TPS51123ARGER

TPS51123A TI1 | Alldatasheet

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 Dual-Synchronous,Step-DownControllerwithOut-of-Audio™ Operationand100-mA LDOsforNotebookSystemPower Check forSamples: TPS51123A 1FEATURES APPLICATIONS 2• Wide-InputVoltageRange: 5.5V to28 V • Notebook Computers

• Output VoltageRange: 2 V to5.5V • I/OSupplies
• Built-in100-mA 5-V/3.3-VLDO withSwitches • System Power Supplies
• Built-in1% 2-V ReferenceOutput DESCRIPTION• With/WithoutOut-of-Audio™ Mode Selectable The TPS51123A isa costeffective,dual-synchronousLight-Loadand PWM-Only Operation buck controllertargetedfornotebook system power• Internal1.6-msVoltageServo Soft-Start supplysolutions.Itprovides5-V and 3.3-VLDOs and
• AdaptiveOn-Time ControlArchitecturewith requiresfew externalcomponents.The TPS51123A supportshigh-efficiency,fasttransientresponsesandFour SelectableFrequency Setting providesa combined power-good signal.Out-of-• 4500 ppm/ °C R DS(on) CurrentSensing Audio™ mode light-loadoperationenables low• Built-InOutput Discharge acoustic noise at much higher efficiencythan
• Power Good Output conventionalforcedPWM operation.Adaptiveon- time D-CAP ™ controlprovides convenient and• Built-inOVP/UVP/OCP efficientoperation.The part operateswith supply• Thermal Shutdown (Non-latch) inputvoltagesranging from 5.5 V to 28 V and
• 24-PinQFN (RGE) Package supportsoutputvoltagesfrom 2 V to 5.5 V. The TPS51123A is availablein a 24-pinQFN package and is specifiedfrom -40°C to 85°C ambient temperaturerange. Table1.DifferencesBetween theTPS51123 and TPS51123A TPS51123 TPS51123A VREG5: atleast33 µF VREG5: 10 µF orlarger(X5R orX7R) VREG3: atmost 10 µF VREG3: 10 µF orlarger(X5R orX7R)LDO Output CapacitanceRequirement (1µF acceptableatno load) (1µF acceptableatno load) VREF: 0.22µF to1 µF VREF: 0.22µF to1 µF (X5R orX7R) Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsof Texas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Out-of-Audio,D-CAP aretrademarksofTexas Instruments. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 2011–2012,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.

(QFN-24) LL1 DRVL1 LL2 DRVL2 13 14 15 16 17 18 EN0 SKIPSEL GND VIN VREG5 ENC 6 5 4 3 2 1 TRIP2 VFB2 TONSEL VREF VFB1 TRIP1 PowerPAD 220 nF 20 k/c87 20 k/c87 30 k/c87 100 k/c87 VREG5 10 /c109F 5.1 /c87 0.1 /c109F 130 k/c87130 k/c87 3.3 /c109F 330 /c109F VO1 5 V VIN VREG5 ENC VIN 10 /c109F x 2 VIN 5.5 V to 28 V EN0 5.1 /c87 0.1 /c109F 3.3 /c109F 330 /c109F VO2 3.3 V 10 /c109F x 2 10 /c109F 13 k/c87 UDG-10086 VIN TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com This integratedcircuitcan be damaged by ESD. Texas Instrumentsrecommends thatallintegratedcircuitsbe handled with appropriateprecautions.Failuretoobserveproperhandlingand installationprocedurescan cause damage. ESD damage can rangefromsubtleperformancedegradationtocompletedevicefailure.Precisionintegratedcircuitsmay be more susceptibletodamage because verysmallparametricchanges couldcause thedevicenottomeet itspublishedspecifications.

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 ORDERING INFORMATION (1) MINIMU MTA PACKAGE PART NUMBER PINS TRANSPORT MEDIA ECO PLANQUANTI TY PlasticQuad FlatPack Green (RoHS and no-40°C to85°C TPS51123ARGER 24 Tape/Reel 3000(QFN) Sb/Br) (1) Forthemost currentspcificationsand package information,see thePackage OptionAddendum locatedattheend ofthisdatasheetor refertoourweb siteathttp://www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) overoperatingfree-airtemperaturerange(unlessotherwisenoted) PARAMETER VALUE UNIT VBST1, VBST2 -0.3to36 VIN -0.3to30 LL1,LL2 -2.0to30Inputvoltagerange V(1) LL1,LL2,pulsewidth< 20 ns -5.0to30 VBST1, VBST2 (2) -0.3to6 EN0, ENC, TRIP1,TRIP2,VFB1, VFB2, VO1, VO2, TONSEL, SKIPSEL -0.3to6 DRVH1, DRVH2 -1.0to36 Outputvoltagerange DRVH1, DRVH2 (2) -0.3to6 V(1) PGOOD, VREG3, VREG5, VREF, DRVL1, DRVL2 -0.3to6 TJ Junctiontemperaturerange -40to125 Tstg Storagetemperature -55to150 (1) Stressesbeyond thoselistedunder"absolutemaximum ratings"may cause permanentdamage tothedevice.These arestressratings onlyand functionaloperationofthedeviceattheseorany otherconditionsbeyond thoseindicatedunder"recommended operating conditions"isnotimplied.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmay affectdevicereliability. (2) VoltagevaluesarewithrespecttothecorrespondingLLx terminal. DISSIPATION RATINGS 2-oz.traceand copperpad withsolder. DERATING FACTOR ABOVE TAPACKAGE TA < 25°C POWER RATING TA = 85°C POWER RATING= 25°C 24 pinRGE (1) 1.85W 18.5mW/ °C 0.74W (1) Enhanced thermalconductanceby 3 x 3 thermalviasbeneaththermalpad. RECOMMENDED OPERATING CONDITIONS overoperatingfree-airtemperaturerange(unlessotherwisenoted) PARAMETER MIN TYP MAX UNIT Supplyvoltage VIN 5.5 28 VBST1, VBST2 -0.1 34 VBST1, VBST2 (wrtLLx) -0.1 5.5Inputvoltagerange EN0, ENC, TRIP1,TRIP2,VFB1, VFB2, VO1, VO2, -0.1 5.5TONSEL, SKIPSEL VDRVH1, DRVH2 -0.8 34 DRVH1, DRVH2 (wrtLLx) -0.1 5.5 Outputvoltagerange LL1,LL2 -1.8 28 VREF, VREG3, VREG5 -0.1 5.5 PGOOD, DRVL1, DRVL2 -0.1 5.5 TA Operatingfree-airtemperature -40 85 °C Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLink(s):TPS51123A

