for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim's website at www.maxim-ic.com. general description the max1818 low-dropout linear regulator operatesfrom a +2.5v to +5.5v supply and delivers a guaran- teed 500ma load current with low 120mv dropout. the high-accuracy (?%) output voltage is preset at an internally trimmed voltage (see selector guide ) or can be adjusted from 1.25v to 5.0v with an external resis-tive divider. an internal pmos pass transistor allows the low 125? supply current to remain independent of load, making this device ideal for portable battery-operated equip- ment such as personal digital assistants (pdas), cellu- lar phones, cordless phones, base stations, and notebook computers. other features include an active-low open-drain reset output that indicates when the output is out of regula- tion, a 0.1? shutdown, short-circuit protection, and thermal shutdown protection. the device is available in a miniature 800mw 6-pin sot23 package. applications notebook computerscellular and cordless telephones personal digital assistants (pdas) palmtop computers base stations usb hubs docking stations features ? guaranteed 500ma output current ? low 120mv dropout at 500ma ? 1% output voltage accuracy preset at 1.5v, 1.8v, 2.0v, 2.5v, 3.3v, 5v adjustable from 1.25v to 5.0v ? power ok output ? low 125 a ground current ? 0.1 a shutdown current ? thermal overload protection ? output current limit ? tiny 800mw 6-pin sot23 package max1818 500ma low-dropout linear regulator in sot23 ___________________________________________________ _____________ maxim integrated products 1 19-1860; rev 2; 6/08 ordering information * insert the desired two-digit suffix (see selector guide) into the blanks to complete the part number. part* temp range pin-package max1818eut_ _-t -40 c to +85 c 6 sot23 max1818eut_ _#t -40 c to +85 c 6 sot23 typical operating circuit nc max1818 in on off c in 1 f shdn outpok gnd set c out 3.3 f v out to c v in = 2.5v to 5.5v r pok 100k pin configuration pok gnd shdn 16 out 5 set in max1818 sot23 top view 234 note : the max1818 requires a special solder temperature profile described in the absolute maximum ratings section. t = tape and reel. # denotes an rohs-compliant package. selector guide appears at end of data sheet. downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 2 __________________________________________________ _____________________________________ absolute maximum ratings electrical characteristics (v in = v out + 500mv or v in = +2.5v, whichever is greater; shdn = in, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 3) 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 , pok, set to gnd ...................................-0.3v to +6v out to gnd ................................................-0.3v to (v in + 0.3v) output short-circuit duration ...............................................1min continuous power dissipation (t a = +70?) (note 1) 6-pin sot23 (derate 10mw/? above +70?)..............800mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) (note 2) ...................+300? parameter symbol conditions min typ max units input voltage v in 2.5 5.5 v input undervoltage lock-out v uvlo rising, 75mv hysteresis 2.0 2.15 2.3 v i out = 100ma, t a = +25 c, v out 2.0v -1 +1 i out = 100ma, v out < 2.0v -1.5 +1.5 i out = 100ma, t a = -40 c to +85 c -2.5 +2.5 output voltage accuracy(preset mode) v out i out = 1ma to 500ma, v in > v out + 0.5v, t a = -40 c to +85 c -3 +3 % adjustable output voltagerange 1.25 5 v t a = 0 c to +85? 1.225 1.250 1.275 set voltage threshold(adjustable mode) v set v in = 2.7v, i out = 100ma, v out set to 2.0v t a = -40 c to +85 c 1.213 1.288 v guaranteed output current(rms) i out v in 2.7v 500 ma short-circuit current limit i lim v out = 0, v in 2.7v 0.55 0.8 1.8 a in-regulation current limit v out > 96% of nominal value, v in 2.7v 1.6 a set dual mode threshold 50 100 150 mv set input bias current i set v set = 1.25v -100 +100 na i out = 100? 125 250 ground-pin current i q i out = 500ma 140 ? v out = 5v 100 220 v out = 3.3v 120 215 dropout voltage (note 4) v in - v out i out = 500ma v out = 2.5v 210 360 mv line regulation v lnr v in from (v out + 100mv) to 5.5v, i load = 5ma -0.15 0 +0.15 %/v dual mode is a trademark of maxim integrated products note 1: thermal properties are specified with product mounted on pc board with one square-inch of copper area and still air. withminimal copper, the sot23 package dissipates 712mw at +70?. with a quarter square inch of copper, it will dissipate 790mw at +70?. copper should be equally shared between the in, out, and gnd pins. note 2: this device is constructed using a unique set of packaging techniques that imposes a limit on the thermal profile to whichthe device can be exposed during board-level solder attach and rework. the limit permits only the use of the solder profiles recommended in the industry standard specification, ipc jedec-j-std-020a, paragraph 7.6, table 3 for the ir/vpr and convection reflow. preheating is required. hand or wave soldering is not allowed. downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 ___________________________________________________ ____________________________________ 3 electrical characteristics (continued) (v in = v out + 500mv or v in = +2.5v, whichever is greater; shdn = in, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 3) note 3: all devices are 100% production tested at t a = +25 c. limits over the operating temperature range are guaranteed by design. note 4: the dropout voltage is defined as v in - v out , when v out is 100mv below the value of v out measured for v in = v out(nom) + 500mv. since the minimum input voltage is 2.5v, this specification is only meaningful when v out(nom) > 2.5v. for v out(nom) between 2.5v and 3.5v, use the following equations: typical dropout = -93mv/v ? v out(nom) + 445mv; guaranteed maximum dropout = -137mv/v ? v out(nom) +7004mv. for v out(nom) > 3.5v, typical dropout = 120mv; maximum dropout = 220mv. parameter symbol conditions min typ max units load regulation v ldr i out = 1ma to 500ma 0.4 1.0 % output voltage noise 10hz to 1mhz, c out = 3.3? (esr < 0.1 ) 115 ? rms shutdown shutdown supply current i off shdn = gnd, v in = 5.5v 0.1 15 ? v ih 2.5v < v in < 5.5v 1.6 shdn input threshold v il 2.5v < v in < 5.5v 0.6 v shdn = in or gnd, t a = +25? 