general description the max1733/max1734 step-down dc-dc converters deliver over 250ma to outputs as low as 1.25v. these converters use a unique proprietary current-limited con- trol scheme that achieves over 90% efficiency. these devices maintain extremely low quiescent supply cur- rent (40?), and their high 1.2mhz (max) operating fre- quency permits small, low-cost external components. this combination of features makes the max1733/ max1734 excellent high-efficiency alternatives to linear regulators in space-constrained applications. internal synchronous rectification greatly improves effi- ciency and eliminates the external schottky diode required in conventional step-down converters. both devices also include internal digital soft-start to limit input current upon startup and reduce input capacitor requirements. the max1733 provides an adjustable output voltage (1.25v to 2.0v). the max1734 provides factory-preset output voltages (see selector guide ). both are avail- able in space-saving 5-pin sot23 packages. applications cellular, pcs, and cordless telephones pdas, palmtops, and handy-terminals battery-powered equipment features 250ma guaranteed output current synchronous rectifier for over 90% efficiency tiny 5-pin sot23 package 40? quiescent supply current 0.01? logic-controlled shutdown up to 1.2mhz switching frequency fixed 1.8v or 1.5v outputs (max1734) adjustable output voltage (max1733) ?.5% initial accuracy 2.7v to 5.5v input range soft-start limits startup current max1733/max1734 low-voltage, step-down dc-dc converters in sot23 ________________________________________________________________ maxim integrated products 1 gnd out (fb) ( ) are for max1733 only. shdn 15 lx in max1733 max1734 sot23-5 top view 2 34 pin configuration out v out at 250ma input +2.7v to +5.5v lx in max1734 shdn gnd 10 h 22 f 2.2 f typical operating circuit 19-1586; rev 0; 7/00 for free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. for small orders, phone 1-800-835-8769. note: the max1734 offers two output voltages. see the selector guide, then insert the proper designator into the blanks above to complete the part number. ordering information part temp. range pin-package max1733 euk-t -40 c to +85 c 5 sot23-5 m a x1 7 3 4 e u k_ _- t -40 c to +85 c 5 sot23-5 selector guide part v out (v) top mark max1733euk adjustable adky max1734euk18 1.8 adkw max1734euk15 1.5 adkx
max1733/max1734 low-voltage, step-down dc-dc converters in sot23 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = +2.7v to +5.5v, shdn = in, t a = 0? to +85?. typical values are at t a = +25?, unless otherwise noted.) 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. in, shdn to gnd .....................................................-0.3v to +6v out, fb, lx to gnd ....................................-0.3v to (v in + 0.3v) out short circuit to gnd ..........................................continuous continuous power dissipation (t a = +70?) 5-pin sot23 (derate 7.1mw/? above +70?)............571mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units input voltage range v in 2.7 5.5 v startup voltage v start 2.0 v v in rising 1.85 1.95 uvlo threshold v uvlo v in falling 1.55 1.65 v uvlo hysteresis 200 mv quiescent supply current i in no switching, no load (fb/out above trip point) 40 70 a shutdown supply current i shdn shdn = gnd 0.01 4 a outp ut v ol tag e range ( max 1733) v out 1.25 2.0 v i out = 0, t a = +25 c -1.5 +1.5 output voltage accuracy (max1734) i out = 0 to 250ma -3 +3 % load regulation i out = 0 to 250ma 0 %/ma line regulation v in = 2.7v to 5.5v 0 %/v out sense current (max1734) v out = v reg , v in = v shdn = 5v 4 8 a t a = +25 c, v in = 3.6v 1.231 1.250 1.269 fb feedback threshold (max1733) v fb v in = 3.6v 1.220 1.280 v fb leakage current (max1733) i fb v fb = 1.5v 0.001 0.2 a shdn input high voltage v ih 2.7v < v in < 5.5v 1.6 v shdn input low voltage v il 2.7v < v in < 5.5v 0.4 v shdn leakage current i shdn shdn = gnd or in 0.001 1 a high-side current limit i limp 300 425 535 ma low-side current limit i limn 200 325 430 ma i lx = -50ma, v in = 3.0v 0.7 1.4 high-side on-resistance r onp i lx = -50ma, v in = 5.5v 0.5 1.1 ? i lx = -50ma, v in = 3.0v 1.0 2 rectifier on-resistance r onn i lx = -50ma, v in = 5.5v 0.8 1.6 ? rectifier off-current threshold i lxoff 40 ma lx leakage current i lxleak v in = 5.5v, v lx = 0 to v in 0.1 5 a lx reverse leakage current i lxlk , r in unconnected, v lx = 5.5v, shdn = gnd 0.1 5 a minimum on-time t on ( min ) v in = 3.6v 0.28 0.4 0.5 s minimum off-time t off( m in) v in = 3.6v 0.28 0.4 0.5 s
