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. general description the max1698 and max1698a are efficient drivers for white or color leds. they are ideal for large led backlit displays in pdas and laptop computers. numerous benefits include greater simplicity, lower cost, higher efficiency, longer bulb life, and greater reliability when compared to fluorescent (ccfl) and electrolumines- cent (el) lamps. the max1698/max1698a are switch-mode boost con- trollers in which led current, rather than output voltage, is regulated the devices drive series-connected leds with a controlled current that is measured with a typical- ly 15 ? sense resistor, not an expensive fractional-ohm value. led current control and dimming are accom- plished with an adjust input (adj). for larger light out- put, multiple led banks can be connected in parallel with up to 5w total output power. the max1698a has a higher, and more accurately specified, cs current limit than the max1698 for higher- power applications of 5w or more. both devices are supplied in a space-saving 10-pin ?ax package that occupies half the space of an 8-pin so. an evaluation kit (max1698evkit) is available to speed designs. applications battery-powered backlight applications backlight for lcd panels notebook pcs handy terminals pdas features ? over 90% efficiency ? lossless, adjustable led brightness ? space-saving 10-pin max package ? simpler, lower cost, more reliable compared to ccfl or el backlights ? up to 5w output power max1698/max1698a high-efficiency step-up current regulator for leds ________________________________________________________________ maxim integrated products 1 1 2 3 4 5 10 9 8 7 6 ext cs pgnd gnd adj ref v cc max1698 max1698a max top view fb gnd shdn v cc v out c out shdn fb gnd adj ref cs on off pgnd ext d1 v cc v batt l i led r fb r n max1698 max1698a typical operating circuit 19-1621; rev 2; 2/07 pin configuration ordering information part t em p ra n g e pin - pa c k a g e pkg code max1698 eub -40? to +85? 10?ax u10-2 max1698a eub -40? to +85? 10?ax u10-2
max1698/max1698a high-efficiency step-up current regulator for leds 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +3.3v, t a = 0c to +85c , unless otherwise noted. typical values are at t a = +25?.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc , shdn to gnd ..................................................-0.3v to +6v ext, fb, cs, adj, ref to gnd..................-0.3v to (v cc + 0.3v) gnd to pgnd.....................................................................?.3v continuous power dissipation (t a = +70?) 10-pin ?ax (derate 5.6mw/? above +70?) ............444mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature range (soldering, 10s)......................+300? fb = gnd, adj = ref, cs = gnd fb = gnd, adj = ref rising edge fb = gnd v fb = 0.3v adj = ref v adj = 100mv conditions mv 30 50 70 adj start threshold ? 10 15 20 t on(max) maximum on time ? 0.8 1.0 1.2 t off(min) minimum off time a rms 0.8 i cs cs input current a 0.8 1.5 2.5 cs trip current v 2.25 2.4 2.55 undervoltage lockout ? 260 500 i cc v 2.7 5.5 v cc supply voltage quiescent supply current mv 80 undervoltage hysteresis 285 300 315 mv 18 24 30 v fb fb regulation voltage units min typ max symbol parameter v fb = 300mv na -15 15 i fb fb input bias current v 0.03 ref v adj adj input range adj input bias current i adj adj = ref -50 50 na shutdown supply current shdn = gnd 0.01 1 ? ref output voltage v ref i ref = 0 1.20 1.25 1.30 v ref load regulation ? v ref i ref = 0 to 150? -2 -25 mv ref short-circuit current ref = gnd 0.45 1 ma ref power-supply rejection ratio psrr v cc = 2.7v to 5.5v +0.3 +2 mv/v ext driver sink/source current v cc = 5v, ext = 2v 0.2 a ext driver on-resistance v cc = 5v 8 ? shdn input high voltage v ih v cc = 2.7v to 5.5v 2 v shdn input low voltage v il v cc = 2.7v to 5.5v 0.8 v shdn input bias current i shdn v cc = 2.7v to 5.5v -1 1 ? 2.0 2.4 2.8 max1698 max1698a
