OptocouplerApplicationsDESIGNINGFOROPTOCOUPLERSWITHBASEPINOptocouplers(opticalcouplers)aredesignedtoisolateelectricaloutputfromforcompleteeliminationofnoise.Theyhavebeenusedconventionallyassubstitutesforrelaysandpulsetransers.Todayscurrenttechnologyintheareaofmicrocomputerscreatesnewapplicationsforoptocouplers.Thismanualdescribesthecharacteristicsoftypicaloptocouplers.Alsoincludedarenotesondesigningapplicationcircuitsfortypicaloptocouplers(withabasepin)forbettercomprehension.NECstypicaloptocouplerswithorwithoutbasepinsarelistedonthefollowingpages.CaliforniaEasternLaboratoriesABusinessPartnerofNECCompoundSemiconductorDevicesLtd.1AbsoluteMaximumRatingsElectricCharacteristics(TA=25C)(TA=25C)ProductnameFeaturesBVIF(mA)IC(mA)CTR(%)tr(s)tr(s)(Vr.m.s.)(TYP)(TYP)PS2601HighisolationPS2601LvoltageHighVCEO5k805080to60035PS2602(80VMIN.)PS2602LSingletransistorPS2603HighisolationPS2603LvoltageHighCTR5k80200200to2500100100PS2604Darlington-PS2604LtransistorPS2605HighisolationPS2605LvoltageA.C.5k805080to60035HighVCEOPS2606(80VMIN.)PS2606LSingletransistorPS2607HighisolationPS2607LvoltageA.C.5k80200200to3400100100HighCTRPS2608Darlington-PS2608LtransistorPS2621HighisolationPS2621LvoltageLarge5k1505020to5035PS2622currentPS2622LSingletransistorPS2625HighisolationPS2625LvoltageA.C.5k1505020to5035LargePS2626currentPS2626LSingletransistorPS2633HighisolationPS2633LvoltageHighVCEO1000to(300VMIN.)5k8015015000100100HighCTRPS2634Darlington-PS2634LtransitorPS2651HighisolationPS2651L2voltageHighVCEO5k805050to40035(80VMIN.)PS2652SingletransistorPS2652L2PS2653HighisolationPS2653L2voltageHighCTR5k80200200to3400100100Darlington-PS2654transistorsPS2654L2PS2600SeriesOptocouplers(6-PinDual-in-LinePackage)Internalconnection(withabasepin)Note:AproductnamefollowedbyletterLindicatesaproducthavingleadsedforsurfacemount.2Therearetwokindsofoptocouplers(alightemittingdiode(LED)asanandaphototransistorasanoutput)accordingtothetypeofoutputtransistor:SingletransistortypeandDarlington-transistortype.Thesingle-transistortypeoptocouplersareusedtoperhigh-speedswitching(withhigh-speedresponse).TheDarlington-transistortypeoptocouplersareusedtoobtainalargeoutputcurrentbyutilizingasmallcurrent(independentlyofswitchingspeeds).DesigningthecircuitsproperlywillimprovethePS2601optocoupler(SingleTransistortype)byhavingabasepinintermsofswitchingspeedeliminationofnoiseinsignalsandoutputleakagecurrent(collectordarkcurrentandapplicationtohigh-voltagecircuits).APPLICATIONSOFOPTOCOUPLERBASEPINSINCREASINGSWITCHINGSPEEDTheswitchingspeedofanoptocouplerwithabasepincanbeincreasedbyinsertingaresistorbetweenthebaseandtheemitterofitsphototransistorevenwhentheoptocouplerisappliedtoalargeloadresistance.GenerallythephototransistorofanoptocouplersuchasthePS2601hasalargephoto-sensitiveareaonit.Accordinglythejunctioncapacitance(CC-B)betweenthecollectorandthebaseofthephototransistorisgreat(upto20pF)andasaresultitsresponsespeed(turn-offtimetoff)islow.Therelationshipbetweenturn-offtimetoffandcollector-basecapacitanceCC-Bisexpressedby:toffCC-BxhFExRL.(1)wheretoff:Turn-offtime(SeeFig.2-2.)CC-B:Collector-basecapacitancehFE:D.C.currentamplificationfactorRL:LoadresistanceCc-BRLFigure2-1.Collector-BaseCapacitanceCC-BofPhototransistor3Asjudgedfromexpression(1)theturn-offtimetoffisaffectedbycollector-basecapacitanceCC-BD.C.currentamplificationfactorhFEandloadresistanceLR.InactualcircuitdesignCC-BandhFEarefixed.Accordinglytheturn-offtimeissignificantlyaffectedbytheresistanceofloadRL.Graph1showstherelationshipbetweenresponsespeed(tontoff)andloadresistance(RL)intypicalemitterfollower(testcircuit1)havingaloadresistanceof100.PW=100sDuty=110monitor()VCC=5VVoRL=10051IF=5mAPS2601monitorVoGraph1Up:0.2VDIVDOWN:Output0.5VDIV(50sDIV)TestCircuit190%90%10%10%50%OutputtontoffFigure2-2.tontoffMeasuringPoints4Graph2showstherelationshipbetweenresponsespeed(tontoff)andloadresistance(RL)inatypicalemitterfollower(Testcircuit2)havingagreaterloadresistance(5k).monitorVCC=5VVoRL=551IF=5mAPS2601TestCircuit2Graph2Up:0.2VDIVDOWN:Output2VDIV(50sDIV)AsshowninGraph2theturn-offtimeforloadresistanceof5kisabout100s.Similarlytheturn-offtimeforloadresistanceof100kis1to2ms.Thisisalsotruewhentheloadresistanceisconnectedtothecollectorofthephototransistor.Graph3showstherelationshipbetweenresponsespeed(tontoff)andloadresistance(RL)inatypicalcircuit(Testcircuit3)havingcollectorloadresistance(5k)withtheemittergrounded.monitorVCC=5VVoRL=551IF=5mAPS2601TestCircuit3monitorVoGraph3Up:0.2VDIVDOWN:Output2VDIV(50sDIV)monitorVo5monitorVCC=5VVoRL=551IF=5mAPS2601RBEInsertresistorof200khere.TestCircuit4(EmitterFollower)monitorVomonitorVCC=5VVoRL=551IF=5mAPS2601RBEInsertresistorof200khere.monitorVoToreducetheturn-offtimetoffofatestcircuithavingagreaterresistanceinsertaresistorRBEbetweentheemitterandthebaseofthephototransistor.SeeTestcircuit4andTestcircuit5.Graph4and5showtheirandoutputwaves.TestCircuit5(EmitterGrounded)Graph5Up:0.2VDIVDOWN:Output2VDIV(50sDIV)Graph4Up:0.2VDIVDOWN:Output2VDIV(50sDIV)6Theturn-of