general description the max1582/max1582y drive up to six white leds inseries with a constant current to provide display back- lighting for two (main and sub-) displays in cell phones and other handheld devices. this configuration elimi- nates the need for ballast resistors and expensive fac- tory calibra tion. the proprietary dual-output, step-up pulse-width modulation (pwm) converter includes a lowr dson n-channel mosfet switch for high efficiency and maximum battery life.the max1582/max1582y utilize 1mhz current-mode pwm control to allow small input and output capacitors and a small inductor, while minimizing ripple on the input supply and avoiding interference to sensitive circuitry in the equipment. integrated overvoltage protection (27v for the max1582 and 18v for the max1582y) eliminates the need for an external zener diode to protect the ic from open circuit. flexible dimming control utilizes either an analog control signal or direct digital pwm control without external rc filtering. this also increases dimming accuracy at low brightness levels. the pwm dimming signal can be any frequency from 200hz to 200khz. soft- start eliminates inrush current during startup. the max1582 /max1582y are available in tiny 4 ? 4 chip-scale (ucsp ) and 12-pin thin qfn packages. applications cell phones with one or two displayssmart phones, palmtops, and wireless handhelds other handheld devices with dual displays features ? accurate current regulation for uniformillumination ? lights up two led sections for main andsubdisplays ? up to 84% efficiency ? internal high-power, 30v mosfet ? low 15mv p-p input ripple ? flexible dimming control analog dac controlleddirect-digital pwm (no rc required) from 200hz to 200khz ? overvoltage protection to eliminate zener diode ? constant 1mhz pwm operation ? low-profile inductor and capacitors ? soft-start eliminates inrush current ? 2.6v to 5.5v input ? 0.01? (typ) shutdown current ? tiny ucsp (2.1mm ? 2.1mm ? 0.61mm) and thin qfn (4mm ? 4mm) packages max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting ________________________________________________________________ maxim integrated products 1 ordering information 19-2783; rev 2; 8/05 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. evaluation kit available part temp range pin-package top mark m a x1 5 8 2 e be - t -40 c to +85 c 16 ucsp-16 1582ebe m ax 1582e be + t -40 c to +85 c 16 ucsp-16 1582ebe max1582etc -40 c to +85 c 12 thin qfn-ep* aace max1582etc+ -40 c to +85 c 12 thin qfn-ep* aace pin configurations max1582 input 2.6v to 5.5v 2.2 f 0.022 f 0.1 f v+vp ctrl en1 en2 comp 22 h lx out1 pgnd out2 cs gnd 2 to 4 leds main display 2 to 3 leds sub-display 7.5 analog or direct pwm dimming typical application circuit max1582 max1582y 1v+ top view 2vp 3 ctrl out2cs en2 9 8 7 12 11 10 456 pgndlx out1 comp gnd en1 4mm x 4mm thin qfn + a "+" sign will replace the first pin indicator on lead-free packages. pin configurations continued at end of data sheet. * ep = exposed paddle. + denotes lead-free package. ucsp is a trademark of maxim integrated products, inc.ordering information continued at end of data sheet. downloaded from: http:///
max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics(v v+ = +3.0v, v out1 = 20v, l1 = 22?, c out = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = +1.5v, en1 = en2 = v+, t a = 0? to +85? , 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. v+, vp, ctrl to gnd............................................-0.3v to +6.0v pgnd to gnd .......................................................-0.3v to +0.3v lx, out1 to gnd ...................................................-0.3v to +30v out2 to gnd .........................................................-0.3v to +14v comp, cs, en1, en2 to gnd ....................-0.3v to (v v+ + 0.3v) i lx .................................................................................................... 