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EAGLECAD TUTORIAL ECE 445 University of Illinois at Urbana Champaign Department of Electrical and Computer Engineering Instructions This documentation includes explanations of EagleCAD functions/features and ECE 445- specific pointers for both the Eagle assignment and the PCB required for each Senior Design project. This is meant to be supplementary material to a step-by-step guide, like the one linked in the assignment. Appendix A has Eagle’s layer definitions and Appendix B includes PCB layout guidelines. Overview Schematics are the core of all electrical engineering. They represent a universal list of symbols and notations that can be followed by anyone in order to present some sort of circuitry. In fact, one can even think of some as a sort of language that is used to communicate our electrical ideas. Just like a language, we can present an idea in a clear and specific manner, or we can obfuscate it through a dense and complex layout of thoughts. The goal of this tutorial is to help you learn tips and methods to be in the former camp. While schematics are nice from an analytical standpoint, real circuits don’t often follow the same shapes or layout. As you have most likely seen in previous classes, even trying to prototype on a breadboard often has one moving parts around in order to get the proper connections. In this class, you are going to learn how to translate designs from schematics to a realizable printed circuit board, or PCB. EagleCAD is one of many available Electronic Design Automation (EDA) software packages. It allows us to easily design and transition between schematics and circuit layout. EagleCAD has a large amount of popularity with hobbyists, and due to the nature of the projects in this course, you will most likely find that to be of use. You can download the freeware version of EagleCAD here: http://www.cadsoftusa.com/download-eagle/. The lab computers have the full professional versions installed. WARNING: DIFFERENT EAGLE VERSIONS MAY NOT BE COMPATIBLE. This applies both forward and backward. We advise sticking to one version for the entire semester.

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Page 1: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

EAGLECAD TUTORIAL ECE445

UniversityofIllinoisatUrbanaChampaignDepartmentofElectricalandComputerEngineering

Instructions ThisdocumentationincludesexplanationsofEagleCADfunctions/featuresandECE445-specificpointersforboththeEagleassignmentandthePCBrequiredforeachSeniorDesignproject.Thisismeanttobesupplementarymaterialtoastep-by-stepguide,liketheonelinkedintheassignment.

AppendixAhasEagle’slayerdefinitionsandAppendixBincludesPCBlayoutguidelines.

Overview Schematicsarethecoreofallelectricalengineering.Theyrepresentauniversallistofsymbolsandnotationsthatcanbefollowedbyanyoneinordertopresentsomesortofcircuitry.Infact,onecaneventhinkofsomeasasortoflanguagethatisusedtocommunicateourelectricalideas.Justlikealanguage,wecanpresentanideainaclearandspecificmanner,orwecanobfuscateitthroughadenseandcomplexlayoutofthoughts.Thegoalofthistutorialistohelpyoulearntipsandmethodstobeintheformercamp.

Whileschematicsarenicefromananalyticalstandpoint,realcircuitsdon’toftenfollowthesameshapesorlayout.Asyouhavemostlikelyseeninpreviousclasses,eventryingtoprototypeonabreadboardoftenhasonemovingpartsaroundinordertogettheproperconnections.Inthisclass,youaregoingtolearnhowtotranslatedesignsfromschematicstoarealizableprintedcircuitboard,orPCB.

EagleCADisoneofmanyavailableElectronicDesignAutomation(EDA)softwarepackages.Itallowsustoeasilydesignandtransitionbetweenschematicsandcircuitlayout.EagleCADhasalargeamountofpopularitywithhobbyists,andduetothenatureoftheprojectsinthiscourse,youwillmostlikelyfindthattobeofuse.YoucandownloadthefreewareversionofEagleCADhere:http://www.cadsoftusa.com/download-eagle/.Thelabcomputershavethefullprofessionalversionsinstalled.WARNING:DIFFERENTEAGLEVERSIONSMAYNOTBECOMPATIBLE.Thisappliesbothforwardandbackward.Weadvisestickingtooneversionfortheentiresemester.

