New approach to electronic equipment design based on ranking by special characteristics and further optimization of printed wire length has been suggested. The example of research works carried out applying the given approach was presente

Arishin, E. A.

Ivanov, I. V.

Kutyavina, S. K.

Electronic archive of Tomsk Polytechnic University

One of tendencies of electronics development consists in expansion of its application domains that is agreat variety of electronics designed for various fields ofscience and technology is observed. Electronics is complicated, requirements to its reliability are increased,more indicated, intelligent rich problems increasing efficiency and quality of user operation are solved with itshelp. Another tendency is the increase of capabilities ofcomputeraided design (CAD) for endtoend design ata higher level [1].In this connection new problems occur both inschematic and engineering design as well as at their junction.Among the design problems the following onesshould be singled out:• absence of methodical recommendations taking into account modern design styles and occurring problems;• insufficient accounting of all important requirements for the device and specific features of its elements in connection with limited capacities of theirprocessing in CAD;• weak information supply of technicians in the questions of using automatic, interactive and compoundmodes at wide unused capacities of CAD;• complexity of forming placement and routing strategies at the variety of adjustable parameters (for,example tracer SPECCTRA has 169 adjustable parameters);• data exchange rules are not sufficiently formalizedbetween circuit engineers and designers as well asbetween other technicians;• complicity of solving problems of design optimization in CAD as it is multiparametric, weakformalized tasks of labyrinth type requiring highlevelskills both in object domain and informationtechnologies;• increase of requirements for topology of printedconductors due to significant increase of digital circuit speed.The listed problems indicate the fact that the newapproach is required for electronics design in modernCAD and on modern level. It gives information totechnicians required for reducing design period and increasing quality of the product. As it was mentioned in[1] information technologies of design possess not onlygreat facilities but new demands as well for optimal useof these facilities.Information technologies requirements consist inthe fact that limited capacities of design process formalization and accounting all factors influencing the design decisions in comparison with decision variability accepted by man intelligence require special initial information. This information should not be a set of elementary recommendations but a formalized and arrangedinstrument which combines the main modern requirements to the equipment, criteria of selecting qualitativedecisions and capacities of modern CAD within endtoend strategy of device design.To formalize and systemize the whole informationrequired for design the objectoriented approach may beapplied. All parts of the device whether it is a printed circuit board (PCB) or electronic component are the objectswith specified parameters. A set of object properties required for design is limited by a type of applied component,demands to the device, capacities of the applied CAD etc.Combination of these properties by a special method withdemands to the device, criteria of engineering solution selection and CAD capacities gives necessary informationfor generating endtoend design strategy.The term «objectoriented information» can be applied to this information as it describes properties of device objects and their combinations in the form requiredfor making and implementing design decision. However, considering established notions on the combination«objectoriented» itself another term – problemoriented information (POI) is suggested to be applied. Thisterm reflects as well the matter of the aforesaid information but from the point of view of its direct function.POI definition may be determined as: informationdeveloped on the basis of objectoriented approach thestructure and composition of which is determined bythe solved problem.The approach to design based on formation of endtoend design philosophy from problemoriented information is called problemoriented approach.The main goal of this approach application is maximum possible, qualitative, conscious use of CAD features and, first of all, just automated modes which have amajority of adjustable parameters. At such approach themain attention of the developers is given to making quaBulletin of the Томsк Pоlytеchnic University. 