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evaluation kit available general description the max8631x/y charge pump drives up to eight whiteleds with regulated constant current for uniform inten- sity. the main group of leds (m1?4) can be driven up to 30ma per led for backlighting. the flash group of leds (f1?4) is independently controlled and can be driven up to 100ma per led (or 400ma total). two 200ma ldos are on-board to provide power for cam- era functions. the ldos?output voltages are pin-pro- grammable to meet different camera-module requirements. by utilizing adaptive 1x/1.5x/2x charge- pump modes and very-low-dropout current regulators, the max8631x/y achieves high efficiency over the full 1-cell lithium-battery voltage range. the 1mhz fixed-fre- quency switching allows for tiny external components, and the regulation scheme is optimized to ensure low emi and low input ripple. the max8631x/y is available in a 28-pin thin qfn, 4mm x 4mm lead-free package (0.8mm max height). applications camera phones and smartphonesbacklighting and flash pdas, digital cameras, and camcorders features ? powers up to 8 leds up to 30ma/led drive for backlight up to 400ma total drive for flash ? two internal low-noise 200ma ldos ? 94% max/85% avg efficiency (p led /p batt ) over li+ battery discharge ? 0.2% typical led current matching ? adaptive 1x/1.5x/2x mode switchover ? single-wire serial pulse interface for brightness control (32 steps) ? thermal t a derating function ? low input ripple and emi ? 2.7v to 5.5v supply voltage range ? soft-start, overvoltage, and thermal-shutdown protection ? 28-pin thin qfn, 4mm x 4mm package max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn ___________________________________________________ _____________ maxim integrated products 1 ordering information 19-3688; rev 3; 6/08 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max8631xeti+ -40? to +85? 28 thin qfn-ep*4mm x 4mm (t2844-1) max8631yeti+ -40? to +85? 28 thin qfn-ep*4mm x 4mm (t2844-1) pin configuration appears at end of data sheet. main on/off and dimming max8631x/y 1 f 10 f 0.01 f 10 f pinin pgnd gndp1 p2 out main flash output up to 480ma 1 f 1 f ldo1ldo2 c2p c2n 1 f c1p c1n ref setm setf camera module dual-ldo voltage selection input2.7v to 5.5v enm2 enm1 enf enldo m1m2 m3 m4 f1f2 f3 f4 flash on/off dual-ldo on/off typical operating circuit * ep = exposed pad. + denotes a lead-free package. downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 2 __________________________________________________ _____________________________________ absolute maximum ratings electrical characteristics (v in = 3.6v, v gnd = v pgnd = 0v, enm1 = enm2 = enf = in, r setm = r setf = 6.8k , p1 = p2 = unconnected, c ref = 0.01?, t a = -40c to +85c , unless otherwise noted. typical values are at t a = +25?.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. pin, in, out, refbp to gnd................................-0.3v to +6.0v setf, setm, enldo, enm1, enm2, enf, p1, p2, ldo1, ldo2 to gnd....................-0.3v to (v in + 0.3v) m1, m2, m3, m4, f1, f2, f3, f4 to gnd...-0.3v to (v out + 0.3v) c1n, c2n to gnd ......................................... -0.3v to (v in + 1v) c1p, c2p to gnd.............. -0.3v to greater of (v out + 1v) or (v in + 1v) pgnd to gnd .......................................................-0.3v to +0.3v out, ldo1, ldo2 short-circuit to gnd ...................continuous continuous power dissipation (t a = +70?) 