1a r ms continuous power dissipation (t a = +70 c) 12-pin thin qfn (derate 16.9mw/ c above +70 c) ....1349mw 16-pin ucsp (derate 6.5mw/ c above +70 c)..............518mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter conditions min typ max units supply voltage 2.6 5.5 v undervoltage lockout (uvlo)threshold v+ rising or falling 2.10 2.38 2.55 v uvlo hysteresis 40 mv quiescent current no switching, v ctrl = v cs = +0.25v 0.40 0.56 ma t a = +25 c 0.01 1 shutdown supply current en1 = en2 = gnd, out1 = v+ t a = +85 c 0.1 ? max1582 26 27 29 overvoltage lockout (ovlo)threshold (rising) max1582y 17 18 19 v max1582 2 ovlo hysteresis max1582y 1.3 v max1582, v out1 = +26v, en1 = en2 = v+ 20 40 65 max1582y, v out1 = +16v, en1 = en2 = v+ 20 40 65 t a = +25 c 0.01 1 out1 input bias current out1 = v+, en1 = en2 = gnd t a = +85 c 0.05 ? max1582 (v v+ - v diode ) 25.5 output voltage range (note 2) max1582y (v v+ - v diode ) 17.0 v error amplifier ctrl to cs regulation v ctrl = +1.0v, v v+ = +2.6v to +5.5v 0.095 0.100 0.106 v t a = +25 c 0.01 1 cs input bias current v cs = v ctrl / 10 t a = +85 c 1 ? ctrl input resistance 0 < v ctrl < +1v 290 500 780 k cs to comp transconductance v comp = +1.0v 32 50 82 ? oscillator operating frequency 0.80 1.0 1.25 mhz pwm mode 12 minimum duty cycle pulse skipping 0 % maximum duty cycle ctrl = v+, cs = gnd 91 94 % downloaded from: http:///
max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting _______________________________________________________________________________________ 3 electrical characteristics (continued)(v v+ = +3.0v, v out1 = 20v, l1 = 22?, c out = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = +1.5v, en1 = en2 = v+, t a = 0? to +85? , unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter conditions min typ max units n-channel switch lx on-resistance 1.50 2.25 t a = +25 c 0.01 5 lx leakage current v lx = +28v t a = +85 c 0.02 ? lx current limit duty cycle = 90% 450 650 950 ma main and subdisplay on/off switches out1 to out2 on-resistance en1 = gnd, en2 = v+ 2.5 out2 to cs on-resistance en1 = v+, en2 = gnd 2.5 out1 to out2 leakage current e n 1 = e n 2 = v + , v ou t 1 = 25v , v ou t 2 = + 9v , t a = + 85 c 0.05 ? out2 to cs leakage current en1 = en2 = v+, v out2 = 12v, v cs = 0, t a = +85 c 0.05 ? en1 and en2 logic input voltagehigh +2.6v < v v+ < +5.5v 1.6 v en1 and en2 logic input voltagelow +2.6v < v v+ < +5.5v 0.6 v t a = +25 c 0.02 1 en1 and en2 input leakage v v+ = v en1 = v en2 = +5.5v t a = +85 c 0.1 ? electrical characteristics (v v+ = +3.0v, v out1 = +20v, l1 = 22?, c out = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = +1.5v, en1 = en2 = v+, t a = -40? to +85? , unless otherwise noted.) (notes 1, 3) parameter conditions min max units supply voltage 2.6 5.5 v undervoltage lockout (uvlo)threshold v+ rising or falling 2.10 2.55 v quiescent current no switching, v c = +0.25v 0.56 ma max1582 26 29 overvoltage lockout (ovlo)threshold (rising) max1582y 17 19 v out1 input bias current v out1 = +26v, en1 = en2 = v+ 20 65 ? error amplifier ctrl to cs regulation v ctrl = +1.0v, v v+ = +2.6v to +5.5v 0.093 0.107 v ctrl input resistance 0 < v ctrl < +1.0v 290 780 k cs to comp transconductance v comp = 1.0v 32 85 ? oscillator operating frequency 0.75 1.30 mhz downloaded from: http:///
40 6050 8070 90 100 01 0 51 5 2 0 efficiency vs. led current (vs. number of leds) max1582 toc01 led current (ma) efficiency (%) 2 leds 4 leds 6 leds 40 6050 8070 90 100 01 0 51 5 2 0 efficiency vs. led current (vs. input voltage) max1582 toc02 led current (ma) efficiency (%) 4.2 v in 3.6 v in 2.7 v in 40 6050 8070 90 100 01 0 51 5 2 0 efficiency vs. led current (vs. inductance) max1582 toc03 led current (ma) efficiency (%) 10 h 4.7 h 47 h 22 h 0 10 5 15 30 3525 20 40 0 10152025 5 3035404550 input ripple vs. inductance max1582 toc04 inductance ( h) input ripple (mv p-p ) 0 1 2 4 53 6 0 2345 1 678910 input ripple spectrum max1582 toc05 frequency (mhz) input