TestingAnalogChips

2020-01-16 作者:bck体育app怎么下载 150
汽车拖把-许昌发易商贸有限公司

Theworldofanalogcomponentsisbroadanddiverse,andwhiletestinganalogchipsmaynottakeaslongasrunningtestsoncomplexSoCs,therearedifferentrequirementsforanalogdevices.

Onetypeofchipthat’sseeingmoreapplicationthesedaysisanalogmicroelectromechanicalsystemdevices.Automotiveelectronicscallforanumberofanalogchips,alongwithMEMS.

RistoPuhakka,presidentofVLSIResearch,estimatesthetotalanalogtestermarkettobeworthabout$100millionayear,largelyfortestinglinearchipsanddiscretedevices.“Thisiskindofaquiet,sleepysegment,”headds.“Thetestersliveforever.”

Incontrast,theSoCtestermarketismorethan$2billionayearinsales,andmixed-signalICtest,chieflyforradio-frequencyandwirelesschips,isalsolargerthananalogtest.

Xcerraisthemarketleaderforanalogtest,whileTeradyneleadsinmixed-signaltest,closelyfollowedbyAdvantest,accordingtoPuhakka.

Analogchipsenjoyedsalesgrowthof10.2%lastyear,accordingtoWSTS,whichseesthatgrowthmoderatingto6.1%in2018.

“Wehaven’tseenanythingsignificantlyhappeninginanalogtestforawhile,”Puhakkasays.High-powerdevicesforautomotiveapplicationsareagrowtharea.

DerekFloyd,directorofbusinessdevelopmentforAdvantest,saystherearediversetestrequirementsforanalog.Thoserequirementsincludeshrinkingsupplyvoltages,includingsavingenergyforbattery-powereddevicessuchasmobilePMICs,low-leakagemeasurementcapability,precisetrimmingandmeasurementscapability,andalow-noisetestenvironment.Therearealsohigh-voltage/high-currentdesigns,withthesystemcapabilitytoprovidethese—high-voltagesourcesandfloatinghigh-powersources.

bck体育app怎么下载“Precisemeasurementsrequireaveragingofmeasurementsamplestoremovenoise,oftenoverapowerlinecycle,50Hzor60Hz,”Floydsays.“High-currentdevicesrequirepulsetestingtopreventdevicesfromthermaldamageandheatup,whichcausesmeasurementdeviation.Testingadevicewith10Aofcurrentat10Vis100watts,whichwillcausethedevicetoheatuprapidly.Sothecurrentpulseisonlyappliedforamillisecondorso.Devicethresholdtestsrequirevoltage/currentrampgenerationcapabilityofthesystem.Binarysearchalgorithmsarealsousedastheycanbemuchfasterthanusingramps.”

Testinganalogvs.otherchipsAkeydifferenceisthattestinganalogreuiresmostlyparametrictestsreportingmeasurementresults.

“Digital-focuseddevicesmainlyreportpatternpass/failinformation,”saysFloyd.“Dependingonchipcomplexity,between3,000and8,000testresultsaremeasured,whichismoretestresultscomparedwithotherdevices.Butfewerdesign-for-testtechniquesareimplementedthanfordigital.ItisverycomplextoachieveDFTforanalogdesigns.ThereareseveralDFTmethodsaround,suchasusinganinternalA-to-Dconverterviaatestbusorusingloopback.However,itisoftenjustasfasttouseATEresourcesinparallelcomparedwithusingDFT.”

Manyanalogdevicesalsodependonadigitalstatemachine,basedonprotocolssuchasSPI,I2C,orJTAG,whichcontrolsthesignalroutingwithinthedevice.“Oncethesetuphasbeendone,theanalogmeasurementusuallyrequiressomewaittimestoaccountforsettlingcomponentssuchascapacitorsinordertomakerepeatableanalogparametricmeasurements,”hesays.“Thisleadstoamuchmorecomplex‘stop/start’testsequencecomparedwithdigitaltests,whichcanruncontinuously.”

Therearesomesimilaritiesbetweenanaloganddigitalchiptesting,aswell.Thereisasimilarproductionenvironment,includingtestingofmultipletemperatures—hot,coldandambient.Someverylow-costanalogdevicesaresample-testedatthewafer,aswell,andbecausetheprocessesaresomaturetheyieldtypicallyisveryhigh.Ontopofthat,finaltestisdonetoweedoutpotentialpackagingdefects.

“Wehaveseenstronggrowthintheanalogmarket,especiallydrivenbyautomotiveandpowermanagementdevices,henotes.“Themarketindicatescontinuinggrowthmovingforward.”

JoeyTun,principalmarketdevelopmentmanagerforSemiconductorTestatNationalInstruments,alsonotesthediversityandvarietyofanalogchips,rangingfromabasicopamptoanRFfront-endmodule.

“Thefundamentalreasononewouldtestachip,anychip,istoinsurethequality.MostICs,mostchipswillhavesomesortofaspecificationthatcomeswithitthatadesignerwouldusetointegrateintowhateverthatchipwillbedesignedinto,”hesays.“Fortheanalogchips,eventheoperationalamplifiers,theserequirementswillbeanaloginnature.Ratherthanasimplepass/fail,youmaybelookingatthingslikeinputbiascurrent.

“Themeasurementsareabroadercategorythanjustpass/fail.You’rehavingtoprovidesomequantitativedatabasedonwhatthespecificationonthechipis.”