28-pin thin qfn 4mm x 4mm (derate 20.8mw/? above +70?) .............................1666mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter conditions min typ max units in operating voltage 2.7 5.5 v undervoltage-lockout threshold v in rising or falling 2.25 2.45 2.60 v undervoltage-lockout hysteresis 130 mv 1mhz switching, no load, 1.5x or 2x mode 4.0 5.5 1x mode 10% setting, enf = gnd, v enldo = v in , i ldo1 = i ldo2 = 0a 0.4 ma supply current enm1 = enm2 = enf = gnd, v enldo = v in , i ldo1 = i ldo2 = 0a 110 ? t a = +25? 0.01 5 shutdown supply current enm1 = enm2 = enf = enldo = gnd t a = +85? 0.1 ? en_ high voltage v in = 2.7v to 5.5v 1.4 v en_ low voltage v in = 2.7v to 5.5v 0.4 v t a = +25? 0.01 1 en_ input current v en_ = 0v or 5.5v t a = +85? 0.1 ? enm_ or enf low shutdowndelay t shdn see figure 2 2.5 ms enm_ or enf t lo see figure 2 0.5 250.0 ? enm_ or enf t hi see figure 2 0.5 ? initial enm_ or enf t hi only required for first enm_ or enf pulse, see figure 2 200 ? p1, p2 shutdown input current 1 a p1, p2 input impedance 150 k thermal-shutdown threshold temperature rising +160 ? thermal-shutdown hysteresis 20 ? charge pump overvoltage-protection threshold v out rising 5 v soft-start time 2m s downloaded from: http:///
max8631x/y electrical characteristics (continued) (v in = 3.6v, v gnd = v pgnd = 0v, enm1 = enm2 = enf = in, r setm = r setf = 6.8k , p1 = p2 = unconnected, c ref = 0.01?, t a = -40c to +85c , unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter conditions min typ max units 1x to 1.5x or 1.5x to 2x modetransition threshold 90 100 110 mv input voltage-mode transitionhysteresis 150 mv charge-pump maximum outcurrent v in 3.15v, v out = 3.9v 580 ma 1x mode, (v in - v out ) / i out 0.3 1.0 1.5x mode, (1.5v in - v out ) / i out 1.1 4.0 open-loop out resistance 2x mode, (2v in - v out ) / i out 1.5 4.14 charge-pump short-circuitcurrent v out < 1.25v 500 ma switching frequency 1 mhz out pulldown resistance in shutdown enm_ = enf = gnd 5 k led driver set_ bias voltage t a = +25? 0.6 v t a = +25? 0.01 1 set_ leakage in shutdown enm_ = enf = gnd t a = +85? 0.1 ? set_ current range 10 145 ? setm-to-main led current ratio(i m_ /i setm ) 100% setting, m1?4 230 a/a setf-to-flash led current ratio(i f_ /i setf ) 100% setting, f1?4 690 a/a t a = +25? -1.25 +1.25 m_, f_ current accuracy t a = -40? to current derating start temperature -4 +4 % maximum main led sink current r setm = 4.6k , for each m_ 30 ma maximum flash led sink current r setf = 4.12k , i f1 + i f2 + i f3 + i f4 400 ma current-derating-function start temperature +40 ? current-derating-function slope t a = +40? to +85? -1.7 %/? dropout voltage (note 2) 40 90 mv 1.5x and 2x regulation voltage 150 mv t a = +25? 0.01 1 m_, f_ leakage in shutdown enm_ = enf = gnd t a = +85? 0.1 ? ldo_ output voltage accuracy i ldo_ = 150ma, relative to v out(nom) (note 3) -1.7 0 +1.7 % output current range 0 200 ma current limit v ldo_ = 0v 280 475 750 ma soft-start current limit 160 ma 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn ___________________________________________________ ____________________________________ 3 downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 4 __________________________________________________ _____________________________________ electrical characteristics (continued) (v in = 3.6v, v gnd = v pgnd = 0v, enm1 = enm2 = enf = in, r setm = r setf = 6.8k , p1 = p2 = unconnected, c ref = 0.01?, t a = -40c to +85c , unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter conditions min typ max units soft-start done time 100 ? dropout voltage i ldo_ = 200ma (note 4) 120 320 mv load regulation v in = 3.7v, 100? < i ldo_ < 200ma 1.3 % power-supply rejection v out / v in 10hz to 10khz, c ldo_ = 1?, i ldo_ = 10? -60 db output noise voltage (rms) 10hz to 100khz, c ldo_ = 1?, i ldo_ = 10ma 40 ? rms note 1: all devices are 100% production tested at t a = +25?. limits over the operating temperature range are guaranteed by