Buck Current/Voltage Fed Push-Pull PWM …

1 RDQS20 DELAY23 GND11 VCCREF15RT17CT18 SYNC19 CSA 9 CSA+8SS4 CSAO7 CEA 13 VEA 16 VEA+142224321 RAMPCEA+12 CEAOVEAO10 PULLPGNDPUSHSRCBUCKV+DELAYDELAYTQQREF&UV LOSSINHBTUVOSC500 kHzMAX6521 current SenseAmplifierILIM Comparator+3 VCurrent ErrorAmplifierPWM VFlyingDriverPush/PullDriversOSCUVLOV oltage ErrorAmplifier+UC2827-1,UC2827-2UC3827-1 , APRIL1999 REVISEDAPRIL2011 BUCKCURRENT/VOLTAGEFEDPUSH-PULLPWMCONTRO LLERSC heckforSamples:UC2827-1,UC2827-2, UC3827-1,UC3827-21 FEATURESDESCRIPTION IdealforMultipleOutputand/orHighTheUC382 7familyofcontrollerdevicesprovidesanVolt ageOutputVoltageConvertersintegratedcont rolsolutionforcascadedbuckand HighVoltage,HighCurrentFloatingcurrentfe dorvoltagefedpush- UC3827-1 CurrentFedControllerhasvoltagefedmodes,t hepush-pullswitchesaredrivenPush-PullDri verswithOverlappingat50% UC3827-2 VoltageFedControllerhasfedmode, ,thetwoswitchesaredrivenwitha specified AverageCurrentMode.

2 PeakCurrentgaptimebetweentheswitchestopr eventshortingModeorVoltageModewithInputt hetransformeracrosstheenergystoragecapac itorVoltageFeedforwardControlforBuckandt oprohibitexcessivecurrentsflowingthrough thePowerStagedevices. WideBandwidth,LowOffset,Theconverter's ,standardwarranty,andusein 1999 2011, ,UC2827-2UC3827-1,UC3827-2 SLUS365D APRIL1999 (CONTINUED) timingandin , parallelwiththevoltageregulationlooptoas sistonlyin ,userprogrammableoverlaptime(UC3827-1),u serprogrammablegaptime(UC3827-2),a highbandwidthdifferentialcurrentsenseamp lifier, (1)PACKAGESTA= TJPUSH-PULLTOPOLOGYSOIC-24 PDIP-24 PLCC-28 CurrentFedUC2827DW-1UC2827N-1--40 C to85 CVoltageFedUC2827DW-2UC2827N-2-CurrentFe dUC3827DW-1UC3827N-1UC3827Q-10 C to70 CVoltageFedUC3827DW-2UC3827N-2-(1)TheDWa ndQ TRsuffixtothedevicetype( ,UC2827 DWTR-1).

3 THERMALINFORMATIONUC2827-1,UC2827-1,UC28 27-2,UC2827-2,UC3827-1,UC3827-1,THERMALM ETRICUNITSUC3827-2UC3827-2NJ24 PINS24 PINS JAJunction-to-ambientthermalresistance(1 )6070to80 C/W JCtopJunction-to-case(top)thermalresista nce(2)3028(1)Thejunction-to-ambienttherm alresistanceundernaturalconvectionis obtainedin a simulationona JEDEC-standard,high-Kboard,asspecifiedin JESD51-7,in anenvironmentdescribedin JESD51-2a.(2)Thejunction-to-case(top)the rmalresistanceis obtainedbysimulatinga ,buta closedescriptioncanbefoundin ,UC2827-1,UC2827-2,UC2827-2,UC3827-1,UC3 827-1,THERMALMETRICUNITSUC3827-2UC3827-2 DW(1)QLCC28 PINS28 PINS JAJunction-to-ambientthermalresistance(2 )71to8340to65 C/W JCtopJunction-to-case(top)thermalresista nce(3)2430(1)Formoreinformationabouttrad itionalandnewthermalmetrics,seetheICPack ageThermalMetricsapplicationreport,SPRA9 53.

