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參數資料
| 型號： | LTC3541EDD-3 |
| 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, M0-229WEED-2, DFN-10 |
| 文件頁數： | 5/20頁 |
| 文件大小： | 379K |
| 代理商： | LTC3541EDD-3 |
LTC3541-3
35413fc
APPLICATIO S I FOR ATIO
W
U
be obtained by choosing an output capacitor value of
10
Fto22F.
Typically,oncetheESRrequirementforCOUThasbeen
met, the RMS current rating generally far exceeds the
IRIPPLE(P-P) requirement. The output ripple ΔVOUT is
determinedby:
Δ
Δ
+
V
I ESR
fc
OUT
L
OUT
1
8
wheref=operatingfrequency,COUT=outputcapacitance
and
ΔIL=ripplecurrentintheinductor.Forafixedoutput
voltage,theoutputrippleishighestatmaximuminput
voltagesince
ΔILincreaseswithinputvoltage.
Aluminumelectrolyticanddrytantalumcapacitorsareboth
availableinsurfacemountconfigurations.Inthecaseof
tantalum,itiscriticalthatthecapacitorsaresurgetested
foruseinswitchingpowersupplies.Anexcellentchoiceis
theAVXTPSseriesofsurfacemounttantalum.Theseare
speciallyconstructedandtestedforlowESRsotheygive
thelowestESRforagivenvolume.Othercapacitortypes
includeSanyoPOSCAP,KemetT510andT495series,and
Sprague593Dand595Dseries.Consultthemanufacturer
forotherspecificrecommendations.
Using Ceramic Input and Output Capacitors
Highvalue,lowcostceramiccapacitorsarenowbecoming
availableinsmallercasesizes.Theirhighripplecurrent,
high voltage rating, and low ESR make them ideal for
switchingregulatorapplications.SincetheLTC3541-3’s
controlloopdoesnotdependontheoutputcapacitor’sESR
forstableoperation,ceramiccapacitorscanbeusedfreely
toachieveverylowoutputrippleandsmallcircuitsize.
However,caremustbetakenwhenceramiccapacitors
areusedattheinputandtheoutput.Whenaceramic
capacitorisusedattheinputandthepowerissupplied
byawalladapterthroughlongwires,aloadstepatthe
outputcaninduceringingattheinput,VIN.Atbest,this
ringingcancoupletotheoutputandbemistakenasloop
instability.Atworst,asuddeninrushofcurrentthrough
thelongwirescanpotentiallycauseavoltagespikeatVIN,
largeenoughtodamagethepart.
Whenchoosingtheinputandoutputceramiccapacitors,
choose the X5R or X7R dielectric formulations. These
dielectricshavethebesttemperatureandvoltagecharac-
teristicsofalltheceramicsforagivenvalueandsize.
Checking Transient Response
Theregulatorloopresponsecanbecheckedbylooking
attheloadtransientresponse.Switchingregulatorstake
severalcyclestorespondtoastepinloadcurrent.When
aloadstepoccurs,VOUTimmediatelyshiftsbyanamount
equalto(
ΔILOADESR),whereESRistheeffectiveseries
resistanceofCOUT.ΔILOADalsobeginstochargeordis-
chargeCOUT,whichgeneratesafeedbackerrorsignal.The
regulatorloopthenactstoreturnVOUTtoitssteady-state
value.DuringthisrecoverytimeVOUTcanbemonitored
forovershootorringingthatwouldindicateastability
problem.Foradetailedexplanationofswitchingcontrol
looptheoryseeApplicationNote76.
Asecond,moreseveretransientiscausedbyswitching
inloadswithlarge(>1
F)supplybypasscapacitors.The
dischargedbypasscapacitorsareeffectivelyputinparal-
lelwithCOUT,causingarapiddropinVOUT.Noregulator
candeliverenoughcurrenttopreventthisproblemifthe
loadswitchresistanceislowanditisdrivenquickly.The
onlysolutionistolimittherisetimeoftheswitchdrive
so that the load rise time is limited to approximately
(25CLOAD).Thus,a10Fcapacitorchargingto3.3V
wouldrequirea250srisetime,limitingthecharging
currenttoabout130mA.
VLDO/LINEAR REGULATOR
Output Capacitance and Transient Response
TheLTC3541-3isdesignedtobestablewithawiderange
ofceramicoutputcapacitors.TheESRoftheoutputcapaci-
toraffectsstability,mostnotablywithsmallcapacitors.A
minimumoutputcapacitorof2.2
FwithanESRof0.05Ω
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| LTC3541EDD-3#TRPBF | 功能描述:IC REG DL BCK/LINEAR SYNC 10-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數:5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
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