Mitigation of NBTI Induced Performance Degradation in On‐Chip Digital LDOs
Longfei Wang1,2,a, S. Karen Khatamifard1, Ulya R. Karpuzcu3 and Selçuk Köse1
1Department of Electrical Engineering, University of South Florida, Tampa, FL, USA
alongfei@mail.usf.edu
bkose@usf.edu
2Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, USA
ckhatami@umn.edu
dukarpuzc@umn.edu
ABSTRACT
On‐chip digital low‐dropout voltage regulators (LDOs) have recently gained impetus and drawn significant attention for integration within both mobile devices and microprocessors. Although the benefits of easy integration and fast response speed surpass analog LDOs and other voltage regulator types, NBTI induced performance degradation is typically overlooked. The conventional bi‐directional shift register based controller can even exacerbate the degradation, which has been demonstrated theoretically and through practical applications. In this paper, a novel uni‐directional shift register is proposed to evenly distribute the electrical stress and mitigate the NBTI effects under arbitrary load conditions with nearly no extra power and area overhead. The benefits of the proposed design as well as reliability aware design considerations are explored and highlighted through simulation of an IBM POWER8 like processor under several benchmark applications. It is demonstrated that the proposed NBTI‐aware design can achieve up to 43.2% performance improvement as compared to a conventional one.