design. note 2: led dropout voltage is defined as the m_ or f_ to gnd voltage at which current into m_ or f_ drops 10% from the value at m_ or f_ = 0.2v. note 3: (greater of 2.7v or (v ldo_ + 0.5v)) v in 5.5v. note 4: ldo dropout voltage is defined as v in - v out when v out is 100mv below the value of v out measured when v in = v out(nom) + 1v. since the minimum input voltage is 2.7v, this specification is only meaningful when v out(nom) > 2.5v. typical operating characteristics (v in = v en_ = 3.6v, circuit of figure 1, t a = +25?, unless otherwise noted.) efficiency vs. li+ battery voltage driving four main leds max8631x toc01 li+ battery voltage (v) efficiency p led /p batt (%) 3.9 3.6 3.3 3.0 50 60 70 80 90 100 40 2.7 4.2 15ma/led 4.5ma/led 1.5ma/led efficiency vs. li+ battery voltage driving flash led module max8631 toc02 li+ battery voltage (v) efficiency p led /p batt (%) 3.9 3.6 3.3 3.0 50 60 70 80 90 100 40 2.7 4.2 80ma total 160ma total 400ma total battery current vs. supply voltage driving four main leds max8631x toc03 supply voltage (v) battery current (ma) 3.9 3.6 3.3 3.0 20 40 60 80 100 120 0 2.7 4.2 i led = 15ma i led = 4.5ma i led = 1.5ma v in falling v in rising downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn _______________________________________________________________________________________ 5 battery current vs. supply voltage driving flash max8631x toc04 supply voltage (v) battery current (ma) 3.9 3.6 3.3 3.0 100 200 300 400 500 600 700 800 900 0 2.7 4.2 i flash = 400ma i flash = 160ma i flash = 80ma ldo ground pin supply current vs. supply voltage max8631x toc05 supply voltage (v) ground pin supply current ( a) 5.1 4.7 3.9 4.3 3.5 3.1 90 100 110 120 130 140 150 160 80 2.7 5.5 v enm = v enf = 0v, v enldo = v in 150ma, both ldos no load, both ldos input ripple voltage vs. supply voltage with four main leds max8631x toc06 supply voltage (v) input ripple (mv rms ) 5.1 4.7 4.3 3.9 3.5 3.1 0.2 0.4 0.6 0.8 1.0 1.2 0 2.7 5.5 i led = 15ma i led = 4.5ma i led = 1.5ma input ripple voltage vs. supply voltage with flash and main leds max8631x toc07 supply voltage (v) input ripple (mv rms ) 5.1 4.7 3.1 3.5 3.9 4.3 1 2 3 4 5 7 96 8 10 0 2.7 5.5 four main leds at 15ma each i flash = 10ma i flash = 40ma i flash = 100ma led current matching vs. supply voltage with four main leds max8631x toc08 supply voltage (v) main led current (ma) 5.1 4.7 3.9 4.3 3.5 3.1 14.2 14.4 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.014.0 2.7 5.5 led current matching vs. supply voltage with four flash leds max8631x toc09 supply voltage (v) flash led current (ma) 5.1 4.7 4.3 3.9 3.5 3.1 99.098.5 99.5 100.0 100.5 101.0 101.5 102.0 98.0 2.7 5.5 led current vs. ambient temperature with four main leds max8631x toc10 ambient temperature ( c) total led current (ma) 60 35 10 -15 10 20 30 40 50 60 70 0 -40 85 led current vs. ambient temperature with flash max8631x toc11 ambient temperature ( c) total led current (ma) 60 35 10 -15 50 100 150 200 250 300 350 400 450 0 -40 85 individual main led current vs. r setm max8631x toc12 r setm (k ) main led current (ma) 10 10 100 1 100 1 typical operating characteristics (continued) (v in = v en_ = 3.6v, circuit of figure 1, t a = +25?, unless otherwise noted.) downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 6 __________________________________________________ _____________________________________ individual flash led current vs. r setf max8631x toc13 r setf (k ) flash led current (ma) 10 10 100 1000 1 1 100 operating waveforms (1x mode) max8631x toc14 50mv/divac-coupled 20mv/div ac-coupled 2ma/div ac-coupled v out v in i in 400ns/div 4 main leds at 20ma each operating waveforms (1.5x mode) max8631x toc15 50mv/divac-coupled 