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ELECTRICAL CHARACTERISTICS

overoperatingfree-airtemperaturerange,VIN = 12 V (unlessotherwisenoted) PARAMETER CONDITIONS MIN TYP MAX UNIT SUPPLY CURRENT VIN current,T A = 25°C, no load,VO1 = 0 V, IVIN1 VIN supplycurrent1 VO2 = 0 V,EN0=open, ENC = 5 V, 0.55 1.00 mA TRIP1 = TRIP2 = 2 V,VFB1 = VFB2 = 2.05V VIN current,TA = 25°C, no load,VO1 = 5 V, IVIN2 VIN supplycurrent2 VO2 = 3.3V,EN0=open, ENC = 5 V, 4.0 6.5 μA TRIP1 = TRIP2 = 2 V,VFB1 = VFB2 = 2.05V VO1 current,TA = 25°C, no load,VO1 = 5 V, IVO1 VO1 current VO2 = 3.3V,EN0=open, ENC = 5 V, 0.8 1.5 mA TRIP1 = TRIP2 = 2 V,VFB1 = VFB2 = 2.05V VO2 current,TA = 25°C, no load,VO1 = 5 V, IVO2 VO2 current VO2 = 3.3V,EN0=open, ENC = 5 V, 12 100 TRIP1 = TRIP2 = 2 V,VFB1 = VFB2 = 2.05V VIN current,TA = 25°C, no load, μAIVINSTBY VIN standbycurrent 95 150EN0 = 1.2V,ENC = 0 V VIN current,TA = 25°C, no load,IVINSDN VIN shutdowncurrent 10 25EN0 = ENC = 0 V VREF OUTPUT IVREF = 0 A 1.98 2.00 2.02 VVREF VREF outputvoltage V –5 μA < IVREF < 100 μA 1.97 2.00 2.03 VREG5 OUTPUT VO1 = 0 V,IVREG5 < 100 mA, TA = 25°C 4.8 5 5.2 VO1 = 0 V,IVREG5 < 100 mA,VVREG5 VREG5 outputvoltage 4.75 5 5.25 V6.5V < VIN < 28 V VO1 = 0 V,IVREG5 < 50 mA, 5.5V < VIN < 28 V 4.75 5 5.25 IVREG5 VREG5 outputcurrent VO1 = 0 V,VREG5 = 4.5V 100 175 250 mA Turnson 4.55 4.7 4.85 VTH5VSW Switchoverthreshold V Hysteresis 0.15 0.25 0.3 R 5VSW 5 V SW R ON VO1 = 5 V,IVREG5 = 100 mA 1 3 Ω VREG3 OUTPUT VO2 = 0 V,IVREG3 < 100 mA, TA= 25°C 3.2 3.33 3.46 VVREG3 VREG3 outputvoltage VO2 = 0 V,IVREG3 < 100 mA, 6.5V < VIN < 28 V 3.13 3.33 3.5 V VO2 = 0 V,IVREG3 < 50 mA, 5.5V < VIN < 28 V 3.13 3.33 3.5 IVREG3 VREG3 outputcurrent VO2 = 0 V,VREG3 = 3 V 100 175 250 mA Turnson 3.05 3.15 3.25 VTH3VSW Switchoverthreshold V Hysteresis 0.1 0.2 0.25 R 3VSW 3 V SW R ON VO2 = 3.3V,IVREG3 = 100 mA 1.5 4 Ω INTERNAL REFERENCE VOLTAGE VIREF Internalreferencevoltage IVREF = 0 A,beginningofON state 1.95 1.98 2.01 FB voltage,IVREF = 0 A,skipmode 1.98 2.01 2.04 VFB voltage,IVREF = 0 A,OOA mode (1) 2.00 2.035 2.07VVFB VFB regulationvoltage FB voltage,IVREF = 0 A,continuousconduction 2.00mode (1) IVFB VFB inputcurrent VFBx = 2.0V,TA= 25°C -20 20 nA OUTPUT VOLTAGE, VOUT DISCHARGE IDischg VOUT dischargecurrent ENC = 0 V,VOx = 0.5V 10 60 mA (1) Ensuredby design.Not productiontested.

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 ELECTRICAL CHARACTERISTICS (continued) overoperatingfree-airtemperaturerange,VIN = 12 V (unlessotherwisenoted) PARAMETER CONDITIONS MIN TYP MAX UNIT OUTPUT DRIVERS Source,VBSTx - DRVHx = 100 mV 4 8 R DRVH DRVH resistance Sink,VDRVHx - LLx = 100 mV 1.5 4 Ω Source,VVREG5 - DRVLx = 100 mV 4 8 R DRVL DRVL resistance Sink,VDRVLx = 100 mV 1.5 4 DRVHx-offtoDRVLx-on 10 tD Dead time ns DRVLx-offtoDRVHx-on 30 INTERNAL BST DIODE VFBST Forwardvoltage VVREG5-VBSTx ,IF = 10 mA, TA = 25 °C 0.7 0.8 0.9 V IVBSTLK VBST leakagecurrent VBSTx = 34 V,LLx = 28 V,TA = 25 °C 0.1 1 μA DUTY AND FREQUENCY CONTROL tON11 CH1 on time1 VIN = 12 V,VO1 = 5 V,200 kHz setting 2080 tON12 CH1 on time2 VIN = 12 V,VO1 = 5 V,245 kHz setting 1700 tON13 CH1 on time3 VIN = 12 V,VO1 = 5 V,300 kHz setting 1390 tON14 CH1 on time4 VIN = 12 V,VO1 = 5 V,365 kHz setting 1140 tON21 CH2 on time1 VIN = 12 V,VO2 = 3.3V,250 kHz setting 1100 ns tON22 CH2 on time2 VIN = 12 V,VO2 = 3.3V,305 kHz setting 900 tON23 CH2 on time3 VIN = 12 V,VO2 = 3.3V,375 kHz setting 730 tON24 CH2 on time4 VIN = 12 V,VO2 = 3.3V,460 kHz setting 600 tON(min) Minimum on time TA = 25 °C 80 tOFF(min) Minimum offtime TA = 25 °C 300 SOFT-START tSS InternalSS time Internalsoftstart 1.1 1.6 2.1 ms POWERGOOD PG infromlower 92.50% 95% 97.50% VTHPG PG threshold PG infromhigher 102.50% 105% 107.50% PG hysteresis 2.50% 5% 7.50% IPGMAX PG sinkcurrent PGOOD = 0.5V 5 12 mA tPGDEL PG delay DelayforPG in 350 510 670 μs LOGIC THRESHOLD AND SETTING CONDITIONS Shutdown 0.4 VEN0 EN0 settingvoltage V Enable 2.4 IEN0 EN0 current VEN0 = 0.2V 2 3.5 5 μA Shutdown 0.6 VENC ENC thresholdvoltage V Enable 2 Shutdown 350 400 450 VEN(trip) TRIP1,TRIP2 threshold mV Hysteresis 10 30 60 200 kHz/250kHz 1.5 245 kHz/305kHz 1.9 2.1 VTONSEL TONSEL settingvoltage V 300 kHz/375kHz 2.7 3.6 365 kHz/460kHz 4.7 Autoskip 1.5 VSKIPSEL SKIPSEL settingvoltage PWM only 1.9 2.1 V OOA autoskip 2.7 Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLink(s):TPS51123A

SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com ELECTRICAL CHARACTERISTICS (continued) overoperatingfree-airtemperaturerange,VIN = 12 V (unlessotherwisenoted) PARAMETER CONDITIONS MIN TYP MAX UNIT PROTECTION: CURRENT SENSE ITRIP TRIPx sourcecurrent VTRIPx = 920 mV, TA= 25°C 9.4 10 10.6 μA TRIPx currenttemperatureTC ITRIP On thebasisof25°C (2) 4500 ppm/°Ccoefficient ((VTRIPx-GND /9)-24mV -VGND-LLx )voltage,VTRIPx-VOCLoff OCP comparatoroffset -8 0 8 GND = 920 mV VOCL(max) Maximum OCL setting VTRIPx = 5 V 185 205 225 mV ZerocrossdetectionVZC VGND-LLx voltage -5 0 5comparatoroffset VTRIP Currentlimitthreshold VTRIPx-GND voltage(2) 0.515 2 V PROTECTION: UNDERVOLTAGE AND OVERVOLTAGE PROTECTION VOVP OVP tripthreshold OVP detect 110% 115% 120% TOVPDEL OVP propdelay 2 μs UVP detect 55% 60% 65% VUVP OutputUVP tripthreshold Hysteresis 10% tUVPDEL OutputUVP propdelay 20 32 40 μs tUVPEN OutputUVP enabledelay 1.4 2 2.6 ms UNDERVOLTAGE LOCKOUT (UVLO) Wake up 4.1 4.2 4.3 VUVVREG5 VREG5 UVLO threshold Hysteresis 0.38 0.43 0.48 V VUVVREG3 VREG3 UVLO threshold Shutdown (2) VO2-1 THERMAL SHUTDOWN Shutdown temperature(2) 150 TSDN Thermalshutdownthreshold °C Hysteresis(2) 10 (2) Ensuredby design.Not productiontested.

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 DEVICE INFORMATION Table2. TERMINAL I/O DESCRIPTION NAME NO. DRVH1 21 O High-sideN-channelMOSFET driveroutputs.LL referenceddrivers. DRVH2 10 DRVL1 19 O Low-sideN-channelMOSFET driveroutputs.GND referenceddrivers. DRVL2 12 Masterenableinput. EN0 13 I/O Open :LDOs on,and readytoturnbothswitcherchannels. GND :disableallcircuit Channel1 and Channel2 enableinput.Pullup tothevoltageranging3.3-Vto5-V toturnon bothENC 18 I switcherchannels.Shorttogroundtoshutdownthem. GND 15 – Ground. LL1 20 I Switchnode connectionsforhigh-sidedrivers,currentlimitand controlcircuitry. LL2 11 PGOOD 23 O Powergood window comparatoroutputforchannel1 and 2.(LogicalAND) Selectionpinforoperationmode: OOA autoskip:ConnecttoVREG3 orVREG5SKIPSEL 14 I PWM only:ConnecttoVREF Autoskip:ConnecttoGND TRIP1 1 Channel1 and Channel2 enableand OCL tripsettingpins.ConnectresistorfromthispintoGND toI/O setthresholdforsynchronousR DS(on) sense.Shorttogroundtoshutdown a switcherchannel.TRIP2 6 On-timeadjustmentpin. 365 kHz/460kHz setting:connecttoVREG5 TONSEL 4 I 300 kHz/375kHz setting:connecttoVREG3 245 kHz/305kHz setting:connecttoVREF 200 kHz/250kHz setting:connecttoGND VBST1 22 I Supplyinputforhigh-sideN-channelMOSFET driver(boostterminal). VBST2 9 VFB1 2 I SMPS feedbackinputs.Connectwithfeedbackresistordivider. VFB2 5 VIN 16 I Highvoltagepower supplyinputfor5-V/3.3-VLDO. VO1 24 OutputconnectiontoSMPS. These terminalswork as fixedvoltageinputsand outputdischargeI/O inputs.VO1 and VO2 alsowork as 5-V and 3.3-Vswitchoverreturnpower inputrespectively.VO2 7 2-V referencevoltageoutput.Connecta high-qualityX5R orX7R ceramiccapacitorwitha valueVREF 3 O between 220-nFand 1-µF tosignalGND nearthedevice. 3.3-Vpower supplyoutput.Connecta high-qualityX5R orX7R ceramiccapacitorwitha valueof10-VREG3 8 O µF orlargertopower GND nearthedevice.A 1-μF ceramiccapacitorisacceptablewhen notloaded. 5-V power supplyoutput.Connecta high-qualityX5R orX7R ceramiccapacitorwitha valueof10-µFVREG5 17 O orlargertopower GND nearthedevice. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLink(s):TPS51123A

(QFN-24) VO1 PGOOD VO2 VREG3 VBST1 DRVL1 LL1 DRVH1 VBST2 DRVH2 LL2 DRVL2 EN0TRIP2 VFB2 VREF TONSEL VFB1 TRIP1 SKIPSEL GND VIN ENC VREG52 7 8 9 10 11 24 23 22 21 20 19 TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com QFN PACKAGE (TOP VIEW) FunctionalBlock Diagram

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 SwitcherControllerBlock Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLink(s):TPS51123A

-50 0 50 100 150 TJ - Junction Temperature - /c176C IVIN1 - VIN Supply Current1 - /c109A VIN SUPPLY CURRENT1 vs INPUT VOLTAGE 100 200 300 400 500 600 700 800 5 10 15 20 25 VIN - Input Voltage - V IVIN1 - VIN Supply Current1 - /c109A VIN SUPPLY CURRENT2 vs JUNCTION TEMPERATURE -50 0 50 100 150 TJ - Junction Temperature - °C IVI N2 - VIN Supply Current2 - /c109A VIN SUPPLY CURRENT2 vs INPUT VOLTAGE 5 10 15 20 25 VIN - Input Voltage - V IVIN2 - VIN Supply Current2 - /c109A TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS Figure1. Figure2. Figure3. Figure4.

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IVINSTBY –VIN Standby Current – µA 5 10 15 20 25 VIN – Input Voltage – V VIN STANDBY CURRENT vs INPUT VOLTAGE VIN STANDBY CURRENT vs JUNCTION TEMPERATURE 100 150 200 250 50 0 50 100 150 TJ - Junction Temperature - °C IVINSTBY - VIN Standby Current - /c109A VIN SHUTDOWN CURRENT vs JUNCTION TEMPERATURE -50 0 50 100 150 TJ - Junction Temperature - °C IVI NSDN - VIN Shutdown Current - /c109A VIN SHUTDOWN CURRENT vs INPUT VOLTAGE 5 10 15 20 25 VIN - Input Voltage - V IVINSDN - VIN Shutdown Current - /c109A TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) Figure5. Figure6. Figure7. Figure8. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLink(s):TPS51123A

SWITCHING□FREQUENCY vs INPUT□VOLTAGE 100 200 300 400 500 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V fSW - Swithching Frequency - kHz TONSEL =□GND CH1 CH2 CURRENT SENSE CURRENT vs JUNCTION TEMPERATURE 50 0 50 100 150 TJ - Junction Temperature - °C - Current Sense Current - /c109AITRIP SWITCHING□FREQUENCY vs INPUT□VOLTAGE 100 200 300 400 500 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V fSW - Swithching Frequency - kHz TONSEL =□3.3V CH1 CH2 SWITCHING□FREQUENCY vs INPUT□VOLTAGE 100 200 300 400 500 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V fSW - Swithching Frequency - kHz TONSEL =□2V CH1 CH2 TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) Figure9. Figure10. Figure11. Figure12.

