White LED Step-Up Converter in SOT23

Transcription

1 19-228; Rv 2; 8/5 Whit ED Stp-Up onvrtr in SOT23 Gnral Dscription Th drivs whit EDs with a constant currnt to provid backlight in cll phons, PDAs, and othr hand-hld dvics. Th stp-up convrtr topology allows sris connction of th whit EDs so that th ED currnts ar idntical for uniform brightnss. This configuration liminats th nd for ballast rsistors and xpnsiv factory calibration. Othr bnfits includ gratr simplicity, lowr cost, highr fficincy, and gratr rliability. This stp-up PWM convrtr includs an intrnal, highvoltag, low R DSON N-channl MOSFET switch for high fficincy and maximum battry lif. A singl analog voltag Dual Mod input provids a simpl mans of brightnss adjustmnt and on/off control. Fast 1.2MHz currnt-mod PWM control allows for small input and output capacitors and a small inductor whil minimizing rippl on th input supply/battry. Programmabl softstart liminats inrush currnt during startup. Th is availabl in spac-saving 8-pin thin QFN (3mm 3mm) and 8-pin SOT23 packags. Applications ll Phons and Smart Phons PDAs, Palmtops, and Wirlss Handhlds -Books and Subnotbooks Whit ED Display Backlighting Typical Application ircuit Faturs onstant urrnt Rgulation for Uniform Illumination High 87% Efficincy Analog or ogic ontrol of ED Intnsity.8W Output Powr with Intrnal High-oltag MOSFET Switch Small, ow-profil Extrnal omponnts 2.6 to 5.5 Input Rang 13 Maximum Output with Ovrvoltag Protction Optimizd for ow Input Rippl Programmabl Soft-Start.3µA Shutdown urrnt Small 8-pin Thin QFN (3mm 3mm) and 8-Pin SOT23 Packags PART Ordring Information TEMP RANGE PIN- PAKAGE TOP MARK EKA-T -4 to SOT23 AAIM ETA-T -4 to +85 ETA+T -4 to Dnots lad-fr packag. 8 Thin QFN (3mm 3mm) 8 Thin QFN (3mm 3mm) Not: Hand soldring is not rcommndd for th SOT23 packag. AR AR Pin onfiguration 2.6 to μH TOP IEW IN 3.3μF OGI OR DA OMP.15μF + TR OMP X P S D1 1μF R SENSE 5Ω OMP TR X OMP 1 SOT S P TR X THIN QFN 3mm x 3mm S P Dual Mod is a tradmark of Maxim Intgratd Products, Inc. Maxim Intgratd Products 1 For pricing, dlivry, and ordring information, plas contact Maxim/Dallas Dirct! at , or visit Maxim s wbsit at

2 Whit ED Stp-Up onvrtr in SOT23 ABSE MAXIMUM RATINGS + to to +6 P to to +.3 X, to to +14 X to to +.3 TR to to +6 or (+ + 2) OMP, S to to (+ +.3) X urrnt...45a RMS ontinuous Powr Dissipation (T A = +7 ) 8-Pin SOT23 (drat 9.7mW/ abov +7 )...777mW 8-Pin Thin QFN 3mm 3mm (drat 24.4mW/ abov +7 ) mW Oprating Tmpratur Rang...-4 to +85 Junction Tmpratur Storag Tmpratur Rang...-6 to +15 ad Tmpratur (soldring, 1s)...+3 Strsss byond thos listd undr Absolut Maximum Ratings may caus prmannt damag to th dvic. Ths ar strss ratings only, and functional opration of th dvic at ths or any othr conditions byond thos indicatd in th oprational sctions of th spcifications is not implid. Exposur to absolut maximum rating conditions for xtndd priods may affct dvic rliability. D EETRIA HARATERISTIS (+ = 3, = 11, = 33µH, = 1µF, OMP =.15µF, R SENSE = 5Ω, TR = 1, T A = to +85, unlss othrwis notd. Typical valus ar at T A = +25.) PARAMETER ONDITIONS MIN TYP MAX UNITS Supply oltag Undrvoltag ockout Thrshold Quiscnt urrnt Shutdown Supply urrnt Ovrvoltag Thrshold Input Bias urrnt Output oltag Rang ERROR AMPIFIER + rising, 4m hystrsis typical falling Not switching, TR = S = Switching, TR = +, S = 1 2 TR = T A = T A = rising, 1 hystrsis typical falling = 13 TR > TR =.1 1 ma µa µa + - D IOD E 12.5 TR to S Rgulation TR = 2, + = 2.6 to m/ S Input Bias urrnt S = TR / µa TR Input Rsistanc kω TR Dual Mod Thrshold Hystrsis = 25m typical m S in Rgulation + = 2.6 to 5.5, TR = 3.5 %/ OMP Pin Rsistanc to Ground Dvic in shutdown or ovrvoltag kω OMP Output oltag Swing OSIATOR Oprating Frquncy MHz Minimum Duty ycl PWM mod 12 Puls skipping Maximum Duty ycl TR = +, S = % % 2

