VLSI circuits for low-power high-speed asynchronous addition

This paper presents a new low-power high-speed fully static CMOS variable-time adder. The VLSI implementation proposed here is based on the statistical carry look-ahead addition technique. The new circuit takes advantage of an innovative way of using a composition of propagate signals and of appropriately designed overlapped execution modules to reduce average addition time, layout area, and power dissipation. A 56-bit adder designed as described here and realized using AMS 0.35-/spl mu/m CMOS standard cells at 3.3V supply voltage shows an average addition time of about 4.3 ns and a maximum power dissipation of only 50 mW at 200-MHz repetitive frequency using a silicon area of less than 0.23 mm/sup 2/.     

Design and Optimization of On-Chip Interconnects Using Wave-Pipelined Multiplexed Routing

Every new VLSI technology generation has resulted in interconnects increasingly limiting the performance, area, and power dissipation of new processors. Subsequently, it is necessary to devise efficient interconnect design techniques to reduce the impact of VLSI interconnects on overall system design. New optimizations of a wave-pipelined multiplexed (WPM) interconnect routing circuit are described in this paper. These WPM circuits can be used with current interconnect repeater circuits to further reduce interconnect delay, interconnect area, transistor area, and/or power dissipation. For example, new area constrained WPM circuit optimizations illustrate that the interconnect circuit power can be reduced by 26% or the interconnect performance can be improved by 74%. Moreover, in both these cases, because a significant number of repeaters are eliminated, the transistor area can reduce by 41% or 29%, respectively. Finally, the tolerance of WPM circuits to crosstalk noise, power supply noise, clock skew, and manufacturing variations is also presented. This study of tolerance levels defines the conditions under which the WPM circuit will function correctly, and it is shown in this paper for the first time that WPM circuits are robust enough to operate with variability that can be encountered in deep submicrometer technologies.     

A Low-Power Multiphase Circuit Technique

The principle of multiphase MOS digital circuits is briefly discussed and the features of some presently used multi-phase schemes are given. The basic theory and implementation of a six-phase scheme, which make use of a basic principle not normally considered in low-power digital circuitry, are then described, and the first-order equations for power dissipation are derived. The theoretical power dissipation of a six-phase shift register is compared to the power dissipation of equivalent shift registers using other low-power circuit techiques, including the complementary MOS transistor technique, and it is shown that the six-phase technique has the lowest power dissipation from very low frequencies up to a limiting high frequency. Finally, the power dissipation of an actual six-phase circuit is compared to the dissipation predicted from the derived equations.     

Vertically integrated SOI circuits for low-power and high-performance applications

Vertical integration offers numerous advantages over conventional structures. By stacking multiple-material layers to form double gate transistors and by stacking multiple device layers to form multidevice-layer integration, vertical integration can emerge as the technology of choice for low-power and high-performance integration. In this paper, we demonstrate that the vertical integration can achieve better circuit performance and power dissipation due to improved device characteristics and reduced interconnect complexity and delay. The structures of vertically integrated double gate (DG) silicon-on-insulator (SOI) devices and circuits, and corresponding multidevice-layer (3-D) SOI circuits are presented; a general double-gate SOI model is provided for the study of symmetric and asymmetric SOI CMOS circuits; circuit speed, power dissipation of double-gate dynamic threshold (DGDT) SOI circuits are investigated and compared to single gate (SG) SOI circuits; potential 3-D SOI circuits are laid out. Chip area, layout complexity, process cost, and impact on circuit performance are studied. Results show that DGDT SOI CMOS circuits provide the best power-delay product, which makes them very attractive for low-voltage low-power applications. Multidevice-layer integration achieves performance improvement by shortening the interconnects. Results indicate that up to 40% of interconnect performance improvements can be expected for a 4-device-layer integration.     

