Leakage Power Reduction Research Articles

FDSTDL: Low‐power technique for FinFET domino circuits

SummaryMajor issues in designing low‐power high‐speed VLSI circuits are propagation delay, power consumption, and noise tolerance. This paper describes fin field‐effect transistor (FinFET) technology for the design of low‐power VLSI circuits. FinFET uses two gates (front and back) in place of a single gate as in complementary metal‐oxide–semiconductor (CMOS) technology for better control of the channel. A new technique foot driven stack transistor domino logic (FDSTDL) is proposed for designing domino logic circuits in order to reduce leakage power and propagation delay. In this paper, 2‐, 4‐, 8‐, and 16‐input domino OR gates are designed and simulated using existing and proposed techniques in CMOS and FinFET technology. Simulation is done on the 32 nm predictive technology model (PTM) node using HSPICE on a direct current (DC) supply voltage of 0.9 V. The proposed circuit is simulated in two modes of FinFET, short gate (SG) mode, and low power (LP) mode. The proposed technique shows maximum power reduction of 43.45% in SG mode in comparison with conditional stacked keeper domino logic (CSK‐DL) technique and maximum delay reduction of 38.66% in LP mode in comparison with coarse‐mesh finite difference (CMFD) technique at a frequency of 200 MHz.

Half-select free bit-line sharing 12T SRAM with double-adjacent bits soft error correction and a reconfigurable FPGA for low-power applications

This work presents a half-select free 12T SRAM cell with Data-Dependent Feedback Cutting approach to improve the write ability and isolated read path to enhance the read stability. The enhanced read and write ability is 1.95× and 2.84× larger respectively than that of the conventional 6T cell at 0.4 V. The half-select free behavior of proposed cell using the cross-point read/write structure facilitates the bit-interleaving memory architecture to effectively reduce the multi-bits soft error occurrence. The incorporated PMOS stacking effect in inverter pairs of the proposed cell offers the reduced leakage power which is 0.59× to that of 6T, at 0.4 V supply. To further minimize the leakage power at array level, the bit lines between two adjacent cells have been shared that consumes only 0.38× leakage power than that of the conventional 6T array for a 1 KB macro. Moreover, a Reconfigurable FPGA architecture is proposed for low power applications. The simulated static and active power consumption of 12T SRAM based reconfigurable FPGA is 0.22× and 0.45× when compared with the regular 12T FPGA. Finally, a Double Adjacent-bits Error Detection and Correction (DAEDC) scheme is suggested for the proposed bit-interleaved 12T SRAM array, to reduce the soft error effects.

Synthesizable Memory Arrays Based on Logic Gates for Subthreshold Operation in IoT

This paper identifies novel directions of standard-cell-based synthesizable memory design. A compact 18T-bitcell of OR-AND-Invert (OAI) and AND-OR-Invert (AOI) logic gates is presented with bit-selective write and multiplexed read accesses. It reduces the bitcell area by 11%–40% compared to the state-of-the-art clock-gating-based D-latch schemes while avoiding custom-cell design. The improved storage density comes from the tight integration on two levels–coupling the read multiplexing within each bitcell and taking advantage of structured datapath placement in bitcell arrays by using commercial CAD tools. As measured on a 40 nm SRAM of 90 kb, the OAI/AOI-gate-based synthesizable memory features 0.4 V minimum access voltage, 30 fJ minimum read energy per bit, and a leakage power of 1.4 pW per bit at 0.3 V data retention voltage. It is ideally suited for IoT-node design operating in sub- $V_{\mathrm {t}}$ for joint dynamic energy and leakage power reduction. Further, it enables fast turn-around times by IP reuse over technology nodes with minimal (re)design effort.

Enhancing sensitivity-based power reduction for an industry IC design context

For many years, discrete gate sizing has been widely used for timing and power optimization in VLSI designs. The importance of gate sizing optimization has been emphasized by academia for many years, especially since the 2012/2013 ISPD gate sizing contests [1, 2]. These contests have provided practical impetus to academic sizers through the use of realistic constraints and benchmark formats. At the same time, due to simplified delay/power Liberty models and timing constraints, the contests fail to address real-world criteria for gate sizing that are highly challenging in practice. We observe that lack of consideration of practical issues such as electrical and multi-corner constraints – along with limited sets of benchmarks – can misguide the development of contest-focused academic sizers. Thus, we study implications of the “gap” between academic sizers and product design use cases. In this paper, we note important constraints of modern industrial designs that are generally not comprehended by academic sizers. We also point out that various optimization techniques used in academic sizers can fail to offer benefits in product design contexts due to differences in the underlying optimization formulation and constraints. To address this gap, we develop a new robust academic sizer, Sizer, from a fresh implementation of Trident [3]. Experimental results show that Sizer is able to achieve up to 10% leakage power and 4% total power reductions compared to leading commercial tools on designs implemented with foundry technologies, and 7% leakage power reduction on a modern industrial design in the multi-corner multi-mode (MCMM) context.

