Product Order Technical Tools & Support & Folder Now Documents Software Community LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 ® LM2594, LM2594HV SIMPLE SWITCHER Power Converter 150-kHz 0.5-A Step-Down Voltage Regulator 1 Features 3 Description • Newproductavailable:LMR365063-Vto65-V The LM2594xx series of regulators are monolithic 1 integrated circuits that provide all the active functions 0.6-Aultra-smallsynchronousbuckconverter for a step-down (buck) switching regulator, capable of • 3.3-V,5-V,12-V,andadjustableoutputversions driving a 0.5-A load with excellent line and load • Adjustableversionoutputvoltagerange:1.2Vto regulation.Thesedevicesareavailableinfixedoutput 37V(57-VfortheHVversion), ±4%maximum voltages of 3.3 V, 5 V, 12 V, and an adjustable output overlineandloadconditions version, and are packaged in a 8-pin PDIP and a 8- pinsurface-mountSOICpackage. • Availablein8-pinsurface-mountSOICand8-pin PDIPpackages Requiring a minimum number of external • Ensured0.5-Aoutputcurrent components, these regulators are simple to use and feature internal frequency compensation, a fixed- • Inputvoltagerangeupto60V frequency oscillator, and improved line and load • Requiresonlyfourexternalcomponents regulationspecifications. • 150-kHzFixed-frequencyinternaloscillator The new product, LMR36506, offers reduced BOM • TTLshutdowncapability cost, higher efficiency, and smaller solution size with • Lowpowerstandbymode,I typically85μA many other features. See the Device Comparison Q Table to compare specs. Start WEBENCH Design • Highefficiency withLMR36506. • Usesreadily-availablestandardinductors • Thermalshutdownandcurrent-limitprotection DeviceInformation(1) • StartWEBENCHdesignwithLM2594HV PARTNUMBER PACKAGE BODYSIZE(NOM) SOIC(8) 4.90mm×3.91mm 2 Applications LM2597,LM2597HV PDIP(8) 9.81mm×6.35mm • Simplehigh-efficiencystep-down(buck)regulator (1) For all available packages, see the orderable addendum at theendofthedatasheet. • Efficientpreregulatorforlinearregulators • On-cardswitchingregulators • Positive-to-negativeconvertor TypicalApplication FixedOutputVoltageVersions 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectualpropertymattersandotherimportantdisclaimers.PRODUCTIONDATA.

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Table of Contents 1 Features.................................................................. 1 8.1 Overview.................................................................10 2 Applications........................................................... 1 8.2 FunctionalBlockDiagram.......................................10 3 Description............................................................. 1 8.3 FeatureDescription.................................................10 8.4 DeviceFunctionalModes........................................14 4 RevisionHistory..................................................... 2 9 ApplicationandImplementation........................ 15 5 Description(continued)......................................... 3 9.1 ApplicationInformation............................................15 6 PinConfigurationandFunctions......................... 3 9.2 TypicalApplications................................................22 7 Specifications......................................................... 4 10 PowerSupplyRecommendations..................... 29 7.1 AbsoluteMaximumRatings......................................4 11 Layout................................................................... 30 7.2 ESDRatings..............................................................4 11.1 LayoutGuidelines.................................................30 7.3 RecommendedOperatingConditions.......................4 11.2 LayoutExample....................................................30 7.4 ThermalInformation..................................................4 11.3 ThermalConsiderations........................................31 7.5 ElectricalCharacteristics–3.3V..............................5 12 DeviceandDocumentationSupport................. 33 7.6 ElectricalCharacteristics–5V.................................5 7.7 ElectricalCharacteristics–12V...............................5 12.1 RelatedLinks........................................................33 7.8 ElectricalCharacteristics–Adjustable......................6 12.2 SupportResources...............................................33 7.9 ElectricalCharacteristics–AllOutputVoltage 12.3 Trademarks...........................................................33 Versions.....................................................................6 12.4 ElectrostaticDischargeCaution............................33 7.10 TypicalCharacteristics............................................7 12.5 Glossary................................................................33 8 DetailedDescription............................................ 10 13 Mechanical,Packaging,andOrderable Information........................................................... 33 4 Revision History NOTE:Pagenumbersforpreviousrevisionsmaydifferfrompagenumbersinthecurrentversion. ChangesfromRevisionD(May2016)toRevisionE Page • AddedinformationonLMR36506toFeaturesandDescription............................................................................................. 1 ChangesfromRevisionC(April2013)toRevisionD Page • AddedESDRatingstable,FeatureDescriptionsection,DeviceFunctionalModes,ApplicationandImplementation section,PowerSupplyRecommendationssection,Layoutsection,DeviceandDocumentationSupportsection,and Mechanical,Packaging,andOrderableInformationsection.................................................................................................. 1 • RemovedallreferencestodesignsoftwareSwitchersMadeSimple ................................................................................... 1 ChangesfromRevisionB(April2013)toRevisionC Page • ChangedlayoutofNationalSemiconductorDataSheettoTIformat.................................................................................. 31 2 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 5 Description (continued) A standard series of inductors (both through-hole and surface-mount types) are available from several different manufacturers optimized for use with the LM2594xx series. This feature greatly simplifies the design of switch- modepowersupplies. Other features include an ensured ±4% tolerance on output voltage under all conditions of input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 85-μAstandbycurrent.Self-protection features include a two stage frequency reducing current limit for the output switchandanovertemperatureshutdownforcompleteprotectionunderfaultconditions. TheLM2594HVisforapplicationsrequiringaninputvoltageupto60V. 6 Pin Configuration and Functions DorPPackage 8-PinSOICorPDIP TopView NC 1 8 Output NC 2 7 +V IN NC 3 6 Ground Feedback 4 5 ON/OFF Not to scale *Nointernalconnection,butmustbesolderedtoPCBforbestheattransfer. ‡PatentNumber5,382,918. PinFunctions(1) PIN I/O DESCRIPTION NO. NAME 1,2,3 NC — Noconnection 4 Feedback I Sensestheregulatedoutputvoltagetocompletethefeedbackloop. Allowstheswitchingregulatorcircuittobeshutdownusinglogiclevelsignals,thusdropping thetotalinputsupplycurrenttoapproximately80μA.Pullingthispinbelowathreshold voltageofapproximately1.3Vturnstheregulatoron,andpullingthispinabove1.3V(upto 5 ON/OFF I amaximumof25V)shutstheregulatordown.Ifthisshutdownfeatureisnotneeded,the ON/OFFpincanbewiredtothegroundpinoritcanbeleftopen,ineithercase,the regulatorisintheONcondition. 6 Ground — Circuitground ThisisthepositiveinputsupplyfortheICswitchingregulator.Asuitableinputbypass 7 +V I capacitormustbepresentatthispintominimizevoltagetransientsandtosupplythe IN switchingcurrentsneededbytheregulator. Internalswitch.Thevoltageatthispinswitchesbetween(+V −V )andapproximately IN SAT 8 Output O −0.5V,withadutycycleofV /V .Tominimizecouplingtosensitivecircuitry,thePCB OUT IN copperareaconnectedtothispinmustbekepttoaminimum. (1) I=INPUT,O=OUTPUT Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 7 Specifications 7.1 Absolute Maximum Ratings(1)(2) MIN MAX UNIT LM2594 45 Supplyvoltage V LM2594HV 60 ON/OFFpininputvoltage −0.3 25 V Feedbackpinvoltage −0.3 25 V Outputvoltagetoground(steadystate) −1 V Powerdissipation Internallylimited Vaporphase(60s) 215 D8package Leadtemperature Infrared(15s) 220 °C Ppackage(soldering,10s) 260 Maximumjunctiontemperature 150 °C Storagetemperature,T −65 150 °C stg (1) StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.Thesearestressratings only,whichdonotimplyfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderRecommended OperatingConditions.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability. (2) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTISalesOffice/Distributorsforavailabilityandspecifications. 7.2 ESD Ratings VALUE UNIT V Electrostaticdischarge Human-bodymodel(HBM),perANSI/ESDA/JEDECJS-001(1)(2) ±2000 V (ESD) (1) JEDECdocumentJEP155statesthat500-VHBMallowssafemanufacturingwithastandardESDcontrolprocess. (2) Thehuman-bodymodelisa100-pFcapacitordischargedthrougha1.5kresistorintoeachpin. 7.3 Recommended Operating Conditions MIN MAX UNIT LM2594 4.5 40 V Supplyvoltage LM2594HV 4.5 60 V Temperature −40 125 °C 7.4 Thermal Information LM2594,LM2594HV THERMALMETRIC(1) D(SOIC) P(PDIP) UNIT 8PINS 8PINS R Junction-to-ambientthermalresistance(2)(3) 150 95 °C/W θJA (1) Formoreinformationabouttraditionalandnewthermalmetrics,seetheSemiconductorandICPackageThermalMetricsapplication report,SPRA953. (2) ThepackagethermalimpedanceiscalculatedinaccordancetoJESD51-7. (3) Thermalresistancesweresimulatedona4-layer,JEDECboard. 