Design analysis and circuit enhancements for high-speed bipolar flip-flops

The design of high-speed current mode logic latches is discussed, using analytical expressions for delay. An open circuit time constant method is utilized throughout this paper, though similar results were obtained from a charge control analysis. Emphasis is placed on the variables that are under the control of the circuit designer, as opposed to the device designer. Circuit delay is calculated with respect to device area, current density, amplitude, and a keep-alive current. In particular, the keep-alive current gives the circuit designer control over the average transconductance of switching transistors, independent of their bias currents. The cost of the keep-alive current is the loss of output amplitude. The effects of transmission lines and peaking inductors are discussed in a qualitative manner. Latch designs were tested with static divide-by-two frequency dividers. Results of several dividers (both SiGe and InP) are shown and compared with the theory.     

New dynamic flip-flops for high-speed dual-modulus prescaler

A fast pipeline technique using single-phase, edge-triggered, ratioed, high-speed logic flip-flops and D flip-flops is introduced and analyzed. The circuits achieve high speed by reducing the capacitive load and sharing the delay between the combination logic blocks and the storage elements. Also it is suitable for realizing high-speed synchronous counters. A divide-by-128/129 and 64/65 dual-modulus prescaler using the proposed flip-flops is measured in 0.8 μm CMOS technology with the operating clock frequency reaching as high as 1.8 GHz     

Design of low-power high-speed bipolar frequency dividers

A low-power current mode bipolar frequency divider is discussed. Low-power consumption is achieved owing to the design strategy being based on a progressive reduction of bias currents through stages without affecting divider operation speed. The strategy is independent of the process used and simple to design, avoiding the trial-and-error approach based on simulations     

一种高速低功耗BiCMOS脉冲式触发器的通用结构

BiCMOS电路兼具CMOS电路高集成度,低功耗的优点和双极型电路高速大驱动能力的优势,已成为目前国际学术界研究的热点之一。本文提出了一种基于BiCMOS工艺的新型脉冲式触发器的通用结构和设计方法,并设计了两种结构简单的BiCMOS脉冲式D型触发器。应用TSMC 180nm工艺,采用HSPICE模拟表明:所设计的BiCMOS脉冲式D型触发器不仅具有正确的逻辑功能,而且具有高速低功耗大驱动能力的优点,与已有文献提出的BiCMOS D型触发器相比,功耗和PDP均有大幅度降低。     

一种高速低抖动四相位时钟电路的设计

超高速A/D转换器对精准的时钟电路提出严格要求,时钟抖动是影响其精度的重要因素。文章在分析时钟抖动对A/D转换器的影响后,介绍了一种适用于GHz的低抖动四相位时钟电路。电路采用时钟恢复电路、四相位分布网络和相位校正电路,得到占空比稳定、相位误差小的四相位时钟。采用0. 18μm CMOS工艺实现,电路仿真表明,四相位输出时钟抖动102 fs,占空比调整范围30%～70%,功耗277 mW@1. 8 V。     

Very-high-speed Si bipolar static frequency dividers with newT-type flip-flops

This paper presents two circuit techniques for highspeed operation of a master-slave toggle flip-flop circuit (MSTFF). One circuit reduces the gain in latching circuits, and the other uses the transient current of the emitter followers to boost the switching speed. Both the SPICE simulations and the measured results for static 1/8 frequency dividers fabricated using 0.5-μm super self-aligned process technology (SSTIC) show that the maximum operating speed of our MS-TFF's is 10% and 30% faster than that of conventional ones. By applying these technologies, 19.1-GHz and 22.4-GHz Si bipolar static frequency dividers have been fabricated     

基于AD9516的高速四通道时间交叉采样时钟的设计

针对四通道时间交叉采样对时钟的严格要求,提出了使用时钟分配器AD9516给四个交叉采样的模数转换器AD9445提供四路在相位上严格相差90°的110 MHz的采样时钟.在介绍AD9516特性的基础上,详细说明了系统设计电路结构,并利用FPGA模拟高速同步串行口(SPI)协议,实现了DSP利用FPGA当作桥接器件和AD9516通信.     

基于FPGA的高速时钟数据恢复电路的实现

介绍了一种利用输出时钟在具有不同相位的时钟信号之间进行切换实现高速时钟恢复电路的方法。利用Altera公司Quartus软件提供的修改逻辑单元和逻辑块锁定及插入buffer的方法,消除了时钟切换产生的毛刺,弥补了不同相位时钟由于不同的传输延迟而造成的相位偏移。设计的电路实现了数字光端机要求的204．8MHz的工作频率。同时,分析了决定该电路工作频率的主要因素,通过仿真验证使用EP3C10El44C7芯片最高工作频率可以达到400MHz。     

An all-digital phase-locked loop for high-speed clock generation

An all-digital phase-locked loop (ADPLL) for high-speed clock generation is presented. The proposed ADPLL architecture uses both a digital control mechanism and a ring oscillator and, hence, can be implemented with standard cells. The ADPLL implemented in a 0.3-/spl mu/m one-poly-four-metal CMOS process can operate from 45 to 510 MHz and achieve worst case frequency acquisition in 46 reference clock cycles. The power dissipation of the ADPLL is 100 mW (at 500 MHz) with a 3.3-V power supply. From chip measurement results, the P/sub k/-P/sub k/ jitter of the output clock is <70 ps, and the root-mean-square jitter of the output clock is <22 ps. A systematic way to design the ADPLL with the specified standard cell library is also presented. The proposed ADPLL can easily be ported to different processes in a short time. Thus, it can reduce the design time and design complexity of the ADPLL, making it very suitable for system-on-chip applications.     