max1733/max1734 low-voltage, step-down dc-dc converters in sot23 _______________________________________________________________________________________ 3 note 1: all devices are 100% production tested at t a = +25 c. limits over the operating temperature range are guaranteed by design. electrical characteristics (v in = +2.7v to +5.5v, shdn = in, t a = -40 c to +85 c , unless otherwise noted.) (note 1) parameter symbol conditions min max units input voltage range v in 2.7 5.5 v startup voltage v start 2.0 v v in rising, 200mv typical hysteresis 1.95 uvlo threshold v uvlo v in falling 1.55 v quiescent supply current i in no switching (fb/out above trip point) 70 a shutdown supply current i shdn shdn = gnd 4 a outp ut v ol tag e range ( max 1733) v out 1.25 2.0 v output voltage accuracy (max1734) i out = 0 to 250ma -3 +3 % out sense current (max1734) i out v out = v reg , v in = v shdn = 5v 8 a fb feedback threshold (max1733) v fb v in = 3.6v 1.210 1.280 v fb leakage current (max1733) i fb v fb = 1.5v 0.2 a shdn input high voltage v ih 2.7v < v in < 5.5v 1.6 v shdn input low voltage v il 2.7v < v in < 5.5v 0.4 v shdn leakage current i shdn shdn = gnd or in 1 a high-side current limit i limp 300 565 ma low-side current limit i limn 200 430 ma i lx = -50ma, v in = 3.0v 1.4 high-side on-resistance r onp i lx = -50ma, v in = 5.5v 1.1 ? i lx = -50ma, v in = 3.0v 2 rectifier on-resistance r onn i lx = -50ma, v in = 5.5v 1.6 ? lx leakage current i lxleak v in = 5.5v, v lx = 0 to v in 5 a lx reverse leakage current i lxlk , r in unconnected, v lx = 5.5v, shdn = gnd 5 a minimum on-time t on ( min ) 0.25 0.55 s minimum off-time t off( m in) 0.25 0.55 s
max1733/max1734 low-voltage, step-down dc-dc converters in sot23 4 _______________________________________________________________________________________ typical operating characteristics (c in = 2.2f ceramic, c out = 22f tantalum, l = 10h, unless otherwise noted.) 100 1000 30 40 50 60 80 70 90 100 0.1 1 10 efficiency vs. load current (v out = 1.8v) load current (ma) efficiency (%) v in = 5.0v v in = 3.6v v in = 2.7v max1733/4-01 100 1000 30 40 50 60 80 70 90 100 0.1 1 10 efficiency vs. load current (v out = 1.5v) max1733/4-02 load current (ma) efficiency (%) v in = 5.0v v in = 3.6v v in = 2.7v 46 48 50 52 54 56 58 60 62 2.5 3.5 3.0 4.0 4.5 5.0 5.5 no-load supply current vs. supply voltage max1733/4-03 supply voltage (v) supply current (?) v out = 1.5v, t a = -40? v out = 1.5v, t a = +25? v out = 1.8v, t a = +85? v out = 1.8v, t a = +25? 3.0 -3.0 0.1 10 100 1 1000 output accuracy vs. load current (v out = 1.8v) max1733/4-04 load current (ma) output accuracy (%) -2.0 -1.0 0 1.0 2.0 v in = 3.6v, t a = -40 c v in = 5.0v, t a = +25 c v in = 3.6v, t a = +85 c v in = 2.7v, t a = +25 c 3.0 -3.0 0.1 10 100 11000 output accuracy vs. load current (v out = 1.5v) max1733/4-05 load current (ma) output accuracy (%) -2.0 -1.0 0 1.0 2.0 v in = 3.6v, t a = -40 c v in = 2.7v, t a = +25 c v in = 3.6v, t a = +85 c v in = 5.0v, t a = +25 c 1.50 1.25 1.00 0.75 0.50 2.7 3.3 3.0 3.6 3.9 4.2 switching frequency vs. supply voltage max1733/4-06 supply voltage (v) switching frequency (mhz) v out = 1.8v v out = 1.5v i load = 50ma to 250ma light-load switching waveforms max1733/4-07 400ns/div v lx 2v/div v out ac-coupled 20mv/div v in = 3.6v, v out = 1.8v, i load = 20ma heavy-load switching waveforms max1733/4-08 400ns/div v lx 2v/div v out ac-coupled 20mv/div v in = 3.6v, v out = 1.8v, i load = 200ma
max1733/max1734 low-voltage, step-down dc-dc converters in sot23 _______________________________________________________________________________________ 5 typical operating characteristics (continued) (c in = 2.2f ceramic, c out = 22f tantalum, l = 10h, unless otherwise noted.) load-transient response max1733/4-12 4 s/div v out ac-coupled 50mv/div i load 100ma/div v in = 3.6v, v out = 1.8v, i load = 20ma to 200ma light-load line-transient response max1733/4-10 4 s/div v out ac-coupled 50mv/div v in ac-coupled 200mv/div v in = 3.4v to 3.8v, v out = 1.8v, i load = 20ma heavy-load line-transient response max1733/4-11 4 s/div v out ac-coupled 50mv/div v in ac-coupled 200mv/div v in = 3.4v to 3.8v, v out = 1.8v, i load = 200ma soft-start and shutdown response max1733/4-09 200 s/div v out 1v/div v in = 3.6v, v out = 1.8v, r load = 7 ? v shdn 5v/div i in 100ma/div pin description pin name function 1in supply voltage input. input range from +2.7v to +5.5v. bypass with a 2.2 f ceramic capacitor to gnd. 2 gnd ground 3 shdn active-low shutdown input. connect shdn to in for normal operation. in shutdown, lx becomes high impedance and quiescent current drops to 0.01 a. fb max1733 voltage feedback input. fb regulates to 1.25v nominal. connect fb to an external voltage-divider between the output voltage and gnd. 4 out max1734 voltage sense input. out is connected to an internal voltage-divider. 5 lx inductor connection