4 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 7.5 Electrical Characteristics – 3.3 V SpecificationsareforT =25°C,V =40VfortheLM2594and60VfortheLM2594HV(unlessotherwisenoted). J INmax PARAMETER TESTCONDITIONS MIN TYP(1) MAX(2) UNIT SYSTEMPARAMETERS(3)(seeFigure35fortestcircuit) T =25°C 3.432 3.3 3.168 J 4.75V≤V ≤V , VOUT Outputvoltage 0.1A≤ILOIAND≤0IN.5maAx Overfulloperatingtemperature 3.465 3.135 V range η Efficiency V =12V,I =0.5A 80% IN LOAD (1) Typicalnumbersareat25°Candrepresentthemostlikelynorm. (2) Alllimitsensuredatroomtemperatureandattemperatureextremes.Allroomtemperaturelimitsare100%productiontested.Alllimitsat temperatureextremesarespecifiedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Alllimitsareusedto calculateAverageOutgoingQualityLevel(AOQL). (3) Externalcomponentssuchasthecatchdiode,inductor,inputandoutputcapacitors,andvoltageprogrammingresistorscanaffect switchingregulatorsystemperformance.WhentheLM2594xxisusedasshownintheFigure35testcircuit,systemperformanceisas showninthesystemparameters. 7.6 Electrical Characteristics – 5 V SpecificationsareforT =25°C(unlessotherwisenoted). J PARAMETER TESTCONDITIONS MIN TYP(1) MAX(2) UNIT SYSTEMPARAMETERS(3)(seeFigure35fortestcircuit) V Outputvoltage 7V≤VIN≤VINmax, TJ=25°C 4.8 5 5.2 V OUT 0.1A≤ILOAD≤0.5A Overfulloperatingtemperaturerange 4.75 5.25 η Efficiency V =12V,I =0.5A 82% IN LOAD (1) Typicalnumbersareat25°Candrepresentthemostlikelynorm. (2) Alllimitsensuredatroomtemperatureandattemperatureextremes.Allroomtemperaturelimitsare100%productiontested.Alllimitsat temperatureextremesarespecifiedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Alllimitsareusedto calculateAverageOutgoingQualityLevel(AOQL). (3) Externalcomponentssuchasthecatchdiode,inductor,inputandoutputcapacitors,andvoltageprogrammingresistorscanaffect switchingregulatorsystemperformance.WhentheLM2594xxisusedasshownintheFigure35testcircuit,systemperformanceisas showninthesystemparameters. 7.7 Electrical Characteristics – 12 V SpecificationsareforT =25°C(unlessotherwisenoted). J PARAMETER TESTCONDITIONS MIN TYP(1) MAX(2) UNIT SYSTEMPARAMETERS(3)(seeFigure35fortestcircuit) V Outputvoltage 15V≤VIN≤VINmax, TJ=25°C 11.52 12 12.48 V OUT 0.1A≤ILOAD≤0.5A Overfulloperatingtemperaturerange 11.4 12.6 η Efficiency V =25V,I =0.5A 88% IN LOAD (1) Typicalnumbersareat25°Candrepresentthemostlikelynorm. (2) Alllimitsensuredatroomtemperatureandattemperatureextremes.Allroomtemperaturelimitsare100%productiontested.Alllimitsat temperatureextremesarespecifiedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Alllimitsareusedto calculateAverageOutgoingQualityLevel(AOQL). (3) Externalcomponentssuchasthecatchdiode,inductor,inputandoutputcapacitors,andvoltageprogrammingresistorscanaffect switchingregulatorsystemperformance.WhentheLM2594/LM2594HVisusedasshownintheFigure35testcircuit,system performanceisasshowninthesystemparameters. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 7.8 Electrical Characteristics – Adjustable SpecificationsareforT =25°C(unlessotherwisenoted). J PARAMETER TESTCONDITIONS MIN TYP(1) MAX(2) UNIT SYSTEMPARAMETERS(3)(seeFigure35fortestcircuit) 4.5V≤VIN≤VINmax, TJ=25°C 1.193 1.23 1.267 VFB Feedbackvoltage 0V.O1UATp≤roILgOrAaDm≤m0e.d5fAo,r3V, Overfulloperatingtemperaturerange 1.18 1.28 V CircuitofFigure35 η Efficiency VIN=12V,ILOAD=0.5A 80% (1) Typicalnumbersareat25°Candrepresentthemostlikelynorm. (2) Alllimitsensuredatroomtemperatureandattemperatureextremes.Allroomtemperaturelimitsare100%productiontested.Alllimitsat temperatureextremesarespecifiedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Alllimitsareusedto calculateAverageOutgoingQualityLevel(AOQL). (3) Externalcomponentssuchasthecatchdiode,inductor,inputandoutputcapacitors,andvoltageprogrammingresistorscanaffect switchingregulatorsystemperformance.WhentheLM2594/LM2594HVisusedasshownintheFigure35testcircuit,system performanceisasshowninthesystemparameters. 7.9 Electrical Characteristics – All Output Voltage Versions SpecificationsareforT =25°C,V =12Vforthe3.3-V,5-V,andadjustableversion,andV =24Vforthe12-Vversion, J IN IN I =100mA(unlessotherwisenoted). LOAD PARAMETER TESTCONDITIONS MIN TYP(1) MAX(2) UNIT DEVICEPARAMETERS Adjustableversiononly,VFB= TJ=25°C 10 50 Ib Feedbackbiascurrent 1.3V Overfulloperatingtemperaturerange 100 nA fO Oscillatorfrequency See(3) TJ=25°C 127 150 173 kHz Overfulloperatingtemperaturerange 110 173 VSAT Saturationvoltage IOUT=0.5A(4)(5) TJ=25°C 0.9 1.1 V Overfulloperatingtemperaturerange 1.2 Maxdutycycle(ON) See(5) 100% DC Mindutycycle(OFF) See(6) 0% ICL Currentlimit Peakcurrent(4)(5) TJ=25°C 0.65 0.8 1.3 A overfulloperatingtemperaturerange 0.58 1.4 Output=0V(4)(6)(7) 50 μA IL Outputleakagecurrent Output=−1V 2 15 mA IQ Quiescentcurrent See(6) 5 10 mA ON/OFFpin=5V(OFF)(7) 85 μA TJ=25°C 200 Standbyquiescent LM2594 μA ISTBY current Overfulloperatingtemperaturerange 250 TJ=25°C 140 250 LM2594HV μA Overfulloperatingtemperaturerange 300 ON/OFFCONTROL(seeFigure35fortestcircuit) ON/OFFpinlogicinput 1.3 V VIH Low(regulatorON),overfulloperatingtemperaturerange 0.6 V Thresholdvoltage VIL High(regulatorOFF),overfulloperatingtemperaturerange 2 V IH ON/OFFpininput VLOGIC=2.5V(regulatorOFF) 5 15 μA IL current VLOGIC=0.5V(regulatorON) 0.02 5 μA (1) Typicalnumbersareat25°Candrepresentthemostlikelynorm. (2) Alllimitsensuredatroomtemperatureandattemperatureextremes.Allroomtemperaturelimitsare100%productiontested.Alllimitsat temperatureextremesarespecifiedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Alllimitsareusedto calculateAverageOutgoingQualityLevel(AOQL). (3) Theswitchingfrequencyisreducedwhenthesecondstagecurrentlimitisactivated.Theamountofreductionisdeterminedbythe severityofcurrentoverload. (4) Nodiode,inductororcapacitorconnectedtooutputpin. (5) Feedbackpinremovedfromoutputandconnectedto0VtoforcetheoutputtransistorswitchON. (6) Feedbackpinremovedfromoutputandconnectedto12Vforthe3.3-V,5-V,andtheadjustableversion,and15Vforthe12-Vversion, toforcetheoutputtransistorswitchOFF. (7) V =40VfortheLM2594and60VfortheLM2594HV. IN 6 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 7.10 Typical Characteristics Figure1.NormalizedOutputVoltage Figure2.LineRegulation Figure3.Efficiency Figure4.SwitchSaturationVoltage Figure5.SwitchCurrentLimit Figure6.DropoutVoltage Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Typical Characteristics (continued) Figure7.QuiescentCurrent Figure8.StandbyQuiescentCurrent Figure9.MinimumOperatingSupplyVoltage Figure10.ON/OFFThresholdVoltage Figure11.ON/OFFPinCurrent(Sinking) Figure12.SwitchingFrequency 8 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Typical Characteristics (continued) Figure13.FeedbackPinBiasCurrent Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 8 Detailed Description 8.1 Overview The LM2594 SIMPLE SWITCHER® regulator is an easy-to-use, nonsynchronous step-down DC-DC converter with a wide input voltage range from 45 V to up to 60 V for a HV version. The regulator is capable of delivering up to 0.5-A DC load current with excellent line and load regulation. These devices are available in fixed output voltagesof3.3-V,5-V,12-V,andanadjustableoutputversion. The family requires few external components, and thepinarrangementwasdesignedforsimple,optimumPCBlayout. 8.2 Functional Block Diagram 8.3 Feature Description 8.3.1 DelayedStart-Up The circuit in Figure 14 uses the ON/OFF pin to provide a time delay between the time the input voltage is applied and the time the output voltage comes up (only the circuitry pertaining to the delayed start-up is shown). As the input voltage rises, the charging of capacitor C1 pulls the ON/OFF pin high, keeping the regulator off. Once the input voltage reaches its final value and the capacitor stops charging, the resistor R pulls the ON/OFF 2 pinlow,thusallowingthecircuittostartswitching.ResistorR isincluded to limit the maximum voltage applied to 1 the ON/OFF pin (maximum of 25 V), reduces power supply noise sensitivity, and also limits the capacitor, C1, discharge current. When high input ripple voltage exists, avoid long delay time, because this ripple can be coupledintotheON/OFFpinandcauseproblems. This delayed start-up feature is useful in situations where the input power source is limited in the amount of current it can deliver. It allows the input voltage to rise to a higher voltage before the regulator starts operating. Buckregulatorsrequirelessinputcurrentathigherinputvoltages. 