LT1616注意事项.docx
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LT1616注意事项.docx
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LT1616注意事项
1
LT1616
600mA,1.4MHzStep-Down
SwitchingRegulator
inSOT-23
LTCandLTareregisteredtrademarksofLinearTechnologyCorporation.
TheLT®1616isacurrentmodePWMstep-downDC/DC
converterwithinternal0.6Apowerswitch,packagedina
tiny6-leadSOT-23.Thewideinputrangeof3.6Vto25V
makestheLT1616suitableforregulatingawidevarietyof
powersources,from4-cellbatteriesand5Vlogicrailsto
unregulatedwalltransformersandlead-acidbatteries.Its
highoperatingfrequencyallowstheuseoftiny,lowcost
inductorsandceramiccapacitors.Withitsinternalcom-
pensationeliminatingadditionalcomponents,acomplete
400mAstep-downregulatorfitsonto0.15squareinches
ofPCboardarea.
TheconstantfrequencycurrentmodePWMarchitecture
andstableoperationwithceramiccapacitorsresultsin
low,predictableoutputripple.Currentlimitingprovides
protectionagainstshortedoutputs.Thelowcurrent(<1µA)
shutdownprovidescompleteoutputdisconnect,enabling
easypowermanagementinbattery-poweredsystems.
I
WideInputRange:
3.6Vto25V
I
5Vat400mAfrom7Vto25VInput
I
3.3Vat400mAfrom4.7Vto25VInput
I
FixedFrequency1.4MHzOperation
I
UsesTinyCapacitorsandInductors
I
InternallyCompensated
I
LowShutdownCurrent:
<1µA
I
LowVCESATSwitch:
220mVat300mA
I
Tiny6-LeadSOT-23Package
I
WallTransformerRegulation
I
LocalLogicSupplyConversion:
12Vto5V
12Vor5Vto3.3V,2.5Vor1.8V
I
DistributedSupplyRegulation
I
DigitalCameras
I
Battery-PoweredEquipment
3.3VStep-DownConverter
VINBOOST
GNDFB
SHDNSW
5
VIN
4.5VTO25V
OFFON
4
1
6
C3
0.01µF
D1
D2
L1
10µH
23
R2
10k
R1
16.5k
LT1616
C2
10µF
1616TA01
C1
1µF
VOUT
3.3V
300mA:
VIN=4.5VTO25V
400mA:
VIN=4.7VTO25V
C1:
TAIYO-YUDENTMK316BJ105
C2:
TAIYO-YUDENJMK316BJ106ML
D1:
ONSEMICONDUCTORMBR0530
D2:
1N4148
L1:
SUMIDACR43-100
Efficiency
LOADCURRENT(mA)
0
80
90
100
300400
1616G02
70
60
100200500
50
40
30
EFFICIENCY(%)
VIN=5V
VIN=20V
VIN=12V
FEATURESDESCRIPTIO
U
APPLICATIOS
U
TYPICALAPPLICATIO
U
2
LT1616
(Note1)
InputVoltage(VIN).................................................25V
BOOSTPinVoltage.................................................35V
BOOSTPinAboveSWPin......................................25V
SHDNPin...............................................................25V
FBVoltage................................................................6V
CurrentIntoFBPin...............................................±1mA
OperatingTemperatureRange(Note2)..–40°Cto85°C
MaximumJunctionTemperature..........................125°C
StorageTemperatureRange.................–65°Cto150°C
LeadTemperature(Soldering,10sec)..................300°C
TJMAX=125°C,θJA=250°C/W
ORDERPART
NUMBER
S6PARTMARKING
LT1616ES6
LTNB
PARAMETERCONDITIONSMINTYPMAXUNITS
UndervoltageLockout3.353.6V
FeedbackVoltageG1.2251.251.275V
FBPinBiasCurrentVFB=MeasuredVREF+10mVG150600nA
QuiescentCurrentNotSwitching1.92.5mA
QuiescentCurrentinShutdownVSHDN=0V0.012µA
ReferenceLineRegulationVIN=5Vto25V0.005%/V
SwitchingFrequencyVFB=1.1VG11.41.8MHz
FrequencyShiftThresholdonFBPinfSW=700kHz0.44V
MaximumDutyCycleG8087%
SwitchCurrentLimit(Note3)630850mA
SwitchVCESATISW=300mA220350mV
SwitchLeakageCurrent10µA
MinimumBoostVoltageAboveSwitchISW=300mA1.62.5V
BOOSTPinCurrentISW=300mA712mA
SHDNInputVoltageHigh1.8V
SHDNInputVoltageLow0.4V
SHDNBiasCurrentVSHDN=3V815µA
VSHDN=0V0.010.1µA
TheGdenotesspecificationswhichapplyoverthefulloperatingtemperaturerange,otherwisespecificationsareatTA=25°C.