max1733/max1734 detailed description the max1733/max1734 step-down dc-dc converters deliver over 250ma to outputs as low as 1.25v. they use a unique proprietary current-limited control scheme that maintains extremely low quiescent supply current (40a), and their high 1.2mhz (max) operating frequen- cy permits small, low-cost external components. figure 2 is a simplified functional diagram. control scheme the max1733/max1734 use a proprietary, current-lim- ited control scheme to ensure high-efficiency, fast tran- sient response, and physically small external components. this control scheme is simple: when the output voltage is out of regulation, the error comparator begins a switching cycle by turning on the high-side switch. this switch remains on until the minimum on- time of 400ns expires and the output voltage regulates or the current-limit threshold is exceeded. once off, the high-side switch remains off until the minimum off-time of 400ns expires and the output voltage falls out of reg- ulation. during this period, the low-side synchronous rectifier turns on and remains on until either the high- side switch turns on again or the inductor current approaches zero. the internal synchronous rectifier eliminates the need for an external schottky diode. this control scheme allows the max1733/max1734 to provide excellent performance throughout the entire load-current range. when delivering light loads, the high-side switch turns off after the minimum on-time to reduce peak inductor current, resulting in increased efficiency and reduced output voltage ripple. when delivering medium and higher output currents, the max1733/max1734 extend either the on-time or the off- time, as necessary to maintain regulation, resulting in nearly constant frequency operation with high efficien- cy and low output voltage ripple. shutdown mode connecting shdn to gnd places the max1733/ max1734 in shutdown mode and reduces supply cur- rent to 0.01a. in shutdown, the control circuitry, inter- nal switching mosfet, and synchronous rectifier turn off and lx goes high impedance. connect shdn to in for normal operation. soft-start the max1733/max1734 have internal soft-start circuitry that limits current draw at startup, reducing transients on the input source. soft-start is particularly useful for higher impedance input sources, such as li+ and alkaline cells. soft-start is implemented by starting with the current limit at 25% of its full current value and gradually increasing it in 25% steps until the full current limit is reached. see soft-start and shutdown response in the typical operating characteristics section. design information setting the output voltage (max1733) select an output voltage for the max1733 by connect- ing fb to a resistive divider between the output and low-voltage, step-down dc-dc converters in sot23 6 _______________________________________________________________________________________ figure 1. max1733 typical application circuit fb r1 r2 v out c1 2.2 f c2 22 f l1 10 h lx in max1733 shdn gnd input +2.7v to +5.5v shdn control logic p n v ref out (fb) lx in gnd ( ) are for max1733 only. current limit shutdown control digital soft-start max1733 max1734 figure 2. simplified functional diagram
gnd (figure 1). choose r2 to be less than 50k ? : where v ref = 1.25v. inductor selection the max1733/max1734 are optimized to use a 10h inductor over the entire operating range. a 300ma rated inductor is enough to prevent saturation for out- put currents up to 250ma. saturation occurs when the inductor s magnetic flux density reaches the maximum level the core can support and inductance falls. choose a low dc-resistance inductor to improve effi- ciency. tables 1 and 3 list some suggested inductors and suppliers. capacitor selection the max1733/max1734 require output voltage ripple (approximately 30mvp-p) for stable switching behavior. use a 10f to 47f tantalum output capacitor with about 200m ? to 300m ? esr to provide stable switch- ing while minimizing output ripple. choose input and output capacitors to filter inductor currents for accept- able voltage ripple. the input capacitor reduces peak currents and noise at the voltage source. input capaci- tors must meet the input ripple requirements