10 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Feature Description (continued) Figure14. DelayedStart-Up 8.3.2 UndervoltageLockout Some applications require the regulator to remain off until the input voltage reaches a predetermined voltage. Figure 15 shows an undervoltage lockout feature applied to a buck regulator, while Figure 16 and Figure 17 apply the same feature to an inverting circuit. The circuit in Figure 16 features a constant threshold voltage for turnon and turnoff (Zener voltage plus approximately 1 V). If hysteresis is needed, the circuit in Figure 17 has a turnon voltage which is different than the turnoff voltage. The amount of hysteresis is approximately equal to the value of the output voltage. If Zener voltages greater than 25 V are used, an additional 47-kΩ resistor is needed fromthe ON/OFFpintothegroundpintostaywithinthe25Vmaximumlimitofthe ON/OFFpin. Figure15. UndervoltageLockout forBuckRegulator 8.3.3 InvertingRegulator ThecircuitinFigure18convertsapositiveinputvoltagetoanegativeoutput voltage with a common ground. The circuit operates by bootstrapping the regulators ground pin to the negative output voltage, then grounding the feedbackpin,theregulatorsensestheinvertedoutputvoltageandregulatesit. ThiscircuithasanON/OFFthresholdofapproximately13V. Figure16. UndervoltageLockoutforInvertingRegulator Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Feature Description (continued) Thiscircuithashysteresis RegulatorstartsswitchingatV =13V IN RegulatorstopsswitchingatV =8V IN Figure17. UndervoltageLockoutWithHysteresisforInvertingRegulator C —68-μF,25-VTant.Sprague595D IN 120-μF,35-VElec.PanasonicHFQ C —22-μF,20-VTant.Sprague595D OUT 39-μF,16-VElec.PanasonicHFQ Figure18. Inverting −5-VRegulatorWithDelayedStart-Up This example uses the LM2594-5 to generate a −5-V output, but other output voltages are possible by selecting other output voltage versions, including the adjustable version. Because this regulator topology can produce an output voltage that is either greater than or less than the input voltage, the maximum output current greatly dependsonboththeinputandoutputvoltage.Figure19providesaguideastotheamount of output load current possibleforthedifferentinputandoutputvoltageconditions. The maximum voltage appearing across the regulator is the absolute sum of the input and output voltage, and thismustbelimitedtoamaximumof40V.Forexample,whenconverting20 V to −12 V, the regulator would see 32 V between the input pin and ground pin. The LM2594 has a maximum input voltage specification of 40 V (60 VfortheLM2594HV). Additional diodes are required in this regulator configuration. Diode D1 is used to isolate input voltage ripple or noise from coupling through the C capacitor to the output, under light or no load conditions. Also, this diode IN isolation changes the topology to closely resemble a buck configuration thus providing good closed loop stability. TI recommends a Schottky diode for low input voltages (because of its lower voltage drop), but for higher input voltages,afastrecoverydiodecouldbeused. Without diode D3, when the input voltage is first applied, the charging current of C can pull the output positive IN by several volts for a short period of time. Adding D3 prevents the output from going positive by more than a diodevoltage. 12 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Feature Description (continued) Figure19. InvertingRegulatorTypicalLoadCurrent Because of differences in the operation of the inverting regulator, the standard design procedure is not used to select the inductor value. In the majority of designs, a 100-μH, 1-A inductor is the best choice. Capacitor selection can also be narrowed down to just a few values. Using the values shown in Figure 18 provides good resultsinthemajorityofinvertingdesigns. This type of inverting regulator can require relatively large amounts of input current when starting up, even with light loads. Input currents as high as the LM2594 current limit (approximately 0.8 A) are needed for at least 2 ms or more, until the output reaches its nominal output voltage. The actual time depends on the output voltage and thesize of the output capacitor. Input power sources that are current limited or sources that can not deliver these currents without getting loaded down, may not work correctly. Because of the relatively high start-up currents required by the inverting topology, the delayed start-up feature (C1, R and R ) shown in Figure 18 is 1 2 recommended. By delaying the regulator start-up, the input capacitor is allowed to charge up to a higher voltage before the switcher begins operating. A portion of the high input current needed for start-up is now supplied by the input capacitor (C ). For severe start-up conditions, the input capacitor can be made much larger than IN normal. 8.3.4 InvertingRegulatorShutdownMethods To use the ON/OFF pin in a standard buck configuration is simple; pull it below 1.3 V (at 25°C, referenced to ground) to turn regulator ON and pull it above 1.3 V to shut the regulator OFF. With the inverting configuration, some level shifting is required, because the ground pin of the regulator is no longer at ground, but is now setting at the negative output voltage level. Two different shutdown methods for inverting regulators are shown in Figure20andFigure21. Figure20. InvertingRegulatorGroundReferencedShutdown Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Feature Description (continued) Figure21. InvertingRegulatorGroundReferencedShutdownUsingOptoDevice 8.4 Device Functional Modes 8.4.1 DiscontinuousModeOperation The selection guide chooses inductor values suitable for continuous mode operation, but for low current applications and high input voltages, a discontinuous mode design can be a better choice. Discontinuous mode would use an inductor that is physically smaller, and would need only one half to one third of the inductance valueneededforacontinuousmodedesign. The peak switch and inductor currents are higher in a discontinuous design, but at these low load currents (200 mA and below), the maximum switch current is still less than the switchcurrentlimit. Discontinuous operation can have voltage waveforms that are considerably different than a continuous design. The output pin (switch) waveform can have some damped sinusoidal ringing present (see Figure 33). This ringing is normal for discontinuous operation, and is not caused by feedback loop instabilities. In discontinuous operation, there is a period of time where neither the switch nor the diode are conducting, and the inductor current has dropped to zero. During this time, a small amount of energy can circulate between the inductor and the switch or diode parasitic capacitance causing this characteristic ringing. Normally this ringing is not a problem, unless the amplitude becomes great enough to exceed the input voltage, and even then, there is very littleenergypresenttocausedamage. Different inductor types and core materials produce different amounts of this characteristic ringing. Ferrite core inductors have very little core loss and, therefore, produce the most ringing. The higher core loss of powdered iron inductors produce less ringing. If desired, a series RC can be placed in parallel with the inductor to dampen theringing. Figure22. PostRippleFilterWaveform 14 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validateandtesttheirdesignimplementationtoconfirmsystemfunctionality. 9.1 Application Information 9.1.1 InputCapacitor(C ) IN A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground pin. The capacitor must be located near the regulator using short leads. This capacitor prevents large voltage transients fromappearingattheinput,andprovidestheinstantaneouscurrentneededeachtimetheswitchturnson. The important parameters for the input capacitor are the voltage rating and the RMS current rating. Because of the relatively high RMS currents flowing in the input capacitor of the buck regulator, this capacitor must be chosen for its RMS current rating rather than its capacitance or voltage ratings, although the capacitance value andvoltageratingaredirectlyrelatedtotheRMScurrentrating. The RMS current rating of a capacitor could be viewed as a power rating of the capacitor. The RMS current flowing through the capacitors internal ESR produces power which causes the internal temperature of the capacitor to rise. The RMS current rating of a capacitor is determined by the amount of current required to raise theinternaltemperature approximately 10°C above an ambient temperature of 105°C. The ability of the capacitor to dissipate this heat to the surrounding air determines the amount of current the capacitor can safely sustain. Capacitorsthatarephysicallylargeandhavealargesurfaceareatypicallyhasahigher RMS current ratings. For a given capacitor value, a higher voltage electrolytic capacitor is physically larger than a lower voltage capacitor, andthusbeabletodissipatemoreheattothesurroundingair,andthereforehasahigherRMScurrentrating. The consequences of operating an electrolytic capacitor above the RMS current rating is a shortened operating life. The higher temperature speeds up the evaporation of the electrolyte of the capacitor, resulting in eventual failure. Selectinganinput capacitor requires consulting the manufacturers data sheet for maximum allowable RMS ripple current. For a maximum ambient temperature of 40°C, a general guideline would be to select a capacitor with a ripple current rating of approximately 50% of the DC load current. For ambient temperatures up to 70°C, a current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor voltage rating must be at least 1.25 times greater than the maximum input voltage, and often a much higher voltagecapacitorisneededtosatisfytheRMScurrentrequirements. Figure 23 shows the relationship between an electrolytic capacitor value, its voltage rating, and the RMS current it is rated for. These curves were obtained from the Nichicon PL series of low-ESR, high-reliability electrolytic capacitors designed for switching regulator applications. Other capacitor manufacturers offer similar types of capacitors,butalwayscheckthecapacitordatasheet. Standard electrolytic capacitors typically have much higher ESR numbers, lower RMS current ratings and typicallyhaveashorteroperatinglifetime. Because of their small size and excellent performance, surface-mount solid tantalum capacitors are often used for input bypassing, but several precautions must be observed. A small percentage of solid tantalum capacitors can short if the inrush current rating is exceeded. This can happen at turnon when the input voltage is suddenly applied, and of course, higher input voltages produce higher inrush currents. Several capacitor manufacturers do a 100% surge current testing on their products to minimize this potential problem. If high turnon currents are expected, it may be necessary to limit this current by adding either some resistance or inductance before the tantalum capacitor, or select a higher voltage capacitor. As with aluminum electrolytic capacitors, the RMS ripple currentratingmustbesizedtotheloadcurrent. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Application Information (continued) Figure23. RMSCurrentRatingsforLow-ESRElectrolyticCapacitors(Typical) 9.1.2 OutputCapacitor(C ) OUT Anoutputcapacitorisrequiredtofiltertheoutputand provide regulator loop stability. Low impedance or low ESR Electrolytic or solid tantalum capacitors designed for switching regulator applications must be used. When selecting an output capacitor, the important capacitor parameters are; the 100-kHz Equivalent Series Resistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor, the ESR valueisthemostimportantparameter. The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a low ESR value is needed. This value is determined by the maximum allowable output ripple voltage, typically 1% to 2% of the output voltage. But if the ESR of the selected capacitor is extremely low, there is a possibility of an unstable feedback loop, resulting in an oscillation at the output. Using the capacitors listed in the tables, or similartypes,providesdesignsolutionsunderallconditions. If very low output ripple voltage (less than 15 mV) is required, see Output Voltage Ripple and Transients for a post-ripplefilter. An aluminum electrolytic capacitor's ESR value is related to the capacitance value and its voltage rating. In most cases,HighervoltageelectrolyticcapacitorshavelowerESRvalues(seeFigure 24). Often, capacitors with much highervoltageratingsmaybeneededtoprovidethelowESRvaluesrequiredforlowoutputripplevoltage. The output capacitor for many different switcher designs often can be satisfied with only three or four different capacitor values and several different voltage ratings. See Figure 30 and Table 7 for typical capacitor values, voltageratings,andmanufacturerscapacitortypes. Electrolytic capacitors are not recommended for temperatures below −25°C. The ESR rises dramatically at cold temperaturesandtypicallyrisesthreetimesat−25°Candasmuchastentimesat −40°C(seeFigure25). Solid tantalum capacitors have a much better ESR specifications for cold temperatures and are recommended fortemperaturesbelow −25°C. Figure24. CapacitorESRversusCapacitorVoltageRating(TypicalLow-ESRElectrolyticCapacitor) 16 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Application Information (continued) Table1.OutputCapacitorandFeedforwardCapacitorSelectionTable OUTPUT THROUGH-HOLEOUTPUTCAPACITOR SURFACE-MOUNTOUTPUTCAPACITOR VOLTAGE PANASONICHFQ NICHICONPL FEEDFORWARD AVXTPSSERIES SPRAGUE595D FEEDFORWARD (V) SERIES(µF/V) SERIES(µF/V) CAPACITOR (µF/V) SERIES(µF/V) CAPACITOR 1.2 220/25 220/25 0 220/10 220/10 0 4 180/25 180/25 4.7nF 100/10 120/10 4.7nF 6 82/25 82/25 4.7nF 100/10 120/10 4.7nF 9 82/25 82/25 3.3nF 100/16 100/16 3.3nF 12 82/25 82/25 2.2nF 100/16 100/16 2.2nF 15 82/25 82/25 1.5nF 68/20 100/20 1.5nF 24 82/50 120/50 1nF 10/35 15/35 220pF 28 82/50 120/50 820pF 10/35 15/35 220pF 9.1.3 CatchDiode Buck regulators require a diode to provide a return path for the inductor current when the switch turns off. This mustbeafastdiodeandmustbelocatedclosetotheLM2594usingshortleadsandshortprinted-circuittraces. Because of their very fast switching speed and low forward voltage drop, Schottky diodes provide the best performance, especially in low output voltage applications (5 V and lower). Ultra-fast recovery, or high-efficiency rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or EMI problems. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such asthe1N4001seriesaremuchtooslowandmustnotbeused. Figure25. CapacitorESRChangeversusTemperature Table2.DiodeSelectionTable 1-ADIODES VR SURFACEMOUNT THROUGHHOLE SCHOTTKY ULTRAFASTRECOVERY SCHOTTKY ULTRAFASTRECOVERY 1N5817 20V SR102 Allofthesediodesareratedto Allofthesediodesareratedto MBRS130 1N5818 atleast60V. atleast60V. 30V SR103 11DQ03 MBRS140 MURS120 1N5819 MUR120 40V 10BQ040 10BF10 SR104 HER101 10MQ040 11DQ04 11DF1 MBRS160 SR105 50V or 10BQ050 MBR150 more 10MQ060 11DQ05 Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 17 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Table2.DiodeSelectionTable(continued) 1-ADIODES VR SURFACEMOUNT THROUGHHOLE SCHOTTKY ULTRAFASTRECOVERY SCHOTTKY ULTRAFASTRECOVERY MBRS1100 MBR160 10MQ090 SB160 SGL41-60 11DQ10 SS16 9.1.4 InductorSelection All switching regulators have two basic modes of operation: continuous and discontinuous. The difference betweenthetwo types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. Each mode has distinctively different operating characteristics, which can affect the regulators performance and requirements. Most switcher designs operates in the discontinuousmodewhentheloadcurrentislow. TheLM2594(oranyoftheSIMPLE SWITCHER family) can be used for both continuous or discontinuous modes ofoperation. In many cases the preferred mode of operation is the continuous mode. This mode offers greater output power, lower peak switch, inductor, and diode currents, and can have lower output ripple voltage. However, the continuous mode requires larger inductor values to keep the inductor current flowing continuously, especially at lowoutputloadcurrentsandhighinputvoltages. To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 27 through Figure 30). This guide assumes that the regulator is operating in the continuous mode, and selects an inductor that allows a peak-to-peak inductor ripple current to be a certain percentage of the maximum design load current. This peak-to-peak inductor ripple current percentage is not fixed, but is allowed to change as differentdesignloadcurrentsareselected.(SeeFigure26). Figure26. (ΔI )Peak-to-PeakInductorRippleCurrent IND (asaPercentageoftheLoadCurrent)versusLoadCurrent Byallowingthepercentageofinductorripplecurrenttoincreaseforlowloadcurrents,theinductor value and size canbekeptrelativelylow. When operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth type of waveform (depending on the input voltage), with the average value of this current waveform equal to the DCoutputloadcurrent. Inductors are available in different styles such as pot core, toroid, E-core, bobbin core, and so forth, as well as different core materials, such as ferrites and powdered iron. The least expensive, the bobbin, rod or stick core, consists of wire wrapped on a ferrite bobbin. This type of construction makes for a inexpensive inductor; however, because the magnetic flux is not completely contained within the core, it generates more Electro- Magnetic Interference (EMl). This magnetic flux can induce voltages into nearby printed-circuit traces, thus causing problems with both the switching regulator operation and nearby sensitive circuitry, and can give incorrectscopereadingsbecauseofinducedvoltagesinthescopeprobe(seeOpenCoreInductors). 18 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 The inductors listed in the selection chart include ferrite E-core construction for Schott ferrite bobbin core for RencoandCoilcraft,andpowderedirontoroidforPulseEngineering. Exceeding the maximum current rating of the inductor can cause the inductor to overheat because of the copper wire losses, or the core can saturate. If the inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC resistance of the winding). This can cause the switch current to rise very rapidly and force the switch into a cycle-by-cycle current limit, thus reducing the DC output load current. This can also result in overheating of the inductor and the LM2594. Different inductor types have different saturationcharacteristics,andthismustbekeptinmindwhenselectinganinductor. Theinductormanufacturersdatasheetsincludecurrentandenergylimitstoavoidinductorsaturation. Forcontinuousmodeoperation,seetheinductorselectiongraphsinFigure27throughFigure30. Figure27.LM2594xx3.3-V Figure28.LM2594xx5-V Figure29.LM2594xx12-V Figure30.LM2594xxAdjustableVoltage Table3.InductorManufacturersPartNumbers SCHOTTKY RENCO PULSEENGINEERING COILCRAFT INDUCTANCE CURRENT (μH) (A) THROUGH SURFACE THROUGH SURFACE THROUGH SURFACE SURFACE HOLE MOUNT HOLE MOUNT HOLE MOUNT MOUNT L1 220 0.18 67143910 67144280 RL-5470-3 RL1500-220 PE-53801 PE-53801-S DO1608-224 L2 150 0.21 67143920 67144290 RL-5470-4 RL1500-150 PE-53802 PE-53802-S DO1608-154 L3 100 0.26 67143930 67144300 RL-5470-5 RL1500-100 PE-53803 PE-53803-S DO1608-104 L4 68 0.32 67143940 67144310 RL-1284-68 RL1500-68 PE-53804 PE-53804-S DO1608-68 L5 47 0.37 67148310 67148420 RL-1284-47 RL1500-47 PE-53805 PE-53805-S DO1608-473 L6 33 0.44 67148320 67148430 RL-1284-33 RL1500-33 PE-53806 PE-53806-S DO1608-333 L7 22 0.60 67148330 67148440 RL-1284-22 RL1500-22 PE-53807 PE-53807-S DO1608-223 Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 19 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Table3.InductorManufacturersPartNumbers(continued) SCHOTTKY RENCO PULSEENGINEERING COILCRAFT INDUCTANCE CURRENT (μH) (A) THROUGH SURFACE THROUGH SURFACE THROUGH SURFACE SURFACE HOLE MOUNT HOLE MOUNT HOLE MOUNT MOUNT L8 330 0.26 67143950 67144320 RL-5470-2 RL1500-330 PE-53808 PE-53808-S DO3308-334 L9 220 0.32 67143960 67144330 RL-5470-3 RL1500-220 PE-53809 PE-53809-S DO3308-224 L10 150 0.39 67143970 67144340 RL-5470-4 RL1500-150 PE-53810 PE-53810-S DO3308-154 L11 100 0.48 67143980 67144350 RL-5470-5 RL1500-100 PE-53811 PE-53811-S DO3308-104 L12 68 0.58 67143990 67144360 RL-5470-6 RL1500-68 PE-53812 PE-53812-S DO1608-683 L13 47 0.70 67144000 67144380 RL-5470-7 RL1500-47 PE-53813 PE-53813-S DO3308-473 L14 33 0.83 67148340 67148450 RL-1284-33 RL1500-33 PE-53814 PE-53814-S DO1608-333 L15 22 0.99 67148350 67148460 RL-1284-22 RL1500-22 PE-53815 PE-53815-S DO1608-223 L16 15 1.24 67148360 67148470 RL-1284-15 RL1500-15 PE-53816 PE-53816-S DO1608-153 L17 330 0.42 67144030 67144410 RL-5471-1 RL1500-330 PE-53817 PE-53817-S DO3316-334 L18 220 0.55 67144040 67144420 RL-5471-2 RL1500-220 PE-53818 PE-53818-S DO3316-224 L19 150 