3 Whit ED Stp-Up onvrtr in SOT23 D EETRIA HARATERISTIS (continud) (+ = 3, = 11, = 33µH, = 1µF, OMP =.15µF, R SENSE = 5Ω, TR = 1, T A = to +85, unlss othrwis notd. Typical valus ar at T A = +25.) PARAMETER ONDITIONS MIN TYP MAX UNITS N-HANNE SWITH X On-Rsistanc I X = 1mA Ω X akag urrnt = X = 13 T A = T A = X urrnt imit Duty cycl = 65% ma µa D EETRIA HARATERISTIS (+ = 3, = 11, = 33µH, = 1µF, OMP =.15µF, R SENSE = 5Ω, TR = 1, T A = -4 to +85, unlss othrwis notd. (Not 1) PARAMETER ONDITIONS MIN MAX UNITS Supply oltag Undrvoltag ockout Thrshold Quiscnt urrnt Ovrvoltag Thrshold Input Bias urrnt + rising, 4m hystrsis typical falling Not switching, TR = S = +.4 Switching, TR = +, S = 2 + rising, 1 hystrsis typical falling = 13 TR > TR = 1 Output oltag Rang + - DIODE ERROR AMPIFIER TR to S Rgulation TR = 2, + = 2.6 to m/ S Input Bias urrnt S = TR / µa TR Input Rsistanc kω TR Dual Mod Thrshold Hystrsis = 25m typical 1 24 m OMP Pin Rsistanc to Ground Dvic in shutdown or ovrvoltag kω OMP Output oltag Swing OSIATOR Oprating Frquncy MHz Maximum Duty ycl TR = +, S = % N-HANNE SWITH X On-Rsistanc I X = 1mA 2.2 Ω X urrnt imit Duty cycl = 65% ma Not 1: imits ar 1% production tstd at T A = +25. imits ovr th oprating tmpratur rang ar guarantd through corrlation using statistical quality control (SQ) mthods. ma µa 3

4 Whit ED Stp-Up onvrtr in SOT23 Typical Oprating haractristics (S Typical Application ircuit, + = 3, I ED =, = 33µH, = 1µF, OMP =.15µF, R SENSE = 5Ω, TR = 1, 2 EDs, T A = +25, unlss othrwis notd.) EFFIIENY (%) EFFIIENY vs. SUPPY OTAGE 2 EDs 3 EDs I = toc1 EFFIIENY (%) EFFIIENY vs. OAD URRENT 2 EDs 3 EDs toc2 SWITHING FREQUENY (MHz) SWITHING FREQUENY vs. SUPPY OTAGE T A = +85 T A = -4 T A = +25 toc SUPPY OTAGE () OAD URRENT (ma) SUPPY OTAGE () POWER-UP WAEFORMS toc4 POWER-UP WAEFORMS toc5 SHUTDOWN WAEFORMS toc6 TR I IN 1 38mA TR I IN 1 38mA TR I IN 1 38mA I ED t RISE = 15ms OMP =.15μF I ED t RISE = 11ms OMP = 1μF I ED 5ms/div 5ms/div 2μs/div SHUTDOWN WAEFORMS toc7 INE-TRANSIENT RESPONSE toc8 TR TRANSIENT RESPONSE toc9 TR 1 IN TR OMP EENTUAY DEAYS TO + = I ED OMP =.15μF m/div 1mA/div I ED OMP =.15μF mA 2μs/div 5ms/div 2ms/div 4

