A low-power fast tag comparator by modifying charging scheme of wide fan-in dynamic OR gates

In this paper, a new charging scheme for reducing the power consumption of dynamic circuits is presented. The proposed technique is suitable for large fan-in gates where the dynamic node discharges frequently. Simulation results demonstrate that the proposed method is efficiently controlling the internal voltage swing and hence decreasing the power consumption of the wide fan-in OR gate without sacrificing other circuit parameters such as gate speed, area or noise immunity. The power-delay product of a simulated 8-input OR gate is reduced by 46%, compared to its conventional dynamic counterpart in the 90 nm CMOS technology. Another important benefit of the proposed approach is 99X reduction in power dissipation of the gate load by limiting its switching activity. Furthermore, the delay of the proposed circuit experiences only 0.94% variation over 10% fluctuation in the threshold voltages of all transistors for a 32-bit OR gate. Using the proposed technique, a 40-bit tag comparator is simulated at 1 GHz clock frequency. The power consumption of the designed circuit is as low as 1.987 µW/MHz, while the delay and unity noise gain (UNG) of the circuit are 244 ps and 499 mV, respectively.     

Low power wide gates for modern power efficient processors

In this paper, a low power register file and tag comparator is proposed which has lower leakage and higher noise immunity without dramatic speed degradation due to the wide fan-in gates. Simulation of register files and tag comparators designed is done using low-V_th 90 nm CMOS process technology model in all process corners. The results demonstrate 20% power reduction and 2× noise-immunity improvement in the implemented register file using the proposed circuit at the same delay compared to the standard domino circuits. On the other hand, simulation of tag comparators implemented using the other proposed circuit shows 41%, 22% and 7.5% reduction in power, delay and area, respectively compared to the standard footless domino at the same robustness condition. Moreover, the register file and the tag comparator designed with the proposed circuits respectively show 2.48 and 3 times improvement in the defined figure of merit compared to the counterpart circuits designed with the conventional domino circuit. Thus, the proposed are power efficient and suitable approaches for embedded processors with multi-ported register file and fully-associative caches with large number of tag comparators.     

Diode-footed domino: a leakage-tolerant high fan-in dynamic circuit design style

A leakage-tolerant design technique for high fan-in dynamic logic circuits is presented. An NMOS transistor with gate and drain terminals tied together (diode) is added in series with the evaluation network of standard domino circuits. Due to the stacking effect, the leakage of the evaluation path significantly decreases, thereby improving the robustness of the circuit against deep-submicron subthreshold leakage and input noise. To improve the speed of the circuit, a current mirror is also employed in the evaluation network to increase the evaluation current. The proposed technique (diode-footed domino) exhibits considerable improvement in leakage and noise immunity as compared to the standard domino circuits. Simulation results of wide fan-in gates designed using Berkeley Predictive Technology Models of 70-nm technology demonstrate at least 1.9/spl times/ noise-immunity improvement at the same delay compared to the standard domino circuits. Dynamic comparators and multiplexers are designed using the diode-footed domino and conventional techniques to demonstrate the effectiveness of the proposed scheme in improving leakage-tolerance and performance of high fan-in circuits.     

Two new low-power Full Adders based on majority-not gates

Two novel low-power 1-bit Full Adder cells are proposed in this paper. Both of them are based on majority-not gates, which are designed with new methods in each cell. The first cell is only composed of input capacitors and CMOS inverters, and the second one also takes advantage of a high-performance CMOS bridge circuit. These kinds of designs enjoy low power consumption, a high degree of regularity, and simplicity. Low power consumption is targeted in implementation of our designs. Eight state-of-the-art 1-bit Full Adders and two proposed Full Adders are simulated using 0.18 μm CMOS technology at many supply voltages. Simulation results demonstrate improvement in terms of power consumption and power-delay product (PDP).     