0.66 67144050 67144430 RL-5471-3 RL1500-150 PE-53819 PE-53819-S DO3316-154 L20 100 0.82 67144060 67144440 RL-5471-4 RL1500-100 PE-53820 PE-53820-S DO3316-104 L21 68 0.99 67144070 67144450 RL-5471-5 RL1500-68 PE-53821 PE-53821-S DDO3316-683 L26 330 0.80 67144100 67144480 RL-5471-1 — PE-53826 PE-53826-S — L27 220 1.00 67144110 67144490 RL-5471-2 — PE-53827 PE-53827-S — 9.1.5 OutputVoltageRippleandTransients The output voltage of a switching power supply operating in the continuous mode contains a sawtooth ripple voltage at the switcher frequency, and can also contain short voltage spikes at the peaks of the sawtooth waveform. The output ripple voltage is a function of the inductor sawtooth ripple current and the ESR of the output capacitor. A typical output ripple voltage can range from approximately 0.5% to 3% of the output voltage. To obtainlowripplevoltage,theESRoftheoutputcapacitormustbelow;however,cautionmust be exercised when using extremely low ESR capacitors because they can affect the loop stability, resulting in oscillation problems. If very low output ripple voltage is needed (less than 15 mV), TI recommends a post ripple filter (see Figure 35). The inductance required is typically between 1 μH and 5 μH, with low DC resistance, to maintain good load regulation. A low ESR output filter capacitor is also required to assure good dynamic load response and ripple reduction. The ESR of this capacitor can be as low as desired, because it is out of the regulator feedback loop. Figure22showsatypicaloutputripplevoltage,withandwithoutapostripplefilter. When observing output ripple with a scope, it is essential that a short, low inductance scope probe ground connection be used. Most scope probe manufacturers provide a special probe terminator which is soldered onto the regulator board, preferably at the output capacitor. This provides a very short scope ground, thus eliminating the problems associated with the three-inch ground lead normally provided with the probe, and provides a much cleanerandmoreaccuratepictureoftheripplevoltagewaveform. The voltage spikes are caused by the fast switching action of the output switch and the diode, the parasitic inductance of the output filter capacitor, and its associated wiring. To minimize these voltage spikes, the output capacitor must be designed for switching regulator applications, and the lead lengths must be kept very short. Wiring inductance, stray capacitance, as well as the scope probe used to evaluate these transients, all contribute totheamplitudeofthesespikes. When a switching regulator is operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth type of waveform (depending on the input voltage). For a given input and output voltage, the peak-to-peak amplitude of this inductor current waveform remains constant. As the load current increases or decreases, the entire sawtooth current waveform also rises and falls. The average value (or the center) of this currentwaveformisequaltotheDCloadcurrent. If the load current drops to a low enough level, the bottom of the sawtooth current waveform reaches zero, and the switcher smoothly changes from a continuous to a discontinuous mode of operation. Most switcher designs (regardless how large the inductor value is) is forced to run discontinuous if the output is lightly loaded. This is a perfectlyacceptablemodeofoperation. 20 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Figure31. Peak-to-PeakInductor RippleCurrentvsLoadCurrent In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current (ΔI ) can be IND useful for determining a number of other circuit parameters. Parameters such as, peak inductor or peak switch current, minimum load current before the circuit becomes discontinuous, output ripple voltage and output capacitor ESR can all be calculated from the peak-to-peak ΔI . When the inductor nomographs shown in IND Figure 27 through Figure 30 are used to select an inductor value, the peak-to-peak inductor ripple current can immediately be determined. Figure 31 shows the range of (ΔI ) that can be expected for different load currents. IND Figure31alsoshowshowthepeak-to-peakinductor ripple current (ΔI ) changes as the designer goes from the IND lower border to the upper border (for a given load current) within an inductance region. The upper border represents a higher input voltage, while the lower border represents a lower input voltage (see Inductor Selection). These curves are only correct for continuous mode operation, and only if the inductor selection guides are used toselecttheinductorvalue. Considerthefollowingexample: V =5V,maximumloadcurrentof300mA OUT V =15V,nominal,varyingbetween11Vand20V IN TheselectionguideinFigure28showsthattheverticallinefora0.3-Aloadcurrentandthehorizontalline for the 15-V input voltage intersect approximately midway between the upper and lower borders of the 150-μH inductance region. A 150-μH inductor allows a peak-to-peak inductor current (ΔI ) to flow a percentage of the IND maximum load current. Referring to Figure 31, follow the 0.3-A line approximately midway into the inductance region,andreadthepeak-to-peakinductorripplecurrent(ΔI )onthelefthandaxis(approximately150mA ). IND p-p As the input voltage increases to 20 V, it approaches the upper border of the inductance region, and the inductor ripple current increases. Figure 31 shows that for a load current of 0.3 A, the peak-to-peak inductor ripple current (ΔI ) is 150 mA with 15V in, and can range from 175 mA at the upper border (20 V in) to 120 mA at the lower IND border(11Vin). Once the ΔI value is known, the following formulas can be used to calculate additional information about the IND switchingregulatorcircuit. 1. PeakInductororpeakswitchcurrent 2. Minimumloadcurrentbeforethecircuitbecomesdiscontinuous 3. OutputRippleVoltage – =(ΔI )× (ESRofC ) IND OUT – =0.150A×0.240Ω=36mV p-p – or Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 21 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 4. ESRofC OUT 9.1.6 OpenCoreInductors Another possible source of increased output ripple voltage or unstable operation is from an open core inductor. Ferrite bobbin or stick inductors have magnetic lines of flux flowing through the air from one end of the bobbin to the other end. These magnetic lines of flux induces a voltage into any wire or PCB copper trace that comes within the inductor's magnetic field. The strength of the magnetic field, the orientation and location of the PC copper trace to the magnetic field, and the distance between the copper trace and the inductor, determine the amount of voltage generated in the copper trace. Another way of looking at this inductive coupling is to consider the PCB copper trace as one turn of a transformer (secondary) with the inductor winding as the primary. Many millivolts can be generated in a copper trace located near an open core inductor which can cause stability problemsorhighoutputripplevoltageproblems. If unstable operation is seen, and an open core inductor is used, it is possible that the location of the inductor with respect to other PC traces may be the problem. To determine if this is the problem, temporarily raise the inductor away from the board by several inches and then check circuit operation. If the circuit now operates correctly, then the magnetic flux from the open core inductor is causing the problem. Substituting a closed core inductor such as a torroid or E-core corrects the problem, or re-arranging the PC layout may be necessary. Magnetic flux cutting the IC device ground trace, feedback trace, or the positive or negative traces of the output capacitormustbeminimized. Sometimes, locating a trace directly beneath a bobbin inductor provides good results, provided it is exactly in the centeroftheinductor(becausetheinducedvoltages cancel themselves out), but if it is off center one direction or the other, then problems could arise. If flux problems are present, even the direction of the inductor winding can makeadifferenceinsomecircuits. This discussion on open core inductors is not to frighten the user, but to alert the user on what kind of problems to watch out for when using them. Open core bobbin or stick inductors are an inexpensive, simple way of making acompactefficientinductor,andtheyareusedbythemillionsinmanydifferentapplications. 9.2 Typical Applications 9.2.1 SeriesBuckRegulator(FixedOutput) SelectcomponentswithhighervoltageratingsfordesignsusingtheLM2594HVwithaninputvoltage between 40 Vand60V. Copyright © 2016, Texas Instruments Incorporated C —68-μF,35-V,AluminumElectrolyticNichicon“PLSeries” IN C —120-μF,25-VAluminumElectrolytic,Nichicon“PLSeries” OUT D1—1-A,40-VSchottkyRectifier,1N5819 L1—100-μH,L20 Figure32. FixedOutputVoltageVersions 22 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Typical Applications (continued) 9.2.1.1 DesignRequirements Table4liststhedesignparametersofthisexample. Table4.DesignParameters PARAMETER EXAMPLEVALUE Regulatedoutputvoltage(3.3-V,5-Vor12-V),V 5V OUT MaximumDCinputvoltage,V (max) 12V IN Maximumloadcurrent,I (max) 0.4A LOAD 9.2.1.2 DetailedDesignProcedure 9.2.1.2.1 InductorSelection(L1) 1. Select the correct inductor value selection guide from Figure 27, Figure 28, or Figure 29 (output voltages of 3.3 V, 5 V, or 12 V, respectively). For all other voltages, see Detailed Design Procedure for the adjustable version. Usetheinductorselectionguideforthe5-VversionshowninFigure28. 2. From the inductor value selection guide, identify the inductance region intersected by the maximum input voltage line and the maximum load current line. Each region is identified by an inductance value and an inductorcode(LXX). From the inductor value selection guide shown in Figure 28, the inductance region intersected by the 12-V horizontallineandthe0.4-Averticallineis100 μH,andtheinductorcodeisL20. 