5 Whit ED Stp-Up onvrtr in SOT23 Typical Oprating haractristics (continud) (S Typical Application ircuit, + = 3, I ED =, = 33µH, = 1µF, OMP =.15µF, R SENSE = 5Ω, TR = 1, 2 EDs, T A = +25, unlss othrwis notd.) TR TR TRANSIENT RESPONSE toc X I SWITHING WAEFORMS toc mA 17mA I ED 3mA IN_RIPPE 1m/div OMP = 1μF _RIPPE 1m/div 2ms/div 2ns/div PIN NAME FUNTION 1 OMP 2 TR 3 Pin Dscription ompnsation Pin for Error Amplifir. onnct capacitor from OMP to. Startup tim is st by th capacitanc connctd to this pin (.833ms for ach.1µf). OMP passivly dischargs to whn in shutdown. Brightnss/Shutdown Dual Mod ontrol Input. ED brightnss and I shutdown ar controlld by th voltag on TR. oltags btwn 25m and 5.5 or (+ + 2), whichvr is lss, adjust th brightnss from dim to bright, rspctivly. To put th I into shutdown, driv blow 1m or connct to. Ovrvoltag Sns. Whn is gratr than 13.25, th intrnal N-channl MOSFET is turnd off and OMP dcays to. Whn drops blow 12.25, th I will r-ntr soft-start. onnct a 1µF capacitor from to. 4 X Inductor onnction. Drain of th intrnal high-voltag N-channl MOSFET. 5 P Powr Ground. Sourc of th intrnal high-voltag N-channl MOSFET. 6 Ground 7 S 8 + urrnt-sns Fdback Input. onnct a rsistor from this pin to to st th ED bias currnt. This pin rgulats to 7.5% of TR. Supply oltag Input. Th I is powrd from this pin. Input rang is 2.6 to 5.5. Bypass with a cramic capacitor to. 5

