一种新颖的高可靠CMOS SRAM 单元

本文提出了一种新颖的8管抗SUE,高噪声容限的SRAM单元。通过在每个访问晶体管上增加了一个并联的晶体管,上拉PMOS的驱动能力可以设计的比传统单元的PMOS的驱动能力更强,读访问晶体管可以设计得比传统单元的读访问晶体管更弱。因此保持,读噪声容限和临界电荷都有较大提高。仿真结果表明,与传统的6管单元相比,合理设计上拉晶体管尺寸后,临界电荷提高了将近3倍。保持和读静态噪声容限分别提高了72%和141.7%。但该新式单元的面积额外开销为54%,读性能也有所下降,适用于高可靠性应用,如航天,军事等。     

Stability and leakage characteristics of novel conducting PMOS based 8T SRAM cell

The stability and leakage power of SRAMs have become an important issue with scaling of CMOS technology. This article reports a novel 8-transistor (8T) SRAM cell improving the read and write stability of data storage elements and reducing the leakage current in idle mode. In read operation, the bit-cell keeps the noise-vulnerable data ‘low’ node voltage close to the ground level and thus producing near-ideal voltage transfer characteristics essential for robust read functionality. In write operation, a negative bias on the cell facilitates to change contents of the bit. Unlike the conventional 6T cell, there is no conflicting read and write requirement on sizing the transistors. In standby mode, the built-in stacked device in the 8T cell reduces the leakage current significantly. The 8T SRAM cell implemented in a 130 nm CMOS technology demonstrates 2× higher read stability while bearing 20% better write-ability at 1.2 V typical condition and a reduction by 45% in leakage power consumption compared to the standard 6T cell. Results of the bit-cell architecture were also compared to the dual-port 8T SRAM cell. The stability enhancement and leakage power reduction provided with the proposed cell are confirmed under process, voltage and temperature variations.     

130nm工艺极低泄漏电流亚阈值SRAM存储单元设计

本文提出一款工作在亚阈值（200 mV）区域且具有极低泄漏电流的亚阈值SRAM存储单元。该存储单元采用自适应泄漏电流切断机制,该机制在没有带来额外的动态功耗和性能损失的前提下,同时降低动态操作（读/写操作）和静态操作时的泄漏电流。差分读出方式和可配置操作模式的应用,使得本文设计在亚阈值条件下（200 mV）仍然保持足够的鲁棒性。仿真结果表明,相比于参考文献中的亚阈值存储单元本文设计具有：（1）在不同的工艺角下,均具有较大的读噪声容限和保持噪声容限;（2）在动态操作和静态操作时均具有极低的泄漏电流。最后,我们将该存储单元成功的应用于IBM 130nm工艺下的一款 bits存储阵列中,测试结果表明该存储阵列可以在200 mV电源电压条件下正常工作,所对应功耗（包括动态功耗和静态功耗）仅0.13 μW,是常规六管存储单元功耗的1.16%。     

A new low-power 10T SRAM cell with improved read SNM

This paper describes the characteristics of a new 10T structure for SRAM cell that works quite well in the sub-threshold region. This new architecture has good characteristics in write and read delay and energy compared with other new structures. This new 10T topology improves read static noise margin (SNM) and write operation speed with respect to other topologies in the same or even lower power consumption. The new topology has at least 13% lower power consumption compared with the best of recent architectures. Its write characteristics also are similar to those of 6T-SRAM, which has improved write delay and energy. The new 10T SRAM cell also consumes lower power compared with other cells. The stacking is used to suppress the standby leakage through the read path. The simulations were performed using HSPICE 2011 in a 16 nm bulk CMOS Berkeley predictive technology model (BPTM).     