Nonvolatile Spin-Based Radiation Hardened Retention Latch and Flip-Flop

Reduction of leakage power and vulnerability to radiation are of critical challenges in modern nanometer CMOS technologies because of scaling down requirement. Spintronic logic has been progressed to realize these demands based on magnetic-based elements properties especially magnetic tunnel junction (MTJ) such as radiation-hardened, non-volatility, and CMOS process compatibility. A novel soft-error tolerant and highly reliable latch circuit is proposed in this paper which is a promising choice for reliable and low-power architectures. Furthermore, employing the proposed shadow latch based on MTJ cells as a backup structure along with the rad-hard main latch is aimed to the realization of a nonvolatile and SEU-immune flip-flop which is applicable in next-generation CMOS circuits. Simulations of proposed circuits have been performed by SPICE tool and a 45 nm CMOS technology model to evaluate the effectiveness of topologies.

Survey of various Techniques to Reduce Leakage Power in FPGA

FPGA is known as Field Programmable Gate Array that can be programmed in the field after manufacture. It can be reprogrammed to desired application or functionality requirements after manufacturing. The major difference between FPGA and Application Specific Integrated Circuits (ASICs), which are custom manufactured for specific design tasks. Due to their programmable nature, FPGAs are an ideal fit for many different markets. As the industry leader, Xilinx provides comprehensive solutions consisting of FPGA devices, advanced software, and configurable, ready-to-use IP cores for markets and applications. However, the power consumption of FPGAs remains prohibitive for some applications. Power dissipation and Leakage power is the major issue of FPGAs. Thus, low-leakage FPGAs are essential if they are to be used for hand-held applications. Some more techniques are discussed here to reduce power dissipation. Power gating and Clock gating techniques are more efficient for leakage power reduction

A Reliable Leakage Reduction Technique for Approximate Full Adder with Reduced Ground Bounce Noise

In this paper, an effective and reliable sleep circuit is proposed, which not only reduces leakage power but also shows significant reduction in ground bounce noise (GBN) in approximate full adder (FA) circuits. Four 1-bit approximate FA circuits are modified using proposed sleep circuit which uses one NMOS and one PMOS transistor. The design metrics such as average power, delay, power delay product (PDP), leakage power, and GBN are compared with nine other 1-bit FA circuits reported till date. All the comparisons are done using post-layout netlist at 45nm technology. The modified designs achieve reduction in leakage power and GBN up to 60% and 80%, respectively, as compared to the best reported approximate FA circuits. The modified approximate FA also achieves 83% reduction in leakage power as compared to conventional FA. Finally, application level metrics such as peak signal to noise ratio (PSNR) are considered to measure the performance of all the proposed approximate FAs.

State retained dual‐ V th feedback sleeper‐stack for leakage reduction

With the advent of nanoscale devices, due to the problems of leakage power has grown enormously. Reducing leakage power is one of the main challenges in the design of low power circuits. This study presents a delay efficient circuit level leakage reduction technique, which uses dual-Vth named ‘Feedback Sleeper-Stack (FS-S)’ for deep submicron (DSM) technology. FS-S is proposed in order to reduce leakage power dramatically while saving exact logic state. An analytical RC delay model of the FS-S is derived. Comparisons are then carried out in terms of leakage power, total power, delay, area, and power–delay product to the available leakage reduction techniques. 45 nm BSIM4 Predictive Technology Model parameters are used to estimate the changes in power and delay. FS-S is applied to three generic logic circuits to show that the proposed technique is suitable for general logic circuits. Results show that chain of four inverters, NAND3 gate, and C17 circuit with dual-Vth FS-S give 15, 62, and 90% performance levels, respectively, over base case circuit under iso-area condition.

An Approximation Algorithm for Threshold Voltage Optimization

We present a primal-dual approximation algorithm for minimizing the leakage power of an integrated circuit by assigning gate threshold voltages. While most existing techniques do not provide a performance guarantee, we prove an upper bound on the power consumption. The algorithm is practical and works with an industrial sign-off timer. It can be used for post-routing power reduction or for optimizing leakage power throughout the design flow. We demonstrate the practical performance on recent microprocessor units. Our implementation obtains significant leakage power reductions of up to 8% on top of one of the most successful algorithms for gate sizing and threshold voltage optimization. After timing-aware global routing, we achieve leakage power reductions of up to 34%.