6 Whit ED Stp-Up onvrtr in SOT23 Dtaild Dscription Th s high fficincy and small siz mak it idally suitd to driv sris-connctd EDs. It oprats as a boost D-D convrtr that controls output currnt rathr than voltag. Th provids vn illumination by snding th sam output currnt through ach ED, liminating th nd for xpnsiv factory calibration. Th fast 1.2MHz intrnal oscillator allows for a small inductor and small input and output capacitors whil minimizing input and output rippl. Th singl analog control input allows asy adjustmnt of ED brightnss and on/off control. This allows ithr simpl logic-lvl on/off control or a DA to control both brightnss and on/off. In shutdown, supply currnt is rducd to a low.3µa. A programmabl soft-start gradually illuminats th EDs, rducing th inrush currnt during startup. Soft-Start Th attains soft-start by charging OMP gradually with a constant 12µA currnt. Whn OMP riss abov 1.25, th intrnal MOSFET bgins switching, but at a rducd duty cycl. Whn OMP riss abov 2.25, th duty cycl will b at its maximum. Th maximum startup tim is dtrmind by th valu of OMP. For vry.1µf connctd to OMP, th PWM ONTRO X P startup tim will incras by.833ms. Th start tim can b calculatd by: tsoft- START (MAX) = OMP 1 12μA Shutdown Th is put into shutdown whn TR is lss than 1m. In shutdown, supply currnt is rducd to.3µa by powring down th ntir I xcpt for th TR voltag dtction circuitry. OMP is passivly dischargd during shutdown, allowing th dvic to rinitiat a soft-start whnvr th dvic is nabld. Whn in shutdown, th intrnal N-channl FET dos not switch, which lavs a currnt path btwn th input and th EDs through th boost inductor and Schottky diod. Th minimum forward voltag of th ED array must xcd th maximum + to nsur that th EDs rmain off in shutdown. Typical shutdown timing charactristics ar shown in th Typical Oprating haractristics. Ovrvoltag Protction Ovrvoltag protction occurs whn is abov Th protction circuitry stops th intrnal MOS- FET from switching and causs OMP to dcay to. Th dvic coms out of ovrvoltag lockout and into soft-start whn falls blow Dsign Procdur Adjusting ED urrnt Adjusting th s output currnt will chang th brightnss of th EDs. An analog input (TR) and th sns rsistor valu st th output currnt. Output currnt is givn by: 1.2MHz S I ED = TR RSENSE TR 17m SOPE Figur 1. Functional Diagram URRENT SENSE 617kΩ SHUTDOWN 8 5kΩ OMP Th TR voltag rang for adjusting output currnt is 25m to (+ + 2) or 5.5, whichvr is lss. To st th maximum currnt, calculat R SENSE whn TR is at its maximum. Powr dissipation in R SENSE is typically lss than 5mW; thrfor, a standard chip rsistor is sufficint. apacitor Slction Th xact valus of input and output capacitors ar not critical. Th typical valu for th input capacitor is 3.3µF, and th typical valu for th output capacitor is 1.µF. argr valu capacitors can b usd to rduc input and output rippl, but at th xpns of siz and highr cost. 6

7 Whit ED Stp-Up onvrtr in SOT23 Th output currnt and th numbr of EDs in ach lg affct th capacitanc of OMP. Tabl 1 shows th minimum OMP valus ndd to stabiliz th convrtr in worst-cas conditions. If furthr stability analysis is rquird, not that th rror amplifir has 5µA/ transconductanc. Inductor Slction Th valu of th inductor dpnds on th maximum output currnt to th EDs. S Tabl 1 for inductanc valus and pak currnt ratings for th inductor. Schottky Diod Slction Th s high-switching frquncy dmands a high-spd rctification diod. A Schottky diod is rquird du to thir fast rcovry tim and low forward-voltag drop. Ensur that th diod s avrag and pak currnt rating xcd th avrag output currnt and pak inductor currnt, rspctivly. In addition, th diod s rvrs brakdown voltag must xcd. I DIODE(RMS) I IPEAK P Board ayout Du to fast-switching wavforms and high-currnt paths, carful P board layout is rquird. Protoboards and wir-wrap boards should not b usd for valuation. An valuation kit (E kit) is availabl to aid dsign. Whn laying out a board, minimiz trac lngths btwn th I and R SENSE, th inductor, th diod, th input capacitor, and th output capacitor. Kp tracs short, dirct, and wid. Kp noisy tracs, such as th inductor's tracs, away from S. + s bypass capacitor ( IN ) should b placd as clos to th I as possibl. P and should b connctd in only on plac as clos to th I as possibl. Th ground connctions of IN and should b as clos togthr as possibl. Th tracs from + to th inductor and from th Schottky diod to th EDs may b longr. Rfr to th E kit for an xampl of propr layout. Applications Information 2.6 to 5.5 1μH onncting Four or Six EDs Th can driv on, two, or thr lgs of EDs (Figur 2) as long as th total numbr of EDs dos not xcd six. Each lg must contain th sam numbr of EDs and th sam sns-rsistor valu. Adding th scond or third lg dos not affct th sns-rsistor valu (s th Adjusting ED urrnt sction). Thr lgs of two EDs is mor fficint than two lgs of thr EDs (s Efficincy Graphs in th Typical Oprating haractristics); howvr, a third sns rsistor is ndd. Multipl lgs can hav slight currnt mismatchs du to componnt tolrancs. 3.3μF OGI OR DA.1μF X + P TR OMP S D1 1μF R SENSE 5Ω 25Ω 3Ω Tabl 1. omponnt Slction I ED (ma) OF EDs OMP INDUTOR (µf) (µh) I PEAK ( m A ) Figur 2. Six EDs in 3 x 2 onfiguration hip Information TRANSISTOR OUNT: 129 7