max1698/max1698a high-efficiency step-up current regulator for leds _______________________________________________________________________________________ 3 electrical characteristics (v cc = +3.3v, t a = -40c to +85c , unless otherwise noted.) (note 1) conditions v v cc supply voltage 2.7 5.5 units min max symbol parameter fb = gnd 2.0 3.0 minimum off time t off(min) fb = gnd, adj = ref 0.6 1.4 ? maximum on time t on(max) fb = gnd, adj = ref, cs = gnd 921 ? adj start threshold 25 75 mv fb input bias current i fb v fb = 300mv -20 20 na adj input bias current i adj adj = ref -50 50 na shutdown supply current shdn = gnd 1 ? ref output voltage v ref i ref = 0 1.17 1.33 v ref load regulation ? v ref i ref = 0 to 150? -30 mv ref short-circuit current ref = gnd 1 ma ref power-supply rejection ratio psrr v cc = 2.7v to 5.5v +2 mv/v ext on-resistance v cc = 5v 8 ? shdn input high voltage v ih v cc = 2.7v to 5.5v 2 v shdn input low voltage v il v cc = 2.7v to 5.5v 0.8 v shdn input bias current i shdn v cc = 2.7v to 5.5v -1 1 ? note 1: specifications to -40? are guaranteed by design, not production tested. rising edge v undervoltage lockout 2.20 2.65 v adj = 100mv adj = ref mv 13 35 v fb fb regulation voltage 280 320 v fb = 0.3v ? i cc quiescent supply current 500 cs trip current 0.8 3.0 a max1698a max1698
max1698/max1698a high-efficiency step-up current regulator for leds 4 _______________________________________________________________________________________ 0 5 10 15 20 25 045 23 1 678910 mxa1698-01 v batt , v cc (v) output current (ma) output current vs. v batt and v cc 1 chain of 4 leds vs. v cc vs. v batt 0 0.4 0.2 0.8 0.6 1.0 1.2 0 0.6 0.8 0.2 0.4 1.0 1.2 1.4 normalized output current vs. adj voltage mxa1698-02 adj voltage (v) normalized output current 20.0 20.5 21.5 21.0 22.0 0 46810 2 1214161820 mxa1698-03 input voltage (v) output current (ma) output current vs. input voltage 1 chain of 4 leds i batt i out 4 chains of 4 leds 0 200 100 400 300 600 500 700 900 800 1000 0 234 1 567 9 810 battery current vs. battery voltage mxa1698-04 v batt (v) i out, i batt (ma) 0 30 20 10 50 40 90 80 70 60 100 100 400 700 1000 1300 1600 1900 2200 ext rise/fall time vs. c ext mxa1698-05 c ext (p f ) rise/fall time (ns) fall time rise time 0 30 20 10 40 50 60 70 80 90 100 04 26810 efficiency vs. battery voltage mxa1698-06 battery voltage (v) efficiency (%) i out = 80ma 4 chains of 4 leds 0 20 10 40 30 60 50 70 90 80 100 52535 15 45 55 65 75 85 mxa1698-07 output current (ma) efficiency (%) efficiency vs. output current v batt = 5v 4 chains of 4 leds mxa1698-08 i out 50ma/div 5ms/div shutdown/soft-start timing shdn 5v/div i batt 100ma/div 3.3v 0 4 chains of 4 leds i out set to 80ma, mxa1698-09 led and inductor current waveforms inductor current 500ma/div led current 50ma/div 1 s/div typical operating characteristics (circuit of figure 2, v cc = v batt = 3.3v, v adj = v ref , t a = +25?, unless otherwise noted.)