ripple (mv rms ) 0 5 10 2015 25 0 20304050 10 60 70 80 90 100 led current vs. direct-pwm dimming duty cycle max1582 toc06 direct-pwm dimming duty cycle (%) led current (ma) v ctrl = square wave 200hz < freq < 200khz typical operating characteristics (see the typical applications circuit , v v+ = v vp = 3.6v, i led = 15ma, l1 = 22?, c out1 = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = 1.5v, 4 leds, t a = +25?, unless otherwise noted.) max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting 4 _______________________________________________________________________________________ electrical characteristics (continued)(v v+ = +3.0v, v out1 = +20v, l1 = 22?, c out = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = +1.5v, en1 = en2 = v+, t a = -40? to +85? , unless otherwise noted.) (notes 1, 3) parameter conditions min max units maximum duty cycle ctrl = v+, cs = gnd 91 % n-channel switch lx on-resistance 2.25 lx current limit duty cycle = 90% 450 950 ma note 1: limits are 100% production tested at t a = +25? for ucsp parts. limits over the entire operating temperature range are guaranteed by design and characterization but are not production tested. note 2: the minimum output voltage is the input voltage minus the forward voltage drop of the schottky diode: v out(min) = v v+ - v diode note 3: specifications to -40? are guaranteed by design and not production tested. downloaded from: http:///
max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting _______________________________________________________________________________________ 5 pin description switching waveforms max1582 toc07 v in 10mv/divv out 100mv/divv lx 10v/div 500ns/div direct-pwm dimming max1582 toc08 v ctrl 32khz1v/div i in 50ma/div v in 50mv/divv out 5v/div 0ma 0v0v 50 s/div v in = 3.8v li+ battery typical operating characteristics (continued) (see the typical applications circuit , v v+ = v vp = 3.6v, i led = 15ma, l1 = 22?, c out1 = 0.1?, c comp = 0.022?, r sense = 7.5 , v ctrl = 1.5v, 4 leds, t a = +25?, unless otherwise noted.) pin qfn ucsp name function 1a 1v + input voltage supply. input voltage range is 2.6v to 5.5v. connect a 2.2? capacitor from v+ topgnd. 2 a2 vp high-current input supply. connect to v+. 3a 3 ctrl brightness control input. led brightness is controlled by the voltage applied to ctrl. varying thevoltage from 0 to +1.62v adjusts the brightness from dim to bright, respectively. any voltage above +1.62v does not increase brightness. 4a 4 comp compensation input. connect a 0.022? capacitor (c comp ) from comp to gnd. c comp stabilizes the converter and controls soft-start. c comp discharges to gnd when in shutdown. 5 b4 gnd ground. connect to pgnd at a single point near the ic. 6 c4 en1 enable 1 input. drive en1 high to enable the main-display leds. pull en1 low to turn off the main- display leds. pull both en1 and en2 low to place the ic in low-current shutdown mode. 7 d4 en2 enable 2. drive en2 high to enable the subdisplay leds. pull en2 low to turn off the subdisplayleds. pull both en1 and en2 low to place the ic in low-current shutdown mode. 8d 3c s current-sense feedback input. connect a resistor (r sense ) from cs to gnd to set the led bias current. the voltage at cs regulates to v ctrl / 10 or +0.162v, whichever is lower. 9d 2 out2 display switch output. out2 is internally connected to cs when only the main display is lit. out2 is internally connected to out1 when only the subdisplay is lit. out2 is high impedance when both displays are lit and when the ic is shut down. 10 d1 out1 overvoltage sense. when v out1 is greater than 27v (18v on the max1582y), the internal n-channel mosfet turns off until v out1 drops below 25v (16.7v on the max1582y), then the ic re-enters soft-start. connect a 0.1? capacitor from out1 to pgnd. 11 c1 lx inductor connection. during shutdown, this pin is high impedance. 12 b1 pgnd power ground. connect to gnd at a single point near the ic. ep ep exposed paddle. connect directly to gnd and pgnd under the ic. downloaded from: http:///