Page 2: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Schematic Capture Let’sstartwithsomeofthefeaturesofEagle’sschematiccapturetool.Whenyouopen

EagleCAD,theProjectViewerscreenpopsup,andyoucancreateanewprojectbygoingtoFile->New->Project.Nameitwhateveryoulike,butmakesurethegreendotisvisiblenexttotheproject–thisindicatesitistheactiveproject.

Rightclickontheproject,andselectNew->Schematic.Thisshouldpopup:

Whileallthebuttonsavailableonthelefthavesomeusecase,we’llreallyonlybeusingafewofthemfor90%ofthework.Thenextpictureshowswhatfunctionsthesebuttonscommand.

Page 3: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

AddingComponents:Presstheaddpartwindow,andyou’llseealistoflibrariesappear.

Theselibrariesaresuppliedfromavarietyofsources:CadSoft(thecreatorsofEagleCAD),numeroussemiconductorcompanies,andevenjustregularhobbyists.Sincethefiles

Movecomponentsontheschematicaround

Changethenameofacomponent

Drawwiresontheschematic

Labelwiresandotherconnections

Junctiontool-joinintersectionsofwires

Addacomponenttotheschematic

Changethevalueofacomponent

Page 4: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

areverysimpletogeneratefornewcomponents(justsimpleSVGdrawings),youcanfindalibraryfornearlyanypart.Thedownsideisthattheorganizationleavesabittobedesired,butluckilythesearchfeatureissimpleenoughtouse.Fornow,we’llstartoffusingstandardlibraries.

Scrolldowntothelibrarycalledrcl–thisisyourstandardpassiveslibrary.Itcontainssymbols/footprintsforthebasicresistor,capacitor,andinductorparts.Openingitup,it’llhaveseveralsubfolders.SincethisisAmerica,openupR-US.Everythingcontainedinthatsublistisaresistor,butwithadifferentpackage.

Youcantellapartis“through-hole”bylookingatthePCBsymbol.Ifithasgreencircles,it’sathrough-holepartasthoseindicateviasinEagleCAD.Ifithasredsquaresinstead(bottomhalfoflist),thoserepresentpads,soitisasurfacemountpart.

Toaddapart,double-clickanddropitanywhereontheschematic.Tokeepaddingcopiesofit,continueclickingontheschematic.To“letgo,”justclicktheMovetool.UsingMove,left-clicktoselecttheparttomoveandright-clicktorotateparts.

ConnectingComponents:UsetheLineTooltodrawawire(or“net”)betweenthecomponents.Don’tforgettoaddaground,orreferencenode,toeveryschematic.Youcanfindthegroundsymbolunderthesupply1orsupply2libraries.Ifyoulook,you’llseethatgrounddoesn’thaveaboardview–whichmakessense,groundisanelectricalreferencevoltage,notatangible,physicalthing.

SchematicSymbol

PCBSymbol

Page 5: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

UsetheNameTooltogiveyournetsanappropriatename:V_REG,V_OUT,VDD_5V,etc.You’llnoticethatdoesn’treallydoanythingbydefault,weneedtoalsoshowthelabelaswell.UsetheLabelToolandclickontheconnection,thenplacethelabelsomewherenearby.Youcanchangethestyleofyourlabelviathebuttonsonthetopbar,shownbelowwhereI’vechosenbothlabelingstyles.

Creating a New Part SincetheclassassignmentusestheTPS799voltageregulator,thisistheexamplewewill

coverindetail.Youcansearchinthelibraries,butit’snotthere(partdeliberatelychosenthisway).Youcanfindthedatasheethere:http://www.ti.com/lit/ds/symlink/tps799.pdf.Forthesimplicityoftheassignment,we’regoingtousethe“FixedVoltageVersion”onthebottomofthefirstpage.NowthefirstthingtodoistocreateanewlibraryinEagleforthispart.Gototheprojectmanagerwindow,selectyourproject,andrightclickNew->Library.

