Non-ideal return paths, simultaneous switching noise, power delivery, buffer modeling, and digital timing analysis are then explained. The final chapters discuss methods for designing high-speed buses that handle the large number of variables that affect interconnect Digltal, radiated emissions problems and Interconnecct noise minimization, Thekry high-speed measurement techniques. We just sent you an email.

Please click the link in the email to confirm your subscription! OK Subscriptions powered by Strikingly. Return to site. Introduction Noise in power supplies is not only caused by the power supply itself, but also the load s interaction with the power supply i. To lower load induced noise,. Ribbon Cables A ribbon cable is any cable having multiple conductors bound together in a flat, wide strip.

Each dielectric configuration has different high-frequency characteristics. All configurations. Soonwook Hong, Ph. Introduction PV inverters use semiconductor devices to transform the. Distribution is unlimited. A plasma is an electrically. They are. A capacitor is used to store.

What is the SI unit for capacitance? A capacitor basically consists of two. We regret any inconvenience this may cause. For the latest. Define capacitance and state its symbol and unit of measurement. Predict the capacitance of a parallel plate capacitor. Analyze how. In this exercise, you will look at some of their limitations. You will also examine the op amp integrator and. Keysight Technologies Understanding the Fundamental Principles of Vector Network Analysis Application Note Introduction Network analysis is the process by which designers and manufacturers measure the.

Kuhn Sept. Although half-wave rectification. Introduction and Goal: Exploring transient behavior due to inductors and capacitors in DC circuits; gaining experience with lab instruments. To determine the time constant of an RC Circuit, and 2. To determine the capacitance of an unknown capacitor. Chapter 11 Inductors Objectives Describe the basic structure and characteristics of an inductor Discuss various types of inductors Analyze series inductors Analyze parallel inductors Analyze inductive. Each DSL variant respectively operates up a higher frequency level.

In today s applications, high surge currents coming from the dc bus are a. The ATF Modeling Physical Interconnects Part 3 Dr. Complexity of the different discharge modes. Electric E- and D-fields Electrostatic Force Box Norwood, MA , U. Tel: The more familiar network parameters. Tzong-Lin Wu 1 Introduction 6. By Darrell G. Broussard, P. Introduction: As engineers, we are aware that electrical power systems have grown. How much have they grown? When was the last time you specified a volt system, a volt. The majority of these are available either as integrated. Objectives Define electrical current as a rate.

Describe what is measured by ammeters and voltmeters. Explain how to connect an ammeter and a voltmeter in an electrical circuit. Explain why electrons travel. Timing Errors and Jitter Background Mike Story In a sampled digital system, samples have to be accurate in level and time. The digital system uses the two bits of information the signal was this big. Radio Frequency Circuit Design. Transmission Lines Introduction A transmission line guides energy from one place to another.

Optical fibres, waveguides, telephone lines and power cables are all electromagnetic transmission lines. The quality of braided shields is investigated with respect to perfect solid shields. Crosstalk effects. Agilent Measuring Noninsertable Devices Product Note A new technique for measuring components using the C Network Analyzer Introduction The majority of devices used in real-world microwave. Data Transmission Concepts and terminology Transmission terminology Transmission from transmitter to receiver goes over some transmission medium using electromagnetic waves Guided media.

Waves are guided. High Voltage Transient Analysis 4. Surges on Transmission Lines Due to a variety of reasons, such as a direct stroke of lightning on the line, or by indirect strokes, or by switching operations or by faults,. Log in Registration. Search for. Size: px.

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## High-Speed Digital System Design A Handbook of Interconnect Theory and Design Practices

Electric Current Objectives Define electrical current as a rate. Explain why electrons travel More information. The digital system uses the two bits of information the signal was this big More information. Crosstalk effects More information. Measure of relative position in time within a single period of a signal For a periodic signal f t , phase is fractional part t p Data Transmission Concepts and terminology Transmission terminology Transmission from transmitter to receiver goes over some transmission medium using electromagnetic waves Guided media.