一种新型低功耗准动态移位寄存器的模拟

提出一种低功耗准动态移位寄存器电路 ,这种电路静态功耗几乎为 0 ,仅仅存在动态功耗 ;是一种无比电路 ,所有的开关和反相器晶体管按最小尺寸进行设计 ,电路简单 ,面积小 ;该种电路不存在电荷的再分配 ,漏电流损失的电荷可从电源补充。采用 1 .2μm的 CMOS工艺 ,用 PSPICE8.0对该电路进行仿真验证。这种低功耗准动态移位寄存器电路已成功用作 CMOS图像传感器的读出扫描电路。     

Low-power digital systems based on adiabatic-switching principles

Adiabatic switching is an approach to low-power digital circuits that differs fundamentally from other practical low-power techniques. When adiabatic switching is used, the signal energies stored on circuit capacitances may be recycled instead of dissipated as heat. We describe the fundamental adiabatic amplifier circuit and analyze its performance. The dissipation of the adiabatic amplifier is compared to that of conventional switching circuits, both for the case of a fixed voltage swing and the case when the voltage swing can be scaled to reduce power dissipation. We show how combinational and sequential adiabatic-switching logic circuits may be constructed and describe the timing restrictions required for adiabatic operation. Small chip-building experiments have been performed to validate the techniques and to analyse the associated circuit overhead     

A 2-Mb/s 256-state 10-mW rate-1/3 Viterbi decoder

This paper presents a low-power bit-serial Viterbi decoder chip with the code rate r=1/3 and the constraint length K=9 (256 states) for next generation wireless communication applications. The architecture of the add-compare-select (ACS) module is based on the bit-serial arithmetic and implemented with the pass transistor logic circuit. A cluster-based ACS placement and state metric routing topology is described for the 256 bit-serial ACS units, which achieves very high area efficiency. In the trace-back operation, a power efficient trace-back scheme, allowing higher memory read access rate than memory write in a time-multiplexing method, is implemented to reduce the number of iterations required to generate a decoded output. In addition, a low-power application-specific memory suitable for the function of survivor path memory has also been developed. The chip's core, implemented using 0.5-μm CMOS technology, contains approximately 200 K transistors and occupies 2.46 mm by 4.17 mm area. This chip can achieve the decode rate of 20 Mb/s under 3.3 V and 2 Mb/s under 1.8 V. The measured power dissipation at 2 Mb/s under 1.8 V is only about 9.8 mW. The Viterbi decoder presented here can be applied to next generation wide-band code division multiple access (W-CDMA) systems     

一种CMOS微功耗硬件可编程变阻电路

变阻电路作为电路系统中的子功能块,应用范围极其广泛。SOC（片上系统）的发展对其提出了小体积、低功耗的要求。传统开关变阻电路体积大、功耗大,因此需要从结构的角度对变阻电路进行改进。文中基于三态输入的概念,提出一种新型微功耗硬件可编程变阻电路。仅用三端硬件可编程端口,实现了26级变阻电路。使用钟控锁存器结构,在3V电压、10％占空比时钟作用下,电路功耗仅为3μW。结合运放用于线性电压设置,设置电压精度±2％。     

Analogue motion estimation based upon a squaring circuit

Motion estimation (ME) is the most computationally demanding part of the digital video coding process. The use of analogue computational circuits in this application can offer reductions in size and power dissipation. However, analogue circuits are subject to variations which can reduce performance. In this paper the analogue non-idealities are considered, and results are presented for video conferencing applications. Furthermore, a compact MOS squaring circuit for use in analogue ME processors is proposed. The circuit makes use of the inherent square-law characteristic of the MOS transistor in saturation and features small area, low-power and low-voltage operation. Measurements from fabricated samples of the circuit were incorporated in system-level simulations. The results of the simulations confirmed the suitability of the circuit for the intended application.     

Viterbi译码算法Soft Core IP的低功耗设计

介绍了Viterbi译码算法SoftCoreIP的一种低功耗实现方案,对其中的核心功能单元ACS(Adder_Compare_Select)提出了一种改进的设计结构,并介绍了电路时钟的优化技术及低功耗设计技术,经实验证明,确实达到了降低功耗、减小电路规模的设计目的。     

