一种基于锁存器实现时序收敛的方法

扫描链测试,作为一种简单、高效的可测性设计方法,已经广泛应用于集成电路设计中。该方法可以有效地检测出电路制造过程中的缺陷和故障,从而降低芯片的测试成本。但是随着扫描链的插入,芯片物理设计中的时序收敛变得更加复杂,尤其是在扫描链测试的移位模式下,由于时钟偏移的存在,保持时间可能存在大量的时序违例。针对这种情况,本文首先介绍了扫描链测试的基本原理,分析了插入扫描链之后出现保持时间违例的原因,提出了一种基于锁存器的修复时序违例的方法,并详细阐述了对于不同边沿触发的触发器组如何选择相应的锁存器实现时序收敛。最后,将该方法应用于一款电力通信芯片的物理设计,快速、高效地实现了时序的收敛。     

Design methodologies for high-performance noise-tolerant XOR-XNOR circuits

Scaling down to deep submicrometer (DSM) technology has made noise a metric of equal importance as compared to power, speed, and area. Smaller feature size, lower supply voltage, and higher frequency are some of the characteristics for DSM circuits that make them more vulnerable to noise. New designs and circuit techniques are required in order to achieve robustness in presence of noise. Novel methodologies for designing energy-efficient noise-tolerant exclusive-OR-exclusive- NOR circuits that can operate at low-supply voltages with good signal integrity and driving capability are proposed. The circuits designed, after applying the proposed methodologies, are characterized and compared with previously published circuits for reliability, speed and energy efficiency. To test the driving capability of the proposed circuits, they are embedded in an existing 5-2 compressor design. The average noise threshold energy (ANTE) is used for quantifying the noise immunity of the proposed circuits. Simulation results show that, compared with the best available circuit in literature, the proposed circuits exhibit better noise-immunity, lower power-delay product (PDP) and good driving capability. All of the proposed circuits prove to be faster and successfully work at all ranges of supply voltage starting from 3.3 V down to 0.6 V. The savings in the PDP range from 94% to 21% for the given supply voltage range respectively and the average improvement in the ANTE is 2.67X.     

Modified asynchronous wave-pipelining

A modified asynchronous wave-pipelining design method for optimising circuit performance is presented. Using this method, the number of latches in the circuit can be decreased compared with the asynchronous wave-pipelined circuit that uses latches at every gate level. As a result, the latency of the circuit can be reduced drastically and the number of delay elements used in the wave-pipelined circuit can be decreased. To verify the proposed method, the authors have designed and 8×8 multiplier and performed simulations using HSPICE. The latency of the multiplier decreased by 40% when compared with the asynchronous wave-pipelined circuit and a delay latch replaced two delay elements that were used in the wave-pipelined circuit. The designed multiplier works well at 1 GHz     

A review of 0.18-/spl mu/m full adder performances for tree structured arithmetic circuits

The general objective of our work is to investigate the area and power-delay performances of low-voltage full adder cells in different CMOS logic styles for the predominating tree structured arithmetic circuits. A new hybrid style full adder circuit is also presented. The sum and carry generation circuits of the proposed full adder are designed with hybrid logic styles. To operate at ultra-low supply voltage, the pass logic circuit that cogenerates the intermediate XOR and XNOR outputs has been improved to overcome the switching delay problem. As full adders are frequently employed in a tree structured configuration for high-performance arithmetic circuits, a cascaded simulation structure is introduced to evaluate the full adders in a realistic application environment. A systematic and elegant procedure to scale the transistor for minimal power-delay product is proposed. The circuits being studied are optimized for energy efficiency at 0.18-/spl mu/m CMOS process technology. With the proposed simulation environment, it is shown that some survival cells in stand alone operation at low voltage may fail when cascaded in a larger circuit, either due to the lack of drivability or unsatisfactory speed of operation. The proposed hybrid full adder exhibits not only the full swing logic and balanced outputs but also strong output drivability. The increase in the transistor count of its complementary CMOS output stage is compensated by its area efficient layout. Therefore, it remains one of the best contenders for designing large tree structured arithmetic circuits with reduced energy consumption while keeping the increase in area to a minimum.     