and volt- age rating. use the following equation to calculate the maximum rms input current: tables 2 and 3 list some suggested capacitors and suppliers. using ceramic c out with max1733 the circuit of figure 3 is designed to allow the use of ceramic output capacitors with the max1733. feedback is derived from the lx pin instead of the out- put to remove the effects of phase lag in the feedback loop. compared to the standard applications circuit, there are three benefits: 1) availability of ceramic vs. tantalum; 2) size of 2.2f 0805 vs. 22f a-case; 3) out- put ripple less than 10mvp-p vs. greater than 30mvp-p. increase the output capacitance to 4.7f to further reduce the output ripple. note that this circuit exhibits load regulation equal to the series resistance of the inductor multiplied by the load current. this small amount of load regulation is helpful in reducing over- shoot of the output voltage during load transients. i i v v out v rms out out in in = ? () ? ? ? ? ? ? 12 / rr v v out ref 12 1 = ? ? ? ? ? ? ? max1733/max1734 low-voltage, step-down dc-dc converters in sot23 _______________________________________________________________________________________ 7 inductor value (h) manufacturer part number cr43-100 10 sumida cdrh4d18-100 10 coilcraft dt1608c-103 table 1. suggested inductors table 2. suggested capacitors capacitor type manufacturer part number tantalum (22f) taiyo yuden lmk212bj225mg ceramic (2.2f) avx taja226m006r table 3. component suppliers company phone fax avx 843-946-0238 843-626-3123 coilcraft 847-639-6400 847-639-1469 kemet 408-986-0424 408-986-1442 murata 814-237-1431 814-238-0490 usa 847-956-0666 847-956-0702 sumida japan 81-3-3607-5111 81-3-3607-5144 taiyo yuden 408-573-4150 408-573-4159 fb 30k 1000pf 68k 2.2 f x7r output 1.8v at 250ma 10 h lx in max1733 shdn off on 2.2 f x7r gnd li+ 2.7v to 4.2v figure 3. using a ceramic output capacitor with the max1733
max1733/max1734 low-voltage, step-down dc-dc converters in sot23 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 ? 2000 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information layout considerations high switching frequencies make pc board layout a very important part of design. good design minimizes excessive emi on the feedback paths and voltage gra- dients in the ground plane, both of which can result in instability or regulation errors. connect the inductor, input filter capacitor, and output filter capacitor as close to the device as possible, and keep their traces short, direct, and wide. connect their ground pins at a single common node in a star ground configuration. the external voltage-feedback network should be very close to the fb pin, within 0.2 inches (5mm). keep noisy traces, such as the lx trace, away from the volt- age-feedback network; also keep them separate, using grounded copper. the max1733/max1734 evaluation kit data sheet includes a proper pc board layout and routing scheme. chip information transistor count: 1190 process: bicmos
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 max1733, max1734 low-voltage, step-down dc -dc c onverters in sot23 high-efficiency dc-dc solution for low-voltage logic supplies 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: 1-13 of 13 m ax1733 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 max1733euk-tg05 sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1733euk sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1733euk+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis max1733euk-t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1733euk+t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis m ax1734 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 max1734euk18+t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis max1734euk18+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis max1734euk15+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis max1734euk15 sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1734euk18 sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1734euk18-t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis
max1734euk15-t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis max1734euk15+t sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -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 5 8 6 ; rev 0 ; 2 0 0 0 -0 9 -1 5 t his page las t modified: 2 0 0 7 -0 6 -0 6 c ontac t us: send us an email c opyright 2 0 0 7 by m axim i ntegrated p roduc ts , dallas semic onduc tor ? legal n otic es ? p rivac y p olic y
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