Because of this, many currently employed digital system designers do not have the knowledge required for modern high-speed designs. This fact leads to a surprisingly large amount of misinformation to propagate through engineering circles. Often, the concepts of high-speed design are perceived with a sort of mysticism. However, this problem has not come about because the required knowledge is unapproachable. In fact, many of the same concepts have been used for several decades in other disciplines of electrical engineering, such as radio-frequency design and microwave design.

The problem is that most references on the necessary subjects are either too abstract to be immediately applicable to the digital designer, or they are too practical in nature to contain enough theory to fully understand the subject. It is worth noting that everything in this book has been applied to a successful modern design. Typically this involves sending and receiving a series of trapezoidal shaped voltage signals such as shown in Figure 1. The conductive paths carrying the digital signals are known as interconnects.

The interconnect includes the entire electrical pathway from the chip sending a signal to the chip receiving the signal. This includes the chip packages, connectors, sockets, as well as a myriad of additional structures.

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A group of interconnects is referred to as a bus. The region of voltage where a digital receiver distinguishes between a high and a low voltage is known as the threshold region. Within this region, the receiver will either switch high or switch low. On the silicon, the actual switching voltages vary with temperature, supply voltage, silicon process, and other variables.

From the system designers point of view, there are usually high-and low-voltage thresholds, known as Vih and Vil, associated with the receiving silicon, above which and below which a high or low value can be guaranteed to be received under all conditions. Thus the designer must guarantee that the system can, under all conditions, deliver high voltages that do not, even briefly, fall below Vih, and low voltages that remain below Vil, in order to ensure the integrity of the data. Figure 1. In order to maximize the speed of operation of a digital system, the timing uncertainty of a transition through the threshold region must be minimized.

This means that the rise or fall time of the digital signal must be as fast as possible. Ideally, an infinitely fast edge rate would be used, although there are many practical problems that prevent this. Realistically, edge rates of a few hundred picoseconds can be encountered. The reader can verify with Fourier analysis that the quicker the edge rate, the higher the frequencies that will be found in the spectrum of the signal. Herein lies a clue to the difficulty. Every conductor has a capacitance, inductance, and frequency-dependent resistance. At a high enough frequency, none of these things is negligible.

Thus a wire is no longer a wire but a distributed parasitic element that will have delay and a transient impedance profile that can cause distortions and glitches to manifest themselves on the waveform propagating from the driving chip to the receiving chip. The wire is now an element that is coupled to everything around it, including power and ground structures and other traces.

The signal is not contained entirely in the conductor itself but is a combination of all the local electric and magnetic fields around the conductor. The signals on one interconnect will affect and be affected by the signals on another. Furthermore, at high frequencies, complex interactions occur between the different parts of the same interconnect, such as the packages, connectors, vias, and bends.

All these high-speed effects tend to produce strange, distorted waveforms that will indeed give the designer a completely different view of high-speed logic signals. The physical and electrical attributes of every structure in the vicinity of the interconnect has a vital role in the simple task of guaranteeing proper signaling transitions through Vih and Vil with the appropriate timings. These things also determine how much energy the system will radiate. We will see in later chapters how to account for all these things. When a conductor must be considered as a distributed series of inductors and capacitors, it is known as a transmission line.

In general, this must be done when the physical size of the circuit under consideration approaches the wavelength of the highest frequency of interest in the signal. In the digital realm, since edge rate pretty much determines the maximum frequency content, one can compare rise and fall times to the size of the circuit instead, as shown in Figure 1. On a typical circuit board, a signal travels about half the speed of light exact formulas will be in later chapters.

Thus a ps edge rate occupies about 3 in. One of the most difficult aspects of high-speed design is the fact that there are a large number codependent variables that affect the outcome of a digital design. Some of the variables are controllable and some force the designer to live with the random variation. One of the difficulties in high-speed design is how to handle the many variables, whether they are controllable or uncontrollable. Often simplifications can be made by neglecting or assuming values for variables, but this can lead to unknown failures down the road that will be impossible to "root cause" after the fact.