20mv/div ac-coupled 2ma/div ac-coupled v out v in i in 400ns/div 4 main leds at 20ma each operating waveforms (2x mode) max8631x toc16 50mv/divac-coupled 20mv/div ac-coupled 2ma/div ac-coupled v out v in i in 400ns/div 4 main leds at 20ma each, flash at 400ma total startup and shutdown main led response max8631x toc17 5v/div0v 100ma/div 5v/div 0v 0a v enm_ i out v out 1ms/div 4 main leds at 20ma each startup and shutdown flash led response max8631x toc18 5v/div0v 500ma/div 500ma/div5v/div 0v 0a 0a v enf i in v out i out 1ms/div 4 main leds at 20ma each, 400ma total flash typical operating characteristics (continued) (v in = v en_ = 3.6v, circuit of figure 1, t a = +25?, unless otherwise noted.) downloaded from: http:///
max8631x/y single-wire dimming response max8631x toc19 5v/div0v 500ma/div 2v/div 0a0v v enm1, v enm2 i out v out 10ms/div load-transient response near dropout max8631x toc23 50mv/divac-coupled 100ma 1ma v ldo_ i ldo_ 10 s/div v in - v out = 77mv, v ldo_ = 2.6v 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn _______________________________________________________________________________________ 7 ldo dropout voltage vs. output current max8631x toc20 output current (ma) dropout votlage (mv) 150 100 50 20 40 60 80 100 120 140 0 0 200 ldo output voltage accuracy vs. output current xmax8631x toc21 output current (ma) output voltage accuracy (%) 150 100 50 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0 200 load-transient response max8631x toc22 50mv/divac-coupled 100ma 1ma v ldo_ i ldo_ 10 s/div v ldo_ = 2.6v typical operating characteristics (continued) (v in = v en_ = 3.6v, circuit of figure 1, t a = +25?, unless otherwise noted.) downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 8 __________________________________________________ _____________________________________ 0.6v 0.15v selmin error amp 1 main control flash control control and reference max8631xmax8631y enm1 refbp m1 d1 m2 d2 m3 d3 m4 d4 + + + + setm in input 2.7v to 5.5v 1.25v out ldo1ldo2 outputup to 480ma ovd c71 f c61 f c1 10 f c8 0.01 f c510 f error amp 2 r setm 6.81k gnd f1 d5 f2 d6 f3 d7 f4 d8 + + + + gnd enm2 enf enldop1 p2 c3 1 f c1p pingnd pgnd in c1n c2p c2n c4 1 f 1x/1.5x/2x regulating charge pump low- dropout linear regulators setf in error amp 3 r setf 4.12k figure 1. functional diagram and application circuit downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn ___________________________________________________ ____________________________________ 9 pin description pin name function 1 pin supply voltage input. bypass to pgnd with a 10? ceramic capacitor. the input voltage range is2.7v to 5.5v. pin is high impedance during shutdown. 2i n chip supply voltage input. bypass to gnd with a 10? ceramic capacitor as close to the ic aspossible. the input voltage range is 2.7v to 5.5v. in is high impedance during shutdown. 3 gnd ground. connect gnd to system ground and the input bypass capacitor as close to the ic aspossible. 4 ldo1 ldo1 output. bypass with a 1? ceramic capacitor to gnd. ldo1 is pulled to ground through aninternal 400k during shutdown. 5 ldo2 ldo2 output. bypass with a 1? ceramic capacitor to gnd. ldo2 is pulled to ground through aninternal 400k during shutdown. 6 refbp reference filter. bypass refbp with a 0.01? ceramic capacitor to gnd. 7 setf bias current set input for f1?4. the current flowing out of setf sets the maximum (100%) biascurrent into each led. v setf is internally biased to 0.6v. connect a resistor (r setf ) from setf to gnd to set the flash current. r setf = 414 / i led(max) . setf is high impedance during shutdown. 