Analysing the Role of Last Level Caches in Controlling Chip Temperature

Dynamic Thermal Management (DTM) has become a major concern for the chip-designers, as it becomes a challenging task in recent power densed high performance Chip Multi-Processors (CMPs), due to integration of more on-chip components to meet ever increasing demand of processing power. The increased chip temperature incorporates severe circuit errors along with significant increment in leakage power consumption. Traditional DTM techniques apply DVFS or task migration to reduce core temperature, as cores are considered as the hottest on-chip components. Additionally, to commensurate high data demand of these high performance cores, large on-chip Last Level Caches (LLCs) are attached, which are the principal contributors to the on-chip leakage power consumption and occupy the largest on-chip area. As power consumption reduction plays the pivotal role in temperature reduction, hence, this work dynamically shrinks the cache size not only to reduce leakage power consumption, but also, to create on-chip thermal buffers for reducing average chip temperature by exploiting the heat transfer physics. Cache resizing decisions are taken based upon the generated cache hotspots and/or the access patterns, during process execution. Simulation results of the proposed thermal management method are compared with an existing DVFS based method (at cores) and a prior drowsy cache based technique to show its effectiveness.

Digitally Assisted On-Chip Body Bias Tuning Scheme for Ultra Low-Power VLSI Systems

Body bias control is one of the most efficient means to reduce leakage power, adjust process variation, and apply performance boost. However, such control incurs a certain power overhead that has to be reduced, especially in ultra low-power systems. In order to exploit the advantages of body bias control while guaranteeing power efficiency, an on-chip control scheme is required. Conventionally, on-chip body bias control relies on the use of digital–analog converters. However, such analog circuits require a high power supply voltage and an additional power source, resulting in a considerable power overhead and an increased system cost. In this paper, an on-chip “Digitally assisted Automatic Body-bias Tuning” (DABT) scheme for ultra low-power systems is proposed and evaluated. The proposed scheme controls the body bias voltage so as to meet the timing constraints of a given target system. Since DABT is based on “Digitally assisted” circuitries, it can decrease the power supply voltage to near-threshold region and, therefore, a significant amount of power overhead can be reduced. The proposed system is fabricated with the 65-nm silicon on thin box (SOTB) process, a fully depleted silicon on insulator technology. We demonstrate that the chip can achieve the expected functionality, even with 0.35 V of power supply voltage, and with only a few micro watts of power overhead. Moreover, the efficiency of the proposed system is evaluated with a MIPS processor, adopted as a case study. According to the obtained evaluation results, the proposed system can enable 80% of leakage reduction while maintaining the frequency required to meet the timing constraints of the adopted target MIPS processor.

Low leakage SRAM cell for ULP applications

Leakage power is becoming a major concern in battery operated and hand held devices. With the ever reducing size of electronic devices and the use of memory in most of them, the need for low power devices is vastly increasing. These devices are either in active or standby mode of operation. Leakage power in standby mode of operation is of major concern and various methods to minimize it have been proposed at various stages of design cycle. This paper proposes fingering technique that can be used in 6T SRAM cell to reduce leakage power. Leakage power is calculated for 6T SRAM cell designed using two fingers in access transistors and on comparison with conventional 6T SRAM cell, significant reduction in leakage current is obtained. The layout has been designed in UMC 55nm technology using Cadence Virtuoso tool and it has been shown that the leakage power and delay can be reduced.

Reliable N sleep shuffled phase damping design for ground bouncing noise mitigation

Power gating technique is one of the most effective techniques to reduce the leakage power in complex arithmetic logic circuits. But this leakage power reduction technique induces some severe ground bouncing noise during mode transition. To mitigate these issues, in this paper N-Sleep Shuffled Phase Damping (NSSPD) technique is introduced which attains an increased reliability with high energy efficiency. 16-bit Carry Select Adder is designed using 1-bit NSSPD full adder which is a hybrid combination of staggered phase damping and parallel sleep transistor technique for suppressing ground to rail fluctuations, leakage power and to improve lifetime reliability of today's integrated systems. The proposed NSSPD technique is designed and simulated in tanner EDA with 125 nm CMOS technology. The experimental results show that proposed NSSPD technique reduces the power consumption, energy consumption and leakage power to 12%, 21% and 14.56% when compared to the previous super stacking ground bounce noise reduction technique.

Low Dropout Based Noise Minimization of Active Mode Power Gated Circuit

Power gating technique reduces leakage power in the circuit. However, power gating leads to large voltage fluctuation on the power rail during power gating mode to active mode due to the package inductance in the Printed Circuit Board. This voltage fluctuation may cause unwanted transitions in neighboring circuits. In this work, a power gating architecture is developed for minimizing power in active mode and noise is analyzed. The effect of different noise minimization approaches for reducing power supply noise is evaluated in power gating architecture. A new concept of noise minimization technique using Low Dropout Voltage regulator is proposed in this paper. The amount of charge in the internal nodes of the power gating circuit passes through the sleep transistors during the wake-up transition is controlled by the proposed noise minimization techniques. The Low Dropout Voltage Regulator is designed newly in such a way that can be used to reduce bounce noise by minimizing voltage fluctuation on the power rail of power gating circuit. Architectures have been developed in Synopsys Custom Designer tool at iPDK 90nm technology. Percentage saving of noise on the power supply is reduced up to 99%.

