Supply and Threshold Voltage Scaling for Minimum Energy Operation over a Wide Operating Performance Region

Shoya SONODA  Jun SHIOMI  Hidetoshi ONODERA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E104-A    No.11    pp.1566-1576
Publication Date: 2021/11/01
Publicized: 2021/05/14
Online ISSN: 1745-1337
DOI: 10.1587/transfun.2020KEP0013
Type of Manuscript: Special Section PAPER (Special Section on Circuits and Systems)
Category: 
Keyword: 
minimum energy point tracking (MEPT),  dynamic voltage and frequency scaling (DVFS),  adaptive body biasing (ABB),  

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Summary: 
A method for runtime energy optimization based on the supply voltage (Vdd) and the threshold voltage (Vth) scaling is proposed. This paper refers to the optimal voltage pair, which minimizes the energy consumption of LSI circuits under a target delay constraint, as a Minimum Energy Point (MEP). The MEP dynamically fluctuates depending on the operating conditions determined by a target delay constraint, an activity factor and a chip temperature. In order to track the MEP, this paper proposes a closed-form continuous function that determines the MEP over a wide operating performance region ranging from the above-threshold region down to the sub-threshold region. Based on the MEP determination formula, an MEP tracking algorithm is also proposed. The MEP tracking algorithm estimates the MEP even though the operating conditions widely change. Measurement results based on a 32-bit RISC processor fabricated in a 65-nm Silicon On Thin Buried oxide (SOTB) process technology show that the proposed method estimates the MEP within a 5% energy loss in comparison with the actual MEP operation.