8 setm bi as c ur r ent s et inp ut for m 1m 4. the cur r ent fl ow i ng out of s e tm sets the m axi m um ( 100%) b i as cur r ent i nto each le d . v s e t m i s i nter nal l y b i ased to 0.6v . c onnect a r esi stor ( r s e t m ) fr om s e tm to gn d to set the m ai n le d cur r ent. r s e t m = 138 / i l e d ( m ax ) . s e tm i s hi g h i m p ed ance d ur i ng shutd ow n. 9?2 f4?1 400m a c om b i ned c ur r ent fl ash le d c athod e c onnecti on and c har g e- p um p feed b ack. c ur r ent fl ow i ng i nto f_ i s b ased on i s e t f . the char g e p um p r eg ul ates the l ow est f_ vol tag e to 0.15v . gr ound i ng any f_ i np ut for ces ou t to op er ate at ap p r oxi m atel y 5v . c onnect f_ to ou t i f thi s le d i s not p op ul ated . 13?6 m4?1 30ma m ai n le d cathod e connecti on and c har g e- p ump feed b ack. c ur rent fl owi ng i nto m _ i s based on the e n _ confi g ur ation and i s e tm . the char ge p um p reg ulates the l owest m _ inp ut voltag e to 0.15v . gr ound i ng any m _ for ces ou t to oper ate at ap pr oxim atel y 5v . connect m_ to ou t i f thi s le d i s not p op ul ated . 17 p2 default output-voltage select input. p1 and p2 set the ldo1 and ldo2 voltages to one of ninecombinations (table 2). p2 is high impedance in an off condition and shortly after an on condition. 18 enldo ldo output enable. drive to a logic-level high to turn on both ldos. drive to a logic-level low to turnoff both ldos. 19 enm2 enable and dimming control for m1?4. drive both enm1 and enm2 to a logic-level high to turn onthe main leds. drive both enm1 and enm2 to a logic-level low to turn off the main leds. the dimming technique is discussed in the applications information section. 20 enm1 enable and dimming control for m1?4. drive both enm1 and enm2 to a logic-level high to turn onthe main leds. drive both enm1 and enm2 to a logic-level low to turn off the main leds. the dimming technique is discussed in the applications information section. 21 enf enable and dimming control for f1?4. drive enf to a logic-level high to turn on the flash leds.drive enf to a logic-level low to turn off the flash leds. the dimming technique is discussed in the applications information section. 22 c1n transfer capacitor 1 negative connection. connect a 1? ceramic capacitor between c1p and c1n.c1n is internally shorted to in during shutdown. downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 10 _________________________________________________ _____________________________________ detailed description the max8631x/y charge pump drives up to 4 whiteleds in the main display for backlighting and up to 4 white leds for flash, all with regulated constant current for uniform intensity. by utilizing adaptive 1x/1.5x/2x charge-pump modes and very-low-dropout current reg- ulators, it achieves high efficiency over the 1-cell lithi- um-battery input voltage range. 1mhz fixed-frequency switching allows for tiny external components and low input ripple. two on-board 200ma programmable-out- put-voltage ldos are provided to meet camera-module requirements. 1x to 1.5x switchover when v in is higher than v out , the max8631x/y oper- ates in 1x mode and v out is pulled up to v in . the internal current regulators regulate the led current. asv in drops, v m_ (or v f_ ) eventually falls below the switchover threshold of 100mv and the max8631x/ystarts switching in 1.5x mode. when the input voltage rises above v out by approximately 50mv, the max8631x/y switches back to 1x mode. 1.5x to 2x switchover when v in is less than v out but greater than two-thirds v out , the max8631x/y operates in 1.5x mode. the internal current regulators regulate the led current. asv in drops, v m_ (or v f_ ) eventually falls below the switchover threshold of 100mv, and the max8631x/ystarts switching in 2x mode. when the input voltage