max1582/max1582y detailed description the max1582? high efficiency and small size make itideally suited to drive up to six series-connected leds (four leds for the max1582y). separate enable inputs are provided to control the main and subdisplay back- lighting. the max1582/max1582y operate as a boost dc-to-dc converter that regulates output current rather than voltage. it provides even illumination by sourcing the same output current through each led, eliminating the need for expensive factory calibration. the fast 1mhz internal oscillator allows for a small inductor and small input and output capacitors while minimizing input and output ripple. shutdown for main and subdisplay the max1582 /max1582y have two enable inputs (en1 and en2) used to enable or shutdown the main andsubdisplay leds. when en1 and en2 are both high, all leds are lit. with en1 high and en2 low, the main-dis- play leds are lit, and the subdisplay leds are shorted by the max1582 /max1582y. with en1 low and en2 high, the main-display leds are shorted and the subdis- play leds are lit. when both en1 and en2 are low, the max1582/ max1582y enter shutdown, reducing supply current to 0.01? (typ). although the internal n-channel mosfetdoes not switch in shutdown, there is still a dc-current high-efficiency step-up converters for white led main and subdisplay backlighting 6 _______________________________________________________________________________________ slope comp. current sense 114k 336k 50k pwm control ctrl lx cs v+ up to 27v 2.6v to 5.5v dac or pwm comp out1 pgnd overvoltage protection gnd en1 en2 2 to 4 leds 2 to 3 leds out2 d1 1.25v clamp up to 13v vp c in 2.2 f c out1 0.1 f l122 f enable inputs main display subdisplay g m c comp 0.022 f r sense 7.5 shutdown f osc 1.0mhz max1582 figure 1. functional diagram downloaded from: http:///
path between the input and the leds through theinductor and schottky diode. to ensure the leds remain off when the max1582 /max1582y are in shut- down, the minimum input forward voltage of the ledarray must exceed the maximum input voltage. typically, the leakage current through the leds in shut- down is less than 1?. soft-start the max1582 /max1582y attain soft-start by charging c comp gradually with a current source. when v comp rises above 1.25v, the internal mosfet begins switch-ing, but at a reduced duty cycle. when v comp rises above 2.25v, the duty cycle is at its maximum. overvoltage protection ovlo occurs when v out1 rises above 27v (18v for the max1582y). the protection circuitry stops the internalmosfet from switching and causes v comp to decay to gnd. the device comes out of ovlo and into soft-startwhen v out1 falls below 25v (16.7v for the max1582y). design procedure adjusting led current adjusting the max1582 /max1582ys output current changes the brightness of the leds. the led current isset by the voltage at ctrl (v ctrl ) and the sense- resistor value (r sense ): the v ctrl voltage range for adjusting output current is 0 to +1.62v. to set the maximum current, calculater sense when v ctrl is at its maximum as follows: power dissipation in r sense is typically less than 5mw; therefore, a standard chip resistor is sufficient. pwm dimming control ctrl is also used as a digital input, allowing ledbrightness control with a logic-level pwm signal applied directly to ctrl. the frequency range is from 200hz to 200khz, while 0% duty cycle corresponds to zero current and 100% duty cycle corresponds to full current. the error amplifier and compensation capaci- tor form a lowpass filter, so pwm dimming results in dc current to the leds without any additional rc filters required. capacitor selection the exact values of input and output capacitors are notcritical. the typical value for the input capacitor is 2.2?, and the typical value for the output capacitor is 0.1?. larger