max1698/max1698a high-efficiency step-up current regulator for leds _______________________________________________________________________________________ 5 name function 1 v cc ic supply voltage input. power for internal circuitry. input range is 2.7v to 5.5v. 2 shdn active-low shutdown input. in shutdown, the mosfet turns off, but a current path still exists between the input and output. the minimum forward voltage of the led array must exceed the maximum v batt to ensure that the leds are off in shutdown. pin 3 ref 1.25v reference output. capable of sourcing 150? for external loads. this pin is internally compensated. do not connect any bypass capacitors at ref. 4 adj adjust input. allows dynamic adjustment of the output current. fb regulates to 300mv when adj = ref. 6 fb feedback input. connect to the external led current-sense feedback resistor. 8 pgnd power ground 9 cs fet current-sense input 5, 7 gnd ground 10 ext gate driver output pin description undervoltage lockout/ shutdown cs trig q trig q pgnd ext ref gnd adj fb shdn v cc v cc max t on min t off max1698 soft-start 1.25v reference figure 1. functional diagram
max1698/max1698a high-efficiency step-up current regulator for leds 6 _______________________________________________________________________________________ detailed description the max1698/max1698as' high efficiency and small size make them ideally suited to drive leds. they oper- ate as a boost dc-dc converter that controls output current rather than voltage. losses are minimized by a low, 300mv current-sense threshold. in the standard configuration, a feedback resistor, r fb , sets the current through the primary chain of leds. additional chains of matching leds can be added with an equivalent resis- tor. in matched led arrays, the secondary chain cur- rents closely track the primary chain. an optional zener diode, d2, prevents overvoltage in the event that one of the leds in the primary chain becomes an open circuit. the led brightness can be adjusted dynamically by a voltage input at adj. shutdown in shutdown, the supply current is reduced below 1?. ext goes low in shutdown, shutting off the external n- channel fet. this leaves a current path between the input and the leds through the boost inductor and catch diode. the minimum forward voltage of the led array must exceed the maximum v batt to ensure that the leds remain off in shutdown. typical shutdown tim- ing characteristics are shown in the typical operating characteristics. soft-start the max1698/max1698a include a soft-start function that eliminates input current surges at turn-on. they do this by extending the external fet driver (ext) mini- mum off-time during start-up. during the first 512 switching cycles, the minimum off-time is 5?. it is then allowed to drop to 2? for the next 1500 switching cycles. after that time, the minimum off-time falls to the 1? value used during normal operation. (see shutdown/soft-start timing in the typical operating characteristics section.) design procedure setting the maximum led current resistor r fb sets the maximum current in the primary chain of leds: where i ledmax is the maximum led current. adjusting led current r fb sets the maximum led current. this current can be reduced proportional to the voltage at the adj pin (see normalized output current vs. adj voltage in the typical operating characteristics section). figure 3 r mv i fb ledmax = 300 v cc shdn pgnd gnd fb r fb optional dz leds mbr0540 adj ref cs ext max1698 max1698a v cc = 3.3v 10 f v batt = 3.3v 10 h 1 f 15 ? 15 ? 15 ? 15 ? 1 f figure 2. typical operating circuit
max1698/max1698a high-efficiency step-up current regulator for leds _______________________________________________________________________________________ 7 shows the standard method of setting the adj voltage. use the following equation to determine i led : where v adj is the voltage at adj. note that adj volt- ages below 50mv turn the leds off. inductor selection choose an inductor with low dc resistance (in the neighborhood of 100m ? ) to minimize losses. a typical inductance value for l is 10?; however, values from 3.3? to 100? can also be used. higher inductor val- ues reduce the max1698? switching frequency. the typical operating frequency is given by: the max1698/max1698a limit peak inductor current to 1.5a, but also contains a control loop that reduces inductor current as a function of output power. for a given output power, the required inductor peak current rating is approximately set by: i l(peak) = 1.0 p out where p out is the output power to all led banks in watts and i l(peak) is in amperes. capacitor selection the exact value of output capacitance is not critical. typical values for the output capacitor are 0.1? to 10?. larger values help reduce output ripple at the expense of size and higher cost. the requirements of the input capacitor depend on the type of the input voltage source. however, in many applications, the same capacitor type and value are