rises above two-thirds v out by approximately 50mv, the max8631x/y switches back to 1.5x mode. soft-start the max8631x/y includes soft-start circuitry to limitinrush current at turn-on. once the input voltage is applied, the output capacitor is charged directly from the input with a ramped current source (with no charge- pump action) until the output voltage approaches the input voltage. once the output capacitor is charged, the charge pump determines if 1x, 1.5x, or 2x mode is required. in the case of 1x mode, the soft-start is termi- nated and normal operation begins. in the case of 1.5x or 2x mode, soft-start operates until the lowest voltage of m1?4 and f1?4 reaches regulation. if the output is shorted to ground or is pulled to less than 1.25v, the output current is limited by soft-start. true shutdown mode when enm1, enm2, and enf are simultaneously heldlow for 2.5ms or longer, the max8631x/y is shut down and put in a low-current shutdown mode, and the input is isolated from the output. out is internally pulled to gnd with 5k during shutdown. thermal derating the max8631x/y limits the maximum led currentdepending on the die temperature. the maximum led current is set by the r setm and r setf resistors. once the temperature reaches +43?, the led currentdecreases by 1.7%/?. due to the package? exposed paddle, the die temperature is always very close to the pc board temperature. the temperature derating function allows the led cur- rent to be safely set higher at normal operating temper- atures, thereby allowing either a brighter display or fewer leds to be used for normal display brightness. pin description (continued) pin name function 23 c1p transfer capacitor 1 positive connection. connect a 1? ceramic capacitor between c1p to c1n.during shutdown, if out > in, c1p is shorted to out. if out < in, c1p is shorted to in. 24 pgnd power ground. connect pgnd to system ground. pgnd is used for charge-pump switching currents. 25 out charge-pump output. bypass out to gnd with a 10? ceramic capacitor. connect to the anodes ofall the leds. out is internally pulled to ground through a 5k resistor during shutdown. 26 c2p transfer capacitor 2 positive connection. connect a 1? ceramic capacitor between c2p to c2n.during shutdown, if out > in, c2p is shorted to out. if out < in, c2p is shorted to in. 27 c2n transfer capacitor 2 negative connection. connect a 1? ceramic capacitor between c2p and c2n.c2n is internally shorted to in during shutdown. 28 p1 default output-voltage select input. p1 and p2 set the ldo1 and ldo2 voltages to one of ninecombinations (table 2). p1 is high impedance in an off condition and shortly after an on condition. ep exposed paddle. connect to gnd and pgnd. true shutdown is a trademark of maxim integrated products, inc. downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn ___________________________________________________ ___________________________________ 11 thermal shutdown the max8631x/y includes a thermal-limit circuit thatshuts down the ic at approximately +160?. turn-on occurs after the ic cools by approximately 20?. applications information setting the main output current setm controls m1?4 regulation current. current flow-ing into m1, m2, m3, and m4 is a multiple of the current flowing out of setm: i m1 = i m2 = i m3 = i m4 = k x (0.6v / r setm ) where k = 230, and r setm is the resistor connected between setm and gnd (see the typical operating circuit ). setting the flash output current setf controls the f1?4 regulation current. currentflowing into f1, f2, f3, and f4 is a multiple of the cur- rent flowing out of setf. i f1 = i f2 = i f3 = i f4 = n x (0.6v / r setf ) where n = 690. single-wire pulse dimming for more dimming flexibility or