Precomputation-based sequential logic optimization for low power

We address the problem of optimizing logic-level sequential circuits for low power. We present a powerful sequential logic optimization method that is based on selectively precomputing the output logic values of the circuit one clock cycle before they are required, and using the precomputed values to reduce internal switching activity in the succeeding clock cycle. We present two different precomputation architectures which exploit this observation. The primary optimization step is the synthesis of the precomputation logic, which computes the output values for a subset of input conditions. If the output values can be precomputed, the original logic circuit can be “turned off” in the next clock cycle and will have substantially reduced switching activity. The size of the precomputation logic determines the power dissipation reduction, area increase and delay increase relative to the original circuit. Given a logic-level sequential circuit, we present an automatic method of synthesizing precomputation logic so as to achieve maximal reductions in power dissipation. We present experimental results on various sequential circuits. Up to 75% reductions in average switching activity and power dissipation are possible with marginal increases in circuit area and delay     

Phase assignment for synthesis of low-power domino circuits

High performance circuit techniques such as domino logic have migrated from the microprocessor world into more mainstream ASIC designs but domino logic comes at a heavy cost in terms of total power dissipation. A set of results related to automated phase assignment for the synthesis of low-power domino circuits is presented: (1) it is demonstrated that the choice of phase assignment at the primary outputs of a circuit can significantly impact lower dissipation in the domino block, and (2) a method to determine a phase assignment that minimises power consumption in the final circuit implementation is proposed. Preliminary experimental results on a mixture of public domain benchmarks and real industry circuits show potential power savings as high as 34% over the minimum area realisation of the logic. Furthermore, the low-power synthesised circuits still meet timing constraints     

Circuit activity based logic synthesis for low power reliableoperations

A system developed to synthesize both finite state machines and combinational logic for low-power applications, called SYCLOP, is described. SYCLOP tries to minimize the transition density at the internal nodes of a circuit to minimize power dissipation during normal operation. As input signal probabilities and transition densities are considered during the synthesis process, a particular circuit can be synthesized in different ways for different applications that require different types of inputs. For the present state inputs to the combinational circuit of a state machine, simulation was used to determine the signal probabilities and transition densities. The algorithm is not limited by the number of bits used for state assignment. The multilevel optimization process extracts kernels so that there is a balance between area and power optimization. Results have been obtained for a wide range of MCNC benchmark examples     

Bus encoder design for reduced crosstalk,power and area in coupled VLSI interconnects

This research work presents a novel circuit for simultaneous reduction of power, crosstalk and area using bus encoding technique in RC modeled VLSI interconnect. Bus-invert method is used to reduce inter-wire coupling, which is actually responsible for crosstalk, delay and power dissipation in coupled interconnects. The proposed method focuses on simplified and improved encoder circuit for 4, 8 and 16 coupled lines. In past, the researchers developed encoders that usually focused on minimizing power dissipation and/or crosstalk, thereby paying heavy penalty in terms of chip area. However, the proposed encoder and decoder while significantly reducing crosstalk demonstrates an overall reduction of power dissipation by 68.76% through drastically limiting switching activity. Furthermore, while reducing the complexity, chip area and transistor count of the circuit is reduced by more than 57%.     

Low-Power Programmable FPGA Routing Circuitry

We consider circuit techniques for reducing field-programmable gate-array (FPGA) power consumption and propose a family of new FPGA routing switch designs that are programmable to operate in three different modes: high-speed, low-power, or sleep. High-speed mode provides similar power and performance to traditional FPGA routing switches. In low-power mode, speed is curtailed in order to reduce power consumption. Leakage is reduced by 28%–52% in low-power versus high-speed mode, depending on the particular switch design selected. Dynamic power is reduced by 28%–31% in low-power mode. Leakage power in sleep mode, which is suitable for unused routing switches, is 61%–79% lower than in high-speed mode. Each of the proposed switch designs has a different power/area/speed tradeoff. All of the designs require only minor changes to a traditional routing switch and involve relatively small area overhead, making them easy to incorporate into current commercial FPGAs. The applicability of the new switches is motivated through an analysis of timing slack in industrial FPGA designs. It is observed that a considerable fraction of routing switches may be slowed down (operate in low-power mode), without impacting overall design performance.      

低功耗非全摆幅互补传输管加法器

文章提出了一种新型传输管全加器,该全加器采用互补传输管逻辑（Complementary Pass-Transistor Logic）实现.与现有的CPL全加器相比：该全加器具有面积、进位速度和功耗上的优势：并且提供了进位传播信号的输出,可以更简单的构成旁路进位加法器（Carry SkipAdder）.在此全加器基础上可以实现一种新型行波进位加法器（Ripple Carry Adder）,其内部进位信号处于非全摆幅状态,具有高速低功耗的特点.HSPICE模拟表明：对4位加法器而言,其速度接近CMOS提前进位加法器（Carry Look ahead Adder）,而功耗减小了61%.适用于高性能、低功耗的VLSI电路设计.     