As timing becomes more constrained, the simplifications of the past are rapidly dwindling in utility to the modern designer. This book will also show how to incorporate a large number of variables that would otherwise make the problem intractable. Without a methodology for handling the large amount of variables, a design ultimately resorts to guesswork no matter how much the designer physically understands the system. The final step of handling all the variables is often the most difficult part and the one most readily ignored by a designer. A designer crippled by an inability to handle large amounts of variables will ultimately resort to proving a few "point solutions" instead and hope that they plausibly represent all known conditions.

While sometimes such methods are unavoidable, this can be a dangerous guessing game. Of course, a certain amount of guesswork is always present in a design, but the goal of the system designer should be to minimize uncertainty. History confirmed this insightful prediction. Remarkably, computer performance has doubled approximately every 1. One measure of relative processor performance is internal clock rates. By the time this is in print, even the fastest processors on this chart will likely be considered unimpressive. The point is that computer speeds are increasing exponentially. As core frequency increases, faster data rates will be demanded from the buses that feed information to the processor, as shown in Figure 1.

Decreased timing budgets mean that it is evermore important to properly account for any phenomenon that may increase the timing uncertainty of the digital waveform as it arrives at the receiver. This is the root cause of two inescapable obstacles that will continue to make digital system design difficult. The first obstacle is simply that the sheer amount of variables that must be accounted for in a digital design is increasing. As frequencies increase, new effects, which may have been negligible at slower speeds, start to become significant. Generally speaking, the complexity of a design increases exponentially with increasing variable count.

The second obstacle is that the new effects, which could be ignored in designs of the past, must be modeled to a very high precision. Often these new models are required to be three-dimensional in nature, or require specialized analog techniques that fall outside the realms of the digital designer's discipline. The obstacles are perhaps more profound on the subsystems surrounding the processor since they evolve at a much slower rate, but still must support the increasing demands of the processor.

All of this leads to the present situation: There are new problems to solve. Engineers who can solve these problems will define the future. This book will equip the reader with the necessary practical understanding to contend with modern high-speed digital design and with enough theory to see beyond this book and solve problems that the authors have not yet encountered. Read on. It is no longer possible to model interconnects as lumped capacitors or simple delay lines, as could be done on slower designs.

This is because the timing issues associated with the transmission lines are becoming a significant percentage of the total timing margin. Great attention must be given to the construction of the PCB so that the electrical characteristics of the transmission lines are controlled and predictable. In this chapter we introduce the basic transmission line structures typically used in digital systems and present basic transmission line theory for the ideal case. The metal in a typical PCB is usually copper and the dielectric is FR4, which is a type of fiberglass.

The two most common types of transmission lines used in digital designs are microstrips and striplines. A microstrip is typically routed on an outside layer of the PCB and has only one reference plane. There are two types of microstrips, buried and nonburied. A buried sometimes called embedded microstrip is simply a transmission line that is embedded into the dielectric but still has only one reference plane.

A stripline is routed on an inside layer and has two reference planes. Figure 2. In this book, transmission lines are often represented in the form of a cross section.

## High-Speed Digital System Design A Handbook of Interconnect Theory and Design Practices

This is very useful for calculating and visualizing the various transmission line parameters described later. Multiple-layer PCBs such as the one depicted in Figure 2. Control of the conductor and dielectric layers which is referred to as the stackup is required to make the electrical characteristics of the transmission line predictable. In high-speed systems, control of the electrical characteristics of the.

These basic electrical characteristics, defined in this chapter, will be referred to as transmission line parameters. The electrical signal will travel down the transmission line in the way that water travels through a long square pipe. This is known as electrical wave propagation. Just as the waterfront will travel as a wave down the pipe, an electrical signal will travel as a wave down a transmission line. Additionally, just as the water will travel the length of the pipe in a finite amount of time, the electrical signal will travel the length of the transmission line in a finite amount of time.

