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(A) HSPICE macro-model and midpoint-reference generation circuits for MRAM

Title
(A) HSPICE macro-model and midpoint-reference generation circuits for MRAM
Authors
이승연
Issue Date
2003
Department/Major
과학기술대학원 정보통신학과
Publisher
이화여자대학교 과학기술대학원
Degree
Master
Abstract
MRAM(Magnetoresistive Random Access Memory)은 nonvolatility, good write endurance, low supply voltage, low power consumption, high density등의 장점으로 인해, 현재 많이 쓰이고 있는 DRAM(Dynamic RAM), SRAM(Static RAM), Flash Memory 등의 단점을 보완할 수 있는 것으로 평가받고 있으며, 현재 상용화를 위한 활발한 연구가 진행 중에 있다. MRAM은 자성체의 스핀 방향을 정보원으로 하는 비휘발성 메모리로 magneto-resistance material을 storage element로 사용한다. 이는 data switching시 hysteresis, asteroid curve, R-V 특성을 보이게 되는데, HSPICE simulation시 이러한 특성을 나타낼 수 있는 macro-model이 필요하다. 본 논문에서는 MRAM simulation시 MTJ(Magnetic Tunneling Junction)의 hysteretic 특성, asteroid 특성, R-V 특성을 HSPICE에서 재현할 수 있는 macro-model을 제안한다. 또한 종래의 reference cell 회로에 비하여 비교적 정확한 중간 저항 값을 유지하는 새로운 reference cell 회로를 제안하고 이를 본 논문에서 제안한 macro-model을 이용해 simulation한 결과를 보인다.;MRAM (Magnetoresistive Random Access Memory) has several advantages including nonvolatility, good write endurance, low supply voltage, low power consumption, high density over other memories such as DRAM (Dynamic RAM), SRAM (Static RAM), and Flash memory, all of which enables MRAM architectures to be studied for long. The cell of MRAM uses magneto-resistance material as a storage element which has a information data as a polarization of spin in free magnetic layer. This magneto-resistance material has hysteresis, asteroid curve at the thermal variation, and R-V characteristics for switching the data. Therefore a macro-model showing these characteristics is required for MRAM simulation. We propose a macro-model of TMR which can reproduce all of these characteristics on HSPICE. Also we propose a novel sensing scheme, which operates by sensing the difference in voltage between a memory cell and a reference cell for MRAM. In this scheme, we can generate reference resistance having the medium value, (R_(H)+R_(L))/2, for a wide range of applied voltage. New reference-cell circuit improves the sensing margin and guaranties a correct operation of sensing circuit for a wide range of TMR voltage.
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과학기술대학원 > 정보통신학과 > Theses_Master
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