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SWITCHING□FREQUENCY vs INPUT□VOLTAGE 100 200 300 400 500 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V fSW - Swithching Frequency - kHz TONSEL =□5V CH1 CH2 SWITCHING□FREQUENCY vs OUTPUT□CURRENT 100 200 300 400 500 0.001 0.01 0.1 1 10 IOUT -□Output□Current□- A fSW - Swithching Frequency - kHz TONSEL =□GND CH2 Auto-skip CH2□OOA CH2□PWM□Only CH1□PWM□Only CH1 Auto-skip CH1□OOA SWITCHING□FREQUENCY vs OUTPUT□CURRENT 100 200 300 400 500 0.001 0.01 0.1 1 10 IOUT -□Output□Current□- A fSW - Swithching Frequency - kHz TONSEL =□3.3V CH2 Auto-skip CH2□OOA CH2□PWM□Only CH1□PWM□Only CH1 Auto-skip CH1□OOA SWITCHING□FREQUENCY vs OUTPUT□CURRENT 100 200 300 400 500 0.001 0.01 0.1 1 10 IOUT -□Output□Current□- A fSW - Swithching Frequency - kHz TONSEL =□2V CH2 Auto-skip CH2□OOA CH2□PWM□Only CH1□PWM□Only CH1 Auto-skip CH1□OOA TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) Figure13. Figure14. Figure15. Figure16. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLink(s):TPS51123A

SWITCHING□FREQUENCY vs OUTPUT□CURRENT 100 200 300 400 500 0.001 0.01 0.1 1 10 IOUT -□Output□Current□- A fSW - Swithching Frequency - kHz TONSEL =□5V CH2 Auto-skip CH2□OOA CH2□PWM□Only CH1□PWM□Only CH1 Auto-skip CH1□OOA OVP/UVP THRESHOLD VOLTAGE vs JUNCTION TEMPERATURE 100 110 120 130 140 150 -50 0 50 100 150 TJ - Junction Temperature - °C V OVP/VUVP - OVP/UVP Threshold - % VR E G5 OU TPU T VOLTAGE vs OU TPU T CU R R E N T 4.90 4.95 5.00 5.05 0 20 40 60 80 100 IVREG5 - VR E G5 Output Curre nt - m A VVREG5 - VREG5 Output Voltage - V VR E G3 OU TPU T VOLTAGE vs OU TPU T CU R R E N T 3.2 3.25 3.3 3.35 0 20 40 60 80 100 IVREG3 - VR E G3 Output Curre nt - m A VVREG3 - VREG3 Output Voltage - V TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) Figure17. Figure18. Figure19. Figure20.

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4.950 4.975 5.000 5.025 5.050 5.075 0.001 0.01 0.1 1 10 IOUT1 - 5-V Output Current - A VO UT1- 5-V Output Voltage - V PWM Only Auto-skip OOA VREF OUTPUT VOLTAGE vs OUTPUT CURRENT 1.980 1.985 1.990 1.995 2.000 2.005 2.010 2.015 2.020 0 20 40 60 80 100 IVREF - VREF Output Current - /c109A VVREF - VREF Output Voltage - V 5-V□OUTPUT□VOLTAGE vs INPUT□VOLTAGE 4.950 4.975 5.000 5.025 5.050 5.075 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V VOUT1 - 5-V Output Voltage - V IO =□0A IO =□6A 3.3-V□OUTPUT□VOLTAGE vs OUTPUT□CURRENT 3.240 3.270 3.300 3.330 3.360 0.001 0.01 0.1 1 10 IOUT2 -□3.3-V□Output□Current□- A VOUT2 - 3.3-V Output Voltage - V PWM□Only Auto-skip OOA TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) Figure21. Figure22. Figure23. Figure24. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLink(s):TPS51123A

0.001 0.01 0.1 1 10 /c104– Efficiency – % VIN = 20 V VIN = 12 V VIN = 8 V OOA Auto-Skip PWM Only IOUT1 – 5-V Output Current – A 5-V EFFICIENCY vs OUTPUT CURRENT 3.3-V□OUTPUT□VOLTAGE vs INPUT□VOLTAGE 3.240 3.270 3.300 3.330 3.360 6 8 10 12 14 16 18 20 22 24 26 VIN -□Input□Voltage□-□V VOUT2 - 3.3-V Output Voltage - V IO =□0A IO =□6A 3.3-V EFFICIENCY vs OUTPUT CURRENT 100 0.001 0.01 0.1 1 10 IOUT2 - 3.3-V Output Current - A /c104- Efficiency - % Auto-skip PWM Only OOA 5-V Switcher ON VIN=8V VIN=12V VIN=20V TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) Figure25. Figure26. Figure27.

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VOUT1 (100mV/div) IIND (5A/div) IOUT1 (5A/div) VOUT2 (100mV/div) IIND (5A/div) IOUT2 (5A/div) ENC (5 V/div) VOUT2 (2 V/div) PGOOD (5 V/div) ENC (5 V/div) VOUT1 (2 V/div) PGOOD (5 V/div) TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 TYPICAL CHARACTERISTICS (continued) 5-V Load TransientResponse 3.3-VLoad TransientResponse Figure28. Figure29. 5-V StartupWaveforms 3.3-VStartupWaveforms Figure30. Figure31. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 17 ProductFolderLink(s):TPS51123A

VOUT1 (200mV/div) VREG5 (200mV/div) VOUT2 (200mV/div) VREG3 (200mV/div) ENC (10 V/div) VOUT2 (2 V/div) PGOOD (5 V/div) DRVL2 (5 V/div) ENC (10 V/div) VOUT1 (2 V/div) PGOOD (5 V/div) DRVL1 (5 V/div) TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com TYPICAL CHARACTERISTICS (continued) 5-V SwitchoverWaveforms 3.3-VSwitchoverWaveforms Figure32. Figure33. 5-V Soft-stopWaveforms 3.3-VSoft-stopWaveforms Figure34. Figure35.