LabelStyleChanger

Page 6: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

NowisagoodtimetotalkabouthowEagleCADstoresparts.Likeyousawwhenaddingparts,componentsgenerallyhavebothaschematicandboardview.Theschematic,orsymbolview,istheagreeduponelectricalsymbol,andtheboard,orpackageview,isthephysicallayout.Someitems–suchassupplylines(e.g.+5V,GND,VSS)–onlyhaveasymbolview,whereitemslikevias,traces,andwellsonlyhaveaboardview.Whencreatinganewcomponent,wegeneratethesymbolandpackageviewsasynchronously,thencombinethemtogetherwithadeviceview.NotethatEagleCADisnotasimulationsoftwareofanykind,wecancallapartaresistorandgiveitthreeinputsandoneoutput,oracapacitorwithonlyonepin.EagleCADdoesn’tcareaboutwhatthepartiselectricallydoing,onlyphysically.

Let’sstartwithmakinganewsymbol.Inthepop-up,giveyourpartaname,presumablysomethingalongthelinesof“TPS799”.PressSymtoverifywe’recreatingasymbol,thencreateit.

Left:NewDeviceCenter:NewPackageRight:NewSymbol

Page 7: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Wenowhavethesymboleditorviewopen.Beginbyaddinginsomepins.Formostschematics,peoplefindlefttorighttheeasiesttoread(likeabook),sowe’llputthegroundpinonthesideratherthanthebottom.Add5pinsusingtheAddPinTool,thenrenamethemusingtheNameTool.ThegreencircleonthepinistheI/Opoint,sowe’llwantthosefacingoutwards.Again,wetendtoputinputsontheleftandoutputsontheright.Thismakesforalogicalreadingaswedecipheraschematic.

AddPin

DrawLine

ChangeName

Name

AddPin

Line

Page 8: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

FinishupwiththeLineTooltoboxitoff.Trytocenterthepartasmuchaspossibletomakeyourlifeeasierwhenaddingitandmovingitaround.Savethesymbol(aswellasthelibraryifyouhaven’talready).

Nowwe’llhandlethepackage.Thereareseveralwaystodothis,butwe’lldoitthemostmanualwayfornow,justincaseweevergetanewpartthat’snotinEagleatall.Theparthasseveraldifferentpackages,butwe’llusethebiggestoneinthiscase,sinceifweweretoactuallycreatetheboard,itwouldbetheeasiesttouse.Packagescomeinmanydifferenttypesandnames,oftenredundantlysoasyou’llfindout.We’llbeusingtheDDCpackage,alsoknownasPlasticSmallOutline.Whiletheygivemanyviews,we’remostinterestedinthefootprint–thisishowmuchspaceweshouldleaveontheboardfortheparttositin.Dimensionsshownbelowinmillimeters(fromthedatasheet).

Let’sHitNewPackage,PAC,andnameit“TPS799”orsomethingsimilar.Thefollowingwindowshouldopen.Onceagain,verysimilartowhatwehaveseenbefore,butwithtwocriticalnewoptions.TheAddViaToolallowsustoaddaholetothefootprintthatisusedforleadsorpins.TheAddPadToolallowsustoaddapadforanysurfacemountpart.Lastly,we’ll

Page 9: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

needtousetheGridTooltomakesurethattheminimumgridspacinglinesupwiththesmallestsignificantfigurewehave–here0.05mm.

Isuggestusinga0.5mmgrid,witha0.05mmaltsetting.Addapad,andplaceitrelativelynearthecenter.Rightclickonit,Properties,andchangeSmdSizeto“1.1x0.6”.Thisautomaticallysizesthepadtothecorrectdimensions–ifit’soffby90degrees,rotateit.NowusetheRulertogoandmeasureouttheappropriatedistanceforthenextpad.RemembertoholdALTasyoudoso–otherwisewe’llbeonthemaingriddimension,notthefinerone.I’veattachedapictureofwhattheoutputshouldlikebelow.Oncethatisdone,copyandpastethepreviouspadandplaceitalongthesameline.

