Efficiency, Stability, and Reliability Implications of Unbalanced Current Sharing Among Distributed On-Chip Voltage Regulators

Longfei Wang, S. Karen Khatamifard, Orhun Aras Uzun, Ulya R. Karpuzcu, Selçuk Köse

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Power delivery networks with distributed on-chip voltage regulators (VRs) serve as an effective way for fast localized voltage regulation within modern microprocessors. Without careful consideration of the interactions among the distributed VRs and the power grid, unbalanced current sharing (CS) among those regulators may, however, lead to efficiency degradations, stability, and reliability issues, and even malfunctions of the regulators. This paper is a first attempt to investigate the efficiency, stability, and reliability implications of unbalanced CS among distributed on-chip VRs. Benefits of balanced CS are demonstrated with concrete examples, showing the necessity of an appropriate current balancing scheme. An adaptive reference voltage control method and the corresponding control algorithms specifically for distributed on-chip VRs are proposed to balance the CS among regulators at different locations. The proposed techniques successfully balance the CS among distributed VRs and can be applied to different regulator types. Simulation results based on practical microprocessor setups confirm the efficiency, stability, and reliability implications.

Original languageEnglish (US)
Article number8025419
Pages (from-to)3019-3032
Number of pages14
JournalIEEE Transactions on Very Large Scale Integration (VLSI) Systems
Volume25
Issue number11
DOIs
StatePublished - Nov 2017

Bibliographical note

Funding Information:
Manuscript received October 4, 2016; revised January 13, 2017, March 31, 2017, and June 22, 2017; accepted July 28, 2017. Date of publication September 4, 2017; date of current version October 23, 2017. This work was supported in part by the National Science Foundation CAREER Award under Grant CCF-1350451, in part by the National Science Foundation Award under Grant CCF-1421988, and in part by the Cisco Research Award. (Corresponding author: Longfei Wang.) L. Wang, O. A. Uzun, and S. Köse are with the Department of Electrical Engineering, University of South Florida, Tampa, FL 33620 USA (e-mail: longfei@mail.usf.edu; orhunuzun@mail.usf.edu; kose@usf.edu).

Funding Information:
Dr. Karpuzcu is a Fulbright Fellow. She was a recipient of the NSF CAREER Award.

Keywords

  • Current sharing (CS)
  • distributed on-chip voltage regulator (VR)
  • power delivery network (PDN)
  • power efficiency
  • reliability
  • stability

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