An Experimental 0.8 V 256‐kbit SRAM Macro with Boosted Cell Array Scheme

This work presents a low‐voltage static random access memory (SRAM) technique based on a dual‐boosted cell array. For each read/write cycle, the wordline and cell power node of selected SRAM cells are boosted into two different voltage levels. This technique enhances the read static noise margin to a sufficient level without an increase in cell size. It also improves the SRAM circuit speed due to an increase in the cell read‐out current. A 0.18 µm CMOS 256‐kbit SRAM macro is fabricated with the proposed technique, which demonstrates 0.8 V operation with 50 MHz while consuming 65 µW/MHz. It also demonstrates an 87% bit error rate reduction while operating with a 43% higher clock frequency compared with that of conventional SRAM.     

Novel low-power and stable SRAM cells for sub-threshold operation at 45 nm

In scaled technologies with lower supply voltage, conventional Static Random Access Memory (SRAM) cell suffers from unsuccessful read & write operation due to high off state current in sub-threshold region at nanometre technologies. This work proposes new functional low-power designs of SRAM cells with 7, 8, 9 and 12 transistors which operate at only 0.4V power supply in sub-threshold operation at 45 nm technology. Stability analysis is carried out using static noise margins as well as N-curve cell stability metrics. For performance measurement, read/write access time and leakage power consumption in hold mode are analysed. The comparison with published designs shows that two new proposed designs namely M8T, MPT8T have 30% less leakage power consumption along with 2× read stability, 2× write ability, more than 60% faster read & write operation.     

6-T CMOS SRAM单元稳定性分析及设计优化

介绍了一种由两个交叉耦合反向器构成的6-晶体管(6-T)存储单元的噪声容限分析方法.对6-T CMOS SRAM单元的稳定性作了分析及仿真.借助SPICE和MATLAB工具,对存储单元在数据保持和数据读取时的稳定性、数据写入过程中的可靠性及其之间的关系进行了深入研究.对可能影响噪声容限的因素,如单元比、上拉比、MOS管的阈值电压、位线预充电压、电源电压以及温度进行了仿真讨论,并从中得到合适的电路设计参数.流片结果表明,理论分析与实测数据相符.分析数据对基于CSMC O.5μm CMOS工艺的SRAM电路设计优化具有指导作用.     

Variation resilient subthreshold SRAM cell design technique

This article presents a circuit technique for designing a variability resilient subthreshold static random access memory (SRAM) cell. The architecture of the proposed cell is similar to the conventional 10T SRAM cell with the exception that dynamic threshold MOS is used for the read/write access FETs and cell content body bias scheme is used for bitline droppers (FETs used to drop bitlines). Moreover, the proposed bitcell utilises single differential port unlike conventional 10T bitcell which utilises dual differential ports. The proposed design offers 2.1× improvement in T _RA (read access time) and 3.2× improvement in T _WA (write access time) compared to CON10T at iso-device-area and 200?mV. It exhibits three roots in its read voltage transfer characteristic (VTC) even at 150?mV showing its ability to function as a bistable circuit. The combination of write and read VTCs for write static noise margin of the proposed design also shows single root signifying its write-ability even at 150?mV. It proves its robustness against process variations by featuring narrower spread in T _RA distribution (by 1.3×) and in T _WA distribution (by 1.2×) at 200?mV.     

超深亚微米无负载四管与六管SRAM SNM的对比研究

采用基于物理的α指数MOSFET模型与低功耗传输域MOSFET模型，推导了新的超深亚微米无负载四管与六管SRAM存储单元静态噪声容限的解析模型．对比分析了由沟道掺杂原子本征涨落引起的相邻MOSFET的阈值电压失配对无负载四管和六管SRAM单元静态噪声容限的影响。     

一种4-Mb高速低功耗CMOS SRAM的设计

高性能的系统芯片对数据存取速度有了更严格的要求,同时低功耗设计已成为VLSI的研究热点和挑战.本文设计了一款4-Mb(512K×8bit)的高速、低功耗静态存储器(SRAM).它采用0.25μm CMOS标准工艺和传统的六管单元.文章分析了影响存储器速度和功耗的原因,重点讨论了存储器的总体结构、灵敏放大器及位线电路.通过系统优化,达到15ns的存取时间.     

