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general description the max1793 low-dropout linear regulator (ldo) oper-ates from +2.5v to +5.5v and delivers a guaranteed 1a load current with a low 210mv dropout. the high-accu- racy (?%) output voltage is preset at an internally trimmed voltage (see the ordering information ) or can be adjusted from 1.25v to 5.0v with an external resis-tor-divider. an internal pmos pass transistor allows a low 125? supply current, making the max1793 ideal for battery- operated portable equipment. other features include a built-in reset output, low-power shutdown, and short-cir- cuit and thermal-overload protection. the max1793 is available in a 1.5w, 16-pin power tssop package, which is 30% smaller than a sot223 package and only 1.1mm high. ________________________applications notebook computerscordless telephones cellular phones modems handheld instruments pdas and palmtop computers features ? guaranteed 1a output current ? low 210mv dropout at 1a ? up to 1% output voltage accuracy preset at 1.5v, 1.8v, 2.0v, 2.5v, 3.3v or 5.0v adjustable from 1.25v to 5.0v ? reset output (4ms delay) ? low 125 a ground current ? 0.1 a shutdown ? low 115 v rms output noise ? thermal-overload protection ? output current limit ? tiny tssop power package (1.5w) 30% smaller than sot223 (only 1.1mm high) max1793 low-dropout, low i q , 1a linear regulator ___________________________________________________ _____________ maxim integrated products 1 1615 14 13 12 11 10 9 12 34 5 6 7 8 n.c. n.c. outout out out set gnd n.c. top view max1793 tssop inin rst inin shdn n.c. ep pin configuration nc max1793 inin in in in off on c in shdn outout out out rst set gnd c out out reset output typical operating circuit 19-1654; rev 3; 1/12 ordering information ordering information continued at end of data sheet * ep = exposed pad. ? contact factory for other preset output voltages. /v denotes an automotive qualified part. note: devices are also available in a lead(pb)-free/rohs- compliant package. specify lead-free by adding ??to the part number when ordering. for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package v out ? ( v) max1793eue-50 - 40 c to + 85 c 16 tssop-ep* 5.0 or adj max1793eue-33 - 40 c to + 85 c 16 tssop-ep* 3.3 or adj max1793eue-33/v - 40 c to + 85 c 16 tssop-ep* 3.3 or adj downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator 2 __________________________________________________ _____________________________________ absolute maximum ratings electrical characteristics (v in = v out(nom) + 0.5v or v in = 2.5v (whichever is greater), shdn = in, 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 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. in, shdn , rst to gnd ............................................-0.3v to +6v out, set to gnd ........................................-0.3v to (v in + 0.3v) output short-circuit duration ............................................infinite continuous power dissipation (t a = +70?) tssop-ep (derate 19mw/? above +70?) .....................1.5w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? soldering temperature (reflow) lead(pb)- f ree p ackages..............................................+260? packages c ontaining l ead(pb)....................................+240? parameter symbol conditions min typ max units input voltage v in 2.5 5.5 v input undervoltage lockout v in 2.0 2.3 v preset v out 2.5v -1 +1 t a = +85 c, i out = 250ma preset v out < 2.5v -1.5 +1.5 t a = 0 c to +85 c, i out = 250ma -2 +2 output voltage accuracy(preset mode, set = gnd) t a = 0 c to +85 c, i out = 1ma to 1a, v in > v out + 0.5v -3 +3 % t a = +85 c, i out = 250ma, v in = 3v 1.229 1.250 1.271 t a = 0 c to +85 c, i out = 250ma, v in = 3v 1.219 1.281 set voltage threshold(for adjustable output) t a = 0 c to + 85 c , i ou t = 1m a to 1a, v in = 3v 1.212 1.288 v adjustable output voltagerange 1.25 5 v maximum output current i out continuous, v in 3v 1 a rm s short-circuit current limit i lim v out = 0v, v in 3v 1.1 1.8 3.3 a in-regulation current limit v out within 4% of nominal output voltage, v in = 5.5v 2.8 a set pin dual mode threshold 50 150 mv set input bias current i set v set = +1.25v 100 na ground current i gnd i out = 100? 