to reduce the number ofcontrol traces, the max8631x/y supports serial pulse dimming. connect enm1 and enm2 together to enable single-wire pulse dimming of the main leds (or enf only for single-wire pulse dimming of the flash leds). see figure 3. when enm1 and enm2 (or enf) go high simultaneously, the main (or flash) leds are enabled at full brightness. each subsequent low-going pulse (500ns to 250? pulse width) reduces the led currentby 3.125% (1/32), so after one pulse the led current is 96.9% (or 31/32) x i led . the 31st pulse reduces the current to 0.03125 x i led . the 32nd pulse sets the led current back to i led . figure 2 shows a timing diagram for single-wire pulse dimming. because soft-start islonger than the initial t hi , apply dimming pulses quickly upon startup (after initial t hi ) to avoid led current tran- sitioning through full brightness. simple on/off control if dimming control is not required, connect enm1 toenm2 for simple on/off control. drive both enm1 and enm2 to a logic-level high to turn on the main leds. drive both enm1 and enm2 to a logic-level low to turn off the main leds. enf is the simple on/off control for the flash leds. drive enf to a logic-level high to turn on the flash leds. drive enf to a logic-level low to turn off the flash leds. in this case, led current is set by the values of r setm and r setf . driving fewer than 8 leds when driving fewer than 8 leds, two different connec-tion schemes can be used. the first scheme is shown in figure 4 where led drivers are connected together. this method allows increased current through the led and effectively allows total led current to be i led multi- plied by the number of connected drivers. the secondmethod of connection is shown in figure 5 where stan- dard white leds are used and fewer than 8 are con- nected. this scheme does not alter current through each led but ensures that the unused led driver is properly disabled. input ripple for led drivers, input ripple is more important than out-put ripple. input ripple is highly dependent on the source supply? impedance. adding a lowpass filter to the input further reduces input ripple. alternately, increasing c in to 22? cuts input ripple in half with only a small increase in footprint. the 1x mode always hasvery low input ripple. 1 02 4 3 5 27 28 29 30 31 32 shutdown t shdn (2.5ms) 2/32 1/32 3/32 4/32 5/32 27/32 28/32 29/32 30/32 31/32 31/32 32/32 32/32 shutdown i m_ or i f_ enm1 and enm2 or enf t soft-start initial t hi t lo t hi 200 s 500ns 500ns to 250 s figure 2. enm_ and enf timing diagram enm1/enm2 states brightness m1?4 current enm1 = low, enm2 = low shutdown 0 enm1 = high, enm2 = high full brightness 230 x i setm table 1. enm1/enm2 states downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 12 _________________________________________________ _____________________________________ max8631xmax8631y 1 f 10 f 0.01 f 10 f pinin gnd p1 p2 out main flash output up to 480ma 1 f 1 f ldo1ldo2 c2p c2n 1 f c1p c1n refbp setm setf pgnd on/off and voltage selection input2.7v to 5.5v enm2 enm1 enf enldo m1m2 m3 m4 f1f2 f3 f4 4.12k 6.81k figure 4. providing increased led current per led max8631xmax8631y 1 f 10 f 0.01 f 10 f pinin main on/off and dimming gndp1 p2 out main flash output up to 480ma 1 f 1 f ldo1ldo2 c2p c2n 1 f c1p c1n refbp setm setf pgnd voltage selection input2.7v to 5.5v enm2 enm1 enf enldo m1m2 m3 m4 f1f2 f3 f4 4.12k flash on/off and dimming on/off 6.81k figure 3. dimming using single-wire, serial-pulse interface downloaded from: http:///