To take this simple analogy one step further, the voltage on a transmission line can be compared to the height of the water in the pipe, and the flow of the water can be compared to the current. The top line is the signal path and the bottom line is the current return path. The basic electrical characteristics that define a transmission line are its characteristic impedance and its propagation velocity. The characteristic impedance is similar to the width of the water pipe used in the analogy above, and the propagation velocity is simply analogous to speed at which the water flows through the pipe.

To define and derive these terms, it is necessary to examine the fundamental properties of a transmission line. As a signal travels down the transmission line depicted in Figure 2. When the signal reaches an arbitrary point z on the transmission line, the signal path conductor will be at a potential of V i volts and the ground return conductor will be at a potential of 0 V. This voltage difference establishes an electric field between the signal and the ground return conductors. In simpler terms, this means that if a current is flowing through a conductor, it results in a magnetic field around that conductor.

We have therefore established that if an output buffer injects a signal of voltage V i and current I i onto a transmission line, it will induce an electric and a magnetic field, respectively. Note that this analysis implies that the signal is not simply traveling on the signal conductor of the transmission line; rather, it is traveling between the signal conductor and reference plane in the form of an electric and a magnetic field.

Now that the basic electromagnetic properties of a transmission line have been established, it is possible to construct a simple circuit model for a section of the line. If it is assumed that there are no components of the electric or magnetic fields propagating in the z-direction into the page , the electric and magnetic fields will be orthogonal. This is known as transverse electro-magnetic mode TEM.

Transmission lines will propagate in TEM mode under normal circumstances and it is an adequate approximation even at relatively high frequencies. This allows us to examine the transmission line in differential sections or slices along the length of the line traveling in the z-direction into the page. The two components shown in Figure 2. Since there is energy stored in both an electric and a magnetic field, let us include the circuit components associated with this energy storage in our circuit model.

The magnetic field for a differential section of the transmission line can be represented by a series inductance Ldz, where L is inductance per length. The electric field between the signal path and the ground path for a length of dz can be represented by a shunt capacitor C dz, where C is capacitance per length. An ideal model would consist of an infinite number of these small sections cascaded in series.

This model adequately describes a section of a loss-free transmission line i. The series resistor, R dz, represents the losses due to the finite conductivity of the conductor; the shunt resistor, G dz, represents the losses due to the finite resistance of the dielectric separating the conductor and the ground plane, the series inductor, Ldz, represents the magnetic field; and the capacitor, C dz, represents the electric field between the conductor and the ground plane. In the remainder of this book, one of these sections will be known as an RLCG element.

The termination, Z o, in Figure 2. With this simplification, the characteristic impedance can be derived for an infinitely long transmission line. To derive the characteristic impedance of the line, Figure 2. Solving the equivalent circuit of Figure 2. For simplicity, the differential length dz is replaced with a short length of z. It is usually adequate to approximate the characteristic impedance as, since R and G both tend to be significantly smaller than the other terms.

Only at very high frequencies, or with very lossy lines, do the R and G components of the impedance become significant. Lossy transmission lines are covered in Chapter 4. Lossy lines will also yield complex characteristic impedances i. For the purposes of digital design, however, only the magnitude of the characteristic impedance is important.

## High-Speed Digital System Design A Handbook of Interconnect Theory and Design Practices - PDF

The solvers will typically provide the impedance, propagation velocity, and L and C elements per unit length. This is adequate since R and G usually have a minimal effect on the impedance. In the absence of a field solver, the formulas presented in Figure 2. More accurate formulas for characteristic impedance are presented in Appendix A. Propagation delay is usually measured in terms of seconds per meter and is the inverse of the propagation velocity.

The propagation delay of a transmission line will increase in proportion to the square root of the surrounding dielectric constant. The time delay of a transmission line is simply the amount of time it takes for a signal to propagate the entire length of the line.