used for both the input and output capacitors. transistor selection the max1698/max1698a drive an external n-channel mosfet. since the gate drive voltage is derived from v cc , best performance is achieved with low-threshold nfets that specify on-resistance with gate-source volt- ages (v gs ) at the voltage supplied at v cc or less. for best results, minimize the fet? r ds(on) . the external nfet? maximum drain-to-source voltage (v ds(max) ) must exceed the output voltage. catch diode (d1) selection the max1698/max1698as' high-switching frequency demands a high-speed rectifier. schottky diodes are recommended for most applications, due to their fast recovery time and low forward-voltage drop. ensure that the diode? average and peak current ratings exceed the average output current and peak inductor current, respectively. in addition, the diode? reverse breakdown voltage must exceed v out . for output volt- ages exceeding 40v, high-speed silicon rectifiers may be required for their higher breakdown voltages. zener diode for applications requiring open-circuit protection if one of the leds in the primary chain opens, add a zener diode as shown in figure 2. the zener diode protects the mosfet and output capacitor if the current feed- back signal is lost. the zener voltage should exceed the maximum forward voltage of the led network by at least 2v. applications information pcb layout due to fast switching waveforms and high-current paths, careful pcb layout is required. protoboards and wire-wrap boards should not be used for evaluation. an ev kit (max1698evkit) is available to aid most designs. when laying out a board, minimize trace lengths to cs, the inductor, diode, input capacitor, and output capaci- tor. keep traces short, direct, and wide. keep noisy traces, such as the inductor? traces, away from fb. v cc ? bypass capacitor should be placed as close to the ic as possible. refer to the max1698 ev kit for an example of proper layout. i v r led adj fb . = ? 416 gnd ref adj max1698 max1698a 500k figure 3. adjusting led current transistor count: 2180 chip information f v l batt . = ? 067
max1698/max1698a high-efficiency step-up current regulator for leds maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2007 maxim integrated products is a registered trademark of maxim integrated products. inc. 10lumax.eps package outline, 10l umax/usop 1 1 21-0061 rev. document control no. approval proprietary information title: top view front view 1 0.498 ref 0.0196 ref s 6 side view bottom view 0 0 6 0.037 ref 0.0078 max 0.006 0.043 0.118 0.120 0.199 0.0275 0.118 0.0106 0.120 0.0197 bsc inches 1 10 l1 0.0035 0.007 e c b 0.187 0.0157 0.114 h l e2 dim 0.116 0.114 0.116 0.002 d2 e1 a1 d1 min - a 0.940 ref 0.500 bsc 0.090 0.177 4.75 2.89 0.40 0.200 0.270 5.05 0.70 3.00 millimeters 0.05 2.89 2.95 2.95 - min 3.00 3.05 0.15 3.05 max 1.10 10 0.60.1 0.60.1 ? 0.500.1 h 4x s e d2 d1 b a2 a e2 e1 l l1 c gage plane a2 0.030 0.037 0.75 0.95 a1 note: the max1698 does not have an exposed pad. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) revision history pages changed at rev 2: 1, 2, 8
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs m axim > p roduc ts > p ower and battery m anagement max1698, max1698a high-efficiency step-up c urrent regulator for leds quickview technical documents ordering info more information all ordering information notes: other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 1. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 2. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 3. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 4. devices: 1-6 of 6 m ax1698 fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is max1698eub umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1698eub-t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10-2 * -40c to +85c rohs/lead-free: no materials analysis max1698eub+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis max1698eub+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis m ax1698a fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is MAX1698AEUB+ umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis MAX1698AEUB+t umax;10 pin;15 mm dwg: 21-0061j (pdf) use pkgcode/variation: u10+2 * -40c to +85c rohs/lead-free: lead free materials analysis didn't find what you need? next day product selection assistance from applications engineers parametric search applications help quickview technical documents ordering info more information des c ription key features a pplic ations /u s es key spec ific ations diagram data sheet a pplic ation n otes des ign guides e ngineering journals reliability reports software/m odels e valuation kits p ric e and a vailability samples buy o nline p ac kage i nformation lead-free i nformation related p roduc ts n otes and c omments e valuation kits doc ument ref.: 1 9 -1 6 2 1 ; rev 2 ; 2 0 0 7 -0 3 -1 6 t his page las t modified: 2 0 0 7 -0 6 -0 5
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