优化阵列结构的5 ns 32 kb CMOS SRAM及其外围电路

设计了一个地址有效时间为５ｎｓ的３２ｋｂ（２ｋ×１６位）ＣＭＯＳ静态随机存储器。设计中采用优化的阵列结构、分段字线译码,以达到１．７５ｍＷ／ＭＨｚ的低功耗;采用位线平衡技术、高速两级敏感放大器及可预置电压的数据输出缓冲,以提高存储器的读写频率。同时,利用两级敏感放大器的层次式结构降低数据线的电压幅度,进一步降低了功耗。     

高可靠性SRAM中缩短汉明码EDAC电路的失效分析

缩短汉明码及其改进码字被广泛使用在宇航级高可靠性存储器的差错检测与纠正电路中。作为一种成熟的纠正单个错误编码,其单字节内多位翻转导致缩短汉明码失效的研究却很少。这篇文章分析了单字节多位翻转导致缩短汉明码失效的情况,分析了各种可能的错误输出模式,并从理论上给出了其概率计算公式。采用Matlab软件进行的计算机模拟试验表明,理论结果与试验结果基本相符。这篇文章最后分析了ISSI公司在其抗辐射SRAM设计中采用的一种将较长信息位分成相等两部分,分别采用缩短汉明码进行编译码的方案。分析表明,这种编译码方案可以降低失效状态下输出3 bit翻转的概率。     

新型高可靠性低功耗6管SRAM单元设计

提出一种新型的6管SRAM单元结构,该结构采用读/写分开技术,从而很大程度上解决了噪声容限的问题,并且该结构在数据保持状态下,采用漏电流以及正反馈保持数据,从而不需要数据的刷新来维持数据。仿真显示了正确的读/写功能,并且读/写速度和普通6管基本相同,但是比普通6管SRAM单元的读/写功耗下降了39%。     

An ultra-low-power 1 kb sub-threshold SRAM in the 180 nm CMOS process

This paper presents a 1Kb Sub-threshold SRAM in 180nm CMOS process based on a improved 11T SRAM cell with new structure. Final test results verify the function of the SRAM. The minimal operating voltage of the chip is 350mV, where the speed is 165KHz and the leakage power is 42nW and the dynamic power is less than 1uW. The designed SRAM can be used in ultra-low-power SoC.     

An ultra-low-power 1 kb sub-threshold SRAM in the 180 nm CMOS process

This paper presents a 1 kb sub-threshold SRAM in the 180 nm CMOS process based on an improved 11T SRAM cell with new structure. Final test results verify the function of the SRAM. The minimal operating voltage of the chip is 350 mV, where the speed is 165 kHz, the leakage power is 42 nW and the dynamic power is about 200 nW. The designed SRAM can be used in ultra-low-power SoC.     

Design of a novel CMOS/MTJ-based multibit SRAM cell with low store energy for IoT applications

ABSTRACT

With rapid growth of Internet of Things, more and more devices are getting connected, which results in generation of large amount of data. To convert this collected raw data into useful information, it needs to be processed. However, during processing a significant amount of energy is spent in bringing data from off-chip non-volatile memory to on-chip memory. In addition, these devices are generally operated in ‘Normally OFF’ mode, which requires energy intensive boot process for waking up. Addressing these issues, Magnetic Tunnel Junction offers features like non-volatility and high integration density, which allows storage of data and instruction closer to the core. Therefore, this work proposes a hybrid multibit SRAM cell, which integrates MTJ with conventional 6T SRAM cell. The proposed SRAM cell supports multiple bit storage within a single cell. However, one of the critical issues with the MTJ is high-energy consumption while storing data. Hence, we also propose a store assist circuit for multibit SRAM cell, which asynchronously terminates the store operation after its completion to reduce the power consumption. Our simulation results show that the store assist circuit results in reduction of store energy by 35% and 72% when compared with existing multibit non-volatile SRAM.     

