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Article
Publication date: 10 September 2019

Shilpi Birla

Major area of a die is consumed in memory components. Almost 60-70% of chip area is being consumed by “Memory Circuits”. The dominant memory in this market is SRAM, even though…

Abstract

Purpose

Major area of a die is consumed in memory components. Almost 60-70% of chip area is being consumed by “Memory Circuits”. The dominant memory in this market is SRAM, even though the SRAM size is larger than embedded DRAM, as SRAM does not have yield issues and the cost is not high as compared to DRAM. At the same time, the other attractive feature for the SRAM is speed, and it can be used for low power applications. CMOS SRAM is the crucial component in microprocessor chips and applications, and as the said major portion of the area is dedicated to SRAM arrays, CMOS SRAM is considered to be the stack holders in the memory market. Because of the scaling feature of CMOS, SRAM had its hold in the market over the past few decades. In recent years, the limitations of the CMOS scaling have raised so many issues like short channel effects, threshold voltage variations. The increased thrust for alternative devices leads to FinFET. FinFET is emerging as one of the suitable alternatives for CMOS and in the region of memory circuits.

Design/methodology/approach

In this paper, a new 11 T SRAM cell using FinFET technology has been proposed, the basic component of the cell is the 6 T SRAM cell with 4 NMOS access transistors to improve the stability and also makes it a dual port memory cell. The proposed cell uses a header scheme in which one extra PMOS transistor is used which is biased at different voltages to improve the read and write stability thus, helps in reducing the leakage power and active power.

Findings

The cell shows improvement in RSNM (read static noise margin) with LP8T by 2.39× at sub-threshold voltage 2.68× with D6T SRAM cell, 5.5× with TG8T. The WSNM (write static noise margin) and HM (hold margin) of the SRAM cell at 0.9 V is 306 mV and 384  mV. It shows improvement at sub-threshold operation also. The leakage power is reduced by 0.125× with LP8T, 0.022× with D6T SRAM cell, TG8T and SE8T. The impact of process variation on cell stability is also discussed.

Research limitations/implications

The FinFet has been used in place of CMOS even though the FinFet has been not been a matured technology; therefore, pdk files have been used.

Practical implications

SRAM cell has been designed which has good stability and reduced leakage by which we can make an array and which can be used as SRAM array.

Social implications

The cell can be used for SRAM memory for low power consumptions.

Originality/value

The work has been done by implementing various leakage techniques to design a stable and improved SRAM cell. The advantage of this work is that the cell has been working for low voltage without degrading the stability factor.

Details

Circuit World, vol. 45 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 17 June 2021

Alok Kumar Mishra, Vaithiyanathan D., Yogesh Pal and Baljit Kaur

This work is proposed for low power energy-efficient applications like laptops, mobile phones, and palmtops. In this study, P-channel metal–oxide–semiconductor (PMOS)’s are used…

Abstract

Purpose

This work is proposed for low power energy-efficient applications like laptops, mobile phones, and palmtops. In this study, P-channel metal–oxide–semiconductor (PMOS)’s are used as access transistor in 7 transistors (7 T) Static Random Access Memory (SRAM) cell, and the theoretical Static Noise Margin (SNM) analysis for the proposed cell is also performed. A cell is designed using 7 T which consists of 4 PMOS and 3 NMOS. In this paper write and hold SNM is addressed and read SNM is also calculated for the proposed 7 T SRAM cell.

Design/methodology/approach

The authors have replaced N-channel metal–oxide–semiconductor (NMOS) access transistors with the PMOS access transistors, which results in proper data line recovery and provides the desired coupling. An error is likely to occur, if the read operation is performed too often probably by using the NMOS pass gate. It results in an improper recovery of the data line. Instead, by using PMOS as a pass gate, the time required for read operation can be brought down. As we know the mobility (µ) of the PMOS transistor is low, so the authors have used this property into the proposed design. When a low signal is applied to its control gate, the PMOS transistor come up with the desired coupling, when working as a pass gate.

Findings

Feedback switched transistor is used in the proposed circuit, which plays an important role in the write operation. This transistor is in OFF state and PMOS’s work as access transistor, when the proposed cell operating in read mode. This helps in the reduction of power. This work is simulated using UMC 40 nm technology node in the cadence virtuoso environment. The simulated result shows that, write power saving of 51.54% and 61.17%, hold power saving of 25.68% and 48.93% when compared with reported 7 T and 6 T, respectively.

Originality/value

The proposed 7 T SRAM cell provides proper data line recovery at a lower voltage when PMOS works as the access transistor. Power consumption is very less in this technique and it is best suitable for low power applications.

Details

Circuit World, vol. 48 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

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