Design Considerations for Energy-Efficient and Variation-Tolerant Nonvolatile Logic
Design Considerations for Energy-Efficient and Variation-Tolerant Nonvolatile Logic
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DOI：
10.1109/tvlsi.2018.2812700
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发表时间：
2018-03
影响因子：
2.8
通讯作者：
Jinghua Yang;A. Dengi;S. Vrudhula
中科院分区：
文献类型：
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作者：
Jinghua Yang;A. Dengi;S. Vrudhula
由收集的能量供电的系统必须消耗非常低的功率，并承受频繁的电力中断。非易失性逻辑（NVL）通过将系统状态保存在用自旋转移力矩磁隧道结（STT-MTJ）增强的触发器中作为非易失性存储设备来解决后者。STT-MTJ和CMOS晶体管中的制造变化显著降低了良率，导致过度设计和高能耗。详细分析了在驱动电路中进行备份和恢复的设计权衡，并提出了一种新的方法来设计能量最佳的驱动器，以达到给定的产量。接下来，提出了两个非易失性触发器（NVFF）电路的有效设计，其中的备份时间是在每个芯片的基础上确定的，从而最大限度地减少能量浪费，并满足产量约束。为了达到98%的产率，传统的方法将不得不花费比所需的最小值多出近5倍的能量，而所提出的可调方法仅花费比最小值多出26%的能量。还包括在两个较大的功能块中使用时，所提出的NVFF设计的能耗。实验结果是基于一个商业40纳米工艺设计套件，和HSPICE模拟与代工厂提供的统计模型和数据。
Systems powered by harvested energy must consume very low power and withstand frequent interruptions in power. Nonvolatile logic (NVL) addresses the latter by saving the system state in flipflops enhanced with spin-transfer torque magnetic tunnel junctions (STT-MTJs) as the nonvolatile storage devices. Manufacturing variations in the STT-MTJs and in CMOS transistors significantly reduce yield, leading to overdesign and high-energy consumption. A detailed analysis of the design tradeoffs in the driver circuitry for performing backup and restore, and a novel method to design the energy optimal driver for a given yield is presented. Next, efficient designs of two nonvolatile flip-flop (NVFF) circuits are presented, in which the backup time is determined on a per-chip basis, resulting in minimizing the energy wastage and satisfying the yield constraint. To achieve a yield of 98%, the conventional approach would have to expend nearly $5\times $ more energy than the minimum required, whereas the proposed tunable approach expends only 26% more energy than the minimum. Also included are the energy consumption of the proposed NVFF designs when used in two larger function blocks. Experimental results were based on a commercial 40-nm process design kit, and HSPICE simulations with foundry supplied statistical models and data.