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1.3.1RelatedDocumentationfromTexasInstruments
2PCBDesignandPerformance
2.1PCBLayout
PCBDesignandPerformance
ThefollowingdocumentsprovideinformationregardingTexasInstrumentintegratedcircuitsusedinthe
assemblyoftheDAC8555EVM.ThelatestrevisionsofthesedocumentsareavailablefromtheTIwebsite
athttp://www.ti.com.
DataSheetLiteratureNumber
DAC8555SLAS475
REF02SBVS003
OPA627SBOS165
OPA2132SBOS054
ThissectiondiscussesthelayoutdesignoftheDAC8555EVMPCB,describingthephysicaland
mechanicalcharacteristicsoftheEVMaswellasabriefdescriptionofthedemonstrationboardtest
performanceproceduresperformed.Thelistofcomponentsusedinthisevaluationmoduleisalso
included.
TheDAC8555EVMisdesignedtopreservetheperformancequalityoftheDAC8555,thedeviceunder
test(DUT),asspecifiedinthedatasheet.InordertotakefulladvantageoftheEVMcapabilities,usecare
duringtheschematicdesignphasetoproperlyselecttherightcomponentsandtobuildthecircuit
correctly.Thecircuitdesignshouldincludeadequatebypassing,identifyingandmanagingtheanalogand
digitalsignals,andunderstandingthecomponents'electricalandmechanicalattributes.
Theprimarydesignconcernsduringthelayoutprocessareoptimalcomponentplacementandproper
signalrouting.Placethebypasscapacitorsascloseaspossibletothedevicepins,andproperlyseparate
theanaloganddigitalsignalsfromeachother.Inthelayoutprocess,carefullyconsidertheplacementof
thepowerandgroundplanes.Asolidplaneisideal,butbecauseofitsgreatercost,asplitplanecan
sometimesbeusedsatisfactorily.Whenconsideringasplitplanedesign,analyzethecomponent
placementandcarefullysplittheboardintoitsanaloganddigitalsectionsstartingfromtheDUT.The
groundplaneplaysanimportantroleincontrollingthenoiseandothereffectsthatotherwisecontributeto
theerroroftheDACoutput.Toensurethatthereturncurrentsarehandledproperly,routetheappropriate
signalsonlyintheirrespectivesections,meaningthattheanalogtracesshouldonlylaydirectlyaboveor
belowtheanalogsectionandthedigitaltracesinthedigitalsection.Minimizetracelength,butusethe
largestpossibletracewidthallowablewithinthedesign.ThesedesignpracticesareillustratedinFigure2
throughFigure8.
TheDAC8555EVMboardisconstructedonafour-layerPCBusingacopper-cladFR-4laminatematerial.
ThePCBhasadimensionof43,1800mm(1.7000in)by82,5500mm(3.2500in),andtheboardthicknessis
1,5748mm(0.062in).Figure3throughFigure7showtheindividualartworklayers.
Note:Boardlayoutsarenottoscale.Theseareintendedtoshowhowtheboardislaidout;they
arenotintendedtobeusedformanufacturingDAC8555EVMPCBs.
6DAC8555EVMUser'sGuideSLAU204–December2006
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