value capacitors can be used to reduce input and output ripple, but at the expense of size and higher cost. c comp stabilizes the converter and controls soft-start. connect a 0.022? capacitor from comp to gnd. theminimum value for c comp is c out / 10. the soft-start time is found from: inductor selection recommended inductor values range from 10? to 47?. a 22? inductor optimizes the efficiency for most applications, while maintaining a low 15mv p-p input rip- ple. with input voltages near 5v, a larger value of induc- tance may be more efficient. to prevent core saturation, ensure that the inductor saturation current rating exceeds the peak inductor current for the application. calculate the peak inductor current with the following formula: schottky diode selection the max1582 /max1582ys high switching frequency demands a high-speed rectification diode (d1) for opti-mum efficiency. a schottky diode is recommended due to its fast recovery time and low forward-voltage drop. ensure that the diode? average and peak current rating exceeds the average output current and peak inductor current. in addition, the diode? reverse break- down voltage must exceed v out1 . the rms diode current can be calculated from: applications information pc board layout due to fast-switching waveforms and high-currentpaths, careful pc board layout is required. an evalua- tion kit (max1582evkit) is available to speed design. ii i diode rms out peak () ? 1 i vi v vs l peak out max led max in min in min ? + . . () () () () 1 08 08 2 tc v a ss comp . = ? ? ? ? ? ? 125 5 r i sense led max . () = 162 10 i v r led ctrl sense = 10 max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting _______________________________________________________________________________________ 7 downloaded from: http:///
max1582/max1582y when laying out a board, minimize trace lengthsbetween the ic and r sense , the inductor, the diode, the input capacitor, and the output capacitor. keeptraces short, direct, and wide. keep noisy traces, such as the lx node trace, away from cs. the input bypass capacitor (c in ) should be placed as close to the ic as possible. for the thin qfn package, pgnd and gndshould be connected directly to the exposed paddle underneath the ic. the ground connections of c in and c out1 should be as close together as possible. the traces from in to the inductor and from the schottkydiode to the leds can be longer. chip information transistor count: 2546process: bicmos high-efficiency step-up converters for white led main and subdisplay backlighting 8 _______________________________________________________________________________________ pin configurations (continued) max1582 v+ vp ctrl comp pgnd gnd lx en1 out1 out2 cs en2 a 1234 b cd top view (balls soldered down) ucsp ordering information part temp range pin-package top mark m a x1 5 8 2 y e be - t -40 c to +85 c 16 ucsp-16 1582yebe m ax 1582y e be + t -40 c to +85 c 16 ucsp-16 1582yebe max1582yetc -40 c to +85 c 12 thin qfn-ep* aaev max1582yetc+ -40 c to +85 c 12 thin qfn-ep* aaev * ep = exposed paddle. + denotes lead-free package. ucsp is a trademark of maxim integrated products, inc. downloaded from: http:///
max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting _______________________________________________________________________________________ 9 24l qfn thin.eps package outline, 21-0139 2 1 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm package outline, 21-0139 2 2 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) downloaded from: http:///
max1582/max1582y high-efficiency step-up converters for white led main and subdisplay backlighting 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. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2005 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) 16l,ucsp.eps h 1 1 21-0101 package outline, 4x4 ucsp downloaded from: http:///
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