CONSEQUENCES OF INTEGRATION IN DIGITAL SYSTEM DESIGNS
UNIVERSITY OF NIGERIA, NSUKKA FACULTY OF ENGINEERINGDEPARTMENT OF ELECTRONIC ENGINEERING TITLE: CONSEQUENCES OF INTEGRATION IN DIGITAL SYSTEM DESIGNSA TERM-PAPER PREPARED IN PARTIAL FULFILMENT OF THE COURSE DIGITAL ELECTRONICS (ECE471)NAME: Ezeonyido Kingsley Lotanna 2007/147192LECTURER: Engr. V. C. Chijindu.
1 CHAPTER ONE1.0 INTRODUCTION Digital systems design teams are facing exponentially growing complexities andneed processes and tools that reduce the time needed to gain insight into difficultsystem integration problems. A digital system is a data technology that uses discrete (discontinuous) values.By contrast, non-digital (or analog) systems use a continuous range of values torepresent information. Although digital representations are discrete, the informationrepresented can be either discrete, such as numbers, letters or icons, or continuous,such as sounds, images, and other measurements of continuous systems. The designof digital systems begins with the development of a set of specifications outlining therequirements of the desired system. These specifications are usually composed of blockdiagram, timing diagrams, flow-charts and natural language. Initial requirements for newdigital systems and products that are generally expressed in a variety of notationsincluding diagrams and natural language can be automatically translated to a commonknowledge representation for integration, for consistency and completeness analysis,and for further automatic synthesis. An example of digital system is digital information. All digital informationpossesses common properties that distinguish it from analog communicationsmethods:
2Synchronization: In written or spoken human languages synchronization is typicallyprovided by pauses (spaces), capitalization, and punctuation. Machine communicationstypically use special synchronization sequences.Language: All digital communications require a language, which in this context consistsof all the information that the sender and receiver of the digital communication mustboth possess, in advance, in order for the communication to be successful.Errors: Disturbances in a digital communication do not result in errors unless thedisturbance is so large as to result in a symbol being misinterpreted as another symbolor disturb the sequence of symbols. It is therefore generally possible to have an entirelyerror-free digital communicationCopying: Because of the inevitable presence of noise, making many successive copiesof an analog communication is infeasible because each generation increases the noise.Because digital communications are generally error-free, copies of copies can be madeindefinitely.Granularity: When a continuously variable analog value is represented in digital formthere is always a decision as to the number of symbols to be assigned to that value.The number of symbols determines the precision or resolution of the resulting datum.The difference between the actual analog value and the digital representation is knownas quantization error. This property of digital communication is known as granularity. Digital integration is the idea that data or information on any given electronicdevice can be read or manipulated by another device using a standard format.Examples of digital integration
3 Cell phone calendar to public digital calendar (online calendar)In this example, a user has a cell phone with a calendar, as well as a calendar on theInternet. Digital Integration would allow the user to synchronize the two, and thefollowing features could result:The user could plan events and have other users notified. If the Public Digital Calendaris integral with a Blog, then the user could write about the event in it. Building services integration for energy management and building controlA home owner or commercial building manager could utilize digital integration productsto connect intelligent services within a built environment. An intruder detection or accesscontrol system could be used in conjunction with light level sensors to turn lights on andoff. So when you walk into a dark room the lights turn on (if you are allowed to be there)and when you leave they turn off behind you, thus making energy savings by preventinglights from being left on. The same techniques could be used to control HVAC (Heating Ventilation and AirConditioning) systems. Home owners and commercial building managers can use Webbased digital integration to control and manage services within their buildings via a webbrowser interface. The intelligent controllers in Air Conditioning units for example maybe "Web Enabled" using digital integration solutions and products.The digital revolution is upon us in every form. Computer performance doubles every 18months. Networks of high performance servers are replacing mainframes at a dizzyingpace. Personal communication systems are pervasive, from remote sales tools tomedical information systems to networked workgroup tools. What is behind this
4revolution? This work describes consequences of Integration in digital systemsdesign in terms of their implications in the system integration phase.
5 CHAPTER TWO2.0 IMPLICATIONS OF INTEGRATION IN DIGITAL DESIGN In engineering, system integration is the bringing together of the componentsubsystems into one system and ensuring that the subsystems function together as asystem. This effect has many advantages and disadvantages of which we shall reviewin this section. Our CASE STUDY shall be DIGITALLY DESIGNED CIRCUITS andINTEGRATED CIRCUITS.2.1 ADVANTAGES OF INTEGRATION IN DIGITAL DESIGNCASE STUDY: DIGITALLY DESIGNED CIRCUITS Error Correction and Detection: Digital memory and transmission systems can use techniques such as error detection and correction to use additional data to correct any errors in transmission and storage. These techniques are acceptable when the underlying bits are reliable enough that such errors are highly unlikely. High Noise Immunity: The digital circuit will calculate more repeatedly, because of its high noise immunity.PERFORMANCE EVALUATION Efficiency Reduction in Power Loss Output Regulation: Signals represented digitally can be transmitted without degradation due to noise
6 Output Ripple Dynamic Response Reduced power dissipation due to adaptive dead-time control Ability to adjust the output voltage Programmable droop for enhanced current sharing performance Increased flexibility and faster implementation of design changes Option of digital power management interface without size penalty Component Count: The integration in Digital Circuit Design has made it obvious that circuitry now has fewer components than before; this now makes designed systems more portable than usual. Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. A good example of this is the GSM and Landline or Desktop Telephone. Reliability.