On circuit techniques to improve noise immunity of CMOS dynamic logic

Dynamic CMOS logic circuits are widely employed in high-performance VLSI chips in pursuing very high system performance. However, dynamic CMOS gates are inherently less resistant to noises than static CMOS gates. With the increasing stringent noise requirement due to aggressive technology scaling, the noise tolerance of dynamic circuits has to be first improved for the overall reliable operation of VLSI chips designed using deep submicron process technology. In the literature, a number of design techniques have been proposed to enhance the noise tolerance of dynamic logic gates. An overview and classification of these techniques are first presented in this paper. Then, we introduce a novel noise-tolerant design technique using circuitry exhibiting a negative differential resistance effect. We have demonstrated through analysis and simulation that using the proposed method the noise tolerance of dynamic logic gates can be improved beyond the level of static CMOS logic gates while the performance advantage of dynamic circuits is still retained. Simulation results on large fan-in dynamic CMOS logic gates have shown that, at a supply voltage of 1.6 V, the input noise immunity level can be increased to 0.8 V for about 10% delay overhead and to 1.0 V for only about 20% delay overhead.     

High performance dynamic logic incorporating gate voltagecontrolled keeper structure for wide fan-in gates

A new keeper structure for wide fan-in gates is proposed to optimise performance, noise- and skew-tolerance by controlling the gate voltage of the keeper transistor. Simulation results show that the proposed gate voltage controlled keeper scheme improves performance by 13.8 and 26.6% compared with the conventional keeper scheme for 16 and 32 bit wide fan-in dynamic gates     

高速抗噪声CMOS动态电路设计

提出了一种利用窄脉冲发生器驱动输出级,以提高电路抗噪声能力,同时保持动态电路的高速特性的多输入动态逻辑电路.提出了这种电路的分析模型,用于说明电路的抗噪声特性和管子的参数设置.在0.18μm CMOS工艺,1.8V的Vdd电压和55℃的环境温度下,模拟结果表明:与现有的两种技术相比,在相同的最坏延时情况下,新结构具有更好的抗噪声能力,分别提升了12%和8%;而在具有相同的抗噪声能力的情况下,新结构具有更快的速度,分别提高了1.6倍和1.4倍.     

High-Speed,Robust CMOS Dynamic Circuit Design

提出了一种利用窄脉冲发生器驱动输出级，以提高电路抗噪声能力，同时保持动态电路的高速特性的多输入动态逻辑电路. 提出了这种电路的分析模型，用于说明电路的抗噪声特性和管子的参数设置. 在0.18μm CMOS工艺，1.8V的Vdd电压和55℃的环境温度下，模拟结果表明：与现有的两种技术相比，在相同的最坏延时情况下，新结构具有更好的抗噪声能力，分别提升了12%和8%; 而在具有相同的抗噪声能力的情况下，新结构具有更快的速度，分别提高了1.6倍和1.4倍.     

Design and performance of a robust 180 nm CMOS standalone VCO and the integrated PLL

The design details of a low power/wide tuning range phase locked loop (PLL) is presented in 180 nm CMOS together with the simulated and post fabrication measured performance. The PLL has been specifically designed for applications requiring a wide tuning range (1.55–2.28 GHz) while maintaining low power consumption (18 mW) and good phase noise (−100.9 dBc/Hz at 1 MHz). The tuning range represents significant improvement over other reported PLL CMOS implementations. To illustrate the robustness of the architecture, a 90 nm CMOS design is included with a 5.8–9.45 GHz tuning range (48%), phase noise of −111.7 dBc/Hz, and power consumption of 18.6 mW. The stand alone voltage controlled oscillator (VCO) and the PLL were fabricated on a single 180 nm die providing a unique opportunity to analyze and measure both the stand alone VCO phase noise performance and the integrated PLL phase noise performance. The contributions to the PLL phase noise (phase detector, charge pump, VCO, divider, and reference source) are delineated and both the theoretical and measured PLL phase noise performance is discussed. Design tradeoffs are included such as effect of loop bandwidth on phase noise contributions.     