typical operating waveforms shown in the typical operating characteristics show input ripple current in 1x, 1.5x, and 2x mode. ldo output voltage selection (p1 and p2) as shown in table 2, the ldo output voltages, ldo1and ldo2 are pin-programmable by the logic states of p1 and p2. p1 and p2 are tri-level inputs: in, open, and gnd. the input voltage, v in , must be greater than the selected ldo1 and ldo2 voltages. the logic states ofp1 and p2 can be programmed only during enldo low. once the ldo_ voltages are programmed, their values do not change by changing p1 or p2 during enldo high. component selection use only ceramic capacitors with an x5r, x7r, or betterdielectric. see table 3 for a list of recommended parts. connect a 1? ceramic capacitor between ldo1 and gnd, and a second 1? ceramic capacitor between ldo2 and gnd for 200ma applications. the ldo out- put capacitor? (c ldo ) equivalent series resistance (esr) affects stability and output noise. use outputcapacitors with an esr of 0.1 or less to ensure stability and optimum transient response. connect c ldo_ as close to the max8631x/y as possible to minimize theimpact of pc board trace inductance. pc board layout and routing the max8631x/y is a high-frequency switched-capaci-tor voltage regulator. for best circuit performance, use a solid ground plane and place c in , c out , c3, and c4 as close to the max8631x/y as possible. there shouldbe no vias on c in . connect gnd and pgnd to the exposed paddle directly under the ic. refer to themax8631x/y evaluation kit for an example. max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn ___________________________________________________ ___________________________________ 13 max8631xmax8631y 1 f 10 f 0.01 f 10 f pinin gnd p1 p2 out main flash output up to 240ma 1 f 1 f ldo1ldo2 c2p c2n 1 f c1p c1n refbp setm setf pgnd on/off and voltage selection input2.7v to 5.5v enm2 enm1 enf enldo m1m2 m3 m4 f1f2 f3 f4 4.12k 6.81k figure 5. schematic for when fewer than 8 leds is acceptable max8631x max8631y p1 p2 ldo1 (v) ldo2 (v) ldo1 (v) ldo2 (v) in in 3.3 1.8 2.8 2.6 in open 3.0 1.5 2.8 2.8 in gnd 2.8 1.5 2.9 1.5 open in 3.3 1.5 2.6 1.9 open open 2.6 1.8 2.6 2.6 open gnd 2.6 1.5 2.8 1.9 gnd in 3.0 1.8 2.9 1.8 gnd open 2.8 1.8 2.9 1.9 gnd gnd 2.5 1.8 2.9 2.9 table 2. p1 and p2, ldo output voltage selection downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn 14 _________________________________________________ _____________________________________ designation value manufacturer part number description c1, c5 10? tdk c2012x5r0j106m 10? ?0%, 6.3v x5r ceramic capacitors (0805) c3, c4, c6, c7 1? tdk c1005x5r0j105m 1? ?0%, 6.3v x5r ceramic capacitors (0402) c8 0.01? tdk c1005x7r1e103k 0.01? ?0%, 25v x7r ceramic capacitor (0402) d1?4 nichia nscw215t white leds d5 (d5?8) nichia nbcw011t white leds, 4 leds in one package panasonic r setm , r setf as required vishay 1% resistor table 3. recommended components for figure 1 chip information process: bicmos 9 8 11 12 13 1410 23 22 2526 27 28 24 21 20 19 18 17 16 15 1234 56 7 max8631xetimax8631yeti thin qfn 4mm x 4mm, 0.4mm lead pitch top view pgnd c1p enf enm2 p2 m1 m2 m3m4 f1 f2 f3 f4 setm refbp ldo2 ldo1 gnd in pin enm1 enldo c2p c1n c2n out p1 + setf pin configuration package information for the latest package outline information and land patterns, goto www.maxim-ic.com/packages . package type package code document no. 28 tqfn-ep t2844-1 21-0139 downloaded from: http:///
max8631x/y 1x/1.5x/2x white led charge pump with two ldos in 4mm x 4mm thin qfn revision history revision number revision date description pages changed 3 6/08 removed pwm dimming control feature and updated enm_ and enf lowshutdown delay ec values 1, 2, 9?2, 14 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 15 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. downloaded from: http:///

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