2007. V. 311. № 560UDC 621.38.001:681.3.066PROBLEMORIENTED APPROACH TO SOLVING THE PROBLEMS OF ELECTRONIC EQUIPMENT DESIGN IN CADS.K. Kutyavina, E.A. Arishin, I.V. Ivanov*Tomsk Polytechnic University*«Sibirtelekom», TomskEmail: chiun1@yandex.ruNew approach to electronic equipment design based on ranking by special characteristics and further optimization of printed wire lengthhas been suggested. The example of research works carried out applying the given approach was presented.litative design decisions but not to the multiple homogeneous operations typical for operation in interactivemode.To implement designing on such high level it is necessary firstly to search, systematize, structure and classify such initial information as well as technique of itsformation and application.Then the descriptions and results of research worksdevoted to search and optimization of applying problemoriented parameters at designing are given. Theinvestigations wee carried out in the following directions: optimization of PCB construction applying POIand optimization of PCB quality control by simulatingwith POI.1. Optimization of design stages in PCAD medium saving and increasing quality of PCB tracing The aim of the investigations consists in:• search and classification of POI;• determination of possibility of applying PCB automatic arrangement and tracing using POI withoutloss of signal transfer quality and other characteristics of the devices.These problems solution was required by the resultsof studying and analyzing electronics design problemsof in CAD infomedia in Russia.The results of analysis showed that PCB is mainlyconstructed in interactive mode that is confirmed in [6].Engineers do not trust to automatic mode of placementand routing owing to uncertainty of quality assurance atsignal transfer, on the one hand, and on the other hand,they do not possess the techniques of solving polyvalenttasks for selecting parameter optimal combinations forPCB arrangement and tracing policy. The developers oftracer SPECCTRA do not give any references on selecting parameters of PCB arrangement and tracing policythey just propose an averaged variant of the policy whichdoes not take into account the peculiarities of differentchart variants. These are the reason why it is necessaryto carry out investigations with a great number of computer experiments for solving the above mentioned problems.Performing the works in searching for problemoriented information the charts were for the first time classified by design, functional and designfunctional complexity (Fig. 1). To determine maximal length of highfrequency circuits and its accounting at design two problemoriented parameters were applied: functionalcomplexity (circuit ranking depending on signal switching frequency in them) and designfunctional complexity (accounting of maximum allowed length of conductor for the given frequency). Use of these criteriaimplies device circuit division into lowfrequency andhighfrequency and application of various design rulesfor each group. Such approach is explained by the factthat in lowfrequency circuits signals do not lose clearness and real circuit operation coincides perfectly withlogic circuit whereas in highspeed circuits signals aredistorted almost beyond recognition [4].In the paper the technique of applying two abovementioned parameters of POI at PCB construction issuggested. It includes the following stages:I. Circuit ranking according to the maximal frequencies of signal switching in them and determining maximum allowed length.According to the information about signal switchingfrequencies in conductors the developer divides circuitsinto two groups: highfrequency (the length should bestrictly limited) and lowfrequency. Maximum allowedvalue of signal switching frequency in the circuit is determined by two groups of parameters: maximum possible value of frequency at the output of signal source fИ максand maximum possible values of signal switching frequency at receiver inputs fП1 макс...fПn макс. Values fИ макс andfП1 макс...fПn макс may be found out of certificates for properelements. This information may be indicated both explicitly (immediate frequency value) and in the form ofvalues of signal propagation delays in the element whichmay help at frequency value computation.Maximum allowed frequency of signal switching inthe circuit equals to a minimum of fИ макс and fП1 макс...fПn макс.According to this frequency value the circuits are rankedthat is divided into highfrequency and lowfrequencyones.The results of ranking as well as found values of maximum allowed frequency for each conductor are proposed to be entered into the table (Table 1).Then it is necessary to calculate values of maximumallowed length for conductors the length of whichshould be limited and include these data into the table.It may be done both manually calculating values bythe formula (*) and applying the program MaxLengthdeveloped by the author which allows computing rapidly and saving results in the file in the form convenientfor use:(*)where tф is the front length, v=2·109 m/s is the rate ofsignal propagation in the line at medium dielectric