一种基于目标延迟约束缓冲器插入的互连优化模型

基于分布式RLC传输线,提出在互连延迟满足日标延迟的条件下,利用托格朗日函数改变插入缓冲器数目与尺寸来减小互连功耗和面积的优化模型.在65nm CMOS工艺下,对两组不同类型的互连线进行计算比较,验证该模型在改善互连功耗与面积方面的优点.此模碰更适合全局瓦连线的优化,而且互连线越长,优化效果越明显,能够应用于纳米级SoC的计算机辅助设计和集成电路优化设计.     

低功耗电流模互连电路设计

芯片长距离互连时,通过传统的插入缓冲器方法减小延迟存在功耗大、占用芯片面积多等问题。针对这些问题,提出了一种电流模互连电路。这一电路在互连线上传输的信号电压摆幅很小,从而能够有效降低互连功耗、减小信号延迟。通过综合使用强、弱两个驱动器作为信号发送器,进一步减小了信号延迟。对于10 mm的片上互连线,延迟为649 ps,功耗为498μW。为了提高电路在制造工艺发生波动时的鲁棒性,电流模互连结构在驱动电路中添加了电流偏置电路。在Hspice中进行的蒙特卡罗仿真结果表明,180 nm工艺技术下,10 mm互连线的延迟和功耗方差均值比分别为7.91%和12.7%,在工艺发生波动时电路能够稳定工作。     

大容量SRAM中长互连线RC延迟的高速译码电路的研究

文章分析了CMOS逻辑门驱动长互连导线时产生的延迟情况,并给出了驱动的延迟模型。在此基础上提出一种新的考虑RC延迟时高速CMOS逻辑链的设计方法。并使用上述方法设计出一款4MbSRAM的高速译码电路。仿真表明在大扇出、大负载、长互连线的情形下,电路延迟时间仅有1．85ns。比传统的使用等效电容的优化方法快出0．12ns,电路面积节约30％。并且功耗明显的降低。     

工艺变化下互连线分布参数随机建模与延迟分析

随着超大规模集成电路制造进入深亚微米和超深亚微米阶段,电路制造过程中的工艺变化已经成为影响集成电路互连线传输性能的重要因素.文中引入高斯白噪声建立了互连线分布参数的随机模型,并提出基于Elmore延迟度量的工艺变化下的互连延迟估计式;通过简化工艺变化量与互连线参数之间的关系式,对延迟一阶变化量与二阶变化量进行了分析,给出一般工艺变化下互连延迟的统计特性计算方法;另,针对线宽工艺变化推导出互连延迟均值与方差的计算公式.最后通过仿真实验对工艺变化下互连线延迟分析方法及其统计特性计算公式的有效性进行了验证.     

多端互连线网络布线时延的研究

互连线时延是集成电路设计中非常重要的影响因素。本文根据Elmore延迟模型推导出多端互连线的延迟估算公式，得出了在满足设计规则的前提下，多端互连线网络应尽量遵守的布线规则，即互连线之间不要有重叠，且从源点到每个终点都要走最短的曼哈顿路径。这种布线规则可以在不增加芯片面积的基础上使互连线时延减少，这对指导高速IC芯片的版图设计有重要的理论和实践指导意义。     

基于精确时延模型考虑缓冲器插入的互连线优化算法

随着VLSI电路集成度增大和特征尺寸的不断减小,连线的寄生效应不可忽略,互连线的时延在电路总时延中占了很大的比例,成为决定电路性能的主要因素.在互连时延的优化技术中,缓冲器插入是最有效的减小连线时延的方法.本文提出了一个在精确时延模型下,在布线区域内给定一些可行的缓冲器插入位置,对两端线网进行拓扑优化,并同时插入缓冲器以优化时延的多项式时间实现内的算法.我们的算法不但可以实现时延的最小化,也可以在满足时延约束的条件下,最小化缓冲器的插入数目,从而避免不必要的面积和功耗的浪费.     

VDSM集成电路互连特性及RC延迟研究

利用多层金属导体寄生电容模型,详细分析了不同的金属互连线参数对寄生电容的影响,并采用一个闭合公式对超深亚微米级集成电路中的RC互连延迟进行估计.结果表明,当金属导线的纵横比接近2时,线间耦合电容对互连总电容的影响将占主导地位.在超深亚微米工艺条件下,当金属线宽和间距比例W/P的最优质值为0.5～0.6时,计算的互连延迟为最小.此外,还给出了低介电常数材料对互连线电容和延迟的影响,为超深亚微米级的集成电路设计与实现提供有益的参考.     

串扰约束下超深亚微米顶层互连线性能的优化设计

优化顶层互连线性能已成为超深亚微米片上系统(SOC)设计的关键.本文提出了适用于多个工艺节点的串扰约束下顶层互连线性能的优化方法.该方法由基于分布RLC连线模型的延迟串扰解析公式所推得.通过HSPICE仿真验证,对当前主流工艺(90nm),此优化方法可令与芯片边长等长的顶层互连线(23.9mm)的延时减小到182ps,数据总线带宽达到1.43 GHz/ μ m,近邻连线峰值串扰电压控制在0.096V_dd左右.通过由本方法所确定的各工艺节点下的截面参数和性能指标,可合理预测未来超深亚微米工艺条件下顶层互连线优化设计的发展趋势.     

