LTC3210-1 32101fd n Multi-LED Light Supply for Cell Phones/DSCs/PDAs MAIN/CAM LED Controller with 64-Step Brightness Control in 3mm × 3mm QFN The LTC ® 3210-1 is a low noise charge pump DC/DC con- verter designed to drive four MAIN LEDs and one high current CAM LED for camera lighting. The LTC3210-1 requires only four small ceramic capacitors and two cur- rent set resistors to form a complete LED power supply and current controller. Built-in soft-start circuitry prevents excessive inrush cur- rent during start-up and mode changes. High switching frequency enables the use of small external capacitors. Independent MAIN and CAM full-scale current settings are programmed by two external resistors. Shutdown mode and current output levels are selected via two logic inputs. ENM and ENC are toggled to adjust the LED currents via internal counters and DACs. A 6-bit linear DAC (64 steps) provides high resolution brightness control for the MAIN display. The charge pump optimizes efficiency based on the volt- age across the LED current sources. The part powers up in 1x mode and will automatically switch to boost mode whenever any enabled LED current source begins to enter dropout. The LTC3210-1 is available in a 3mm × 3mm × 0.75mm 16-lead QFN package. n Low Noise Charge Pump Provides High Efficiency with Automatic Mode Switching n Multimode Operation: 1x, 1.5x, 2x n Individual Full-Scale Current Set Resistors n Up to 500mA Total Output Current n Single Wire EN/Brightness Control for MAIN and CAM LEDs n 64:1 Linear Brightness Control Range for MAIN Display n Four 25mA Low Dropout MAIN LED Outputs n One 400mA Low Dropout CAM LED Output n Low Noise Constant-Frequency Operation n Low Shutdown Current: 3µA n Internal Soft-Start Limits Inrush Current During Startup and Mode Switching n Open/Short LED Protection n No Inductors n 3mm × 3mm × 0.75mm 16-Lead Plastic QFN Package V BAT (V) 3.0 EFFICIENCY (P LED /P IN ) (%) 60 80 100 32101 TA01b 40 20 50 70 90 30 10 0 3.6 3.8 3.2 4.0 3.4 4.4 4.2 4 LEDs AT 9mA/LED (TYP V F AT 9mA = 3V, NICHIA NSCW100) T A = 25°C 4-LED MAIN Display Efficiency vs V BAT Voltage TYPICAL APPLICATION DESCRIPTION FEATURES APPLICATIONS L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. C1P C1M C2P RM RC GND C2M CPO MLED1 MLED2 MLED3 MLED4 CLED ENM ENC V BAT LTC3210-1 V BAT C1 2.2μF C2 2.2μF C3 2.2μF 30.1k 1% 24.3k 1% ENM ENC C4 2.2μF 32101 TA01 MAIN CAM
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LTC3210-1
�32101fd
n Multi-LEDLightSupplyforCellPhones/DSCs/PDAs
MAIN/CAM LED Controllerwith 64-Step Brightness Control
in 3mm × 3mm QFN
TheLTC®3210-1isalownoisechargepumpDC/DCcon-verterdesignedtodrivefourMAINLEDsandonehighcurrent CAM LED for camera lighting. The LTC3210-1requiresonlyfoursmallceramiccapacitorsandtwocur-rentsetresistorstoformacompleteLEDpowersupplyandcurrentcontroller.
n Low Noise Charge Pump Provides High Efficiency with Automatic Mode Switching
n Multimode Operation: 1x, 1.5x, 2x n Individual Full-Scale Current Set Resistorsn Up to 500mA Total Output Currentn Single Wire EN/Brightness Control for MAIN and
CAM LEDsn 64:1 Linear Brightness Control Range for
MAIN Displayn Four25mALowDropoutMAINLEDOutputsn One400mALowDropoutCAMLEDOutputn LowNoiseConstant-FrequencyOperationn LowShutdownCurrent:3µAn InternalSoft-StartLimitsInrushCurrentDuring
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, RM = 30.1k, RC = 24.3k, ENM = high, unless otherwise noted.
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, RM = 30.1k, RC = 24.3k, ENM = high, unless otherwise noted.
Initially,whenthepartisinshutdown,aweakswitchconnectsVBATtoCPO.ThisallowsVBATtoslowlychargethe CPO output capacitor to prevent large chargingcurrents.
TheLTC3210-1alsoemploysasoft-startfeatureonitscharge pump to prevent excessive inrush current andsupplydroopwhenswitching into thestep-upmodes.ThecurrentavailabletotheCPOpinisincreasedlinearlyoveratypicalperiodof150µs.Soft-startoccursatthestartofboth1.5xand2xmodechanges.
Figure 3. Typical 1.5x ROL vs Temperature Figure 4. Typical 2x ROL vs Temperature
WhentheLTC3210-1operatesineither1.5xmodeor2xmode,thechargepumpcanbemodeledasaThevenin-equivalent circuit to determine the amount of currentavailable from the effective input voltage and effectiveopen-loopoutputresistance,ROL(Figure2).
InshutdownmodeallthecircuitryisturnedoffandtheLTC3210-1drawsaverylowcurrentfromtheVBATsup-ply.Furthermore,CPOisweaklyconnectedtoVBAT.TheLTC3210-1entersshutdownmodewhenboththeENMandENCpinsarebroughtlowat150µs(typ).ENMandENChave250kinternalpulldownresistorstodefinetheshutdown state when the drivers are in a high imped-ancestate.
