

  • Venue:
  • Proceedings of the 2004 IEEE/ACM International conference on Computer-aided design
  • Year:
  • 2004

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Abstract

Unbuffered latches are often used in high-performance designs with custom timing flows. Adding these circuits to a standard library enables improved designs without blowing the library size. We observe a high potential frequency gain (up to 16%) for smaller power consumption. Accurate models for static timing analysis are required to reach a good point on the safety to performance trade-off. We are proposing a complete modeling methodology that can fit in a standard timing analysis flow. An accurate n-model is presented for the input impedance of an unbuffered latch with less than 2% error. We also present a new setup criteria required for these latches. We also show that more advanced waveform models are required to model the output. A Weibull waveform model proves to be effective in this case.