4 (2)Thejunction-to-ambientthermalresistan ceundernaturalconvectionis obtainedin a simulationona JEDEC-standard,high-Kboard,asspecifiedin JESD51-7,in anenvironmentdescribedin JESD51-2a.(3)Thejunction-to-case(top)the rmalresistanceis obtainedbysimulatinga ,buta closedescriptioncanbefoundin 1999 2011,TexasInstrumentsIncorporatedUC2827- 1,UC2827-2UC3827-1, APRIL1999 REVISEDAPRIL2011 ABSOLUTEMAXIMUMRATINGS(1)UC2827-1UC2827- 2 UNITSUC3827-1UC3827-2 Supplyvoltage,VCC20 CEAO,CEA+,CEA-,CSAO,CSA+,CSA-,CT,DELAY,P USH, pull , ,RT,SS,SYNC,VEA+,VEAO,VInputvoltagerange V+andBUCK90 SRC90-VCCI/Ocontinuous 250mABUCK driverI/Opeak 1AI/Ocontinuous 200mAPUSH/ pull driverI/Opeak 65to150 Junctiontemperature 55to150 CLeadtemperature(soldering,10sec)300(1)

5 , ,VVCC= 15V,VV+= ,CCT= 340pF,RRT= 10k , RDELAY= , VSRC= VGND= VBUCK=VPUSH= VPULL outputsnoload,TJ= TAPARAMETERTESTCONDITIONSMINTYPMAXUNITSU PPLYVCCUVLO, 8 V1000 AIVCCS upplycurrentrun3245mAIV+ AVIO10mVAVOL8095dBGBW(1)Gainbandwidth14 MHzVOLLow-leveloutputvoltageIVEAO= 0 A (Noload) 0 A (Noload) 1 5 AVIO5mVAVOL80110dBGBW(1)Gainbandwidth152 9 MHzVOLLow-leveloutputvoltageICEAO= 0 A (Noload) 0 A (Noload) (1) (1) 1999 2011,TexasInstrumentsIncorporated3UC2827 -1,UC2827-2UC3827-1,UC3827-2 SLUS365D APRIL1999 (continued)Unlessotherwisespsecified,VVC C= 15V,VV+= ,CCT= 340pF,RRT= 10k , RDELAY= , VSRC= VGND= VBUCK=VPUSH= VPULL outputsnoload,TJ= TAPARAMETERTESTCONDITIONSMINTYPMAXUNITCU RRENTERRORAMPLIFIERIB 1 5 AVIO10mVAVOL80110dBGBW(2)GainbandwidthAt 100kHz, 0 A (NoLoad) 0 A (NoLoad) (2) (dsch) nFLoad(3)40100nstFALLF alltIme1 nF,Load3080nsIBUCK= 15mA, V+ buck (4) 150mA,V+ buck (4) 15mA(5) = 150mA(5) nFload50100nstFALLF alltIme1 nFload35100nsOverlaptimeUCx827-11 nFloads(6)100250400nsNonoverlappingtime( 7)UCx827-2100250500nsIPUSH/ pull = 10mA,VCC PUSH23V(8)VOHHigh-leveloutputvoltageIPUS H/ pull = 100mA,VCC (8)

6 IPUSH/ pull = 10mA(8) 100mA(8) 0V 35 50 <VVCC<20V520mVLoadregulation0 mA<IIO<10mA820mVSOFTSTARTVOLLow-levelout putvoltagesaturationVVCC= 7 V250500mVISSSoft-startcurrent 5 12 25 A(2) (3)MeasuretherisetimefromwhenBUCK crosses1 V untilit crosses9 V.(4)ToforceBUCK high,forceVCSAO= ,VCEAO= ,a 25-k pulldownresistorfromRAMP toground,andVCT= (5)ToforceBUCKlow,forceVCSAO= ,VCEAO= ,a 10-k pulldownresistorfromRAMP toground,andVCT= (6)Theoverlaptimeis measuredfromthepointatwhichtherisingedge ofPUSH/ pull crosses5 V untilthefallingedgeofPULL/ push crosses5V.(7)Thenon-overlaptimeis measuredfromthepointatwhichthefallingedg eofPUSH/ pull crosses5 V untiltherisingedgeofPULL/ push crosses5 V.