Scalability of Globally Asynchronous QCA (Quantum-Dot Cellular Automata) Adder Design

The concept of clocking for QCA, referred to as the four-phase clocking, is widely used. However, inherited characteristics of QCA, such as the way to hold state, the way to synchronize data flows, and the way to power QCA cells, make the design of QCA circuits quite different from VLSI and introduce a variety of new design challenges. The most severe challenges are due to the fact that the overall timing of a QCA circuit is mainly dependent upon its layout. This issue is commonly referred to as the “layout = timing” problem. To circumvent the problem, a novel self-timed circuit design technique referred to as the Locally Synchronous, globally asynchronous design for QCA has been recently proposed. The proposed technique can significantly reduce the layout–timing dependency from the global network of QCA devices in a circuit; therefore, considerably flexible QCA circuit design is be possible. Also, the proposed technique is more scalable in designing large-scale systems. Since a less number of cells is used, the overall area is smaller and the manufacturability is better. In this paper, numerous multi-bit adder designs are considered to demonstrate the layout efficiency and robustness of the proposed globally asynchronous QCA design technique.     

The effect of propagation delay uncertainty on the speed oftime-of-flight digital optoelectronic circuits

Time-of-flight synchronization is a new digital design methodology for optoelectronics that eliminates latches, allowing higher clock rates than alternative timing schemes. Synchronization is accomplished by precisely balancing connection delays. Circuits use pulse-mode signaling and clock gates to restore pulse timing. Many effective pipeline stages are created within combinational logic without extra hardware bounding the stages. Time-of-flight design principles are applicable to packet routing and sorting processors for optical interconnection networks. Circuits are unique because the clock rate is limited primarily by imprecision in propagation delay rather than absolute delay, as in circuits with latches. We develop a general model of delay uncertainty and focus on the effect that static and dynamic uncertainty accumulated over circuit paths has on the minimum feasible clock period. We present a method for traversing the circuit graph representation of a time-of-flight circuit to compute arrival time uncertainty at each pulse interaction point. Arrival time uncertainties give rise to pulse width and overlap constraints. From these constraints we formulate a constrained minimization to find the minimum clock period. We demonstrate our method on circuits implemented with 2×2 electro-optic switches and optical waveguides and find the electronic component of path uncertainty frequently limits speed     

Circuit Design Techniques for a First-Generation Cell Broadband Engine Processor

The Cell Broadband Engine (Cell BE) is a multicore system-on-chip (SoC), implemented in a 90-nm high-performance silicon-on-insulator (SOI) technology, and optimized, within the triple constraints of area, power, and performance, to run at frequencies in excess of 3 GHz. The large scale of the design ($sim$75 million logic transistors, and about 750 000 latches and flip-flops), high-volume requirements, and the desire to support multiple manufacturing facilities dictated a need for very robust circuit practices, but at the same time, the high-frequency goal drove the use of more aggressive styles in certain critical regions of the design. This paper describes the local clock design, along with the various latches and flip-flops deployed, followed by a discussion of the circuit techniques used for the digital logic implementation, including special considerations for high-speed synthesized control logic, semi-custom and full-custom static circuit design and full-custom dynamic logic circuits. In addition, the synergistic processor element (SPE) circuit design is described, followed by the techniques and issues associated with the SRAM design. Finally, the methods used for electrical verification are described, these being an important part of the strategy for ensuring overall design robustness and first-silicon success.     

Design for Low Power and Reliable Flexible Electronics: Self-Tunable Cell-Library Design

We propose a self-tunable pseudo-CMOS cell library to address the key challenges of circuit design for flexible electronics. This cell library provides the building blocks for designing complex circuits which are able to operate at a low supply voltage. The circuit reliability is greatly improved by incorporating the post-fabrication tunability into the cells to compensate for the device degradation (e.g., $Delta V_{rm TH}$). Logic gates, such as latches and flip-flops, and larger building blocks, such as shift-registers are, developed to demonstrate the key features and feasibility of this proposed cell library.      

Two FIFO ring performance experiments

Asynchronous circuits are often perceived to operate slower than equivalent clocked circuits. We demonstrate with fabricated chips that asynchronous circuits can be every bit as fast as clocked circuits. We describe two high-speed first-in-first-out (FIFO) circuits that we used to compare the performance of asynchronous FIFOs with that of conventionally clocked shift registers. The first FIFO circuit uses a pulse-like protocol, which we call the Asynchronous Symmetric Persistent Pulse Protocol (asP*), to advance data along a pipeline of conventional latches. Use of this protocol requires careful management of circuit delays. The second FIFO circuit uses a transition signaling protocol and special transition latches to store data. These transition latches are fast, but they are about 50% larger than conventional latches. Measurements obtained from chips fabricated in 0.6 μm CMOS and from SPICE simulations show that the throughput of the first FIFO design matches that of a conventionally clocked shift register design, with a maximum throughput of 1.1 Giga data items per second. The throughput of the second design exceeds the performance of the asP* design and achieves a maximum throughput of 1.7 Giga data items per second. We have extensively tested the chips and have found them to operate reliably over a very wide range of conditions     