Modular implementation of efficient self-checking checkers for the Berger code

A technique for designing efficient checkers for conventional Berger code is proposed in this paper. The check bits are derived by partitioning the information bits into two blocks, and then using an addition array to sum the number of 1's in each block. The check bit generator circuit uses a specially designed 4-input 1's counter. Two other types of 1's counters having 2 and 3 inputs are also used to realize checkers for variable length information bits. Several variations of 2-bit adder circuits are used to add the number of 1's. The check bit generator circuit uses gates with fan-in of less than or equal to 4 to simplify implementation in CMOS. The technique achieves significant improvement in gate count as well as speed over existing approaches.     

用于SDH STM-4光发射机的4:1复接器和激光驱动器

采用CSMC0.6μm CMOS工艺设计实现了速率为622Mbps的4∶1复接器和激光二极管驱动器电路。4∶1复接器采用树型结构,由3个2∶1复接器组成。激光二极管驱动器电路由两级差分放大器和一级电流开关构成,级间采用源级跟随器隔离。电路芯片尺寸为1.5mm×0.7mm。电路采用单一正5V电压供电,功耗约为900mW。测试结果表明,电路的最高工作速率超过1.25Gbps速率,输出最大电流超过85mA。     

A 4:1 Multiplexer using dual chirality CNTFET-based domino logic in nano-scale technology

ABSTRACT

This paper proposes a 4:1 Multiplexer (MUX) designed using proposed Dual Chirality High-Speed Noise Immune Domino Logic (DCHSNIDL) technique for designing lower delay noise immune domino logic circuits in Carbon Nanotube Field Effect Transistors (CNTFETs) technology. Dynamic power consumption, speed and noise immunity of the circuit are improved by changing the threshold voltage of the CNTFETs. The chirality indices of the carbon nanotubes (CNTs) are varied to change the threshold voltage of the CNTFETs. Simulations are carried out for 32 nm Stanford CNTFET model in HSPICE for 2-, 4-, 8- and 16-input domino OR gates at a clock frequency of 200 MHz on a DC supply voltage of 0.9V. The proposed DCHSNIDL domino circuit reduces power consumption by a maximum of 61.77% and propagation delay by a maximum of 55.11% compared to Current-Mirror Based Process Variation Tolerant (CPVT) circuit in CNTFET technology. The proposed CNTFET-based domino technique shows a maximum reduction of 96.31% in power consumption compared to its equivalent circuit in CMOS technology for a 4-input OR gate. The proposed technique shows an improvement of 1.04× to 1.35× times in Unity Noise Gain (UNG) compared to various existing techniques in CNTFET technology. The 4:1 MUX designed using proposed technique has 48.91% lower propagation delay and consumes 52.80% lower power compared to MUX using CPVT technique.     

Robust low leakage controlled keeper by current-comparison domino for wide fan-in gates

In this paper, a new design for low leakage and noise immune wide fan-in domino circuits is presented. The proposed technique uses the difference and the comparison between the leakage current of the OFF transistors and the switching current of the ON transistors of the pull down network to control the PMOS keeper transistor, yielding reduction of the contention between keeper transistor and the pull down network from which previously proposed techniques have suffered. Moreover, using the stacking effect, leakage current is reduced and the performance of the current mirror is improved. Results of simulation in high performance 16 nm predictive technology model (PTM) demonstrate that the proposed circuit exhibits about 39% less power consumption, and nearly 2.57 times improvement in noise immunity with a 41% die area overhead for a 64-bit OR gate compared to a standard domino circuit.     

Differential current switch logic: a low power DCVS logic family

Differential current switch logic (DCSL), a new logic family for implementing clocked CMOS circuits, has been developed. DCSL is in principle a clocked differential cascode voltage switch logic circuit (DCVS). The circuit topology outlines a generic method for reducing internal node swings in clocked DCVS logic circuits. In comparison to other forms of clocked DCVS, DCSL achieves better performance both in terms of power and speed by restricting internal voltage swings in the NMOS tree. DCSL circuits are capable of implementing high complexity high fan-in gates without compromising gate delay. Automatic lock-out of inputs on completion of evaluation is a novel feature of the circuit. Three forms of DCSL circuits have been developed with varying benefits in speed and power. SPICE simulations of circuits designed using the 1.2 μm MOSIS SCMOS process indicate a factor of two improvement in speed and power over comparable DCVS gates for moderate tree heights     