125 200 ? max1793-33, -50 210 350 dropout voltage (note 1) v in - v out i out = 1a, set = gnd max1793-25 270 450 mv line regulation ? v lnr v in from (v out + 0.1v) to +5.5v, i out = 5ma, set = gnd -0.15 0 +0.15 %/v load regulation ? v ldr i out = 100? to 1a 0.7 % output voltage noise 10hz to 1mhz, c out = 6.8? (esr < 0.1 ? ) 115 ? rms shutdown supply current i off shdn = gnd, v in = +5.5v 0.1 16 ? output pulldown resistance in shutdown shdn = gnd 5 k ? downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator _______________________________________________________________________________________ 3 electrical characteristics (continued) (v in = v out(nom) + 0.5v or v in = 2.5v (whichever is greater), shdn = in, t a = +0c to +85c , unless otherwise noted. typical values are at t a = +25?.) electrical characteristics (v in = v out(nom) + 0.5v or v in = 2.5v (whichever is greater), shdn = in, t a = -40c to +85c , unless otherwise noted.) (note 2) parameter symbol conditions min typ max units v ih 1.6 shdn input threshold v il +2.5v < v in < +5.5v 0.6 v shdn input bias current i shdn shdn = gnd or in 0.01 1 a rst output low voltage v ol i sink = 1ma 0.1 v operating voltage range forrst valid i sink = 100? 1.0 5.5 v rst output high leakage v rst = +5.5v 0.01 1 a rst trip level referred to nominal v out rising edge 90 94 96 % v out rst release delay rising edge 1.5 4.0 8.0 ms thermal shutdown temperature t shdn typical thermal hysteresis = 20? 170 ? parameter symbol conditions min typ max units input voltage v in 2.5 5.5 v input undervoltage lockout v in 2.0 2.3 v i out = 250ma -2.5 2.5 output voltage accuracy(preset mode, set = gnd) i out = 1ma to 1a, v in > v out + 0.5v -3.2 3.2 % i out = 250ma, v in = 3v 1.216 1.284 set voltage threshold (for adjustable output) i out = 1ma to 1a, v in = 3v 1.210 1.290 v adjustable output voltagerange 1.25 5 v maximum output current i out continuous, v in 3v 1 a rms short-circuit current limit i lim v out = 0v, v in 3v 1.1 3.3 a set pin dual mode threshold 50 150 mv set input bias current i set v set = +1.25v 100 na ground current i gnd i out = 100? 200 ? max1793-33, -50 350 dropout voltage (note 1) v in - v out i out = 1a, set = gnd max1793-25 450 mv line regulation ? v lnr v in from (v out + 0.1v) to +5.5v, i out = 5ma, set = gnd -0.15 0.15 %/v shutdown supply current i off shdn = gnd, v in = +5.5v 16 ? v ih 1.6 shdn input threshold v il +2.5v < v in < +5.5v 0.6 v shdn input bias current i s h d n shdn = gnd or in 1 a rst output low voltage v ol i sink = 1ma 0.1 v downloaded from: http:///
1 10 100 1000 output voltage vs. load current max1793 toc01 load current (ma) output voltage (v) 3.3053.303 3.293 3.295 3.2993.297 3.301 0 1.00.5 2.01.5 3.02.5 3.5 02 3 14 5 output voltage vs. input voltage max1793 toc02 input voltage (v) output voltage (v) i out = 0 i out = 1a 3.270 3.2853.280 3.275 3.2953.290 3.3153.310 3.305 3.300 3.320 -40-200 20406080 output voltage vs. temperature max1793 toc03 temperature ( c) output voltage (v) i out = 250ma 0 50 150100 200 250 02 3 14 5 ground current vs. input voltage max1793 toc04 input voltage (v) ground current ( a) i out = 0 i out = 1a 1 10 100 1000 ground current vs. load current max1793 toc05 load current (ma) ground current ( a) 250225 200 175 150 0 7550 25 125100 110 140130 120 160150 200190 180 170 210 -40 -20 0 20 temperature ( c) 40 60 80 ground current vs. temperature max1793 toc06 ground current ( a) i out = 250ma i out = 0 typical operating characteristics (circuit of figure 2, v in = +5v, v shdn = v in ,v out = +3.3v, t a = +25?, unless otherwise noted.) max1793 low-dropout, low i q , 1a linear regulator 4 __________________________________________________ _____________________________________ parameter symbol conditions min typ max units operating voltage range forrst valid i sink = 10? 1.0 5.5 v rst output high leakage v rst = +5.5v 1 a rst trip level referred to nominal v out rising edge 90 96 % v out rst release delay rising edge 1.5 8.0 ms electrical characteristics (continued) (v in = v out(nom) + 0.5v or v in = 2.5v (whichever is greater), shdn = in, t a = -40c to +85c , unless otherwise noted.) (note 2) note 1: 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) + 0.5v. since the minimum input voltage is 2.5v, this specification in only meaningful when v out(nom) 2.5v. for v out(nom) between 2.5v and 3.3v, use the following equations: typical dropout = 210mv + (3.3v - v out(nom) x 75mv/v; guaranteed maximum dropout = 350mv + (3.3v - v out(nom) x 125mv/v. for v out(nom) > 3.3v: typical dropout = 210mv; guaranteed maximum dropout = 350mv. note 2: specifications to t a = -40? are guaranteed by design and not production tested. downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator _______________________________________________________________________________________ 5 0 100 50 200150 250 300 0 600 800 200 400 1000 1200 dropout voltage vs. load current max1793 toc07 load current (ma) dropout voltage (mv) 60 0 0.01 0.1 1 10 100 1000 power-supply rejection ratio vs. frequency max1793 toc08 frequency (khz) psrr (db) 10 40 5030 20 i out = 250ma 10 0.01 0.01 0.1 1 10 100 1000 output noise spectral density vs. frequency max1793 toc09 frequency (khz) noise ( v/ hz) 1 0.1 i out = 250ma typical operating characteristics (continued) (circuit of figure 2, v in = +5v, v shdn = v in ,v out = +3.3v, t a = +25?, unless otherwise noted.) 