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012

APPLICATION INFORMATION

The main controlloopoftheswitchmode power supply(SMPS) isdesignedas an adaptiveon-timepulsewidth modulation(PWM) controller.Itsupportsa proprietaryD-CAP ™ mode. D-CAP ™ mode does notrequireexternal compensationcircuitand issuitableforlow externalcomponent countconfigurationwhen used withappropriate amount ofESR attheoutputcapacitor(s). At the beginningof each cycle,the synchronoustop MOSFET is turnedon, or becomes ‘ON ’ state.This MOSFET isturnedoff,orbecomes OFF state,afterinternalone shottimerexpires.Thisone shotisdetermined by VIN and VOUT tokeep frequencyfairlyconstantoverinputvoltagerange,hence itiscalledadaptiveon-time control.The MOSFET isturnedon again when the feedbackpointvoltage,VVFBx , decreased to match with internal2-V reference.The inductorcurrentinformationisalsomonitoredand shouldbe below theovercurrent thresholdto initiatethisnew cycle.Repeatingoperationin thismanner, the controllerregulatesthe output voltage.The synchronousbottomor therectifyingMOSFET isturnedon atthebeginningofeach OFF stateto keep theconductionlossminimum.The rectifyingMOSFET isturnedoffbeforethetopMOSFET turnson atnext switchingcycleor when inductorcurrentinformationdetectszerolevel.Intheauto-skipmode or theOOA skip mode, thisenablesseamless transitiontothereducedfrequencyoperationatlightloadconditionso thathigh- efficiencyiskeptoverbroadrangeofloadcurrent. AdaptiveOn-Time Controland PWM Frequency TPS51123A does not have a dedicatedoscillatoron board.However, the partruns withpseudo-constant frequencyby feed-forwardingthe inputand outputvoltageintothe on-time,one-shottimer.The on-timeis controlledinverseproportionaltotheinputvoltageand proportionaltotheoutputvoltageso thatthedutyratiois keptas VOUT /VIN technicallywiththesame cycletime.The frequenciesaresetby theTONSEL pinas shown in Table3. Table3.TONSEL Connection and SwitchingFrequency SWITCHING FREQUENCY (kHz) TONSEL CONNECTION CH1 CH2 GND 200 250 VREF 245 305 VREG3 300 375 VREG5 365 460 Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 19 ProductFolderLink(s):TPS51123A

Switching ModulatorVoltage Divider IoIcIL Vc Output Capacitor fSW O 1f 2 ESR C 4/c61 /c163/c112 /c180 /c180 TPS51123A SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com Loop Compensation From small-signalloopanalysis,a buck converterusingD-CAP TM mode can be simplifiedas below. Figure36. SimplifyingtheModulator The outputvoltageiscompared withinternalreferencevoltageafterdividerresistors,R1 and R2. The PWM comparatordeterminesthetimingtoturnon high-sideMOSFET. The gainand speed ofthecomparatorishigh enough tokeep thevoltageatthebeginningofeach on cyclesubstantiallyconstant.For theloopstability,the 0dB frequency,f0,definedbelowneed tobe lowerthan1/4oftheswitchingfrequency. (1) As f0 isdeterminedsolelyby theoutputcapacitor'scharacteristics,loopstabilityofD-CAP TM mode isdetermined by the capacitor'schemistry.For example,specialtypolymer capacitors(SP-CAP) have Co in the orderof several100 μF and ESR inrangeof10 m Ω.These make f0 on theorderof100 kHz orlessand theloopwillbe stable.However, ceramiccapacitorshave f0 at more than 700 kHz, which isnot suitableforthisoperational mode. Ramp Signal The TPS51123A adds a ramp signaltothe2-V referenceinordertoimproveitsjitterperformance.As described inthe previoussection,the feedbackvoltageiscompared withthe referenceinformationto keep the output voltageinregulation.By addinga smallramp signaltothereference,thedignal-to-noiseratioattheonsetofa new switchingcycleisimproved.Thereforethe operationbecomes lessjitterand stable.The ramp signalis controlledto startwith-20 mV at the beginningof ON-cycleand to become 0 mV at the end of OFF-cyclein steadystate.By usingthisscheme, theTPS51123A improvejitterperformancewithoutsacrificingthereference accuracy.

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/c40 /c41 f IN OUT OUT OUT(LL) IN 2 L V V V V /c180 /c180 /c180 /c45 /c180/c61 TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 LightLoad ConditioninAuto-SkipOperation The TPS51123A automaticallyreducesswitchingfrequencyat lightloadconditionsto maintainhigh-efficiency. This reductionof frequencyis achievedsmoothlyand withoutincreaseof VOUT ripple.Detailoperationis describedas follows.As the outputcurrentdecreasesfrom heavy loadcondition,the inductorcurrentisalso reducedand eventuallycomes tothepointthatitsvalleytoucheszerocurrent,which istheboundarybetween continuousconductionand discontinuousconductionmodes. The rectifyingMOSFET isturnedoffwhen thiszero inductorcurrentis detected.As the load currentfurtherdecreased,the converterruns in discontinuous conductionmode and ittakeslongerand longertodischargetheoutputcapacitortothelevelthatrequiresnext ON cycle.The ON timeiskeptthesame as thatintheheavy loadcondition.Inreverse,when theoutputcurrent increasefromlightloadtoheavy load,switchingfrequencyincreasestothepresetvalueas theinductorcurrent reaches to the continuousconduction.The transitionload pointto the lightload operationIOUT(LL) (i.e.the thresholdbetween continuousand discontinuousconductionmode) can be calculatedas follows; (2) where fisthePWM switchingfrequency. Switchingfrequencyversusoutputcurrentin the lightload conditionisa functionof L, VIN and VOUT , but it decreasesalmostproportionaltotheoutputcurrentfromtheIOUT(LL) shown inEquation2.For example,itise60 kHz atIOUT(LL)/5ifthefrequencysettingis300 kHz. Out-of-Audio™ Light-LoadOperation Out-of-Audio™ (OOA) light-loadmode isa unique controlfeaturethatkeeps the switchingfrequencyabove acousticaudiblefrequenciestowardvirtuallyno loadconditionwhilemaintainingbestofthearthighconversion efficiency.When the Out-of-Audio™ operationis selected,OOA controlcircuitmonitorsthe statesof both MOSFET and forcetochange intotheON stateifbothofMOSFETs areoffformore than32 μs.Thismeans that the top MOSFET isturnedon even ifthe outputvoltageishigherthan the targetvalueso thatthe output capacitoristendstobe overcharged. The OOA controlcircuitdetectstheover-voltageconditionand beginstomodulatetheon timetokeep theoutput voltageregulated.As a result,theoutputvoltagebecomes 0.5% higherthannormallight-loadoperation. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 21 ProductFolderLink(s):TPS51123A

SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com Enable and SoftStart EN0 isthecontrolpinofVREG5, VREG3 and VREF regulators.Bringthisnode down toGND disablesthose threeregulatorsand minimizetheshutdown supplycurrentto10 μA. Pullingthisnode up to3.3V or5 V willturn thethreeregulatorson tostandbymode. The two switchmode power supplies(channel-1,channel-2)become readytoenableatthisstandbymode. The TPS51123A has an internal,1.6ms, voltageservosoft-startforeach channel. Both channel1 and channel2 can be enabledsimultaneouslywiththeENC pinwhen onlytheOCL tripsetting resistanceisconnectedtoTRIPx pin.Channel 1 and channel2 can be disabledindependentlyby shortingthe TRIPx pintogroundwhen theENC pinvoltageishigherthanitsenablethreshold,whichistypically1.26V. After enablingchannel1 and/orchannel2, an internalDAC beginsramping up the referencevoltageof the PWM comparator.Smooth controloftheoutputvoltageismaintainedduringstartup.As TPS51123A sharesone DAC withboth channels,ifTRIPx pinbecomes higherthan the enablethresholdvoltagewhileanotherchannelis startingup,soft-startispostponeduntilanotherchannelsoft-starthas completed.IfbothofTRIP1 and TRIP2 become higherthan the enable thresholdvoltageat the same time (within60 µs),both channelsstartup simultaneously. Table4.EnablingState EN0 ENC TRIP1 TRIP2 VREF VREG5 VREG3 CH1 CH2 GND No effect(1) No effect(1) No effect(1) Off Off Off Off Off Open Low No effect(1) No effect(1) On On On Off Off Open High Low Low On On On Off Off Open High High Low On On On On Off Open High Low High On On On Off On Open High High High On On On On On (1) Eitherhighorlow,does no affecttheenablestate. VREG5/VREG3 LinearRegulators There aretwo setsof100-mA standbylinearregulatorswhichoutputs5 V and 3.3V, respectively.The VREG5 servesas themain power supplyfortheanalogcircuitryofthedeviceand providesthecurrentforgatedrivers. The VREG3 isintendedmainlyforauxiliary3.3-Vsupplyforthenotebooksystemduringstandbymode. Add a high-qualityX5R orX7R ceramiccapacitorwitha valueof10-µF orlargerplacedclosetotheVREG5 and VREG3 pinstostabilizeLDOs. ForVREG3, a 1-µF ceramiccapacitorisacceptablewhen notloaded. VREG5 Switch Over When theVO1 voltagebecomes higherthan4.7V AND channel-1internalpowergood flagisgenerated,internal 5-V LDO regulatorisshutoffand theVREG5 outputisconnectedtoVO1 by internalswitchoverMOSFET. The 510-μs powergood delayhelpsa switchoverwithoutglitch. VREG3 Switch Over When the VO2 voltagebecomes higherthan 3.15 V AND channel-2internalpowergood flagisgenerated, internal3.3-VLDO regulatorisshutoffand the VREG3 outputisconnectedto VO2 by internalswitchover MOSFET. The 510-μs powergood delayhelpsa switchoverwithoutglitch. Powergood The TPS51123A has one powergood outputthatindicatesa highstatewhen bothswitcheroutputsarewithinthe targets(AND gated).The powergood functionisactivatedwith2-ms internaldelayafterENC goes high.Ifthe outputvoltagebecomes within±5% ofthetargetvalue,internalcomparatorsdetectpower good stateand the powergood signalbecomes highafter510-μs internaldelay.ThereforePGOOD goes higharound 2.5ms after ENC goes high.Iftheoutputvoltagegoes outsideof±10% ofthetargetvalue,thepowergood signalbecomes low after2-μs internaldelay.The powergood outputisan open drainoutputand isneeded to be pulledup outside.

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/c40 /c41 /c40 /c41 /c40 /c41 /c40 /c41TRIP TRIP TRIP R k I AV mV 24 mV 9 /c87 /c180 /c109/c61 /c45 /c40 /c41 /c40 /c41 /c40 /c41 f IN OUT OUTTRIP RIPPLE TRIP OCP INDS on DS on V V VV I V 1I R 2 R 2 L V /c45 /c180/c61 /c43 /c61 /c43 /c180 /c180 /c180 TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 Also note that,inthe case of Auto-skipor Out-of-Audio™ mode, ifthe outputvoltagegoes +10% above the targetvalueand thepower-goodsignalflagslow,thentheloopattemptstocorrecttheoutputby turningon the low-sidedriver(forcedPWM mode).Afterthefeedbackvoltagereturnstobe within+5% ofthetargetvalueand thepower-goodsignalgoes high,thecontrollerreturnsback toauto-skipmode orOut-of-Audio™ mode. Output DischargeControl When ENC islow,theTPS51123A dischargesoutputsusinginternalMOSFET which isconnectedtoVOx and GND. The currentcapabilityoftheseMOSFETs islimitedtodischargeslowly. Low-Side Driver The low-sidedriverisdesignedtodrivehighcurrentlow R DS(on) N-channelMOSFET(s). The drivecapabilityis representedby itsinternalresistance,whichare4 Ω forVREG5 toDRVLx and 1.5Ω forDRVLx toGND. A dead time to preventshoot throughisinternallygeneratedbetween top MOSFET offto bottom MOSFET on, and bottomMOSFET offtotopMOSFET on.5-V biasvoltageisdeliveredfrom VREG5 supply.The instantaneous drivecurrentissuppliedby an inputcapacitorconnectedbetween VREG5 and GND. The averagedrivecurrent isequaltothegatechargeatVgs = 5 V timesswitchingfrequency.Thisgatedrivecurrentas wellas thehigh- side gate drivecurrenttimes5 V makes the drivingpower which need to be dissipatedfrom TPS51123A package. High-SideDriver The high-sidedriverisdesignedtodrivehighcurrent,low R DS(on) N-channelMOSFET(s). When configuredas a floatingdriver,5-V biasvoltageisdeliveredfromVREG5 supply.The averagedrivecurrentisalsocalculatedby thegatechargeatVgs = 5 V timesswitchingfrequency.The instantaneousdrivecurrentissuppliedby theflying capacitorbetween VBSTx and LLx pins.The drivecapabilityisrepresentedby itsinternalresistance,whichare4 Ω forVBSTx toDRVHx and 1.5Ω forDRVHx toLLx. CurrentProtection TPS51123A has cycle-by-cycleovercurrentlimitingcontrol.The inductorcurrentismonitoredduringthe‘OFF ’ stateand thecontrollerkeeps the‘OFF ’stateduringtheinductorcurrentislargerthantheovercurrenttriplevel. In order to provideboth good accuracy and cost effectivesolution,TPS51123A supportstemperature compensated MOSFET R DS(on) sensing.The TRIPx pinshouldbe connectedto GND throughthe tripvoltage settingresistor,R TRIP.TRIPx terminalsourcesITRIP current,whichis10 μA typicallyatroom temperature,and the triplevelisset to the OCL tripvoltageVTRIP as below.Note thatthe VTRIP islimitedup to about 205 mV internally. (3) Note thatwhen TRIPx voltageisunder a certainthershould(typically0.4V),theswitcherchannelconcernedis shutdown. The inductorcurrentismonitoredby thevoltagebetween GND pinand LLx pinso thatLLx pinshould be connectedtothedrainterminalofthebottomMOSFET properly.Itriphas 4500 ppm/°C temperatureslopeto compensate thetemperaturedependency oftheR DS(on).GND isused as thepositivecurrentsensingnode so thatGND shouldbe connectedto the propercurrentsensingdevice,i.e.the source terminalof the bottom MOSFET. As thecomparisonisdone duringtheOFF state,VTRIP setsvalleyleveloftheinductorcurrent.Thus,theload currentatovercurrentthreshold,IOCP ,can be calculatedinEquation4. (4) Inan overcurrentcondition,thecurrenttotheloadexceeds thecurrenttotheoutputcapacitorthustheoutput voltagetends to falldown. Eventually,itends up withcrossingthe under voltageprotectionthresholdand shutdownbothchannels. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 23 ProductFolderLink(s):TPS51123A

SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com Overvoltageand UndervoltageProtection TPS51123A monitorsa resistordividedfeedbackvoltagetodetectoverand under voltage.When thefeedback voltagebecomes higherthan115% ofthetargetvoltage,theOVP comparatoroutputgoes highand thecircuit latchesas thetopMOSFET driverOFF and thebottomMOSFET driverON. Also,TPS51123A monitorsVOx voltagedirectlyand ifitbecomes greaterthan5.75V theTPS51123A turnsoff thetopMOSFET driver. When the feedbackvoltagebecomes lowerthan 60% of the targetvoltage,the UVP comparatoroutputgoes highand an internalUVP delaycounterbeginscounting.After32 μs,TPS51123A latchesOFF both top and bottom MOSFETs drivers,and shut offboth driversof anotherchannel.This functionisenabled after2 ms followingENC has become high.

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/c40 /c41 OUTV 2.0R1 R2 2.0 /c45/c61 /c180 /c40 /c41 /c40 /c41/c40 /c41 /c40 /c41 /c40 /c41 /c40 /c41/c40 /c41 /c40 /c41f f OUT OUT OUT OUTIN max IN max IND ripple IN max OUT max IN max 1 3 I I V V V V V V L V V /c180 /c180 /c180 /c45 /c180 /c45 /c180 /c61 /c61 /c180 /c40 /c41 /c40 /c41 /c40 /c41/c40 /c41 /c40 /c41f OUT OUTIN m axTRIP IND peak DS on IN m ax V 1 R L V V V I V/c180 /c45 /c180 /c61 /c43 /c180 /c40 /c41 /c40 /c41 /c40 /c41 /c40 /c41 /c40 /c41 fOUT RIPPLE V 20 mV 1 D 20 mV LESR 2 V I 2 V /c180 /c180 /c45 /c180 /c180/c61 /c45 /c180 TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 UVLO Protection TPS51123A has VREG5 under voltagelockout protection(UVLO). When the VREG5 voltageislowerthan UVLO thresholdvoltagebothswitchmode power suppliesare shutoff.Thisisnon-latchprotection.When the VREG3 voltageislowerthan(VOUT2 -1 V),bothswitchmode power suppliesarealsoshutoff Thermal Shutdown TPS51123A monitorsthetemperatureofitself.Ifthetemperatureexceeds thethresholdvalue(typically150°C), TPS51123A isshutoffincludingLDOs. Thisisnon-latchprotection. ExternalPartsSelection The externalcomponents selectionismuch simpleinD-CAP ™ Mode. 1.Determine outputvoltage The outputvoltageisprogrammed by the voltage-dividerresistor,R1 and R2, as shown inFigure36. R1 is connectedbetween VFBx pinand theoutput,and R2 isconnectedbetwen theVFBx pinand GND. Recommended R2 valueisfrom10 kΩ to20 kΩ.DetermineR1 usingequationas below. (5) 2.Choose theInductor The inductancevalueshouldbe determinedtogivetheripplecurrentofapproximately1/4to1/2ofmaximum outputcurrent.Largerripplecurrentincreasesoutputripplevoltageand improvesS/N ratioand helpsstable operation. (6) The inductoralsoneeds to have low DCR to achievegood efficiency,as wellas enough room above peak inductorcurrentbeforesaturation.The peak inductorcurrentcan be estimatedas follows. (7) 3.Choose theOutput Capacitor(s) Organicsemiconductorcapacitor(s)orspecialtypolymercapacitor(s)arerecommended. DetermineESR tomeet requiredripplevoltage.A quickapproximationisas shown inEquation8.Thisequationisbased on thatrequired outputrippleslopeisapproximately20 mV perTSW (switchingperiod)intermsofVFB terminalvoltage. where

• D isthedutycycle
• therequiredoutputrippleslopeisapproximately20 mV pertSW (switchingperiod)intermsofVFB terminal voltage (8) 4.Choose theLow-Side MOSFET Itishighlyrecommended thatthe low-sideMOSFET shouldhave an integratedSchottkybarrierdiode,or an externalSchottkybarrierdiodeinparalleltoachievestableoperation. Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 25 ProductFolderLink(s):TPS51123A

SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com Layout Considerations Certainpointsmust be consideredbeforestartinga layoutwork usingtheTPS51123A.

• TPS51123A has onlyone GND pinand specialcareofGND tracedesignmakes operationstable,especially when bothchannelsoperate.Group GND terminalsofoutputvoltagedividerofbothchannelsand theVREF capacitoras closeas possible,and connectthem toan innerGND planewithPowerPad and theovercurrent settingresistor,as shown inthe thinGND lineof Figure37. Thistraceisnamed SignalGround (SGND). Group groundterminalsofVIN capacitor(s),VOUT capacitor(s)and sourceoflow-sideMOSFETs as closeas possible,and connectthem toanotherinnerGND planewithGND pinofthedeviceand theGND terminalof VREG3 and VREG5 capacitors,as shown inthe boldGND lineof Figure37. Thistraceisnamed Power Ground (PGND). SGND shouldbe connectedtoPGND atthemiddlepointbetween groundterminalofVOUT capacitors.
• Inductor,VOUT capacitor(s),VIN capacitor(s)and MOSFETs arethepower components and shouldbe placed on one sideofthePCB (solderside).Power components ofeach channelshouldbe atthesame distance from the TPS51123A. Other smallsignalpartsshouldbe placedon anotherside(component side).Inner GND planesshouldshieldand isolatethesmallsignaltracesfromnoisypower lines.
• PCB tracedefinedas LLx node,whichconnectstosourceofhigh-sideMOSFET, drainoflow-sideMOSFET and high-voltagesideoftheinductor,shouldbe as shortand wideas possible.
• A high-qualityX5R orX7R ceramicbypass capacitorshouldbe placedclosetothedeviceand tracesshould be no longerthan10 mm. Use thefollowingcapacitancevalues. – VREG5: 10 µF orlarger – VREG3: 10 µF orlarger(1µF isacceptablewhen notloaded) – VREF: between 220 nF and 1 µF
• Connect the overcurrentsettingresistorsfrom TRIPx to SGND and closeto the device,rightnextto the deviceifpossible.
• The dischargepath(VOx) shouldhave a dedicatedtracetotheoutputcapacitor;separatefrom theoutput voltagesensingtrace.When LDO5 isswitchedoverVo1 traceshouldbe 1.5mm withno loops.When LDO3 isswitchedoverand loadedVO2 traceshouldalsobe 1.5mm withno loops.There isno restrictionforjust monitoringVox.Make thefeedbackcurrentsettingresistor(theresistorbetween VFBx toSGND) closetothe device.Placeon thecomponent sideand avoidviasbetween thisresistorand thedevice.
• Connectionsfrom thedriverstotherespectivegateofthehigh-sideor thelow-sideMOSFET shouldbe as shortas possibletoreducestrayinductance.Use 0.65-mm (25mils)orwidertraceand via(s)ofatleast0.5 mm (20mils)diameteralongthistrace.
• Allsensitiveanalog tracesand components such as VOx, VFBx, VREF, GND, EN0, TRIPx, PGOOD, TONSEL and SKIPSEL shouldbe placedaway fromhigh-voltageswitchingnodes such as LLx,DRVLx, and DRVHx nodes toavoidcoupling.
• Traces forVFB1 and VFB2 should be shortand laidaparteach otherto avoid channel to channel interference.
• In orderto effectivelyremove heat from the package,preparethermalland and solderto the package’s thermalpad.Three by threeormore viaswitha 0.33-mm (13mils)diameterconnectedfromthethermalland totheinternalground planeshouldbe used tohelpdissipation.Thisthermallandunderneaththepackage shouldbe connectedtoSGND, and shouldNOT be connectedtoPGND.