72.2 DISADVANTAGES OF INTEGRATION IN DIGITAL SYSTEM DESIGN CASE STUDY: DIGITALLY DESIGNED CIRCUITS MORE POWER COMSUPTION: Digital circuits use more energy than analog circuits to accomplish the same tasks, thus producing more heat. In portable or battery-powered systems this can limit use of digital systems. HIGH COST OR VERY EXPENSIVE: Digital circuits are sometimes more expensive, especially in small quantities. QUANTIZATION ERRORS: Most useful digital systems must translate from continuous analog signals to discrete digital signals. This causes quantization errors. Quantization error can be reduced if the system stores enough digital data to represent the signal to the desired degree of fidelity. CLIFF EFFECT: In some systems, if a single piece of digital data is lost or misinterpreted, the meaning of large blocks of related data can completely change. Because of the cliff effect, it can be difficult for users to tell if a particular system is right on the edge of failure, or if it can tolerate much more noise before failing. DIGITAL FRAGILITY: Digital fragility can be reduced by designing a digital system for robustness. For example, a parity bit or other error management method can be inserted into the signal path. These schemes help the system detect errors, and then either correct the errors, or at least ask for a new copy of
8 the data. In a state-machine, the state transition logic can be designed to catch unused states and trigger a reset sequence or other error recovery routine. INTERMITTENT PROBLEMS: Bad designs have intermittent problems such as "glitches", vanishingly-fast pulses that may trigger some logic but not others, "runt pulses" that do not reach valid "threshold" voltages, or unexpected combinations of logic states. SLOW CALCULATION: Since digital circuits are made from analog components, digital circuits calculate more slowly than low-precision analog circuits that use a similar amount of space and power. METASTABILITY: Where clocked digital systems interface to analogue systems or systems that are driven from a different clock, the digital system can be subject to metastability where a change to the input violates the set-up time for a digital input latch. This situation will self-resolve, but will take a random time, and while it persists can result in invalid signals being propagated within the digital system for a short time.
9 CHAPTER THREE3.0 SUMMARIES AND CONCLUSIONS ON DIGITAL SYSTEM DESIGN CONSEQUENCES3.1 SUMMARYThe performance of the analog and digital designs was similar in the following areas: Efficiency Ripples of the output voltage Predicted reliabilityThe performance of the digital design was measured to be significantly better than thatof the analog version in these areas: Output voltage regulation Dynamic response Size of the designed system Output powerIn addition to the measured data, the digital design offers benefits not available with theanalog implementation such as: Reduced power dissipation due to adaptive dead-time control
10 Ability to adjust the output voltage Programmable droop for enhanced current sharing performance Increased flexibility and faster implementation of design changes Option of digital power management interface without size penalty3.2 CONCLUSION The digital design was equal to or better than the analog reference design inalmost all respects. Component count for the digital design is somewhat higher due to aslightly different implementation of the power train details which offset the savings ofcomponents in the control section. Further optimization of the design should eliminatethe difference in component count. The performance attributes and additional benefits of digital design systemsummarized above shows that integration in digital design techniques have an excitingfuture in electronics and IT world in terms high performance, portability, and reliability.
11 REFERENCES1. Paul Horowitz and Winfield Hill, The Art of Electronics 2nd Ed. Cambridge University Press, Cambridge, 1989 ISBN 0-521-37095-7 page 471.2. Tocci, R. 2006. Digital Systems: Principles and Applications (10th Edition). Prentice Hall. ISBN 0131725793.3. Eleclectronic Design Automation for Integrated Circuits Handbook, by Lavagno, Martin, and Scheffer, ISBN 0-8493-3096-3 A survey of the field of electronic design automation, one of the main enablers of modern IC design.4. CIS 8020 – Systems Integration, Georgia State University.5. An Introduction to School of Information Engineering, Information Engineering Program, Beijing: Beijing University of Posts and Telecommunications.6. Texas Instruments Inc: UCD91xx Digital Power Controller Datasheet, September 2006, www.ti.com.7. Ericsson Power Modules AB: “Performance Improvements for OEM System designers – a Digital Control Case Study”, September, 2006, www.ericsson.com.8. Wikipedia: “Digital Integration”, www.wikipedia.com.