140 0 0.001 0.01 0.1 1 output noise vs. load current 6040 max1793 toc10 load current (a) output noise ( v rms ) 100 120 20 80 line-transient response max1793 toc11 100 s/div v in 5v 3.4v10mv/div ac-coupled v out i out = 100ma load-transient response max1793 toc12 40 s/div i out 1a100ma 20mv/div ac-coupled v out output noise max1793 toc13 4ms/div 100 v/div downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator 6 __________________________________________________ _____________________________________ shutdown response max1793 toc14 40 s/div v out 2v/div5v/div v shdn i out = 100ma reset output response max1793 toc15 1ms/div v in 5v/div 2v/div2v/div v out rst typical operating characteristics (continued) (circuit of figure 2, v in = +5v, v shdn = v in ,v out = +3.3v, t a = +25?, unless otherwise noted.) pin description pin name function 1, 8, 9, 16 n.c. no connection. not internally connected. 2? in regulator input. supply voltage ranges from +2.5v to +5.5v. bypass with a 4.7? capacitor to gnd(see the capacitor selection and regulator stability ). these inputs are internally connected, but they also must be externally connected for proper operation. 6 rst reset output. open-drain output is low when v out is 6% below its nominal value. rst remains low while the output voltage (v out ) is below the reset threshold and for at least 4ms after v out rises above the reset threshold. connect a 100k ? pullup resister to out to obtain an output voltage. 7 shdn active-low shutdown input. a logic-low disables the output and reduces the supply current to 0.1?.in shutdown, the rst output is low and out is pulled low through an internal 5k ? resistance. connect shdn to in for normal operation. 10 gnd ground. this pin and the exposed pad also function as a heatsink. solder both to a large pad or to thecircuit-board ground plane to maximize power dissipation. 11 set voltage-setting input. connect to gnd to select the factory-present output voltage. connect set to anexternal resistor-divider for adjustable-output operation. 12?5 out regulator output. bypass with a 6.8?, low-esr capacitor to gnd. connect all out pins together atthe ic. ? p exposed pad. connect to the ground plane. ep also functions as a heatsink. solder to the circuit-boardground plane to maximize thermal dissipation. downloaded from: http:///
detailed description the max1793 features dual mode operation, allow-ing a fixed output or an adjustable output from +1.25v to +5v. the regulators are guaranteed to supply 1a of output current. as figure 1 shows, the device consists of a +1.25v ref- erence, error amplifier, mosfet driver, p-channel pass transistor, internal feedback voltage-divider, dual mode comparator, and 4ms reset output. the +1.25v reference is connected to the inverting input of the error amplifier. the error amplifier com- pares this reference with the selected feedback voltage and amplifies the difference. the mosfet driver reads the error signal and applies the appropriate drive to the p-channel transistor. if the feedback voltage is lower than the reference, the pass transistor? gate is pulled lower, allowing more current to pass and increase theoutput voltage. if the feedback voltage is high, the pass transistor? gate is pulled up, allowing less current to pass to the output. the low v out comparator senses when the feedback voltage has dropped 6% below itsexpected level, causing rst to go low. the output voltage is fed back through either an inter-nal resistor-divider connected to out or an external resistor network connected to set. the dual mode comparator examines v set and selects the feedback path. if v set is below 50mv, the internal feedback path is used and the output is regulated to the factory-presetvoltage. max1793 low-dropout, low i q , 1a linear regulator ___________________________________________________ ____________________________________ 7 dual mode is a trademark of maxim integrated products, inc. 1175mv in out 100mv nmos 4ms 4ms delay timer r1r2 pmos outset gnd shdn in rst shutdown logic 1.25v reference mosfet driver with foldback current limit error amp shutdown thermal sensor 94% v out detector dual modecomparator max1793 figure 1. functional diagram downloaded from: http:///