Review a Low Power CMOS Charge Pump using Power Gating Techniques to Reduce Leakage Power

In most case, charge pump circuit is designed based on capacitor, where voltage is increased at each stage depending on each stage voltage gain. Major elements are all charge pumps circuits one is Pumping capacitors and diode connected MOS.To increases pumping efficiency is very higher for each stage of charge pump circuits. Pumping efficiency are limiting by two parameters one is parasitic capacitance and threshold voltage. The power dissipated from the circuit can be increased by attain of leakage current .To resist this leakage in the circuits the supply voltage is major concern. To reduce the leakage with the help of power gating technique .Charge pump circuits are to be designed and verified by using tanner t-spice tools.

Thermal energy aware proportionate scheduler for multiprocessor systems

As per Moore’s law, the power consumption and heat solidity of the multiprocessor systems are increasing proportionately. High temperature increases the leakage power consumption of the processor and thus probably escort to thermal runaway. Efficiently managing the energy consumption of the multiprocessor systems in order to increase the battery lifetime is a major challenge in multiprocessor platforms. This article presents Thermal Energy aware proportionate scheduler (TEAPS) to reduce leakage power consumption. Simulation experiment illustrate that TEAPS reduces 16% of energy consumption with respect to Mixed Proportionate Fair (PFAIR-M) and 36% of energy consumption with respect to Proportionate Fair (PFAIR) Schedulers on the system consisting of 20 processors under full load condition.

Low power domino logic circuits in deep-submicron technology using CMOS

Leakage power and propagation delay are the two major challenges in designing CMOS VLSI circuits, in deep sub-micron technology. This paper proposes a novel technique: Foot Driven Stack Transistor Domino Logic (FDSTDL) for designing CMOS domino logic gates for the reduction in leakage power and improved noise performance. Two, four, eight and sixteen input OR gates are designed using existing and proposed techniques. These logic gates are simulated on the PTM 32 nm node using HSPICE (Level = 54) in CMOS technology at a clock frequency of 100 MHz. Simulation results are compared based on power consumption, propagation delay and unity noise gain. Simulation results show that proposed domino technique has a maximum power reduction of 59.47% as compared to the CSK-DL technique and maximum delay reduction of 44.6% as compared to the M-HSCD technique in CMOS technology.

Leakage Power Reduction by Using Power Gating Methods in Differential Amplifier

Leakage Power Reduction by Using Power Gating Methods in Differential Amplifier

MPGA: an evolutionary state assignment for dynamic and leakage power reduction in FSM synthesis

As the development of deep-submicron and nano-technology, leakage power minimisation becomes as important as dynamic power reduction in IC design. In order to achieve low-power state assignment for finite-state machine (FSM) synthesis, a multi-population genetic algorithm (MPGA)-based state assignment method is proposed. MPGA consists of an outer-loop and a set of inner-GAs. In MPGA, inner-GA is a local search component for finding low-power state assignment. Selection, crossover and mutation are used to perform variations on individuals. Cost function is defined based on power dissipation formulation of complementary metal oxide semiconductor (CMOS) gate for dynamic power and leakage power estimation. The outer-loop is used to optimise the parameters of inner-genetic algorithm (GA) through population variation schema, intra-specific competition and newborn. Twenty-three FSMs that were commonly used as benchmarks are employed to test the effectiveness of MPGA and compare different state assignment methods. Experimental results show MPGA achieves a significant improvement over the previous publications both on dynamic power and leakage power reduction in most benchmarks.

An Exploration of Applying Gate-Length-Biasing Techniques to Deeply-Scaled FinFETs Operating in Multiple Voltage Regimes

With the aggressive downscaling of process technologies and the importance of battery-powered systems, reducing leakage power consumption has become a crucial design challenge for IC designers. In addition, the traditional bulk CMOS technologies face significant challenges related to short-channel effects and process variations. FinFET devices have attracted a lot of attention as an alternative to bulk CMOS in sub-32nm technology nodes. This paper presents a device-circuit cross-layer framework to utilize fine-grained gate-length biased FinFETs for circuit leakage power reduction in near- and super-threshold ( $V_T$ ) operation regimes. The impacts of cell-level and transistor-level Gate-Length Biasing (GLB) on circuit speed and leakage power are studied using a 7 nm FinFET technology.