基于物理α指数MOSFET模型的SRAM存储体单元优化

存储体单元是静态随机存储器(SRAM)最基本、最重要的组成部分,它在改善系统性能、提高芯片可靠性、降低成本与功耗等方面都起到了积极的作用.该文采用物理α指数MOSFET模型建立了与SRAM存储体单元相关的功耗,延迟的性能模型,并结合存储体单元面积模型以及可靠性分析,提出了一种存储体单元结构优化方法.实验结果表明采用此优化方法得出的存储体单元结构降低了功耗,访问时间以及面积,与仿真结果相比误差小于10%,实验仿真结果证明了性能模型和优化方法的有效性和正确性.     

深亚微米VLSI电路中互连线的几何优化设计

基于三维 L aplace方程的 Silvaco Interconnect3D模拟程序数值解 ,对互连寄生电容进行了计算 ,其结果用于 0 .2 5μm CMOS技术互连延迟及串扰的 SPICE模拟中。模拟结果表明 ,基于W/ P=0 .3～ 0 .4的布线准则可以获得最优的互连延迟与串扰 (Crosstalk)特性 ,通过优化互连线及驱动管的几何尺寸可以显著地减小互连线的延迟及串扰噪声。     

Low-power repeaters driving RC and RLC interconnects with delay and bandwidth constraints

Interconnect plays an increasingly important role in deep-submicrometer very large scale integrated technologies. Multiple design criteria are considered in interconnect design, such as delay, power, and bandwidth. In this paper, a repeater insertion methodology is presented for achieving the minimum power in an RC interconnect while satisfying delay and bandwidth constraints. These constraints determine a design space for the number and size of the repeaters. The minimum power is shown to occur at the edge of the design space. With delay constraints, closed form solutions for the minimum power are developed, where the average error is 7% as compared with SPICE. With bandwidth constraints, the minimum power can be achieved with minimum-sized repeaters. The effects of inductance on the delay, bandwidth, and power of an RLC interconnect with repeaters are also analyzed. By including inductance, the minimum interconnect power under a delay or bandwidth constraint decreases as compared with an RC interconnect.     

Design methodology for synthesizing clock distribution networksexploiting nonzero localized clock skew

An integrated top-down design methodology is presented in this brief for synthesizing high performance clock distribution networks based on application dependent localized clock skew. The methodology is divided into four phases: (1) determining an optimal clock skew schedule composed of a set of nonzero clock skew values and the related minimum clock path delays; (2) designing the topology of the clock distribution network with delays assigned to each branch based on the circuit hierarchy, the aforementioned clock skew schedule, and minimizing process and environmental delay variations; (3) designing circuit structures to emulate the delay values assigned to the individual branches of the clock tree; and (4) designing the physical layout of the clock distribution network. The clock distribution network synthesis methodology is based on CMOS technology. The clock lines are transformed from distributed resistive capacitive interconnect lines into purely capacitive interconnect lines by partitioning the RC interconnect lines with inverting repeaters. Variations in process parameters are considered during the circuit design of the clock distribution network to guarantee a race-free circuit. Nominal errors of less than 2.5% for the delay of the clock paths and 7% for the clock skew between any two registers belonging to the same global data path as compared with SPICE Level-3 are demonstrated     

On Modeling of Parallel Repeater-Insertion Methodologies for SoC Interconnects

Parallel repeaters are proven to outperform serial repeaters in terms of delay, power and silicon area when regenerating signals in system-on-chip (SoC) interconnects. In order to avoid fundamental weaknesses associated with previously published parallel repeater-insertion models, this paper presents a new mathematical modeling for parallel repeater-insertion methodologies in SoC interconnects. The proposed methodology is based on modeling the repeater pull-down resistance in parallel with the interconnect. Also, to account for the effect of interconnect inductance, two moments were used in the transfer function, as opposed to previous Elmore delay models which consider only one moment for RC interconnects. A direct consequence of this new type of modeling is an increased challenge in the mathematical modeling of interconnects. HSpice electrical and C++/MATLAB simulations are conducted to assess the performance of the proposed optimization methodology using a 0.25-$mu$m CMOS technology. Simulation results show that this repeater-insertion methodology can be used to optimize SoC interconnects in terms of propagation delay, and provide VLSI/SoC designers with optimal design parameters, such as the type as well as the position and size of repeaters to be used for interconnect regeneration, faster than with conventional HSpice simulations.      

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.     