AddVia

GridEdit

AddPad

Ruler

Page 10: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Nowthisisclearlygoingtogetprettypainfulifwewanttodothisforeverypad.Fortunatelyforus,wecangetaroundthiswithalittlemath.Deletetherulerdrawingfornow,wewon’tneedit.Addanothernewpadviacopypaste,justputtingitanywhere.Rightclick,selectPropertiesonthefirstpad,andnoteitsPosition.Nowdothesametothenewlyaddedpad,butjustmoveittotheappropriatepoint–either0.95mmup,or2.7mmout.Absolutepositiondoesn’tmeananythinghere–onlyrelative.Oncethat’sdone,gobackandnamethepads!Anypatternworks:[12345],[TopLeft,MidLeft,BotLeft,TopRight,BotRight],[NWWSWSENE],aslongasyoucantellwhichiswhich.Finalimageshouldlooklikesomethingbelow.Don’tforgettoverifyyourlayoutwitharuler–neverhurtstodouble-check.

Saveit,thengobacktothetopandopenaNewDevice.Onceagain,let’scallitTPS799.Thefollowingwindowwillshowup.Thisshouldbetheeasiestoftheprevioussteps–allwedoisconnectthedots!ThebuttonhighlightedontheleftshowstheAddSymbolTool,andthehighlightednewbuttonistheAddPackageTool.Thereshouldonlybeoneofeachinthislibrary,goaheadandaddtheschematicandpackagewecreated.

Page 11: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

NowhitConnect,andlet’sconnectthedots(pardonthepun).Youcanfindtheorderinthedatasheet,generallyunderasectioncalled“PinMapping”or“PinConfiguration”.Gothrough,selecttheappropriatePinNameandPadName,andthenhitConnect.Proceedforallfiveoptions,andyoushouldendupwithaconfigurationshownbelow.

Finishitoffandwe’re(almost)goodtogo!Beforewefinishthis,let’sgoaheadandlearnonemorewayofdoingthis.Thelargemajorityofpartsyou’llbemakingwillprobablybeIC’s.NearlyallIC’scomeincommonpackages,sothere’snosenseinre-inventingthewheelwhenitcomestodrawingpackages.EagleCADstoresallitsreferenceICfootprintsinref-packages.lbr,orifyouaren’tcomfortablewithyoursolderingskills,ref-packages-longpad.lbr.Theonlydifferenceisthelongpadvarianthas,nosurprise,largerpadsinordertogivemoresolderingarea.

ThetrickypartaboutthisisthatyouhavetoknowthatmanyICfootprintsaretheexactsamephysically,buttheyhaveplentyofnamevariants.Forexample,thepartwehavehereisgiventousasDDCorR-PDSO-G5,butisfoundinref-packagesasSOT23-5L.Whileyouhaveyouroldlibraryopen,gobacktotheprojectviewer.GotoLibraries->ref-packages-longpad.lbr->SOT23-5L.Rightclick,CopytoLibrary.Thiswillcopyaversionofthefootprinttoyourlibrary,sowhenyougotomakeanewsymbol,youcanseeyounowhavetwofootprintstochoosefrom–theonewedesigned,andtheonegiventous.

Page 12: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Thechoiceisyoursonwhichmethodtouse.Bothhavetheirprosandcons,andunfortunatelyunlessyougetluckywiththefootprint,takealittletime.Regardless,nowthatwehaveourpartcreated,it’stimetoaddittotheschematicandmoveontothePCBlayout.

Toaddthenewlymadeparttoyourschematic,gotothetoptoolbarandhitLibrary->Use.Thelibraryyoujustcreatedshouldbeinthedefaultfolder,openitandthepartsinitwillbeavailabletous.Additinandwireitup.Don’tforgettofinishthefullvoltageregulatorschematicfortheassignment,includingthepassivecomponentsrequiredfortheTPS799towork.Seethescreenshotfromthedatasheetbelow:

Onelastimportantnoteisthegreen“junction”dotswhenwirescross.ThesearedonewiththeJunctionTool,labeledinourbuttonsfigureatthebeginning.WheneverwecrosswiresinEagleCAD,bydefaulttheseareNOTconnected.Weneedtoaddthegreendottoensuretheyareindeedtouching.It’sanicevisualaid,aswellasawaytoconfirmthatwedointendtoconnectwireswhenwecrossthem.WecancheckforthisandothersmallproblemswiththeERCTool,ElectricalRuleCheck.It’sthebottomleftmostbutton,pressitandseewhaterrorsyouget.Feelfreetoignoreanyirrelevantonesanddealwiththeimportantones.

