參數(shù)資料
型號(hào): LTC3541EDD-2
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: 1.25 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PDSO10
封裝: 3 X 3 MM, PLASTIC, MO-229WEED-2, DFN-10
文件頁數(shù): 7/20頁
文件大?。?/td> 335K
代理商: LTC3541EDD-2
LTC3541-2
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APPLICATIO S I FOR ATIO
W
U
1.TheVINquiescentcurrentlossinthebuckisduetotwo
components:theDCbiascurrentasgivenintheElectrical
Characteristicsandtheinternalmainswitchandsynchro-
nousswitchgatechargecurrents.Thegatechargecurrent
resultsfromswitchingthegatecapacitanceoftheinternal
powerswitches.Eachtimethegateisswitchedfromhigh
tolowtohighagain,apacketofcharge,dQ,movesfrom
VINtoground.TheresultingdQ/dtisthecurrentoutof
VINthatistypicallylargerthantheDCbiascurrentand
proportionaltofrequency.BoththeDCbiasandgatecharge
lossesareproportionaltoVINandthustheireffectswill
bemorepronouncedathighersupplyvoltages.
2.I2Rlossesarecalculatedfromtheresistancesofthe
internalswitches,RSW,andexternalinductorRL.Incon-
tinuousmode,theaverageoutputcurrentflowingthrough
inductorLis“chopped”betweenthemainswitchandthe
synchronousswitch.Thus,theseriesresistancelooking
into the SW pin is a function of both top and bottom
MOSFETRDS(ON)andthedutycycle(DC)asfollows:
RSW=(RDS(ON)TOP)(DC)+(RDS(ON)BOT)(1–DC)
TheRDS(ON)forboththetopandbottomMOSFETscan
beobtainedfromtheTypicalPerformanceCharacteristics
curves.Thus,toobtainI2Rlosses,simplyaddRSWto
RLandmultiplytheresultbythesquareoftheaverage
outputcurrent.
3.LossesintheVLDO/linearregulatorareduetotheDCbias
currentsasgivenintheElectricalCharacteristicsandtothe
(VIN–VOUT)voltagedropacrosstheinternaloutputdevice
transistor.
Other losses when the buck and VLDO regulator are
in operation (ENBUCK and ENVLDO equal logic high),
includingCINandCOUTESRdissipativelossesandinduc-
torcorelosses,generallyaccountforlessthan2%total
additionalloss.
THERMAL CONSIDERATIONS
The LTC3541-2 requires the package backplane metal
(GNDpin)tobewellsolderedtothePCboard.Thisgives
the DFN package exceptional thermal properties. The
power handling capability of the device will be limited
bythemaximumratedjunctiontemperatureof125°C.
TheLTC3541-2hasinternalthermallimitingdesignedto
protectthedeviceduringmomentaryoverloadconditions.
Forcontinuousnormalconditions,themaximumjunction
temperatureratingof125°Cmustnotbeexceeded.Itis
importanttogivecarefulconsiderationtoallsourcesof
thermalresistancefromjunctiontoambient.Additional
heatsourcesmountednearbymustalsobeconsidered.
Forsurfacemountdevices,heatsinkingisaccomplished
byusingtheheat-spreadingcapabilitiesofthePCboard
anditscoppertraces.Copperboardstiffenersandplated
throughholescanalsobeusedtospreadtheheatgener-
atedbypowerdevices.
ToavoidtheLTC3541-2exceedingthemaximumjunction
temperature,somethermalanalysisisrequired.Thegoal
ofthethermalanalysisistodeterminewhetherthepower
dissipatedexceedsthemaximumjunctiontemperatureof
thepart.Thetemperatureriseisgivenby:
TR=PDθJA
wherePDisthepowerdissipatedbytheregulatorandθJA
isthethermalresistancefromthejunctionofthedieto
theambienttemperature.
Thejunctiontemperature,TJ,isgivenby:
TJ=TA+TR
whereTAistheambienttemperature.
相關(guān)PDF資料
PDF描述
LTC3541EDD-2#TR 1.25 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PDSO10
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