The style and value of the capacitors used with theLTC3210-1determineseveralimportantparameterssuchasregulatorcontrolloopstability,outputripple,chargepumpstrengthandminimumstart-uptime.
Bothstyleandvalueoftheoutputcapacitorcansignifi-cantlyaffectthestabilityoftheLTC3210-1.AsshownintheBlockDiagram, theLTC3210-1usesacontrol looptoadjustthestrengthofthechargepumptomatchtherequiredoutputcurrent.Theerrorsignalof the loop isstoreddirectlyontheoutputcapacitor.Theoutputcapacitoralsoservesasthedominantpoleforthecontrolloop.Topreventringingorinstability,itisimportantfortheoutputcapacitortomaintainatleast1.3µFofcapacitanceoverallconditions.
Inaddition,excessiveoutputcapacitorESR>100mΩwilltendtodegradetheloopstability.MultilayerceramicchipcapacitorstypicallyhaveexceptionalESRperformanceandwhencombinedwithatightboardlayoutwillresultinverygoodstability.AsthevalueofCCPOcontrolstheamountofoutputripple,thevalueofCVBATcontrolstheamount of ripple present at the input pin (VBAT). TheLTC3210-1’sinputcurrentwillberelativelyconstantwhilethechargepumpiseitherintheinputchargingphaseor
Due to the high switching frequency and the transientcurrentsproducedbytheLTC3210-1,carefulboardlayoutisnecessary.Atruegroundplaneandshortconnectionsto all capacitors will improve performance and ensureproperregulationunderallconditions.
Figure 5. 10nH Inductor Used for Input Noise Reduction (Approximately 1cm of Board Trace)
theoutputchargingphasebutwilldroptozeroduringtheclocknonoverlaptimes.Sincethenonoverlaptimeissmall(~35ns),thesemissing“notches”willresultinonlyasmallperturbationontheinputpowersupplyline.NotethatahigherESRcapacitorsuchastantalumwillhavehigherinputnoiseduetothehigherESR.Therefore,ceramiccapacitorsarerecommendedforlowESR.InputnoisecanbefurtherreducedbypoweringtheLTC3210-1throughaverysmallseriesinductor,asshowninFigure5.A 10nH inductor will reject the fast current notches,therebypresentinganearlyconstant-currentloadtotheinputpowersupply.Foreconomy,the10nHinductorcanbefabricatedonthePCboardwithabout1cm(0.4")ofPCboardtrace.
applicaTions inFormaTion
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or aluminum should never be used for the flying capaci-tors since their voltage can reverse upon start-up of the LTC3210-1. Ceramic capacitors should always be used for the flying capacitors.
Theflyingcapacitorscontrolthestrengthofthechargepump.Inordertoachievetheratedoutputcurrentitisnecessarytohaveatleast1.6µFofcapacitanceforeachoftheflyingcapacitors.Capacitorsofdifferentmaterialslosetheircapacitancewithhighertemperatureandvoltageatdifferentrates.Forexample,aceramiccapacitormadeofX7Rmaterialwillretainmostofitscapacitancefrom–40°Cto85°CwhereasaZ5UorY5Vstylecapacitorwillloseconsiderablecapacitanceoverthatrange.Capacitorsmayalsohaveaverypoorvoltagecoefficientcausingthemtolose60%ormoreoftheircapacitancewhentheratedvoltageisapplied.Therefore,whencomparingdifferentcapacitors, it isoftenmoreappropriatetocomparetheamountofachievablecapacitanceforagivencasesizeratherthancomparingthespecifiedcapacitancevalue.For
To calculate the power efficiency (η) of a white LEDdriverchip, theLEDpowershouldbecomparedto theinputpower.Thedifferencebetweenthesetwonumbersrepresentslostpowerwhetheritisinthechargepumporthecurrentsources.Statedmathematically,thepowerefficiencyisgivenby:
Forhigherinputvoltagesandmaximumoutputcurrent,therecanbesubstantialpowerdissipationintheLTC3210-1.Ifthejunctiontemperatureincreasesaboveapproximately150°Cthethermalshutdowncircuitrywillautomaticallydeactivatetheoutputcurrentsourcesandchargepump.Toreducemaximumjunctiontemperature,agoodthermalconnectiontothePCboardisrecommended.Connectingtheexposedpadtoagroundplaneandmaintainingasolidgroundplaneunder thedevicewill reduce the thermalresistanceofthepackageandPCboardconsiderably.
applicaTions inFormaTion
LTC3210-1
��32101fd
UD Package16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
package DescripTion
3.00 0.10(4 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.45 0.05(4 SIDES)
NOTE:1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)2. DRAWING NOT TO SCALE3. ALL DIMENSIONS ARE IN MILLIMETERS4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE5. EXPOSED PAD SHALL BE SOLDER PLATED6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
PIN 1TOP MARK(NOTE 6)
0.40 0.10
BOTTOM VIEW—EXPOSED PAD
1.45 0.10(4-SIDES)
0.75 0.05 R = 0.115TYP
0.25 0.05
1
PIN 1 NOTCH R = 0.20 TYPOR 0.25 45 CHAMFER
15 16
2
0.50 BSC
0.200 REF
2.10 0.053.50 0.05
0.70 0.05
0.00 – 0.05
(UD16) QFN 0904
0.25 0.050.50 BSC
PACKAGE OUTLINE
LTC3210-1
��32101fd
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresenta-tionthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
revision hisToryREV DATE DESCRIPTION PAGE NUMBER
D 6/10 RemovalofPDCpackageinformationfromdatasheet. 1to16