Page 13: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Making the PCB PCBdesignisjustabigpuzzle.Allwetrytodoismatchourschematicbyconnectingthepadsandvias,withageneralgoalofminimizingarea.Eachboardconsistsofseverallayersto“route”(orconnect)on,seeAppendixA.ThefreeversionofEagleallowsyoutousetwolayers,thepaidversionontheEWSmachinesallowsfour.

ThefirststepistoswitchfromschematicviewtoPCBview.Pressthehighlightedbuttoninthetoolbartocreatetheboardview.You’llbepresentedwiththescreenbelow.WhatEagleCADhasdoneissavethenetlist(ornodelist)fromtheschematic,andconnectedallthepartsthatneedtobeconnectedwithyellowwires.Thewhitesquareistheworkarea,soitcanbeanarbitrarysize.TodefinetheactualsizeofthePCB,drawintheborderwithtraceswidth=0ontheDimensionlayer.

Beginbymovingsomeofthepartsintotheworkarea.TheRouteTool iswhatweusetomaketheseconnections.Whenyouselectit,you’llseeoneofthetoolbarsshowamenu

likeso .Thedropdownbarchooseswhatlayerwerouteon,andadditionally,eachlayeriscolorcodedsoyoucanalwaysvisuallyconfirmaswell.

Youcanonlyroutebetweennodes,sopickanypartwithayellowlineandbegin.Whenyouclickonepad/via,thenodesisneedstoconnecttolightup.Agreenviarepresentsaholethatgoesallthewaythroughtheboard,soyoucanconnectonanylayer.Aredorbluepadiscreatedonlyonitscorrespondingside,soyouwillneedtodrawontheappropriateside.Theselineswedrawrepresentcoppertraces,whichisaconductivematerial.Thereforeifyouoverlaptheselines,oraccidentallyoverlapalinewithapad/viathatyou’renotsupposedto,you’llbecreatinganelectricalshort.Watchoutforthat,andonlyconnectwhat’ssupposedto!

Continueaddingpartsonandconnectingthem.Everyonceinawhile,hittheRatsnet

Tool .Thistoolredrawstheyellowelectricallinestotheshortestconfigurationpossible.

Page 14: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Belowyou’llseeapartiallayoutwhereaviaisrequired.Theproblemhereismyclosestconnectionisonthebottom,butmypadisonthetop.

Forthiscase,IwouldstartoffRouteToolonthetopside,selectingthepad.WhenIgettoanotcrowdedspot,withtheRouteToolstillselected,changethedropdownmenufrom“Top”to“Bottom”andfinishthetrace.Seethatsmallgreensquareinthemiddle?EagleCADautomaticallyplacedaviaformetoshort+connectmytwotraces.

Howwideshouldonemakethesetraces?Whereshouldtheywindupgoing?Thefirstruleofthumbisdrawwhatyoucanmanufacture.IfusingtheECEshop,youshouldimporttheirDRCrulesandusetheirmin-spacing/width/etcguidelines,bothfoundhere:http://eshop.ece.illinois.edu/pcbdesign/designreq/designreq.php

Problemconnection

…Someotherstuff

Page 15: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Afteryou’vemettheserequirements,thenyoucanreferencesomeoftherecommendedpracticeinAppendixB.

Let’sgetintoabitmoredetailaboutsomeoftheothertoolsinEagleCAD.Forone,you

can’tdeletetraces,youripthemusingtheRip-UpTool .Youcandeletepartsandholesandotheraddedcomponents,butnottraces.

