 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LTC4011 Datasheet(PDF) 14 Page - Linear Technology |
|
|
|||||||||||||||||||||||||||||
LTC4011 Datasheet(HTML) 14 Page - Linear Technology |
|
|
14 / 26 page  LTC4011 4011fb operaTion 12 CC EA ITH IPROG R3 Q PWM CLOCK S R R4 R1 BAT 11 SENSE RSENSE 15 BGATE 17 TGATE LTC4011 VCC P N R2 4011 F02 Figure2.LTC4011PWMControlLoop PWMCurrentSourceController AnintegralpartoftheLTC4011isthePWMcurrentsource controller.Thechargerusesasynchronousstep-down architecturetoproducehighefficiencyandlimitedthermal dissipation.Thenominaloperatingfrequencyof550kHz allowsuseofasmallerexternalfiltercomponents.The TGATEandBGATEoutputshaveinternallyclampedvolt- ageswings.Theysourcepeakcurrentstailoredtosmaller surface-mountpowerFETslikelytoappearinapplications providinganaveragechargecurrentof3Aorless.During thevariouschargingstates,theLTC4011usesthePWM controllertoregulateanaveragevoltagebetweenSENSE andBATthatrangesfrom10mVto100mV. AconceptualdiagramoftheLTC4011PWMcontrolloop isshowninFigure2. The voltage across the external current programming resistorRSENSEisaveragedbyintegratingerroramplifier EA.Aninternalprogrammingcurrentisalsopulledfrom inputresistorR1.TheIPROG•R1productestablishesthe desiredaveragevoltagedropacrossRSENSE,andhence, theaveragecurrentthroughRSENSE.TheITHoutputof theerroramplifierisascaledcontrolcurrentfortheinput ofthePWMcomparatorCC.TheITH•R3productsetsa peakcurrentthresholdforCCsuchthatthedesiredaver- agecurrentthroughRSENSEismaintained.Thecurrent comparatoroutputdoesthisbyswitchingthestateofthe SRlatchattheappropriatetime. Atthebeginningofeachoscillatorcycle,thePWMclock setstheSRlatchandtheexternalP-channelMOSFETis switchedon(N-channelMOSFETswitchedoff)torefresh thecurrentcarriedbytheexternalinductor.Theinductor current and voltage drop across RSENSEbegintorise linearly. During normal operation, the PFET is turned off(NFETon)duringthecyclebyCCwhenthevoltage differenceacrossRSENSEreachesthepeakvaluesetby theoutputofEA.Theinductorcurrentthenrampsdown linearlyuntilthenextrisingPWMclockedge.Thiscloses theloopandmaintainsthedesiredaveragechargecurrent intheexternalinductor. LowDropoutCharging Afterchargingisinitiated,theLTC4011doesnotrequire thatVCCremainatleast500mVaboveBATbecausesitu- ationsexistwherelowdropoutchargingmightoccur.In oneinstance,parasiticseriesresistancemaylimitPWM headroom (between VCCandBAT)as100%chargeis reached.AsecondcasecanarisewhentheDCadapter selectedbytheenduserisnotcapableofdeliveringthe currentprogrammedbyRSENSE,causingtheoutputvolt- ageoftheadaptertocollapse.Whileinlowdropout,the LTC4011PWMrunsnear100%dutycyclewithafrequency thatmaynotbeconstantandcanbelessthan550kHz. Thechargecurrentwilldropbelowtheprogrammedvalue toavoidgeneratingaudiblenoise,sotheactualcharge delivered to the battery may depend primarily on the LTC4011chargetimer. InternalDieTemperature TheLTC4011providesinternalovertemperaturedetection toprotectagainstelectricaloverstress,primarilyatthe FETdriveroutputs.Ifthedietemperaturerisesabovethis thermallimit,theLTC4011stopsswitchingandindicates afaultaspreviouslydiscussed. |
|
|
Link URL |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link to Datasheet | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