3. Selectanappropriateinductorfromthefourmanufacturer'spartnumberslistedinTable3. The inductance value required is 100 μH. See row L20 of Table 3 and choose an inductor part number from any of the four manufacturers shown. (In most instance, both through-hole and surface-mount inductors are available.) 9.2.1.2.2 OutputCapacitorSelection(C ) OUT 1. In the majority of applications, low ESR (Equivalent Series Resistance) electrolytic capacitors between 82 μF and 220 μF and low-ESR, solid tantalum capacitors between 15 μF and 100 μF provide the best results. This capacitor must be located close to the IC using short capacitor leads and short copper traces. Do not use capacitorslargerthan220μF.Foradditionalinformation,seeOutputCapacitor(C ). OUT 2. To simplify the capacitor selection procedure, see Figure 30 for quick design component selection. This table contains different input voltages, output voltages, and load currents, and lists various inductors and output capacitorsthatprovidesthebestdesignsolutions. From Figure 30, locate the 5-V output voltage section. In the load current column, choose the load current line that is closest to the current required for the application; for this example, use the 0.5-A line. In the maximum input voltage column, select the line that covers the input voltage required for the application; in this example, use the 15-V line. The rest of this line shows the recommended inductors and capacitors that providesthebestoverallperformance. The capacitor list contains both through hole electrolytic and surface mount tantalum capacitors from four different capacitor manufacturers. TI recommends using both the manufacturers and the manufacturer's seriesthatarelistedinTable5. In this example, aluminum electrolytic capacitors from several different manufacturers are available with the rangeofESRnumbersneeded: 120-μF, 2-5V PanasonicHFQSeries 120-μF, 2-5V NichiconPLSeries 3. The capacitor voltage rating for electrolytic capacitors must be at least 1.5 times greater than the output voltage, and often require much higher voltage ratings to satisfy the low ESR requirements for low output ripplevoltage. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 23 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com For a 5-V output, a capacitor voltage rating at least 7.5 V or more is required. But, in this example, even a low ESR, switching grade, 120-μF, 10-V aluminum electrolytic capacitor would exhibit approximately 400 mΩ of ESR (see Figure 24 for the ESR vs voltage rating). This amount of ESR would result in relatively high output ripple voltage. To reduce the ripple to 1% of the output voltage, or less, a capacitor with a higher voltage rating (lower ESR) must be selected. A 16-V or 25-V capacitor reduces the ripple voltage by approximatelyhalf. 9.2.1.2.3 CatchDiodeSelection(D1) 1. The catch diode current rating must be at least 1.3 times greater than the maximum load current. Also, if the power supply design must withstand a continuous output short, the diode must have a current rating equal to the maximum current limit of the LM2594. The most stressful condition for this diode is an overload or shortedoutputcondition. See Table 2. In this example, a 1-A, 20-V, 1N5817 Schottky diode provides the best performance, and will notbeoverstressedevenforashortedoutput. 2. Thereversevoltageratingofthediodemustbeatleast1.25timesthemaximuminputvoltage. 3. This diode must be fast (short reverse recovery time) and must be located close to the LM2594 using short leads and short printed circuit traces. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency, and must be the first choice, especially in low output voltage applications. Ultra-fast recovery, or high-efficiency rectifiers also provide good results. Ultra- fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N4001 mustnotbeusedbecausetheyaretooslow. 9.2.1.2.4 InputCapacitor(C ) IN A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large voltage transients from appearing at the input. In addition, the RMS current rating of the input capacitor must be selected to be at least ½ the DC load current. The capacitor manufacturers data sheet must be checked to assure that this current rating is not exceeded. Figure 23 shows typical RMS current ratings for several different aluminumelectrolyticcapacitorvalues. ThiscapacitormustbelocatedclosetotheICusingshortleadsandthevoltageratingmustbeapproximately 1.5 timesthemaximuminputvoltage. If solid tantalum input capacitors are used, TI recommends that they be surge current tested by the manufacturer. Use caution when using ceramic capacitors for input bypassing, because it may cause severe ringing at the V IN pin. The important parameters for the Input capacitor are the input voltage rating and the RMS current rating. With a nominal input voltage of 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 18 V (1.5×V )isnecessary.Thenexthighercapacitorvoltageratingis25V. IN The RMS current rating requirement for the input capacitor in a buck regulator is approximately ½ the DC load current.Inthis example, with a 400-mA load, a capacitor with a RMS current rating of at least 200 mA is needed. Figure 23 can be used to select an appropriate input capacitor. From the curves, locate the 25-V line and note which capacitor values have RMS current ratings greater than 200 mA. Either a 47-μF or 68-μF, 25-V capacitor canbeused. For a through hole design, a 68-μF, 25-V electrolytic capacitor (Panasonic HFQ series or Nichicon PL series or equivalent) would be adequate. Other types or other manufacturers' capacitors can be used provided the RMS ripplecurrentratingsareadequate. For surface-mount designs, solid tantalum capacitors are recommended. The TPS series available from AVX, andthe593DseriesfromSpraguearebothsurgecurrenttested. Foradditionalinformation,seeInputCapacitor(C ). IN 24 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Table5.LM2594xxFixedVoltageQuickDesignComponentSelectionTable OUTPUTCAPACITOR CONDITIONS INDUCTOR THROUGHHOLE SURFACEMOUNT OUTPUT LOAD MAXINPUT PANASONIC NICHICON AVXTPS SPRAGUE INDUCTANCE INDUCTOR VOLTAGE CURRENT VOLTAGE HFQSERIES PLSERIES SERIES 595DSERIES (μH) (#) (V) (A) (V) (μF/V) (μF/V) (μF/V) (μF/V) 5 33 L14 220/16 220/16 100/16 100/6.3 7 47 L13 120/25 120/25 100/16 100/6.3 0.5 10 68 L21 120/25 120/25 100/16 100/6.3 3.3 40 100 L20 120/35 120/35 100/16 100/6.3 6 68 L4 120/25 120/25 100/16 100/6.3 0.2 10 150 L10 120/16 120/16 100/16 100/6.3 40 220 L9 120/16 120/16 100/16 100/6.3 8 47 L13 180/16 180/16 100/16 33/25 10 68 L21 180/16 180/16 100/16 33/25 0.5 15 100 L20 120/25 120/25 100/16 33/25 5 40 150 L19 120/25 120/25 100/16 33/25 9 150 L10 82/16 82/16 100/16 33/25 0.2 20 220 L9 120/16 120/16 100/16 33/25 40 330 L8 120/16 120/16 100/16 33/25 15 68 L21 82/25 82/25 100/16 15/25 18 150 L19 82/25 82/25 100/16 15/25 0.5 30 220 L27 82/25 82/25 100/16 15/25 12 40 330 L26 82/25 82/25 100/16 15/25 15 100 L11 82/25 82/25 100/16 15/25 0.2 20 220 L9 82/25 82/25 100/16 15/25 40 330 L17 82/25 82/25 100/16 15/25 9.2.1.3 ApplicationCurves Loadtransientresponsefordiscontinuousmode V =20V,V =5V,I =100mAto200mA IN OUT LOAD Discontinuousmodeswitchingwaveforms L=33μH,COUT=220μF,COUTESR=60mΩ V =20V,V =5V,I =200mA A:Outputvoltage,50mV/div.(AC) IN OUT LOAD L=33μH,C =220μF,C ESR=60mΩ B:100-mAto200-mAloadpulse OUT OUT A:Outputpinvoltage,10V/div. B:Inductorcurrent,0.2A/div. C:Outputripplevoltage,20mV/div. Figure33.HorizontalTimeBase:2μs/div Figure34.HorizontalTimeBase:200μs/div Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 25 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 9.2.2 SeriesBuckRegulator(AdjustableOutput) Copyright © 2016, Texas Instruments Incorporated C —68-μF,35-V,AluminumElectrolyticNichicon“PLSeries” IN C —120-μF,25-VAluminumElectrolytic,Nichicon“PLSeries” OUT D1—1-A,40-VSchottkyRectifier,1N5819 L1—100-μH,L20 R —1kΩ,1% 1 C —SeeFeedforwardCapacitor(C ) FF FF Figure35. AdjustableOutputVoltageVersion 9.2.2.1 DesignRequirements Table6liststhedesignparametersofthisexample. Table6.DesignParameter PARAMETER EXAMPLEVALUE Regulatedoutputvoltage,V 20V OUT Maximuminputvoltage,V (max) 28V IN Maximumloadcurrent,I (max) 0.5A LOAD Switchingfrequency,F Fixedatanominal150kHz 9.2.2.2 DetailedDesignProcedure 9.2.2.2.1 ProgrammingOutputVoltage SelectingR andR ,asshowninFigure35. 1 2 UseEquation1toselecttheappropriateresistorvalues. (1) SelectR tobe1kΩ,1%.SolveforR usingEquation2. 1 2 (2) Select a value for R between 240 Ω and 1.5 kΩ using Equation 3. The lower resistor values minimize noise 1 pickup in the sensitive feedback pin. (For the lowest temperature coefficient and the best stability with time, use 1%metalfilmresistors.) 26 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 (3) R =1k(16.26−1)=15.26k,closest1%valueis15.4kΩ 2 R =15.4kΩ 2 9.2.2.2.2 InductorSelection(L1) 1. CalculatetheinductorVoltmicrosecondconstantE ×T(V × μs)withEquation4. where • V =internalswitchsaturationvoltage=0.9V SAT • V =diodeforwardvoltagedrop=0.5V (4) D 2. CalculatetheinductorVolt•microsecondconstant(E × T)withEquation5. (5) 3. Use the E × T value from the previous formula and match it with the E × T number on the vertical axis of the InductorValueSelectionGuideshowninFigure30. E×T=35.2(V×μs) (6) 4. Onthehorizontalaxis,selectthemaximumloadcurrent:I (max)=0.5A LOAD 5. Identify the inductance region intersected by the E × T value and the maximum load current value. Each regionisidentifiedbyaninductancevalueandaninductorcode(LXX). From the inductor value selection guide shown in Figure 30, the inductance region intersected by the 35 (V × μs)horizontallineandthe0.5-Averticallineis150 μH,andtheinductorcodeisL19. 