constant =2,25 [7].II. Limitation of wire length in CAD.According to the results of computations (Table 1)the developer places a limitation on conductor length inPCAD PCB. To perform this operation the algorithmand instruction for user were developed [8].Table 1. The results of ranking circuits and computation ofacceptable conductor length III. Arrangement and tracing of the card taking intoaccount the obtained limitations for highfrequency netlength.Net Connection Termination style Frequency, MHz Length, mmA2DD26 Input –54DD36 Output 9A41А3 Output 7,368DD28 Input –/ 4,ìàêñ ôl t v=Control, computer engineering and information science61To optimize the placement and tracing the experiments on PCB construction for selected circuit diagramwere carried out. Placement and tracing of the card were performed in three variants: applying interactive, automatic and mixed modes (Fig. 2).After tracing in three given modes its results werecompared by several criteria (Fig. 3). On the given barcharts column № 1 refers to interactive mode, column№ 2 refers to automatic one and column № 3 – to themixed mode.The analysis of the experiment results allows makingthe following conclusions:1. Mixed mode of design is the most efficient due tothe minimum of interactive processing and application of automatic tracing.2. Quality of tracing performed with POI application isthe most defined as:• reliability of circuit operation is supported owingto limitation of maximal length of highfrequency circuits at interactive tracing;• tracing variant obtained in automatic mode isoptimized as total wire length and a number ofviaholes are minimized due to optimization ofPOI application policy (circuit classification bydesign complexity).As a result, increasing productivity of design engineer approaches significantly to CAD facilities at considerable decrease of his labor tension, reduction of PCBdesign time and support of reliability of circuit operation.2. Investigation of PCB design quality by electromagneticcompatibility in PCAD 2002CAD facilities by simulation of digital signal originby printed conductor subject to the possible distortionswere studied in the paper. Having analyzed the facilitiesof simulation the technique of designing investigationprocess of PCB quality subject to occurring disturbances was developed.It became clear while working on the technique thatsignal quality may be checked up by simulation for alldevice circuits with numerous combinations of signalparameters in the considered and neighbor circuits.However, such redundancy is not appropriate becauseof the following reasons:• high time expenditures for simulation;• labor of results analysis because of their large amount;• ambiguity at developing references for disturbancedecrease (it is not clear exactly what measurersshould be assumed for decreasing disturbances in aconcrete circuit).Therefore, it was suggested to divide nets into groupsand each circuit ranking. In this case classification byfunctional complexity was used (Fig. 1). Ranking wascarried out by the following criteria:• importance of the performed function;• frequency of signal switching in a net;• noiseimmunity of the elements connected to a net.Bulletin of the Томsк Pоlytеchnic University. 2007. V. 311. № 562Fig. 1. Classification of problemoriented parameters of electrical circuitsPROBLEMORIENTED PARAMETERS OF ELECTRICAL CIRCUITSDesign complexity (accounting a number of internal and external interconnects)Digital circuit with ratio 1:2Highfrequency nets Accounting highfrequency wire lengthAccounting lowfrequency wire lengthLowfrequency netsDigital circuit with ratio 1:6Digitalanalog (analogdigital) circuit with ratio 1:2Digitalanalog (analogdigital) circuit with ratio 1:6Functional complexity (net ranking depending on signal frequency)Designfunctional complexity (accounting wire length depending on signal frequency)Control, computer engineering and information science63Fig. 2. Variants of placement obtained in different modes: а) interactive, b) automatic and (c) mixed???Fig. 3. Comparison of tracing results by criteria: (а) executiontime; (b) total length of conductors and (c) number ofviaholesNets may be divided by the performed function intogroups according to possible common consequenceswhich are the result of signal distortion in it. For example, failure in timing signals or control nets by possibleconsequences is worth than a simple data distortion.Importance of nets inside of one group may be differentas well.Noiseimmunity of an element is defined by element reaction on voltage surge on its input. Highspeedelement may react on voltage pulse caused by a crosstalk(Fig. 5, b) whereas a lowfrequency element does notreact on this pulse [2, 3]. Therefore, highfrequency circuits and elements are more vulnerable than lowfrequency ones therefore, they are more important.Net ranking allows determining how detailed signaldistortion should be