MakingPlanes:Eaglealsoallowsustouseshapes/planesonourPCB.NodeslikeGNDandVDD(power)arebestdrawnasplanes,formanyreasons.Ifyou’recurious,checkwithyourTA.

Todothis,makeabox(usuallyjustinsidethePCBedge)usingtheShapeTool .Don’toverlapendpointandstartpoint,youmightgetsomeuglyerrorsifyoudo,justconnecttheendrighttothestart.Youshouldhaveanicedottedboxaroundyourcircuitlikeso.

NowusetheNameTooltonamethebox.Thenameisgoingtobewhateversignalyouwanttofillthatareawith,soyouhavetochooseanetnamethatyouassignedintheschematicview.HitRatsNesttoseetheoutcome.Alargemajorityoftheboardshouldbecomeentirelyred(iftopside)orblue(bottomside.Rightclickonthebox(theoutline,notthefilledinarea),andselectProperties,thenunderPolygon,changeIsolate.Thisistheparameterthatdetermineshowmuchseparationexistsbetweenthefillandtheothersignalsonthatlevel.Becarefulaboutmakingittoosmall,asyou’llfindithardertosolderto,aswellasincreasingtheriskofcouplingsignalstogether.Adecentvalueis50mil.

Almostdone!JustlikeintheschematichowwehadtheElectricalRuleCheck,herewe

havetheDesignRuleCheck .WhiletheERClooksourcircuitoverandseesifwehaveanythingwiredoddly,theDRCnotonlytellsusifwelaidoutanythingstrangely,italsowarnsusifwedidanythingthatisn’tpossibletobemanufactured.WhileEaglemayallowyoutoplacepartsapartwithnanometer,goodlucktryingtofindsomeonewhowillactuallymakethat!Mostservices,likeourECEshop,offeradesignrulelistingsoyoucangoinandfindoutexactlyhowwidetomakeyourtraces,orhowfaraparttospreadyourparts.Followthelinkearlierinthissectiontodownloadtheshop’sDRCrules.

PCBborder(definedonDimensionslayer)

Yourcircuit’s

PCBlayout

Page 16: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Thelasttoolwehaven’treallytalkedaboutistheAutoRouter .Thisisforgoodreason–ittendstosuck.PCBlayout,andEDAingeneral,isahugeunsolvedproblemintermsofautomation.Whilewithdigitalsolutionsthereisenoughreductionthattheproblemismoremanageable,analoglayoutisstillabitofanartthathasn’tbeencompletelymastered.TheAutoRouterwillmostlikelyfindasolution,butit’sfarfromoptimalmostofthetime.

Creating Gerbers Whilenotrequiredfortheassignment,it’sgoodtolearnhowtogofromtheEagleCADboardfiletogerberfiles.Thegerberformatisabinaryvectorimagefiletypethatisthecommonmediumformanufacturers.Plentyoffreeandonlinegerberviewersexistifyouwishtoviewwhatisactuallybeingoutputted,butiteffectivelyjustslicesthePCBlayerbylayerandlistseachxbyypointasaregion.

SelecttheCAMProcessor(highlightedabove)togetstarted.SelectFile,Open,Jobandselectgerber274x.Thewindowshouldpopulatewithseveraltabs,eachrepresentinganewoutputfile.Eachoutputfileisanew“slice”oftheboard.PressingProcessJobatthebottomwillcreateallofthesefilesinthesamedirectoryasyourproject.

Whyaretheresomanyfilesforatwolayerboard?Wellyoucanseewhateach“slice”actuallyisinthelayertabontheright.Wehaveourtopandbottomsolder,aswellassoldermask,silkscreen,andadrillfiletonotatealltheholesintheboard.Fancierboardsrequireevenmorelayers,withitemslikegluepointsandsolderstoppoints.