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www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 Figure37. Ground System Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 27 ProductFolderLink(s):TPS51123A

SLUSAA6B –APRIL 2011–REVISED MARCH 2012 www.ti.com Figure38. PCB Layout

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(QFN24) 13 14 15 16 VBST1 DRVL1 LL1 DRVH1 VBST2 DRVH2 LL2 DRVL2 EN0 TRIP2 VFB2 VREF TONSEL VFB1 2 1 TRIP1 SKIPSEL 19 GND VIN ENC VO1 5V/8A 3.3/c109H IRF7821 VO1_GND PGND 10 /c109F 0.1/c109F VIN VO2 3.3V/8A 3.3 /c109H IRF7821 VO2_GND 0.1 /c109F VIN PowerPAD C11 10 /c109F VREG5 C10 POSCAP 330/c109F PGND 5.1/c87 VIN 5.5 ~ 28V 5.1/c87 10 /c109F 10 /c109F PGND POSCAP 330 /c109F 5V/100mA PGND 30k/c87 20k/c87 13k/c87 SGND VREG5 VREG5 100k/c87 PGND 20k/c87 0.22/c109F PGND SGND 130k/c87 SGND 130k/c87 ENC 10 /c109F PGND 3.3V/100mA 10 /c109F EN0 PGNDPGND SGND FDS6690AS FDS6690AS UDG-10085 SGND TPS51123A www.ti.com SLUSAA6B –APRIL 2011–REVISED MARCH 2012 ApplicationCircuit Figure39. 5-V/8-A,3.3-V/8-AApplicationCircuit(245-kHz/305-kHzSetting) Table5.ListofMaterialsfor5-V/8-A,3.3-V/8-AApplicationCircuit REFERENCE SPECIFICATION MANUFACTURER PART NUMBER DESIGNATOR C1, C2, C8, C9 10 μF/25V TaiyoYuden TMK325BJ106MM C3, C11 10 μF/6.3V TDK C2012X5R0J106K C5, C10 330 μF/6.3V/25m Ω Sanyo 6TPE330ML L1,L2 3.3μH, 15.6A,5.92m Ω TOKO FDA1055-3R3M Q1, Q3 30 V,9.5m Ω IR IRF7821 Q2, Q4 (1) 30 V,12 m Ω Fairchild FDS6690AS (1) Use a MOSFET withan integratedSchottkybarrierdiode(SBD) forthelow-side,oradd an SBD inparallelwitha normalMOSFET.

REVISION HISTORY

Changes from RevisionA (May 2011 )toRevisionB Page Copyright© 2011–2012,Texas InstrumentsIncorporated SubmitDocumentationFeedback 29 ProductFolderLink(s):TPS51123A

www.ti.com 15-Mar-2012 Addendum-Page 1 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/ Ball Finish MSL Peak Temp (3) Samples (Requires Login) TPS51123ARGER ACTIVE VQFN RGE 24 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS51123ARGET ACTIVE VQFN RGE 24 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR (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) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. 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.

*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Reel Diameter (mm) Reel Width W1 (mm) (mm) (mm) (mm) (mm) W (mm) Pin1 Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 Pack Materials-Page 1

*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TPS51123ARGER VQFN RGE 24 3000 367.0 367.0 35.0 TPS51123ARGET VQFN RGE 24 250 210.0 185.0 35.0 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 Pack Materials-Page 2

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Buyeracknowledgesand agreesthatitissolelyresponsibleforcompliancewithalllegal,regulatoryand safety-relatedrequirements concerningitsproducts,and any use ofTIcomponents initsapplications,notwithstandingany applications-relatedinformationorsupport thatmay be providedby TI.Buyerrepresentsand agreesthatithas allthenecessaryexpertisetocreateand implementsafeguardswhich anticipatedangerousconsequencesoffailures,monitorfailuresand theirconsequences,lessenthelikelihoodoffailuresthatmightcause harm and takeappropriateremedialactions.BuyerwillfullyindemnifyTIand itsrepresentativesagainstany damages arisingoutoftheuse ofany TIcomponents insafety-criticalapplications. Insome cases,TIcomponents may be promotedspecificallytofacilitatesafety-relatedapplications.Withsuch components,TI’s goalisto helpenablecustomerstodesignand createtheirown end-productsolutionsthatmeet applicablefunctionalsafetystandardsand requirements.Nonetheless,such components aresubjecttotheseterms. No TIcomponents areauthorizedforuse inFDA ClassIII(orsimilarlife-criticalmedicalequipment)unlessauthorizedofficersoftheparties have executeda specialagreementspecificallygoverningsuch use. OnlythoseTIcomponents whichTIhas specificallydesignatedas militarygradeor“enhanced plastic”aredesignedand intendedforuse in military/aerospaceapplicationsorenvironments.Buyeracknowledgesand agreesthatany militaryoraerospaceuse ofTIcomponents whichhave not been so designatedissolelyattheBuyer's risk,and thatBuyerissolelyresponsibleforcompliancewithalllegaland regulatoryrequirementsinconnectionwithsuch use. TIhas specificallydesignatedcertaincomponents whichmeet ISO/TS16949 requirements,mainlyforautomotiveuse.Components which have notbeen so designatedareneitherdesignednorintendedforautomotiveuse;and TIwillnotbe responsibleforany failureofsuch components tomeet such requirements. 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