VIN=10V,VBOOST=15V,unlessotherwisenoted.(Note2)
ABSOLUTEAXIURATIGS
WWWU
PACKAGE/ORDERIFORATIO
UUW
BOOST1
GND2
FB3
6SW
5VIN
4SHDN
TOPVIEW
S6PACKAGE
6-LEADPLASTICSOT-23
ELECTRICALCHARACTERISTICS
Note1:
AbsoluteMaximumRatingsarethosevaluesbeyondwhichthelife
ofthedevicemaybeimpaired.
Note2:
TheLT1616Eisguaranteedtomeetperformancespecifications
from0°Cto70°C.Specificationsoverthe–40°Cto85°Coperating
temperaturerangeareassuredbydesign,characterizationandcorrelation
withstatisticalprocesscontrols.
Note3:
Currentlimitguaranteedbydesignand/orcorrelationtostatictest.
Slopecompensationreducescurrentlimitathigherdutycycle.
Consultfactoryforpartsspecifiedwithwideroperatingtemperatureranges.
3
LT1616
TYPICALPERFORACECHARACTERISTICS
UW
Efficiency,VOUT=5V
LOADCURRENT(mA)
0
80
90
100
300400
1616G01
70
60
100200500
50
40
30
EFFICIENCY(%)
VIN=8V
VIN=24V
VIN=12V
LOADCURRENT(mA)
0
80
90
100
300400
1616G02
70
60
100200500
50
40
30
EFFICIENCY(%)
VIN=5V
VIN=20V
VIN=12V
SWITCHCURRENT(mA)
0
0
SWITCHVOLTAGE(mV)
100
200
300
400
500
200400
1616G03
600
Efficiency,VOUT=3.3VSwitchVoltageDrop
MaximumLoadCurrent
atVOUT=5VBOOSTPinCurrent
INPUTVOLTAGE(V)
0
LOADCURRENT(mA)
300
400
20
1616G04
200
100
5101525
500
L=15µH
L=6.8µH
L=10µH
OUTPUTLIMITED
BYDISSIPATION
MaximumLoadCurrent
atVOUT=3.3V
INPUTVOLTAGE(V)
0
LOADCURRENT(mA)
300
400
20
1616G05
200
100
5101525
500
L=10µH
L=4.7µH
OUTPUTLIMITED
BYDISSIPATION
SWITCHCURRENT(mA)
0
BOOSTPINCURRENT(mA)
6
8
10
1616G06
4
2
0
200400
12
14
16
600
SwitchCurrentLimit
DUTYCYCLE(%)
0
SWITCHCURRENTLIMIT(mA)
600
TYPICAL
800
1000
80
1616G07
400
200
0
204060100
MINIMUM
FeedbackPinVoltage
TEMPERATURE(°C)
–50
1.22
FEEDBACKPINVOLTAGE(V)
1.23
1.24
1.25
1.26
1.27
–2502550
1616G08
75100
UndervoltageLockout
TEMPERATURE(°C)
–50
3.1
UNDERVOLTAGELOCKOUT(V)
3.2
3.3
3.4
3.5
3.7
–2502550
1616G11
75100
3.6
4
LT1616
TYPICALPERFORACECHARACTERISTICS
UW
OscillatorFrequency
TEMPERATURE(°C)
–50
SWITCHINGFREQUENCY(MHz)
0.75
1.00
1.25
2575
1616G09
0.50
0.25
0
–25050
1.50
1.75
2.00
100
SHDNPinCurrent
SHDNPINVOLTAGE
0
0
SHDNPINCURRENT(µA)
20
40
60
80
100
120
5101520
1616G10
25
UUU
PIFUCTIOS
BOOST(Pin1):
TheBOOSTpinisusedtoprovideadrive
voltage,higherthantheinputvoltage,totheinternal
bipolarNPNpowerswitch.
