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Electronics 2015, 4(1), 150-172;

Optimally Fortifying Logic Reliability through Criticality Ranking

Department of Electrical Engineering and Computer Sciences, University of Central Florida, Orlando, FL 32816, USA
Author to whom correspondence should be addressed.
Academic Editor: Mostafa Bassiouni
Received: 27 October 2014 / Accepted: 3 February 2015 / Published: 13 February 2015
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With CMOS technology aggressively scaling towards the 22-nm node, modern FPGA devices face tremendous aging-induced reliability challenges due to bias temperature instability (BTI) and hot carrier injection (HCI). This paper presents a novel anti-aging technique at the logic level that is both scalable and applicable for VLSI digital circuits implemented with FPGA devices. The key idea is to prolong the lifetime of FPGA-mapped designs by strategically elevating the VDD values of some LUTs based on their modular criticality values. Although the idea of scaling VDD in order to improve either energy efficiency or circuit reliability has been explored extensively, our study distinguishes itself by approaching this challenge through an analytical procedure, therefore being able to maximize the overall reliability of the target FPGA design by rigorously modeling the BTI-induced device reliability and optimally solving the VDD assignment problem. Specifically, we first develop a systematic framework to analytically model the reliability of an FPGA LUT (look-up table), which consists of both RAM memory bits and associated switching circuit. We also, for the first time, establish the relationship between signal transition density and a LUT’s reliability in an analytical way. This key observation further motivates us to define the modular criticality as the product of signal transition density and the logic observability of each LUT. Finally, we analytically prove, for the first time, that the optimal way to improve the overall reliability of a whole FPGA device is to fortify individual LUTs according to their modular criticality. To the best of our knowledge, this work is the first to draw such a conclusion. View Full-Text
Keywords: criticality analysis; VLSI; logic circuit; discriminative; voltage scaling criticality analysis; VLSI; logic circuit; discriminative; voltage scaling

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Bai, Y.; Alawad, M.; DeMara, R.F.; Lin, M. Optimally Fortifying Logic Reliability through Criticality Ranking. Electronics 2015, 4, 150-172.

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