max1793 internal p-channel pass transistor the max1793 features a 1a p-channel mosfet passtransistor. unlike similar designs using pnp pass tran- sistors, p-channel mosfets require no base drive, which reduces quiescent current. pnp-based regula- tors also waste considerable current in dropout when the pass transistor saturates and use high base-drive currents under large loads. the max1793 does not suf- fer from these problems and consumes only 225? of quiescent current under heavy loads, as well as in dropout. output voltage selection the max1793 features dual mode operation. in presetvoltage mode, the output of the max1793 is set to an internally trimmed voltage (see the ordering information ). select this mode by connecting set to gnd (figure 2).in adjustable mode, an output is selected between +1.25v and +5v using two external resistors connected as a voltage-divider to set (figure 3). the output volt- age is determined by the following equation: v out = v set [1 + (r1/r2)] where v set = +1.25v. to simplify resistor selection: r1 = r2 [(v out /v set ) ?1] since the input bias current at set is less than 100na,large resistance values can be used for r1 and r2 to minimize power consumption without losing efficiency. up to 125k ? is acceptable for r2. in preset voltage mode, the impedance from set tognd should be less than 10k ? . otherwise, spurious conditions could cause the voltage at set to exceedthe 50mv dual-mode threshold. shutdown a logic-low on shdn disables the max1793. in shut- down, the pass transistor, control circuitry, reference,and all internal circuits are turned off, reducing supply current to typically 0.1?. connect shdn to in for nor- mal operation. in shutdown, rst goes low and out is discharged to gnd with a 5k ? internal resistance. rst comparator the max1793 features a low v out indicator that asserts when the output voltage falls out of regulation. theopen-drain rst output goes low when out falls 6% below its nominal output voltage. rst remains low for 4ms after out has returned to its nominal value. a100k ? pullup resistor from rst to a suitable logic sup- ply voltage (typically out) provides a logic control sig-nal. rst can be used as a power-on-reset (por) signal to a microcontroller or can drive an external led to indi-cate power failure. rst is low during shutdown. current limiting the max1793 features a current limit that monitors thepass transistor, typically limiting short-circuit output current to 1.8a. the current limit is increased to approximately 2.8a when the output voltage is in regu- lation, improving performance with large transient loads. the output can be shorted to ground for an indefinite period of time without damaging the device. thermal-overload protection thermal-overload protection limits total power dissipa- tion in the max1793. when the junction temp erature exceeds t j = +170?, a thermal sensor turns off the pass transistor, allowing the ic to cool. the thermal sen- sor turns the pass transistor on once the ic? junction temperature drops approximately 20?. continuousshort-circuit conditions will result in a pulsed output. low-dropout, low i q , 1a linear regulator 8 __________________________________________________ _____________________________________ nc max1793 inin in in in off on c in = 4.7 f shdn outout out out rst set gnd c out = 6.8 f out reset output figure 2. typical operating circuit with preset output voltage nc max1793 inin in in in off on c in = 4.7 f shdn outout out out rst set gnd r2 r1 c out = 6.8 f out reset output figure 3. typical operating circuit with adjustable output voltage downloaded from: http:///
thermal-overload protection is designed to safeguardthe max1793 in the event of fault conditions. for con- tinuous operation, do not exceed the absolute maxi- mum junction-temperature rating of t j = +150?. operating region and power dissipation maximum power dissipation of the max1793 dependson the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. the power dis- sipated by the device is: p = i out (v in ?v out ). the resulting maximum power dissipation is: p max = [(t j(max) ?t a )/( jc + ca )] where (t j(max) ?t a ) is the temperature difference between the maximum allowed die junction (+150?) andthe surrounding air, jc (junction-to-case) is the thermal resistance of the package chosen, and ca is the thermal resistance from the case through the pcb, copper traces,and other materials to the surrounding air. figure 4 shows allowable power dissipation for typical pcbs at +25?, +50?, and +70? ambient temperatures. the max1793 tssop-ep package features an