Wave-pipelining: a tutorial and research survey

Wave-pipelining is a method of high-performance circuit design which implements pipelining in logic without the use of intermediate latches or registers. The combination of high-performance integrated circuit (IC) technologies, pipelined architectures, and sophisticated computer-aided design (CAD) tools has converted wave-pipelining from a theoretical oddity into a realistic, although challenging, VLSI design method. This paper presents a tutorial of the principles of wave-pipelining and a survey of wave-pipelined VLSI chips and CAD tools for the synthesis and analysis of wave-pipelined circuits     

An ant colony based mapping of quantum circuits to nearest neighbor architectures

Although this decade is witnessing tremendous advancements in fabrication technologies for quantum circuits, this industry is facing several design challenges and technological constraints. Nearest Neighbor (NN) enforcement is one such design constraint that demands the physical qubits to be adjacent. In the last couple of years, this domain has made progress starting from designing advanced algorithms to improved synthesis methodologies, even though developing efficient design solutions remains an active area of research.Here, we propose such a synthesis technique that efficiently transforms quantum circuits to NN designs. To find the NN solution, we have taken help of an ant colony algorithm which completes the circuit conversion in two phases: in the first phase, it finds the global qubit ordering for the input circuit and, in the second phase, a heuristic driven look-ahead scheme is executed for local reordering of gates. The proposed algorithm is first fitted into a 1D design and, later, mapped to 2D and 3D configurations. The combination of such heuristic and the meta-heuristic schemes has resulted promising solutions in the transformation of quantum circuits to NN-compliant architectures. We have tested our algorithm over a wide spectrum of benchmarks and comparisons with state-of-the-art design approaches showed considerable improvements.     

Discrete-Dopant-Induced Timing Fluctuation and Suppression in Nanoscale CMOS Circuit

As the dimensions of semiconductor devices continue to be reduced, device fluctuations have become critical to determining the accuracy of timing in circuits and systems. This brief studies the discrete-dopant-induced timing characteristic fluctuations in 16-nm-gate complementary metal–oxide–semiconductor (CMOS) circuits using a 3-D “atomistic” coupled device–circuit simulation. The accuracy of the simulation has been confirmed by using the experimentally calibrated transistor physical model. For a 16-nm-gate CMOS inverter, 3.5%, 2.4%, 18.3%, and 13.2% normalized fluctuations in the rise time, fall time, high-to-low delay time, and low-to-high delay time, respectively, are found. Random dopants may cause significant timing fluctuations in the studied circuits. Suppression approaches that are based on the circuit and device design viewpoints are implemented to examine the associated characteristic fluctuations. The use of shunted transistors in the circuit provides similar suppression to the use of a device with doubled width. However, both approaches increase the chip area. To eliminate the need to increase the chip area, channel engineering approaches (vertical and lateral) are proposed, and their effectiveness in reducing the timing fluctuation is demonstrated.      

Critical paths in circuits with level-sensitive latches

This paper extends the classical notion of critical paths in combinational circuits to the case of synchronous circuits that use level-sensitive latches. Critical paths in such circuits arise from setup, hold, and cyclic constraints on the data signals at the inputs of each latch and may extend through one or more latches. Two approaches are presented for identifying these critical paths and verifying their timing. The first implicitly checks all paths using a relaxation-based solution procedure. Results of this procedure are used to calculate slack values, which in turn identify satisfied and violated critical paths. The second approach is based on a constructive algorithm which generates all the critical paths in a circuit and then verifies that their timing constraints are satisfied. Algorithms are evaluated and compared using circuits from the ISCAS89 sequential benchmark suite and the Michigan High Performance Microprocessor Project     

Multi-bit upset aware hybrid error-correction for cache in embedded processors

For the processor working in the radiation environment in space, it tends to suffer from the single event effect on circuits and system failures, due to cosmic rays and high energy particle radiation. Therefore, the reliability of the processor has become an increasingly serious issue. The BCH-based error correction code can correct multi-bit errors, but it introduces large latency overhead. This paper proposes a hybrid error correction approach that combines BCH and EDAC to correct both multi-bit and single-bit errors for caches with low cost. The proposed technique can correct up to four-bit error, and correct single-bit error in one cycle. Evaluation results show that, the proposed hybrid error-correction scheme can improve the performance of cache accesses up to 20% compared to the pure BCH scheme.     