studied in each net, how many testsshould be carried out, how many different variants ofadjustments for simulation parameters should be used.Quality is suggested to be studied in sequence reflected in Fig. 4.Nets are ranked on the stage of gathering preliminary information. Within this paper ranking was carriedout in two stages:Fig. 4. Algorithm of quality research of printed circuit board bysimulation 1. Division of nets into groups by importance andfrequency of signal switching ranking each group.2. Each net ranking according to the information oncomponent noise immunity.The example of net ranking is given in Table 2. Inthis case nets were combined into three groups: sync,control and information nets.Table 2. Table of circuit, element and rank characteristics Each net rank is composed of two components.Highorder digit is the group rank and the rest digits isthe circuit rank inside this group. Net and group ranksare numbered in ascending order by decreasing qualityand noise immunity.Net Notionof SSISSI part typeULmin,ВULmax,ВUHmin,ВUHmax,ВRankSync netsCLK0 U1, U6 SN74ACT2440FN –1 0,8 2 7 102OSCU2 SN74ACT2440FN –1 0,8 2 7 101U4 TLC3405880GA –0,8 0,7 2 6,8 Control netsHRDU2 SN74ACT2440FN –1 0,8 2 7 202U4 TLC3405880GA –0,8 0,7 2 6,8 AEN U2 SN74ACT2440FN –1 0,8 2 7 201StartEndyesyesnonoInformation acquisitionand preliminary analysisof the device circuitsSimulation of signal passage through the printedconductorsAnalysis of simulationresultsDevelopment of references for increasing noiseimmunityAresimulation resultssufficient for quality estimation?Is itnecessary to assume the measures for increasing noise immunity??Number of viasс?Wire total length, mmb?Execution time, sBulletin of the Томsк Pоlytеchnic University. 2007. V. 311. № 564abFig. 5. Variations of signal distortions in conductors: а) signaledge distortion because of reflection effect; b) constantsignal distortion because of crosstalks For example, rank 102 is given to net CLK0. It means that the group in which there is this net is the mostimportant and the net itself is the second by importanceamong of its group.Then it is necessary to determine quantity of testsfor each net and medium adjustments for each testsubject to net rank. This information should be introduced into test table that allows simulating as soon aspossible.If quality research reveals signal distortions in longunmatched wires (Fig. 5, a) or possible signal distortions due to crosstalks (Fig. 5, b) then analyzing simulation results and generating decisions on increasingdevice noise immunity the circuit rank determines gravity of deviations in signal quality and importance ofmeasures to be assumed for supporting this signal integrity.The results of researches on electronics design optimization in CAD showed that intelligent design systemsoperate more efficiently if they get intelligent structuredinformation taking into account possibilities and peculiarities of used system as input parameters and adjustments. At such approach the design process itself changes qualitatively as the main attention is given to analyzing device features, developing and implementing endtoend design philosophy but not to its numerous homogeneous operations typical for design in interactivemode.Control, computer engineering and information science65REFERENCES1. Razevig V.D. Printed circuit board design in PCAD 2001. – Moscow: SolonR, 2001. – 557 p.2. Nenashev A.P., Koledov L.A. Foundations of designing microelectronic equipment. – Moscow: Radio i Svyaz, 1981. – 109 p.3. Barns J. Electronic design: Methods of controlling noises: Translatedfrom English. – Moscow: Mir, 1990. – 246 p.4. Jonson G., Graham M. Designing highspeed digital devices: elementary course of black art: Translated from English. – Moscow:Publishing house «Williams», 2006. – 1016 p.5. Kutyavina S.K., Kosheleva S.Yu., Zherdev A.A. Optimization ofdesigning printed circuit boards in the medium CAD PCAD 2001subject to design complexity of electronic circuits // Modern facilities and systems of automation: Transactions of the IV theoretical andpractical conference. – Tomsk, TUSUR, 2004. – P. 124–128.6. Steshenko V.B. PCAD. Design of printed circuit boards. – St.Petersburg: BHVPeterburg, 2003. – 652 p.7. Ovsischer P.I., Livshits I.I., Orchinskiy A.K.  et al. Arrangement anddesign of microelectronic equipment: Handbook / Ed. by Vysotskiy B.F., Pestryakov V.B., Pyatlin O.A. – Moscow: Radio i Svyaz,1982. – 270 p.8. Kutyavina S.K., Arishin E.A. Optimization of design stages in CADmedia for increasing quality of PCB tracing // Molodezh i Sovremennye informatsionnye Tehnologii: Collected papers of the IV AllRussian theoretical and practical conference for students, postgraduate and young scientists. – Tomsk: TPU Press, 2006. – P. 72–75.Received on 06.06.2007

Problem-oriented approach to solving the problems of electronic equipment design in CAD

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