Page 17: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Appendix A

EAGLECAD LAYER REFERENCE

ECE445UniversityofIllinoisatUrbanaChampaign

DepartmentofElectricalandComputerEngineering

Manylayersareprefixedwithat<X>forTop<X>orb<X>forBottom<X>.Thelayer

LayerNumber(s)

Name Purpose

1-16 Top->Bottom

ThewireroutingmetallayersforthePCB.Alsocalled“traces”ontheboard.Fortwolayerboards,onlyusetheTop(red)andBottom(blue)layerstodrawconnections.Alsoshowsthesurfacemountpadsforrespectivesides.

17 Pads Somewhatconfusingly,EagleCADdefinespadsaseverythrough-holeconnectionofapart.Whileweoftencallthisa“via”,thosehaveaseparatedefinition.

18 Vias Whenatracefromlayers1to16switchestoanotherlayer(ie,from[1]Topto[16]Bottom),agreenviaiscreatedtoverticallyshorttheselayers.Bydefault,thisisafullboard(toptobottom)short.Whileitispossibletodoblindvias(shortonly[3]to[5],forexample),thecostisextremelyprohibitive.

19 Unrouted Thisistheairwirelayerthatshowsallthe“birds-eyeconnections”foralltheparts.AfinishedPCBdesignshouldhavenothingonthislayer.TheRatsnestbuttonwilltellyouhowmanyconnectionsareleft.

20 Dimension Thissetsthephysicalsizeoftheboard.Anythingoutsideofthisshape(usuallyrectangular,butcanbeanything)willnotbemanufactured.

Page 18: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

21-22 Place Thisisadecorativelayerforshowingpartsphysicalprofiles.Thislayerisdrawnwithsilkscreenandisgenerallyusedtomakesurepartsdonotphysicallyoverlap.

23-24 Origins Theoriginisthesmallcross(+)signifyingthecenterofthepart.Thisismostlyusedtohelptheuserselectparttheyintendtointhedesignphase,andisrarelymanufactured.

25-26 Name Self-explanatory.Canbemovedwiththe“Smash”tool.27-28 Value Self-explanatory.Canbemovedwiththe“Smash”tool.29-30 Stop Forserviceshopboards,thislayerdoesnothing.Butwhen

makingaboardataprofessionalmanufacturer,theentireboardiscoveredinsoldermaskbydefault.Thislayerspecificsthesoldermaskfreesections(soldermaskSTOP),andeffectivelyshowsthefreetosoldertoareas.Thisisingeneralslightlylargerthanthepadorviaitself.

31-32 Cream Forserviceshopboards,thislayerdoesnothing.Ifyou’remakingastencilfortheboard,thislayerdefinesthestenciloutline.Thisshouldbethesameasallthetopandbottompads.

33-34 Finish Forserviceshopboards,thislayerdoesnothing.Forhighqualityboards,thissetstheplatingandfinishused.

35-36 Glue Forserviceshopboards,thislayerdoesnothing.Whenusingadvancedsurfacemountsolderingtechniques,suchaswavesoldering,manufacturersoftenspecifyplacinggluetokeepsomepartsinplaceduringtheextremeheatstress.Thisisgenerallyplacedinthecenterofparts.

37-38 Test Forserviceshopboards,thislayerdoesnothing.Thisisforestablishingautomatedtestingpoints.

39-40 Keepout Thislayerisusedwithpolygons.Ifpartsareplacedwithinthisshape,theDRCwillthrowerrors.

41-43 Restrict Thislayerisusedwithpolygons.Iftracesareplacedwithinthisshape,theDRCwillthrowerrors.

44 Drills Thislayershowsallconducting(plated)holesintheboard.45 Holes Thislayershowsallnon-conductingholesintheboard.

Generallyformechanicalformounting.

Page 19: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

Appendix B

GUIDELINES FOR LAYOUT ECE445

UniversityofIllinoisatUrbanaChampaignDepartmentofElectricalandComputerEngineering

1. FOLLOWTHEPCBSHOP’sRULES:http://eshop.ece.illinois.edu/pcbdesign/designreq/designreq.php

2. Figureoutifyoursignalishigh-speed.Agoodruleofthumbisdescribedbelow:a. FigureouttheTriseofyourfastestsignal(usuallyaclock)b. CalculatetheTdelayofthatsignal–distancetraveleddividedbyvelocity(velocitywill

dependonyourdielectricmaterial-aninternetsearchwillusuallyturnupcommoneffectivedielectricconstants,!!.YoucanapproximateFR-4tobe4.7,althoughthisvarieswithfrequency.Velocity= !!!