PDSOI CMOS SRAM单元临界电荷的确定

PDSOI CMOS SRAM单元的临界电荷(Critical Charge)是判断SRAM单元发生单粒子翻转效应的依据.利用针对1.2μm抗辐照工艺提取的PDSOI MOSFET模型参数,通过HSPICE对SRAM 6T存储单元的临界电荷进行了模拟,指出了电源电压及SOI MOEFET寄生三极管静态增益β对存储单元临界电荷的影响,并提出了在对PDSOI CMOS SRAM进行单粒子辐照实验中,电源电压的最恶劣偏置状态应为电路的最高工作电压.     

纳米工艺SRAM单元的尺寸效应研究与优化

集成电路工艺尺寸减小至纳米级时,尺寸效应的出现会导致SRAM读写可靠性下降。针对传统六管SRAM单元,采用蝶形曲线法对尺寸效应进行了分析,对不同工艺尺寸(90 nm~7 nm)的静态噪声容限进行了研究。分析了漏极致势垒降低效应、反向短沟道效应、正/负偏压温度不稳定性效应等物理效应,据此拟合出一个静态噪声容限经验公式。最后,对SRAM单元尺寸效应进行了优化,提高了SRAM单元的稳定性。     

A new asymmetric 6T SRAM cell with a write assist technique in 65 nm CMOS technology

A new asymmetric 6T-SRAM cell design is presented for low-voltage low-power operation under process variations. The write margin of the proposed cell is improved by the use of a new write-assist technique. Simulation results in 65 nm technology show that the proposed cell achieves the same RSNM as the asymmetric 5T-SRAM cell and 77% higher RSNM than the standard 6T-SRAM cell while it is able to perform write operation without any write assist at V_DD=1 V. Monte Carlo simulations for an 8 Kb SRAM (256×32) array indicate that the scalability of operating supply voltage of the proposed cell can be improved by 10% and 21% compared to asymmetric 5T- and standard 6T-SRAM cells; 21% and 53% lower leakage power consumption, respectively. The proposed 6T-SRAM cell design achieves 9% and 19% lower cell area overhead compared with asymmetric 5T- and standard 6T-SRAM cells, respectively. Considering the area overhead for the write assist, replica column and the replica column driver of 2.6%, the overall area reduction in die area is 6.3% and 16.3% as compared with array designs with asymmetric 5T- and standard 6T-SRAM cells.     

Design and analysis of noise margin,write ability and read stability of organic and hybrid 6-T SRAM cell

This paper analyzes SRAM cell designs based on organic and inorganic thin film transistors (TFTs). The performance in terms of static noise margin (SNM), read stability and write ability for all-p organic (Pentacene–Pentacene), organic complementary (Pentacene–C₆₀) and hybrid complementary (Pentacene–ZnO) configurations of SRAM cell is evaluated using benchmarked industry standard Atlas 2-D numerical device simulator. Moreover, the cell behaviour is analyzed at different cell and pull-up ratios. The electrical characteristics and performance parameters of individual TFT used in SRAM cell is verified with reported experimental results. Furthermore, the analytical result for SNM of all-p organic SRAM cell is validated with respect to the simulated result. Besides this, the cell and pull-up ratios of the hybrid and organic SRAM cells are optimized for achieving best performance of read and write operations and thereafter, the results are verified analytically also. The SNM of hybrid cell is almost two times higher than the all-p SRAM, whereas this improvement is just 18% in comparison to the organic memory cell. On the other hand, the organic complementary SRAM cell shows an improvement of 26% and 22% for the read stability in comparison to the all-p organic and hybrid SRAM cells, respectively. Contrastingly, this organic cell demonstrates a reduction of 16% in the SNM and an increment of 76% in write access time in comparison to the hybrid cell. To achieve an overall improved performance, the organic complementary SRAM cell is designed such that the access transistors are pentacene based p-type instead of often used n-type transistor. Favorably, this organic SRAM design shows reasonably lower write access time in comparison to the cell with n-type access OTFTs. Moreover, this cell shows adequate SNM and read stability that too at substantially lower width of p-type access OTFTs.