LVDCSL: a high fan-in, high-performance, low-voltage differentialcurrent switch logic family

This paper presents a low voltage differential current switch logic (LVDCSL) gate capable of achieving high performance for large fan-in gates. High fan-in is enabled by using a large height predischarged N-channel metal-oxide-semiconductor (NMOS) trees. The power penalty of an increased number of internal nodes in the gate is mitigated by restricting their voltage swings. The salient features of this low-voltage DCSL family are high speed for high fan-in large stack height NMOS trees, low power due to restricted internal voltage swings, simple interface to static complementary metal-oxide-semiconductor (CMOS), and a latching nature which locks out inputs once outputs are evaluated. Results show that LVDCSL is capable of working at under 2 V in a 0.35% CMOS process while being faster than comparable Domino gates. At the same time total power consumption is reduced. LVDCSL achieves 40% delay improvement and 22% power reduction in comparison with dual rail Domino gates for 8 bit carry look-ahead circuits. Results for the critical path of an adder reveal that the complexity afforded by the gate, effectively decreases the number of logic levels and leads to improved performance     

Design and simulation of an ultra-low power high performance CMOS logic: DMTGDI

An ultra-low power, high speed dual mode CMOS logic family called DMTGDI is introduced. This logic family takes over and improves main characteristics of Gate Diffusion Input (GDI) and Dual Mode Logic (DML). Simulations have been performed in 90 nm CMOS on a single bit full adder. DMTGDI shows 60% performance improvement over conventional DML, and significant reduction of power-delay product (PDP), of about 95% in static mode, and 75% in dynamic mode. Monte Carlo simulations reveal that DMTGDI is more robust under process variation comparing to conventional DML. Post layout simulation demonstrates negligible effect of parasitic elements on performance of the single bit adder.     

Subterranean power lines in high-density integrated Josephsoncircuits

We found from simulations that wide power lines are required to make bias currents of Josephson gates uniform. Magnetic noise due to large power current decreases the critical current of the adjacent gate. To enhance circuit integration and to stabilize circuit operation, we proposed a power line laid under the ground plane. The gates can be located above the power line inserting the ground plane. The new power line can make whole chip areas active for gates however wide the line is. We confirmed that the ground plane shields the gates from magnetic noise. We fabricated some test circuits using the new power lines and confirmed their operations     

Robustness aware high performance high fan-in domino OR logic design

A novel technique using a keeper with a simultaneous low supply voltage and low body voltage is proposed to improve the overall performance of high fan-in OR gates without modifying the physical dimensions of the keeper. Simulation results of a 16-input domino OR gate using 45 nm CMOS technology show that the proposed technique could trade off between a high power/speed efficient operation and the robustness to noise effectively.Also, a Monte Carlo analysis indicates that the proposed domino OR gate is more robust to parameter variation compared to a conventional domino OR gate.     

Graphene nanoribbon crossbar architecture for low power and dense circuit implementations

Crossbar array is a promising nanoscale architecture which can be used for logic circuit implementation. In this work, a graphene nanoribbon (GNR) based crossbar architecture is proposed. This design uses parallel GNRs as device channel and metal as gate, source and drain contacts. Schottky-barrier type graphene nanoribbon field-effect transistors (SB-GNRFETs) are formed at the cross points of the GNRs and the metallic gates. Benchmark circuits are implemented using the proposed crossbar, Si-CMOS and multi-gate Si-CMOS approaches to evaluate the performance of the crossbar architecture compared to the conventional CMOS logic design. The compact SPICE model of SB-GNRFET was used to simulate crossbar-based circuits. The CMOS circuits are also simulated using 16 nm technology parameters. Simulation results of benchmark circuits using SIS synthesis tool indicate that the GNR-based crossbar circuits outperform conventional CMOS circuits in low power applications. Area optimized cell libraries are implemented based on the asymmetric crossbar architecture. The area of the circuit can be more reduced using this architecture at the expense of higher delay. The crossbar cells can be combined with CMOS cells to exhibit better performance in terms of EDP.