GND(Pin2):
TietheGNDpintoalocalgroundplanebelow
theLT1616andthecircuitcomponents.Returnthefeed-
backdividertothispin.
FB(Pin3):
TheLT1616regulatesitsfeedbackpinto1.25V.
Connectthefeedbackresistordividertaptothispin.Set
theoutputvoltageaccordingtoVOUT=1.25V(1+R1/R2).
AgoodvalueforR2is10k.
Iftheinternal amplifier damageVOUT=0.81V(1+R1/R2).
Notethatthis module iseasytobedamaged wheninuse,
SHDN(Pin4):
TheSHDNpinisusedtoputtheLT1616in
shutdownmode.TietogroundtoshutdowntheLT1616.
Tieto2Vormorefornormaloperation.Iftheshutdown
featureisnotused,tiethispintotheVINpin.
VIN(Pin5):
TheVINpinsuppliescurrenttotheLT1616’s
internalregulatorandtotheinternalpowerswitch.Thispin
mustbelocallybypassed.
SW(Pin6):
TheSWpinistheoutputoftheinternalpower
switch.Connectthispintotheinductor,catchdiodeand
boostcapacitor.
5
LT1616
BLOCKDIAGRA
W
3
Σ
R
DRIVERQ1
S
OSC
SLOPE
COMP
FREQUENCY
FOLDBACK
INTREG
AND
UVLO
VC
gm
1.25V
FB
1616BD
2
GND
5VIN
4SHDN
Q
Q
1BOOST
6SW
OPERATIOU
TheLT1616isaconstantfrequency,currentmodeBuck
regulator.The1.4MHzoscillatorenablesanRSflip-flop,
turningontheinternal600mApowerswitchQ1.Anampli-
fierandcomparatormonitorthecurrentflowingbetween
theVINandSWpins,turningtheswitchoffwhenthiscurrent
reachesaleveldeterminedbythevoltageatVC.Anerror
amplifiermeasurestheoutputvoltagethroughanexternal
resistordividertiedtotheFBpin.Thisamplifierservosthe
switchcurrenttoregulatetheFBpinvoltageto1.25V.An
activeclampontheVCnodeprovidescurrentlimit.
Aninternalregulatorprovidespowertothecontrolcir-
cuitry.Thisregulatorincludesanundervoltagelockoutto
preventswitchingwhenVINislessthan~3.5V.The
(RefertoBlockDiagram)
SHDNpinisusedtoplacetheLT1616inshutdown,
disconnectingtheoutputandreducingtheinputcurrent
tolessthan1µA.
Theswitchdriveroperatesfromeithertheinputorfrom
theBOOSTpin.Anexternalcapacitoranddiodeareused
togenerateavoltageattheBOOSTpinthatishigherthan
theinputsupply.Thisallowsthedrivertofullysaturatethe
internalbipolarNPNpowerswitchforefficientoperation.
TheoscillatorreducestheLT1616’soperatingfrequency
whenthevoltageattheFBpinislow.Thisfrequency
foldbackhelpstocontroltheoutputcurrentduringstart-
upandoverload.
6
LT1616
APPLICATIOSIFORATIO
WUUU
TheLT1616efficientlyconvertspowerfromaninputvolt-
agesourcetoaloweroutputvoltageusinganinductorfor
energystorage.TheLT1616usesitsinternalpowerswitch
andanexternalcatchdiode(D1oftheapplicationcircuit
onthefirstpageofthisdatasheet)toproduceapulse-
widthmodulatedsquarewave.InductorL1andoutput
capacitorC2filterthissquarewavetoproduceaDCoutput
voltage.Anerroramplifierregulatestheoutputbycom-
paringtheoutput(dividedbythefeedbackresistorstring
R1andR2)toaninternalreference.TheLT1616uses
currentmodecontrol;insteadofdirectlymodulatingthe
pulsewidth,theerroramplifiercontrolsthepeakcurrent
intheswitchandinductor.Currentmodecontro
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