An open-loop clock deskewing circuit for high-speed synchronous DRAM

An open-loop clock deskewing circuit (CDC) for high-speed synchronous DRAM is described. Unlike the conventional circuits, the CDC does not require an additional measure delay line, thus power consumption is reduced. The delay is measured directly from the main delay line and both the input and output ports of the delay line are movable. The CDC provides a deskewed clock within two clock cycles.     

A high-speed, low-power clock generator for a microprocessorapplication

This paper discusses the design of the clock generator for the Alpha 21264. As the speed performances are of primary concern in the whole design, the clock-generator jitter and phase misalignment must be as low as possible in a very noisy environment. A dedicated on-chip voltage regulator based on a bandgap reference has been designed to reduce the effect of supply noise on the clock generator. To avoid a large voltage drop across the power-supply bond wires during the startup sequence, the core frequency can be increased by steps in one period of the core clock, with a limited frequency overshoot and no missing pulses. The circuit has been implemented in a CMOS 0.35 μm process. The voltage-controlled-oscillator frequency range is between 350 MHz and 2.8 GHz, with a peak-to-peak cycle-to-cycle jitter lower than 16 ps. While booting Unix on a system, the maximum phase misalignment is lower than ±100 ps     

An advanced PSA technology for high-speed bipolar LSI

An advanced method for polysilicon self-aligned (PSA) bipolar LSI technology has realized a miniaturized transistor for high performance. By introducing the overlapping structure for double polysilicon electrodes, the emitter area is reduced to 1 µm × 3 µm and the base junction is reduced to 0.3 µm. The CML integrated circuit composed of this transistor has achieved a minimum propagation delay time of 0.29 ns/gate with power dissipation of 1.48 mW/gate. Compared to the conventional PSA method, this technology promises to fabricate higher speed and higher density LSI's.     

Applications of high-speed data acquisition for bipolar device-yield analysis

An in-line process-monitoring system has been established in a high-volume manufacturing environment which has defined a data base that can be accessed for retrieval and display of data using histograms and scatter plots. Applications of high-speed data acquisition have been expanded to include wafer mapping which illustrates device and process parameters and their relationship to die yield. These relationships can be determined with a 95-percent confidence level.     

Partial-SOI isolation structure for reduced bipolar transistorparasitics

A bipolar isolation structure with the capability of significantly reducing collector-base capacitance and base resistance is presented. Partial SOI, with SOI surrounding the collector opening, can be used to reduce the collector window width in combination with any emitter-base self-aligned bipolar device structure, and in particular for device structures that feature sublithographic emitter width. Near-ideal transistor Gummel characteristics and a minimum ECL gate delay of 24 ps have been achieved with a nonoptimized lateral device layout, and simulations suggest that sub-20-ps delay at reduced switch current will be possible by using the optimized partial-SOI isolation structure     

A high-speed four-phase clock generator for low-power on-chip SerDes applications

In this work we present a low-power, low-area and high-speed fully CMOS quadrature clock generator for on-chip SerDes applications. The device utilizes a couple of differential prescalers for high speed frequency division and four duty cycle adjusters to set the duty cycle of the produced clock signals at 50% of the clock period. The circuit was implemented with the STMicroelectronics 65 nm process technology using only 125 transistors and it occupies an active area of under 2.34 μm². With a power supply of 1.1 V the complete circuit consumes 89.56 μW at room temperature.     

DESIGN OF nMOS QUATERNARY FLIP-FLOPS AND THEIR APPLICATIONS

By using the theory of clipping voltage-switches, two kinds of master/slave nMOS quaternary flip-flops are designed. These flip-flops have the capability of two-input presetting and double-rail complementary outputs. It is shown that these flip-flops are effectively suitable to design nMOS quaternary sequential circuits by designing two examples of hexadecimal up-counter and decimal up-counter. Supported by Youth Science & Technology Foundation of Ningbo Science & Technology Commission and by Natural Science Foundation of Zhejiang Province, China     

Design of testable sequential circuits by repositioning flip-flops

This paper presents a technique to enhance the testability of sequential circuits by repositioning flip-flops. A novel retiming for testability technique is proposed that reduces cycle lengths in the dependency graph, converts sequential redundancies into combinational redundancies, and yields retimed circuits that usually require fewer scan flip-flops to break all cycles (except self-loops) as compared to the original circuit. Our technique is based on a new minimum cost flow formulation that simultaneously considers the interactions among all strongly connected components (SCCs) of the circuit graph to minimize the number of flip-flops in the SCCs. A circuit graph has a vertex for every gate, primary input and primary output. If gatea has a fanout to gateb, then the circuit graph has an arc from vertexa to vertexb. Experimental results on several large sequential circuits demonstrate the effectiveness of the proposed retiming for testability technique in reducing the number of partial scan flip-flops.     

Scheme for distributing high-speed clock signals in a large digital system

The details of a clock distribution circuit for a large digital system operating at 250 MHz are presented. The arrangement provides pulse compression control and preserves the clock timing at the 100 ps level even when parts of the circuit are replaced.<>