Design Techniques for NBTI-Tolerant Power-Gating Architectures

While negative bias temperature instability (NBTI) effects on logic gates are of major concern for the reliability of digital circuits, they become even more critical when considering the components for which even minimal parametric variations impact the lifetime of the overall circuit. pMOS header transistors used in power-gated architectures are one relevant example of such components. For these types of devices, an NBTI-induced current capability degradation translates into a larger -drop effect on the virtual- rail, which unconditionally affects the performance and, thus, the reliability of all power-gated cells. In this brief, we address the problem of designing NBTI-tolerant power-gating architectures. We propose a set of efficient NBTI-aware circuit design solutions, including both static and dynamic strategies, that aim at improving the lifetime stability of power-gated circuits by means of oversizing, body biasing, and stress-probability reduction while minimizing the design overheads. Experimental results prove the effectiveness of such techniques when applied to a suite of benchmarks mapped onto a 45-nm industrial CMOS technology library. In particular, we prove that it is possible to achieve more than ten times of lifetime extension with respect to a traditional power-gating approach.