Incremental Bitline Voltage Sensing Scheme with Half-Adaptive Threshold Reference Scheme in MLC PRAM

Junyoung Ko, Younghwi Yang, Jisu Kim, Younghoon Oh, H. K. Park, Seong Ook Jung

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Research on phase-change random access memory (PRAM) for multilevel cells (MLCs) has been actively conducted owing to the advantages of PRAM cells, such as large resistance margin and fast read/write access time. However, the resistance drift (R-drift), which increases the resistance of the PRAM cells with time, should be overcome to achieve MLC PRAM operation. In this paper, we introduce sensing methods with R-drift tolerance, namely, drift-resilient cell-state metric and incremental bitline voltage (IBV), and compare these sensing methods in terms of the sensing margin and read access time. In addition, we propose a sensing scheme for IBV (IBVSS) with a half-adaptive threshold reference scheme (H-ATRS) to achieve high-R-drift tolerance in severe R-drift conditions with a small layout area for the reference cell. Verification of the IBVSS with H-ATRS is performed by HSPICE simulation using the 0.25-μm model parameters used in the peripheral circuit of Samsung's 20-nm PRAM technology. From the simulation, we find that the IBVSS with H-ATRS achieves more than 1 V of sensing margin under severe R-drift conditions, which ensures stable read operation in the MLC PRAM with 304 ns of sensing time.

Original languageEnglish
Article number7835212
Pages (from-to)1444-1455
Number of pages12
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume64
Issue number6
DOIs
Publication statusPublished - 2017 Jun

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering

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