Designing soft-edge flip-flop-based linear pipelines operating in multiple supply voltage regimes

Qing Xie, Yanzhi Wang, Massoud Pedram

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Soft-edge flip-flop (SEFF) based pipelines can improve the performance and energy efficiency of circuits operating in the super-threshold (supply voltage) regime by enabling the opportunistic time borrowing. The application of this technique to the near-threshold regime of operation, however, faces a significant challenge due to large circuit parameter variations that result from manufacturing process imperfections. In particular, delay lines in SEFFs have to be over-designed to provide larger transparency windows to overcome the variation in path delays, which causes them to consume more power. To address this issue, this paper presents a novel way of designing delay lines in SEFFs to have a large enough transparency window size and low power consumption. Two types of linear pipeline design problems using the SEFFs are formulated and solved: (1) designing energy-delay optimal pipelines for the general usage that requires SEFFs to operate in both the near-threshold and super-threshold regimes, and (2) designing minimum energy consumed pipelines for particular use case with a minimum operating frequency constraint. Design methods are presented to derive requisite pipeline design parameters (i.e.; depth and sizing of delay lines in SEFFs) and operating conditions (i.e.; supply voltage and operating frequency of the design) in presence of process-induced variations. HSPICE simulation results using ISCAS benchmarks demonstrate the efficacy of the presented design methods.

Original languageEnglish (US)
Pages (from-to)318-328
Number of pages11
JournalIntegration, the VLSI Journal
Issue number3
StatePublished - Jun 2014
Externally publishedYes


  • Near-threshold computing
  • Pipelined circuits design
  • Process variation
  • Soft-edge flip-flop

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture
  • Electrical and Electronic Engineering


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