Thermal-Aware Methodology for Repeater Insertion in Low-Power VLSI Circuits

In this paper, the impact of thermal effects on low-power repeater insertion methodology is studied. An analytical methodology for thermal-aware repeater insertion that includes the electrothermal coupling between power, delay, and temperature is presented, and simulation results with global interconnect repeaters are discussed for 90- and 65-nm technology. Simulation results show that the proposed thermal-aware methodology can save 17.5% more power consumed by the repeaters compared to a thermal-unaware methodology for a given allowed delay penalty. In addition, the proposed methodology also results in a lower chip temperature, and thus, extra leakage power savings from other logic blocks.     

Interconnect design strategy: structures, repeaters and materialswith strategic system performance analysis (S2PAL) model

In this paper, we propose a novel methodology for scheming an interconnect strategy, such as what interconnect structure should be taken, how repeaters should be inserted, and when new metal or dielectric materials should be adopted. In the methodology, the strategic system performance analysis model is newly developed as a calculation model that predicts LSI operation frequency and chip size with electrical parameters of transistors and interconnects as well as circuit configuration. The analysis with the model indicates that interconnect delay overcomes circuit block cycle time at a specific length; D_c-cross. Here tentatively, interconnects shorter than D_c-cross are called local interconnects, and interconnects longer than that as global ones. The cross-sectional structures for local and global tiers are optimized separately. We also calculate global interconnect pitch and the chip size enlarged by the global interconnect pitch and the inserted repeaters, and then estimate the effectiveness of introducing new materials for interconnects and dielectrics     

Logic Gates as Repeaters (LGR) for Area-Efficient Timing Optimization

Logic gates as repeaters (LGRs)-a methodology for delay optimization of CMOS logic circuits with resistance-capacitance (RC) interconnects is described. The traditional interconnect segmentation by insertion of repeaters is generalized to segmentation by distributing logic gates over interconnect lines, reducing the number of additional, logically useless inverters. Expressions for optimal segment lengths and gate scaling are derived. Considerations are presented for integrating LGR into a VLSI design flow in conjunction with related methods. Several logic circuits have been implemented, optimized and verified by LGR. Analytical and simulation results were obtained, showing significant improvement in performance in comparison with traditional repeater insertion, while maintaining low complexity and small area     

High speed interconnect through device optimization for subthreshold FPGA

Field programmable gate array (FPGA) consumes a significant amount of static and dynamic power due to the presence of additional logic for providing more flexibility as compared to application specific integrated circuits (ASICs). The fabrication cost of ASICs is rising exponentially in deep submicron and hence it is important to investigate different techniques for reducing FPGA power consumption so that they can also be employed in place of ASICs in portable energy constrained applications. It is also important to investigate the possibility of extending the use of FPGA even to subthreshold region for ultra low power (ULP) applications. Interconnect resources of an FPGA consumes most of the chip power, area and also determines the overall circuit delay. Subthreshold circuits show orders of magnitude power saving over superthreshold circuits. Improving the performance of subthreshold circuits is a main design challenge at the circuit and device levels to spread their application area. This paper proposes to improve the performance of subthreshold FPGA in terms of delay and switching energy by optimizing and operating interconnect drivers in the near threshold operating region. The possibility of inserting repeaters and the suitability of CNT as an interconnect in the subthreshold region are also explored. The simulation of FPGA interconnect resources using the proposed technique shows 67%, 73.33% and 61.8% increase in speed and 35.72%, 39% and 35.44% reduction in switching energy for Double, Hex and Long interconnect segments, respectively, over the conventional one.     

基于一种新的时空编码技术的片上总线的低延迟低能耗设计

在深亚微米设计中,降低能耗和传播延迟是片上全局总线所面对的两个最主要设计目标.本文提出了一种用于片上全局总线的时空编码方案,它既提高了性能又降低了峰值能耗和平均能耗.该编码方案利用空间总线倒相编码和时间编码电路技术的优点,在消除相邻连线上反相翻转的同时,减少了自翻转数和耦合翻转数.在应用该总线编码技术降低总线延时和能耗的设计中,给出了一种总线上插入中继驱动器的设计方法,以确定它们合适的尺寸和插入位置,使得在满足目标延时和翻转斜率要求的同时总线总的能耗最小.该方法可用来为各种编码技术获得翻转斜率约束下的总线能耗与延时的优化折中.     

基于一种新的时空编码技术的片上总线的低延迟低能耗设计

在深亚微米设计中,降低能耗和传播延迟是片上全局总线所面对的两个最主要设计目标.本文提出了一种用于片上全局总线的时空编码方案,它既提高了性能又降低了峰值能耗和平均能耗.该编码方案利用空间总线倒相编码和时间编码电路技术的优点,在消除相邻连线上反相翻转的同时,减少了自翻转数和耦合翻转数.在应用该总线编码技术降低总线延时和能耗的设计中,给出了一种总线上插入中继驱动器的设计方法,以确定它们合适的尺寸和插入位置,使得在满足目标延时和翻转斜率要求的同时总线总的能耗最小.该方法可用来为各种编码技术获得翻转斜率约束下的总线能耗与延时的优化折中.