7 (8)TotogglePUSHorPULL intoa desiredstate, 1999 2011,TexasInstrumentsIncorporatedfOSC+ CCT(Hz)tDELAY+RDELAY200W 10*9(s)1234 56789101112242322212019181716151413V+BUC KSRCSSRAMPCEAOCSAOCSA+CSA VEAOGNDCEA+PUSHVCCPULLPGNDDELAYSYNCCTRTV EA REFVEA+CEA N, J OR DW PACKAGES(TOP VIEW)3 2 113 14567891011 PGNDNCNCDELAYSYNCCTRTSSRAMPCEAOCSAOCSA+C SA VEAO415161718 CEA+CEA VEA+REFNCVEA SRCBUCKNCV+Q PACKAGE(TOP VIEW)28 27 262524232221201912 GNDPUSHVCCPULLNC No internal connection(1)(2)UC2827-1,UC2827-2UC3827- 1, APRIL1999 REVISEDAPRIL2011 PLCC-28(QPACKAGE)CONNECTIONDIAGRAMS(TOPV IEW)DIL-24(NorJ,DWPACKAGES)(TOPVIEW)Term inalFunctionsTERMINALI/ODESCRIPTIONN a floatingdriver, (low).

8 CEA+ + ,thebuckgatedriveCSAO78 Opulseis resistorRT, practicalmaximumvalueforthedischargecurr entis givenbyequation(1)A ,RDELAY,is 18k . Thedelayoroverlaptimeis givenbyequation(2) ,voltagesense,currentsense, imperativetopreventlarge, 50% (low).Copyright 1999 2011,TexasInstrumentsIncorporated5 IRT+ VRRT(3)UC2827-1,UC2827-2UC3827-1,UC3827- 2 SLUS365D APRIL1999 (continued)TERMINALI/ODESCRIPTIONN 50% (low).TheRAMP voltage ,aftera 700mVinternallevelshift,is resistortoVINanda capacitortoGNDprovideaninputvoltagefeedf orwardsignalforthebuckcontrollerin , ,theRAMP pinhasa ,orbyconnectingbotha resistorfromVCCtoRAMP anda + offREF1516 Owhenthechipis in equation(3).

9 Thechargecurrentshouldbelessthan500 ART1719 ItokeepCT'sdischargepeakcurrentlessthan2 0mA,whichis CT' ,whichsetsthemaximumdutycycle,is setinternallyandis VVCC. Also,duringturn-offtransientsofthebucksw itch,thevoltageatSRCcangoto ,SSis bidirectionalpinfortheoscillator., whentheoscillatorcapacitor,CT, is 0 therecommendedsynchronizationcircuitis notused,a 1 k is recommendedtobypassVCC2327 IthispintobothGNDandPGND groundconnectionswithgoodqualityhighfreq uencycapacitorsVEA+ +11 IdiodemustbeconnectedfromVCCtoV+ Thereservoircapacitormustbeconnectedbetw eenV+ 1999 2011,TexasInstrumentsIncorporated+ VOSCILLATORVREF10 VRTCTVDG 99086 IRT+ VRRTUC2827-1,UC2827-2UC3827-1, APRIL1999 showninEquation1.

10 A resistor(RT) connectedtopinRTsetsthelinearchargecurre nt:(1)Thetimingcapacitor(CCT) is linearlychargedwiththechargecurrentforci ngtheOSCpintochargetoa ,theRSflip-flopissetdrivingCLKSYN highandRDEAD lowwhichdischargesCCT. CTcontinuestodischargeuntilit reachesa thresholdandresetstheRSflip-flopwhichrep eatsthechargingsequenceasshownin Figure2 AsshowninFigure3, , thesynchronizationthresholdis , , 1999 2011,TexasInstrumentsIncorporated7 OSCCLKSYNOUTTHRESHOLDC hargingVAO V0 VVDG 99087 CLKSYN BUSOSC1 OSC2 OSC3 OSC10 SYNCSYNCSYNCSYNC100 pF100 pF100 pF100 pF10 kWVDG 99085UC2827-1,UC2827-2UC3827-1,UC3827-2 SLUS365D APRIL1999 ( 0 - 2 V)to( 2 V)SLUS365A8/2005 ImprovedCMRRofCEAfrom( 0 - 5 V)to( 5 V)