exposed thermal pad on its underside. this pad lowers the ther- mal resistance of the package by providing a direct heat conduction path from the die to the pcb. additionally, the ground pin (gnd) also channels heat. connect the exposed thermal pad and gnd to circuit ground by using a large pad (minimum 1in 2 recommended), or mul- tiple vias to the ground plane. applications information capacitor selection and regulator stability capacitors are required at the input and output of themax1793. connect a 4.7? capacitor between in and ground (c in ) and a 6.8? capacitor between out and ground (c out ). c in serves only to lower the source impedance of the input supply and may be smaller than4.7? when the max1793 is powered from regulated power supplies or low-impedance batteries. the output capacitor? equivalent series resistance (esr) affects stability and output noise. c out esr should be 0.5 ? or less to ensure stability and optimum transient response. surface-mount ceramic capacitors have verylow esr and are commonly available in values up to 10?. other low-esr (< 0.5 ? ) capacitors, such as sur- face-mount tantalum or os-con, may also be used.connect c in and c out as close to the ic as possible to minimize the impact of pcb trace inductance. noise, psrr, and transient response the max1793 output noise is typically 115? rms during normal operation. this is suitably low for most applica-tions. see the output noise plot in the typical operating characteristics . the max1793 is designed to achieve low dropout volt-age and low quiescent current in battery-powered sys- tems while still maintaining good noise, transient response, and ac rejection. see the typical operating characteristics for a plot of power-supply rejection ratio (psrr) vs. frequency. when operating from verynoisy sources, supply noise rejection and transient response can be improved by increasing the values of the input and output capacitors and employing passive postfiltering. input-output (dropout) voltage a regulator? minimum input-to-output voltage differential(dropout voltage) determines the lowest usable supply voltage. in battery-powered systems, this determines the useful end-of-life battery voltage. since a p-channel mosfet is used as the pass device, dropout voltage is the product of r ds(on) and load current (see the electrical characteristics and dropout voltage vs. load current in the typical operating characteristics ). the max1793 operating current typically remains below225? in dropout. max1793 low-dropout, low i q , 1a linear regulator ___________________________________________________ ____________________________________ 9 0 0.6 0.8 1.60.4 0.2 1.0 1.2 1.4 1.8 2.0 1 03 24 5 6 maximum output current vs. input-output differential voltage input-output differential voltage (v) maximum output current (a) maximum continuous current maximum supply voltage t a = +50 c t j(max) = +150 c t a = +70 c t a = +25 c figure 4. power operating region: maximum output current vs. input-output differential voltage downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator 10 _________________________________________________ _____________________________________ ordering information (continued) * ep = exposed pad. ? contact factory for other preset output voltages. /v denotes an automotive qualified part. note: devices are also available in a lead(pb)-free/rohs- compliant package. specify lead-free by adding ??to the part number when ordering. part temp range pin-package v out ? ( v) max1793eue-25 - 40 c to + 85 c 16 tssop-ep* 2.5 or adj max1793eue-20 - 40 c to + 85 c 16 tssop-ep* 2.0 or adj max1793eue-18 - 40 c to + 85 c 16 tssop-ep* 1.8 or adj max1793eue-15 - 40 c to + 85 c 16 tssop-ep* 1.5 or adj package information for the latest package outline information and land patterns(footprints), go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only.package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline no. land pattern no. 16 tssop-ep u16e-3 21-0108 90-0120 downloaded from: http:///
max1793 low-dropout, low i q , 1a linear regulator 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. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. 11 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2012 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 8/00 initial release 1 11/00 added output voltages and updated electrical characteristics . 1?, 7? 2 9/09 added the automotive version of the max1793. 1 3 1/12 added lead-free options and updated soldering temperature and pin description 1, 2, 6, 10 downloaded from: http:///

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