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LTC3210-2 Datasheet(PDF) 9 Page - Linear Technology |
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LTC3210-2 Datasheet(HTML) 9 Page - Linear Technology |
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9 / 16 page  LTC3210-2/LTC3210-3 321023fb operaTion Power Management The LTC3210-2/LTC3210-3 uses a switched capacitor chargepumptoboostCPOtoasmuchas2timesthe inputvoltageupto5.1V.Thepartstartsupin1xmode.In thismode,VBATisconnecteddirectlytoCPO.Thismode providesmaximumefficiencyandminimumnoise.The LTC3210-2/LTC3210-3willremainin1xmodeuntilanLED currentsourcedropsout.Dropoutoccurswhenacurrent source voltage becomes too low for the programmed current to be supplied. When dropout is detected, the LTC3210-2/LTC3210-3 will switch into 1.5x mode. The CPOvoltagewillthenstarttoincreaseandwillattempt toreach1.5xVBATupto4.6V.Anysubsequentdropout willcausetheparttoenterthe2xmode.TheCPOvoltage willattempttoreach2xVBATupto5.1V.Thepartwillbe resetto1xmodewheneverthepartisshutdownorwhen ENCgoeslow. Atwophasenonoverlappingclockactivatesthecharge pumpswitches.Inthe2xmodetheflyingcapacitorsare chargedonalternateclockphasesfromVBATtominimize inputcurrentrippleandCPOvoltageripple.In1.5xmodethe flyingcapacitorsarechargedinseriesduringthefirstclock phaseandstackedinparallelonVBATduringthesecond phase.Thissequenceofcharginganddischargingtheflying capacitorscontinuesataconstantfrequencyof800kHz. LED Current Control TheMLEDcurrentsaredeliveredbythefourprogram- mablecurrentsources.32linearcurrentsettings(0mA to20mA,RM=30.1k)areavailablebystrobingtheENM pin.Eachpositivestrobeedgedecrementsa5-bitdown Figure 1. Current Programming Timing Diagram counter which controls a 5-bit linear DAC. When the desiredcurrentisachievedENMisstoppedhigh.The outputcurrentthenchangestotheprogrammedvalue after150µs(typ).ThecounterwillstopwhentheLSB isreached.Theoutputcurrentissetto0whenENMis toggledlowaftertheoutputhasbeenenabled.Ifstrobing isstartedwithin150µs(typ),afterENMhasbeensetlow, thecounterwillcontinuetocountdown.After150µs(typ) thecounterisreset. TheCLEDcurrentisdeliveredbyaprogrammablecurrent source.Eightlinearcurrentsettings(0mAto380mA,RC =24.3k)areavailablebystrobingtheENCpin.Eachposi- tivestrobeedgedecrementsa3-bitdowncounterwhich controlsa3-bitlinearDAC.Whenthedesiredcurrentis reached,ENCisstoppedhigh.Theoutputcurrentthen changestotheprogrammedvalueafter150µs(typ).The counterwillstopwhentheLSBisreached.Theoutput currentissetto0whenENCistoggledlowaftertheoutput hasbeenenabled.Ifstrobingisstartedwithin150µs(typ) afterENChasbeensetlow,thecounterwillcontinueto countdown.After150µs(typ)thecounterisreset. Thefull-scaleoutputcurrentiscalculatedasfollows: MLEDfull-scaleoutputcurrent =(1.215V/(RM+500))•525 CLEDfull-scaleoutputcurrent =(1.215V/(RC+500))•7700 WhenbothENMandENCareheldlowformorethan 150µs(typ)thepartwillgointoshutdown.SeeFigure1 fortiminginformation. ENCresetsthemodeto1xonafallingedge. tPW ≥ 200ns ENM = ENC = LOW SHUTDOWN tEN 150µs (TYP) tSD 150µs (TYP) PROGRAMMED CURRENT ENM OR ENC LED CURRENT 321023 F01 |
Similar Part No. - LTC3210-2 |
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Similar Description - LTC3210-2 |
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