8 Whit ED Stp-Up onvrtr in SOT23 Packag Information (Th packag drawing(s) in this data sht may not rflct th most currnt spcifications. For th latst packag outlin information, go to PIN 1 I.D. DOT (SEE TE 6) b 1 E SEE DETAI "A" E1 SYMBO A A1 A2 b D E E1 2 1 MIN MAX BS..65 BS REF. 8 SOT23, 8.EPS D 2 A A2 A1 GAUGE PANE SEATING PANE TE: 1. A DIMENSIONS ARE IN MIIMETERS. 2. FOOT ENGTH MEASURED FROM EAD TIP TO UPPER RADIUS OF HEE OF THE EAD PARAE TO SEATING PANE. 3. PAKAGE INE EXUSIE OF MOD FASH & META BURR. 4. PAKAGE INE INUSIE OF SODER PATING. 5. OPANARITY 4 MIS. MAX. 6. PIN 1 I.D. DOT IS.3 MM ÿ MIN. OATED ABOE PIN SODER THIKNESS MEASURED AT FAT SETION OF EAD BETWEEN.8mm AND.15mm FROM EAD TIP. 8. MEETS JEDE MO178. PROPRIETARY INFORMATION TITE: DETAI "A" PAKAGE INE, SOT-23, 8 BODY APPROA DOUMENT ONTRO. RE D 1 8

9 Whit ED Stp-Up onvrtr in SOT23 Packag Information (continud) (Th packag drawing(s) in this data sht may not rflct th most currnt spcifications. For th latst packag outlin information, go to PIN 1 INDEX AREA D E A2 DETAI A E2 b N D2.35x.35 PIN 1 ID [(N/2)-1] x REF. 6, 8, &1, DFN THIN.EPS A1 -DRAWING T TO SAEk A PAKAGE INE, 6,8,1 & 14, TDFN, EXPOSED PAD, 3x3x.8 mm G 1 2 OMMON DIMENSIONS SYMBO MIN. MAX. A.7.8 D E A k.25 MIN. A2.2 REF. PAKAGE ARIATIONS PKG. ODE N D2 E2 JEDE SPE b [(N/2)-1] x T ±.1 2.3±.1.95 BS MO229 / WEEA.4± REF T ±.1 2.3±.1.95 BS MO229 / WEEA.4± REF DOWNBONDS AOWED T ±.1 2.3±.1.65 BS MO229 / WEE.3± REF T ±.1 2.3±.1.65 BS MO229 / WEE.3± REF T ±.1 2.3±.1.65 BS MO229 / WEE.3± REF YES T ±.1 2.3±.1.5 BS MO229 / WEED-3.25±.5 2. REF T ±.1 2.3±.1.4 BS ± REF YES T ±.1 2.3±.1.4 BS ± REF PAKAGE INE, 6,8,1 & 14, TDFN, EXPOSED PAD, 3x3x.8 mm -DRAWING T TO SAE G 2 2 Maxim cannot assum rsponsibility for us of any circuitry othr than circuitry ntirly mbodid in a Maxim product. No circuit patnt licnss ar implid. Maxim rsrvs th right to chang th circuitry and spcifications without notic at any tim. Maxim Intgratd Products, 12 San Gabril Driv, Sunnyval, A Maxim Intgratd Products Printd USA is a rgistrd tradmark of Maxim Intgratd Products, Inc.