Circuit and Latch Capable of Masking Soft Errors with Schmitt Trigger

In VLSIs, soft errors resulting from radiation-induced transient pulses frequently occur. In recent high-density and low-power VLSIs, the operation of systems is seriously affected by not only soft errors occurring on memory systems and the latches of logic circuits but also those occurring on the combinational parts of logic circuits. The existing tolerant methods for soft errors on the combinational parts do not provide enough high tolerant capability with small performance penalty. This paper proposes a class of soft error masking circuits by using a Schmitt trigger circuit and a pass transistor. The paper also presents a construction of soft error masking latches (SEM-latches) capable of masking transient pulses occurring on combinational circuits. Moreover, simulation results show that the proposed method has higher soft error tolerant capability than the existing methods. For supply voltage V _DD ?=?3.3 V, the proposed method is capable of masking transient pulses of magnitude 4.0 V or less.     

GaAs基E/D PHEMT技术单片集成微波开关及其逻辑控制电路

利用GaAs基E/D PHEMT技术单片集成微波开关及其逻辑控制电路的制作工艺和设计方法,采用0.8μm GaAsE/D PHEMT工艺,制备出性能良好的解码器功能内置的DC～10GHz SPDT MMIC,基本实现逻辑电路与开关电路的集成.开关电路在DC～10GHz内插入损耗小于1.6dB,隔离度大于24dB;整个电路只需要1位控制信号,有效地减少了开关电路的控制端口数目,节省了芯片面积,为GaAs多功能电路的研究奠定了基础.     

Low cost and highly reliable radiation hardened latch design in 65 nm CMOS technology

As a consequence of technology scaling down, gate capacitances and stored charge in sensitive nodes are decreasing rapidly, which makes CMOS circuits more vulnerable to radiation induced soft errors. In this paper, a low cost and highly reliable radiation hardened latch is proposed using 65 nm CMOS commercial technology. The proposed latch can fully tolerate the single event upset (SEU) when particles strike on any one of its single node. Furthermore, it can efficiently mask the input single event transient (SET). A set of HSPICE post-layout simulations are done to evaluate the proposed latch circuit and previous latch circuits designed in the literatures, and the comparison results among the latches of type 4 show that the proposed latch reduces at least 39% power consumption and 67.6% power delay product. Moreover, the proposed latch has a second lowest area overhead and a comparable ability of the single event multiple upsets (SEMUs) tolerance among the latches of type 4. Finally, the impacts of process, supply voltage and temperature variations on our proposed latch and previous latches are investigated.     

Toward a systematic design methodology for large multigigahertzrapid single flux quantum circuits

Rapid single flux quantum (RSFQ) digital circuits have reached the level of medium- to large-scale of integration. At this level, existing design methodologies, developed specifically for RSFQ circuits, have become computationally inefficient. Applying mature semiconductor methodologies to the design of RSFQ circuits, one encounters substantial difficulties originating from the differences between both technologies. In this paper, a new design methodology aimed at large-scale RSFQ circuits is proposed. This methodology is based on a semiconductor semicustom design approach. An established design methodology for small-stale RSFQ digital circuits, based on circuit (junction-level) simulation and device parameter optimization, is used for the design of basic RSFQ cells. A library composed of about 20 basic RSFQ cells has been developed based on this approach. A novel design methodology for large-scale circuits, presented in this paper, is based on logic (gate-level) simulation and timing optimization. This methodology has been implemented around the Cadence integrated design environment and used successfully at the University of Rochester for the design of two large-scale digital circuits     

40 nm CMOS工艺下的低功耗容软错误锁存器

为了降低集成电路的软错误率,该文基于时间冗余的方法提出一种低功耗容忍软错误锁存器。该锁存器不但可以过滤上游组合逻辑传播过来的SET脉冲,而且对SEU完全免疫。其输出节点不会因为高能粒子轰击而进入高阻态,所以该锁存器能够适用于门控时钟电路。SPICE仿真结果表明,与同类的加固锁存器相比,该文结构仅仅增加13.4%的平均延时,使得可以过滤的SET脉冲宽度平均增加了44.3%,并且功耗平均降低了48.5%,功耗延时积(PDP)平均降低了46.0%,晶体管数目平均减少了9.1%。