,c=speedoflight)

c. RatioofTrise/Tdelay>6:yourcircuitswillbehaveasexpectedfromyourschematic(i.e.wirescanbetreatedasshorts).Goto#10.

d. RatioofTrise/Tdelay<2.5:youwillneedtothinkofyourwireasatransmissionline,goto#3.

e. Ifyourratioissomewhereinbetween,youshoulddiscusswithyourTA.Tobesafeyoucouldstillabidebythepracticesforhigh-speedlayouts.

3. Youwouldwanttocontrolimpedance,usuallyto50ohmifsingle-ended.YoucoulddothisbyfiguringoutthethicknessofthePCBdielectricanditsmaterial,andthenusinganonlinecalculatorfordeterminingthewidthofyourtrace.TalktothePCBshoptoletthemknowyouneedcontrolledimpedance-anyGNDallaroundthetracewillmatter.

4. IdeallyyouwantsolidGNDplaneunderneaththeentirelengthofthetracefromtransmittertoreceiver.

5. Giveyourselfplentyofseparationbetweenthetraces(especiallyifyouhaveothernoise-sensitivecircuits).Acoupleofmmminimum,greaterspacewherepossible.

6. Avoidchangingmaterialsbetweentransmitterandreceiver(trytostayononePCB,trynottosolderwiresin-betweenorgothroughaconnector).

Page 20: EAGLECAD TUTORIAL - University Of Illinois...Schematic Capture Let’s start with some of the features of Eagle’s schematic capture tool. When you open EagleCAD, the Project Viewer

7. Avoidviatransitionswherepossible.Ifyouhavetodivebetweenlayersmakesurethereturnpathhasawaytofollowthesignal.

8. Terminateyourlines-usuallyaseriesresistorclosetothetransmitterisused.TalktoyourTAaboutthepropervalueinyourapplication.

9. Designyourpowerdeliveryverycarefully-youneedplentyofbulkandhighfrequency(usuallysmaller-value)capacitorsinparallelfordecoupling.TheseneedtobeclosetoVDDpinsonyourchipsspewingouthigh-speedsignals.

10. Fornoise-sensitivecircuits(analogaudio,senselines,anythingextremelylowvoltageorhighimpedance,etc),grouptheseasfaraspossibleawayfromdigitallogicwithhighclockrates.

11. ConsiderisolatedGNDplanesifyouhaveananalogportionandadigitalportion.Trueelectricalisolationcanbedonewithoptocouplersandtransformers,butasimplersolutionisaGNDmoat,wherethequieteranalogGNDisacopperislandenclosedbya“moat”ofno-fill,separatingitfromthesurrounddigitalGND.Theseareconnectedatonepointonly,topreventtoomuchDCvoltagedrift.Allanalogsignals(ontheirlayeraboveorbelowtheplane)arereferencedtotheanalogGNDandviceversafordigitalsignals-nosignalscrossoverthemoat.TalktoyourTAabouttheimplementation.

12. Considerusingseparatepowersourcesforthesensitivecircuits-anLDOisagoodoption.

13. Ifyouhaveapartthat’sinasmallordifficulttosolderpackage,tryusingasocketormakingabreakoutboardtosolderintoyourmainboard.Thisway,ifyoumessupsolderingthesmallconnections,youwon’tbreakyourmainboard.

14. Ifyouhavetheroom,considermakingpowerplanes.CreateshapesjustlikefortheGNDplane,butthistime,namethemyourVDDnetnames.EachVDDwithsubstantialcurrentconsumption(DCortransient)shouldideallyhaveitsownplane,withplentyofbulkdecouplingattheoutputofitsownregulator.


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