6. Selectanappropriateinductorfromthefourmanufacturer'spartnumberslistedinTable3. From Table 3, locate line L19, and select an inductor part number from the list of manufacturers' part numbers. 9.2.2.2.3 OutputCapacitorSelection(C ) OUT 1. In the majority of applications, low ESR electrolytic or solid tantalum capacitors between 82 μF and 220 μF provide the best results. This capacitor must be located close to the IC using short capacitor leads and short copper traces. Do not use capacitors larger than 220 μF. For additional information, see Output Capacitor (C ). OUT 2. To simplify the capacitor selection procedure, see Table 7 for a quick design guide. This table contains differentoutputvoltages,andlistsvariousoutputcapacitorsthatprovidesthebestdesignsolutions. From Table 7, locate the output voltage column. From that column, locate the output voltage closest to the output voltage in your application. In this example, select the 24-V line. Under Output Capacitor (C ), OUT select a capacitor from the list of through hole electrolytic or surface mount tantalum types from four different capacitor manufacturers. TI recommends that both the manufacturers and the manufacturers series that are listedinTable7. In this example, through hole aluminum electrolytic capacitors from several different manufacturers are available. 82-µF,50-VPanasonicHFQSeries 120-µF,50-VNichiconPLSeries 3. The capacitor voltage rating must be at least 1.5 times greater than the output voltage, and often much highervoltageratingsareneededtosatisfythelowESRrequirementsneededforlowoutputripplevoltage. For a 20-V output, a capacitor rating of at least 30-V or more is required. In this example, either a 35-V or 50-V capacitor would work. A 50-V rating was chosen because it has a lower ESR which provides a lower outputripplevoltage. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 27 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Other manufacturers or other types of capacitors may also be used, provided the capacitor specifications (especially the 100-kHz ESR) closely match the types listed in Table 7. Refer to the capacitor manufacturers datasheetforthisinformation. 9.2.2.2.4 FeedforwardCapacitor(C ) FF For output voltages greater than approximately 10 V, an additional capacitor is required. The compensation capacitor is typically between 50 pF and 10 nF, and is wired in parallel with the output voltage setting resistor, R . It provides additional stability for high output voltages, low input or output voltages, and very low ESR output 2 capacitors,suchassolidtantalumcapacitorscalculatedwithEquation7. (7) This capacitor type can be ceramic, plastic, silver mica, and so forth (because of the unstable characteristics of ceramiccapacitorsmadewithZ5Umaterial,theyarenotrecommended). Table 7 contains feedforward capacitor values for various output voltages. In this example, a 1-nF capacitor is needed. 9.2.2.2.5 CatchDiodeSelection(D1) 1. The catch diode current rating must be at least 1.3 times greater than the maximum load current. Also, if the power supply design must withstand a continuous output short, the diode must have a current rating equal to the maximum current limit of the LM2594. The most stressful condition for this diode is an overload or shortedoutputcondition. See Table 2. Schottky diodes provide the best performance, and in this example a 1-A, 40-V, 1N5819 Schottky diode is a good choice. The 1-A diode rating is more than adequate and will not be overstressed evenforashortedoutput. 2. Thereversevoltageratingofthediodemustbeatleast1.25timesthemaximuminputvoltage. 3. This diode must be fast (short reverse recovery time) and must be placed close to the LM2594 using short leads and short printed circuit traces. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency, and must be the first choice, especially in low output voltage applications. Ultra-fast recovery or high-efficiency rectifiers are also good choices, but some types with an abrupt turnoff characteristic may cause instability or EMl problems. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N4001 series must not be usedbecausetheyaretooslow. 9.2.2.2.6 InputCapacitor(C ) IN A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground to prevent large voltage transients from appearing at the input. In addition, the RMS current rating of the input capacitor must be selected to be at least ½ the DC load current. The capacitor manufacturers data sheet must be checked to assure that this current rating is not exceeded. Figure 23 shows typical RMS current ratings for several different aluminumelectrolyticcapacitorvalues. ThiscapacitormustbelocatedclosetotheICusingshortleadsandthevoltageratingmustbeapproximately 1.5 timesthemaximuminputvoltage. If solid tantalum input capacitors are used, TI recommends that they be surge current tested by the manufacturer. Use caution when using ceramic capacitors for input bypassing, because it may cause severe ringing at the V IN pin. The important parameters for the Input capacitor are the input voltage rating and the RMS current rating. With a nominal input voltage of 28 V, an aluminum electrolytic aluminum electrolytic capacitor with a voltage rating greater than 42 V (1.5 × V ) is required. Because the next higher capacitor voltage rating is 50 V, a 50-V IN capacitor must be used. The capacitor voltage rating of (1.5 × V ) is a conservative guideline, and can be IN modifiedsomewhatifdesired. The RMS current rating requirement for the input capacitor of a buck regulator is approximately ½ the DC load current.Inthisexample,witha400mAload,acapacitorwithaRMScurrentratingofatleast200mAisneeded. 28 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 Figure 23 shows curves that can be used to select an appropriate input capacitor. From the curves, locate the 50-V line and note which capacitor values have RMS current ratings greater than 200 mA. A 47-μF, 50-V low ESRelectrolyticcapacitorisneeded. For a through-hole design, a 47-μF, 50-V electrolytic capacitor (Panasonic HFQ series or Nichicon PL series or equivalent) would be adequate. Other types or other manufacturers' capacitors can be used provided the RMS ripplecurrentratingsareadequate. For surface mount designs, solid tantalum capacitors are recommended. The TPS series available from AVX, andthe593DseriesfromSpraguearebothsurgecurrenttested. Foradditionalinformation,seeInputCapacitor(C ). IN Table7.OutputCapacitorandFeedforwardCapacitorSelectionTable OUTPUT THROUGH-HOLEOUTPUTCAPACITOR SURFACE-MOUNTOUTPUTCAPACITOR VOLTAGE PANASONICHFQ NICHICONPLSERIES FEEDFORWARD AVXTPS SPRAGUE595D FEEDFORWARD (V) SERIES(μF/V) (μF/V) CAPACITOR SERIES(μF/V) SERIES(μF/V) CAPACITOR 1.2 220/25 220/25 0 220/10 220/10 0 4 180/25 180/25 4.7nF 100/10 120/10 4.7nF 6 82/25 82/25 4.7nF 100/10 120/10 4.7nF 9 82/25 82/25 3.3nF 100/16 100/16 3.3nF 12 82/25 82/25 2.2nF 100/16 100/16 2.2nF 15 82/25 82/25 1.5nF 68/20 100/20 1.5nF 24 82/50 120/50 1nF 10/35 15/35 220pF 28 82/50 120/50 820pF 10/35 15/35 220pF 9.2.2.3 ApplicationCurves Continuousmodeswitchingwaveforms Loadtransientresponseforcontinuousmode VIN=20V,VOUT=5V,ILOAD=400mA VIN=20V,VOUT=5V,ILOAD=200mAto500mA L=100μH,COUT=120μF,COUTESR=140mΩ L=100μH,COUT=120μF,COUTESR=140mΩ A:Outputpinvoltage,10V/div. A:Outputvoltage,50mV/div.(AC) B:Inductorcurrent,0.2A/div. B:200-mAto500-mAloadpulse C:Outputripplevoltage,20mV/div. Figure36.HorizontalTimeBase:2μs/div Figure37.HorizontalTimeBase:50μs/div 10 Power Supply Recommendations The LM2594 is designed to operate from an input voltage supply up to 45 V and 60 V (HV version). This input supplymustbewellregulatedandabletowithstandmaximuminputcurrentandmaintainastablevoltage. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 29 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com 11 Layout 11.1 Layout Guidelines As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can generate voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines must be wide printed circuit traces and must be kept as short as possible. For best results, external components must be placed as close to the switcher lC as possible using groundplaneconstructionorsinglepointgrounding. If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and C wiring can cause OUT problems. When using the adjustable version, take special care regarding as to the location of the feedback resistors and the associated wiring. Physically place both resistors near the IC, and route the wiring away from the inductor, especiallyanopencoretypeofinductor. 11.2 Layout Example C =10-μF,35-V,SolidTantalumAVX,TPSseries IN C =00-μF,10-VSolidTantalumAVX,TPSseries OUT D1=1-A,40-VSchottkyRectifier,surfacemount L1=100-μH,L20,CoilcraftDO33 Figure38. TypicalSurface-MountPCBLayout,FixedOutput(2XSize) C =10-μF,35-V,SolidTantalumAVX,TPSseries IN C =100-μF,10-VSolidTantalumAVX,TPSseries OUT D1=1-A,40-VSchottkyRectifier,surfacemount L1=100-μH,L20,CoilcraftDO33 R1=1kΩ,1% R = UseformulainDesignProcedure 2 C = SeeTable7 FF Figure39. TypicalSurface-MountPCBLayout,AdjustableOutput(2XSize) 30 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 11.3 Thermal Considerations The LM2594xx is available in two packages: an 8-pin through-hole PDIP and an 8-pin surface-mount SOIC. Both packages are molded plastic with a copper lead frame. When the package is soldered to the printed-circuit board (PCB),thecopperandtheboardaretheheatsinkfortheLM2594andtheotherheatproducingcomponents. For best thermal performance, wide copper traces must be used and all ground and unused pins must be soldered to generous amounts of PCB copper, such as a ground plane (one exception to this is the output (switch pin, which must not have large areas of copper). Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and even double-sided or multilayer boards provide a better heat path to the surrounding air. Unless power levels are small, sockets are not recommended because of the addedthermalresistanceitaddsandtheresultanthigherjunctiontemperatures. Package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that affects the junction temperature. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are trace width, printed-circuit copper area, copper thickness, single- or double-sided multilayer board, and the amount of solder on the board. The effectiveness of the PCB to dissipate heat also depends on the size, quantity, and spacing of other components on the board. Furthermore,someofthesecomponentssuchasthecatchdiodeadds heat to the PCB and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material, and the DC resistance,itcouldeitheractasaheatsinktakingheatawayfromtheboard,oritcouldaddheattotheboard. CircuitDataforTemperatureRiseCurve(8-PinPDIP) Capacitors Throughholeelectrolytic Inductor Throughhole,Schott,100 μH Diode Throughhole,1-A,40-V,Schottky PCB 4squareinchessinglesided2oz.copper(0.0028″) Figure40. JunctionTemperatureRise,8-PinPDIP Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 31 ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV SNVS118E–DECEMBER1999–REVISEDMAY2020 www.ti.com Thermal Considerations (continued) CircuitDataforTemperatureRiseCurve (SurfaceMount) Capacitors Surfacemounttantalum,moldedDsize Inductor Surfacemount,CoilcraftDO33,100μH Diode Surfacemount,1-A,40-V,Schottky PCB 4squareinchessinglesided2oz.copper(0.0028″) Figure41. JunctionTemperatureRise,8-PinSOIC Figure 40 and Figure 41 show the LM2594 junction temperature rise above ambient temperature with a 500-mA load for various input and output voltages. This data was taken with the circuit operating as a buck switcher with all components mounted on a PCB to simulate the junction temperature under actual operating conditions. This curve is typical, and can be used for a quick check on the maximum junction temperature for various conditions, butkeepinmindthattherearemanyfactorsthatcanaffectthejunctiontemperature. 32 SubmitDocumentationFeedback Copyright©1999–2020,TexasInstrumentsIncorporated ProductFolderLinks:LM2594 LM2594HV

LM2594,LM2594HV www.ti.com SNVS118E–DECEMBER1999–REVISEDMAY2020 12 Device and Documentation Support 12.1 Related Links The table below lists quick access links. Categories include technical documents, support and community resources,toolsandsoftware,andquickaccesstosampleorbuy. Table8.RelatedLinks TECHNICAL TOOLS& SUPPORT& PARTS PRODUCTFOLDER SAMPLE&BUY DOCUMENTS SOFTWARE COMMUNITY LM2594 Clickhere Clickhere Clickhere Clickhere Clickhere LM2594HV Clickhere Clickhere Clickhere Clickhere Clickhere 12.2 Support Resources TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight fromtheexperts.Searchexistinganswersoraskyourownquestiontogetthequickdesignhelpyouneed. Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do notnecessarilyreflectTI'sviews;seeTI'sTermsofUse. 12.3 Trademarks E2EisatrademarkofTexasInstruments. SIMPLESWITCHERisaregisteredtrademarkofTexasInstruments. Allothertrademarksarethepropertyoftheirrespectiveowners. 12.4 Electrostatic Discharge Caution Thesedeviceshavelimitedbuilt-inESDprotection.Theleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoam duringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates. 12.5 Glossary SLYZ022—TIGlossary. Thisglossarylistsandexplainsterms,acronyms,anddefinitions. 13 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of thisdocument.Forbrowser-basedversionsofthisdatasheet,refertotheleft-handnavigation. Copyright©1999–2020,TexasInstrumentsIncorporated SubmitDocumentationFeedback 33 ProductFolderLinks:LM2594 LM2594HV

PACKAGE OPTION ADDENDUM www.ti.com 7-May-2020 PACKAGING INFORMATION Orderable Device Status Package Type Package Pins Package Eco Plan Lead/Ball Finish MSL Peak Temp Op Temp (°C) Device Marking Samples (1) Drawing Qty (2) (6) (3) (4/5) LM2594HVM-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-12 LM2594HVM-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-3.3 LM2594HVM-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H M-5.0 LM2594HVM-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-5.0 LM2594HVM-ADJ NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H M-ADJ LM2594HVM-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-ADJ LM2594HVMX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-12 LM2594HVMX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-3.3 LM2594HVMX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-5.0 LM2594HVMX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594H & no Sb/Br) M-ADJ LM2594HVN-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS SN Level-1-NA-UNLIM -40 to 125 LM2594HV & no Sb/Br) N-12 P+ LM2594HVN-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV & no Sb/Br) N-3.3 P+ LM2594HVN-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV & no Sb/Br) N-5.0 P+ LM2594HVN-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV & no Sb/Br) N-ADJ P+ LM2594M-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-12 LM2594M-3.3 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594 M-3.3 LM2594M-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-3.3 Addendum-Page 1

PACKAGE OPTION ADDENDUM www.ti.com 7-May-2020 Orderable Device Status Package Type Package Pins Package Eco Plan Lead/Ball Finish MSL Peak Temp Op Temp (°C) Device Marking Samples (1) Drawing Qty (2) (6) (3) (4/5) LM2594M-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594 M-5.0 LM2594M-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-5.0 LM2594M-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-ADJ LM2594MX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-12 LM2594MX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-3.3 LM2594MX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-5.0 LM2594MX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS SN Level-1-260C-UNLIM -40 to 125 2594 & no Sb/Br) M-ADJ LM2594N-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N & no Sb/Br) -12 P+ LM2594N-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N & no Sb/Br) -3.3 P+ LM2594N-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N & no Sb/Br) -5.0 P+ LM2594N-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N & no Sb/Br) -ADJ P+ (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Addendum-Page 2

PACKAGE OPTION ADDENDUM www.ti.com 7-May-2020 (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 3

PACKAGE MATERIALS INFORMATION www.ti.com 7-May-2020 TAPE AND REEL INFORMATION *Alldimensionsarenominal Device Package Package Pins SPQ Reel Reel A0 B0 K0 P1 W Pin1 Type Drawing Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant (mm) W1(mm) LM2594HVMX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594HVMX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594HVMX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594HVMX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594MX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594MX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594MX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2594MX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 PackMaterials-Page1

PACKAGE MATERIALS INFORMATION www.ti.com 7-May-2020 *Alldimensionsarenominal Device PackageType PackageDrawing Pins SPQ Length(mm) Width(mm) Height(mm) LM2594HVMX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594HVMX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594HVMX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594HVMX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594MX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594MX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594MX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2594MX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0 PackMaterials-Page2

PACKAGE OUTLINE D0008A SOIC - 1.75 mm max height SCALE 2.800 SMALL OUTLINE INTEGRATED CIRCUIT C SEATING PLANE .228-.244 TYP [5.80-6.19] .004 [0.1] C A PIN 1 ID AREA 6X .050 [1.27] 8 1 2X .189-.197 [4.81-5.00] .150 NOTE 3 [3.81] 4X (0 -15 ) 4 5 8X .012-.020 B .150-.157 [0.31-0.51] .069 MAX [3.81-3.98] .010 [0.25] C A B [1.75] NOTE 4 .005-.010 TYP [0.13-0.25] 4X (0 -15 ) SEE DETAIL A .010 [0.25] .004-.010 0 - 8 [0.11-0.25] .016-.050 [0.41-1.27] DETAIL A (.041) TYPICAL [1.04] 4214825/C 02/2019 NOTES: 1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not exceed .006 [0.15] per side. 4. This dimension does not include interlead flash. 5. Reference JEDEC registration MS-012, variation AA. www.ti.com

EXAMPLE BOARD LAYOUT D0008A SOIC - 1.75 mm max height SMALL OUTLINE INTEGRATED CIRCUIT 8X (.061 ) [1.55] SYMM SEE DETAILS 1 8 8X (.024) [0.6] SYMM (R.002 ) TYP [0.05] 5 4 6X (.050 ) [1.27] (.213) [5.4] LAND PATTERN EXAMPLE EXPOSED METAL SHOWN SCALE:8X SOLDER MASK SOLDER MASK METAL OPENING OPENING METAL UNDER SOLDER MASK EXPOSED METAL EXPOSED METAL .0028 MAX .0028 MIN [0.07] [0.07] ALL AROUND ALL AROUND NON SOLDER MASK SOLDER MASK DEFINED DEFINED SOLDER MASK DETAILS 4214825/C 02/2019 NOTES: (continued) 6. Publication IPC-7351 may have alternate designs. 7. Solder mask tolerances between and around signal pads can vary based on board fabrication site. www.ti.com

EXAMPLE STENCIL DESIGN D0008A SOIC - 1.75 mm max height SMALL OUTLINE INTEGRATED CIRCUIT 8X (.061 ) [1.55] SYMM 1 8 8X (.024) [0.6] SYMM (R.002 ) TYP [0.05] 5 4 6X (.050 ) [1.27] (.213) [5.4] SOLDER PASTE EXAMPLE BASED ON .005 INCH [0.125 MM] THICK STENCIL SCALE:8X 4214825/C 02/2019 NOTES: (continued) 8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 9. Board assembly site may have different recommendations for stencil design. www.ti.com

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