Temperature-Tracking Sensing Scheme With Adaptive Precharge and Noise Compensation Scheme in PRAM

Phase-change random access memory (PRAM) is considered to be one of the most promising storage class memory candidates. In this paper, several circuit techniques are introduced to satisfy the target yield and sensing time requirements of an 8-Gb PRAM. First, we propose a temperature-tracking reference current generator to compensate for the variation in data current caused by the change in the resistance of phase-change materials. Second, an adaptive precharge scheme to solve the problem of large parasitic resistances and capacitances of a global bitline is proposed. Finally, we introduce noise compensation schemes to reduce coupling noise. The verification of the proposed circuit techniques is performed by HSPICE simulation using the 0.25- $\mu{\rm m}$ model parameters used in peripheral circuit of Samsung's 20 nm PRAM technology. The sensing scheme using temperature tracking reference current generator achieves $9.32\sigma$ ( $\sim$ 100%) of read access pass yield in 8-Gb PRAM and 99 ns of the sensing time is achieved using the adaptive precharge scheme and noise compensation schemes.