Bus-invert coding for low-power I/O

Technology trends and especially portable applications drive the quest for low-power VLSI design. Solutions that involve algorithmic, structural or physical transformations are sought. The focus is on developing low-power circuits without affecting too much the performance (area, latency, period). For CMOS circuits most power is dissipated as dynamic power for charging and discharging node capacitances. This is why many promising results in low-power design are obtained by minimizing the number of transitions inside the CMOS circuit. While it is generally accepted that because of the large capacitances involved much of the power dissipated by an IC is at the I/O little has been specifically done for decreasing the I/O power dissipation. We propose the bus-invert method of coding the I/O which lowers the bus activity and thus decreases the I/O peak power dissipation by 50% and the I/O average power dissipation by up to 25%. The method is general but applies best for dealing with buses. This is fortunate because buses are indeed most likely to have very large capacitances associated with them and consequently dissipate a lot of power     

A step-down boosted-wordline scheme for 1-V battery-operated fastSRAM's

Fast and low-power circuit techniques for battery-operated low-voltage SRAM's are described. To shorten the read access time with low power dissipation, the step-down boosted-wordline scheme, which is combined with current-sense amplifiers, is proposed. Boosting a selected-wordline voltage shortens the bitline delay before the stored data are sensed. The power dissipation while selecting a wordline is suppressed by stepping down the selected-wordline potential. Moreover, to reduce the standby power, a switched-capacitor-type boosted-pulse generator, which is controlled by an address transition detection (ATD) signal, is used. A 61 kword×16-bit organization SRAM test chip was fabricated using the 0.5-μm multithreshold-voltage CMOS (MTCMOS) process. The power dissipation in the memory array is reduced to 57% (1 mW) at 10 kHz operation in comparison with the conventional boosted-wordline scheme     

An energy-efficient analog front-end circuit for a sub-1-V digital hearing aid chip

A low-power energy-efficient adaptive analog front-end circuit is proposed and implemented for digital hearing-aid applications. It adopts the combined-gain-control (CGC) technique for accurate preamplification and the adaptive-SNR (ASNR) technique to improve dynamic range with low power consumption. The CGC technique combines an automatic gain control and an exponential gain control together to reduce power dissipation and to control both gain and threshold knee voltage. The ASNR technique changes the value of the signal-to-noise ratio (SNR) in accordance with input amplitude in order to minimize power consumption and to optimize the SNR by sensing an input signal. The proposed analog front-end circuit achieves 86-dB peak SNR in the case of third-order /spl Sigma//spl Delta/ modulator with 3.8-/spl mu/Vrms of input-referred noise voltage. It dissipates a minimum and maximum power of 59.4 and 74.7 /spl mu/W, respectively, at a single 0.9-V supply. The core area is 0.5 mm/sup 2/ in a 0.25-/spl mu/m standard CMOS technology.     

A 90-nm CMOS Low-Power GSM/EDGE Multimedia-Enhanced Baseband Processor With 380-MHz ARM926 Core and Mixed-Signal Extensions

To meet the widely varying speed and power requirements of multifunctional mobile devices, an appropriate combination of technology features, circuit-level low-power techniques, and system architecture is implemented in a GSM/Edge baseband processor with multimedia and mixed-signal extensions. Power reduction techniques and performance requirements are derived from an analysis of relevant use cases and applications. The 44 mm² baseband processor is fabricated in a 90-nm low-power CMOS technology with triple-well option and dual-gate oxide core devices. The ARM926 core achieves a maximum clock frequency of 380 MHz at 1.4-V supply due to the usage of thin oxide (1.6 nm) devices. Power dissipation can be adapted to the performance requirements by means of combined voltage and frequency scaling to reduce active power consumption in medium-performance mode by 68%. To reduce leakage currents during standby mode, large SRAM blocks, nFET sleep transistors, and circuit components with relaxed performance requirements are implemented using devices with 2.2-nm gate oxide thickness