Headds,“Whatisspecialaboutanalogtestatahighlevelisthattheparametersofanalogtestaregoingtobeinsomesortofanalogform,suchasthevoltagelevelandthecurrentlevel.That’sonthesimpleside.OnanRFpoweramplifier,youmayhavetomeasurethingslikenoisefloor,youmayhavetomeasurethingslikegain,youmayhavetomeasurethateverychannelpowerofthatparticularRFstandardonthatanalogchip.Thingscangetquiteabitmoresophisticated,moredifficultactually,asyougointotheseothertypesofanalogICs.Thediversityofthetypeofmeasurementisprettyhigh.Itreallydependsonwhatthechipis.Someofthemarenon-trivialtypesofmeasurements,thingslikemeasuringanoisefigureonanRFpoweramplifier.Thesearenoteasymeasurementsanymore.Yourequireprettyspecializedtestequipment.”

“Efficiencydoesmatter,”Tunsays.“AlotoftheICvendorsarealwaysfightingthecost,ortimepressures,fittingintoadesigncycle,fittingintoamarketwindow.Weareworkingwithalotofcustomersverycloselytohelpthemacceleratetheirtime-to-market.”

“Thereisalotofdevelopmentinopamps,”saysChristopherLemoine,productmarketingdirectorinXcerra’sATEgroup.“Therearealwayshigher-performanceopamps,lowerbiascurrents,gettingclosertotherails,younowhavezero-headroomopampswhereyoucanoperaterightdowntothegroundrail.Atthesametime,alotoftheperformancehasn’tchangedawholelot.”

BrianBogie,Xcerra’sseniordirectorofproductmarketingfortheXcerralineaimedatlower-pincountanalogandpowermanagementdevices,notesthatisoneaspectoftheanalogworldthatisverydifferentfromothertypesofdevices.“Oncethesepartsareinproductionoradoptedbyusers,theyhavearelativelygoodlongevityinthefieldcomparedwithmoreconsumer-orienteddigitaldevices,whichchangeyearly,orevenmorefrequentlythanthat.That’swhycustomersdemandareallylonglifetimeintheanalogworld.”

Lemoinenotes,“Thesearewhatwecallcatalogparts—signalconditioning,gluepartsthatarebringingtogetherdifferentpartsofthesystem.They’realittlebitmorestableintermsofthegenerationschangingsorapidly.Forus,wealsobucketdiscretesinanalog.Ifyougetdownintodiscretes,someoftheotherrequirementsareveryhighvoltages,soyouget1,000volts,veryhighcurrents,100ampsormoreofpulsedcurrent.Therearesomespecialrequirementsthatwehavespecializedinstrumentationtohandle.”

Analogcomponentscanrangefrommicrovoltstothousandsofvolts,andfrompicoampstohundredsofamperes,accordingtoBogie.Thekeyistoweedoutthenoisefromthesignal.

“Wehavespecialfront-endinstrumentationthatisairwiredtohandlepicoampcurrents,”Lemoinesays.“IfyoudoalaminatedPCB,theleakageofthePCBitselfwouldmasktheperformanceoftheopamp,sowehaveanairwiredfront-endinterface.That’sanimportantareatohavesomeflexibility,whereyoucanhaveareaforafamilyboardorforaninterfaceboardthatcanhandlesomeofthosespecializedrequirements,andthenputthatinfrontofyourmoregeneral-purposeinstrumentation.Yourgeneral-purposeinstrumentationbecomesmoreofanenginebehindthefront-endsignalprocessing.”

IncreasinginterestinMEMSdevices,particularlyforautomotiveandIoTapplications,isstartingtoboostdemandacrossthissector,aswell.

“We’restartingtoseesomehigh-demandproducts,like,analogMEMSdrivingdemandforvery-high-parallelsolutions,”Lemoinesays.“That’swhat’sdrivingsomeofthesepartsontotheDiamondx.TheDiamondxplatformisreallyanSoCplatform.We’veintroducedafive-slotversionofDiamondxthatwhereithelpsusscaledowntosomeofthelower-pincountsrequiredforthesedeviceswhereyoudon’thavetohaveabigsystem,youcanhaveareallysmallsystem,butitstillhassomeofthehigherperformancecapabilitiesrequiredforMEMStesting.”

Analogpartsoftenhaveshortertesttimesthanmorecomplicateddevices,butthereisawidevarietyofanalogcomponentsandtesttimescanvarywidely.Analogtestingusuallydoesn’tallowforthetestpatternsthatelectronicdesignautomationtoolscangeneratefordigitallogic,usingsimulationoutputs.ButhandcraftedanalogdevicessometimesneedhandcraftedDFTtechnology.

“ItsoundslikeanalogisinsomewayssimplerthanSoCordigital,butatthesametime,you’rereallyclosertotheintrinsictransistorperformance,”saysLemoine.Becauseit’sapureanalogpart,andsometimesit’sasingletransistorthatyou’redealingwith,you’rereallygettingbacktobasics,fundamentalsasin,‘Howdoesthistransistorwork’Youhavemorevisibilityintotheprocessvariation.”

ConclusionAnalogdevicesareadifferentsemiconductorspeciesthanthemicroprocessors,microcontrollers,applicationprocessors,memories,andothercommonchipsthatmostpeoplearefamiliarwith.Thesedevicescandealwithverylowvoltagesandveryhighvoltages,includingvoltagesthatwouldfrymostotherchips.

Thephysicalworldisanalog,andbeingabletosensethatworldrequiresanalogtechnology.Butitalsorequiresspecializedequipmenttotestthosedevices,andthatisn’tgoingtochangeanytimeintheforeseeablefuture.