1 25 shdn input bias current i shdn t a = +85? 5 na pok output pok output low voltage v ol pok sinking 1ma 0.01 0.1 v operating voltage range forvalid pok pok sinking 100? 1.0 5.5 v pok = 5.5v, t a = +25? 1 25 pok output high leakagecurrent t a = +85? 5 na pok threshold rising edge, referred to v out(nominal) 90 93 96 % thermal protection thermal shutdown temperature t shdn 170 c thermal shutdown hysteresis t shdn 20 c typical operating characteristics (v in = (v out + 500mv) or +2.5v, whichever is greater; shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.) 0 5025 125100 75 150 175 225200 250 0 1.0 1.5 0.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 ground pin current vs. input voltage max1818 toc01 input voltage (v) ground pin current ( a) i load = 150ma 3.3v output 2.5v output 1.8v output 40 7055 85 130 145115 100 160 0 0.2 0.3 0.4 0.5 0.1 0.6 0.7 0.8 0.9 1.0 max1818 toc02 load current (a) ground pin current ( a) ground pin current vs. load current 3.3v output 2.5v output 1.8v output 110 130120 150140 160 170 -40 10 -15 35 60 85 max1818 toc03 temperature ( c) ground pin current ( a) ground pin current vs. temperature 1.5v output 5.0v output i load = 150ma downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 4 __________________________________________________ _____________________________________ typical operating characteristics (continued) (v in = (v out + 500mv) or +2.5v, whichever is greater; shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.) 0 6030 120 90 150 180 0 0.2 0.1 0.3 0.4 0.5 max1818 toc04 load current (a) dropout voltage (mv) v out = 3.3v dropout voltage vs. load current t a = +85 c t a = +25 c t a = -40 c -3.0 -2.0-2.5 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 max1818 toc05 load current (a) output voltage accuracy (%) 0 0.2 0.3 0.4 0.1 0.5 0.6 0.7 0.9 0.8 1.0 output voltage accuracy vs. load current 3.3v output 2.5v output 1.8v output -3.0 -2.0-2.5 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 -40 -15 10 35 60 85 max1818 toc06 temperature ( c) output voltage accuracy (%) output voltage accuracy vs. temperature v out = 1.5v to 5.0v i load = 150ma power-supply rejection ratio vs. frequency max1818 toc07 80 0 20 10 psrr (db) 40 30 50 60 70 0.01 0.1 1 10 100 1000 frequency (khz) c out = 3.3 f v out = 3.3v r load = 100 line transient max1818 toc08 v in v out 2.5v10mv/div 3.5v 100 s/div 500mv/div load-transient response max1818 toc09 i out v out 500ma 100ma 20mv/div 40 s/div v in = 3.3v v out = 2.5v load-transient response near dropout max1818 toc10 v out 100mv/div 200ma 0 i out 10 s/div v in = v out + 100mv v out = 3.3v power-on reset max1818 toc11 v in v pok v out 00 0 2v/div 10ms/div downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 ___________________________________________________ ____________________________________ 5 shutdown waveform max1818 toc12 pok shutdown voltage v out 00 2v/div 0 200 s/div 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 2.5 3.0 3.5 4.0 4.5 5.0 5.5 short-circuit current limit vs. supply voltage max1818 toc13 supply voltage (v) short-circuit current limit (a) v out(nom) = +2v detailed description the max1818 is a low-dropout, low-quiescent-currentlinear regulator designed primarily for battery-powered applications. the device supplies loads up to 500ma and is available with preset output voltages. as illustrat- ed in figure 1, the max1818 consists of a 1.25v refer- ence, error amplifier, p-channel pass transistor, and internal feedback voltage-divider. the 1.25v reference is connected to the error amplifier, which compares this reference with the feedback volt- age and amplifies the difference. if the feedback volt- age is lower than the reference voltage, the pass-transistor gate is pulled lower, which allows morecurrent to pass to the output and increases the output voltage. if the feedback voltage is too high, the pass- transistor gate is pulled up, allowing less current to pass to the output. the output voltage is fed back through either an inter- nal resistive 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. pin description pin name function 1i n regulator input. supply voltage can range from 2.5v to 5.5v. bypass with a 1 f capacitor to gnd (see capacitor selection and regulator stability ). 2 pok open-drain pok output. pok remains low while the output voltage (v out ) is below the pok threshold. connect a 100k pull-up resistor from pok to out to obtain an output voltage. 3 shdn active-low shutdown input. a logic low reduces supply current below 15 a. in shutdown, the pok output is low, and out is high impedance. connect to in for normal operation. 4 gnd ground 5 set voltage-setting input. connect to gnd for preset output. connect to a resistive voltage-divider betweenout and gnd to set the output voltage between 1.25v and 5.0v. 6 out regulator output. sources up to 500ma. bypass with a 3.3 f low-esr capacitor to gnd. use a 4.7 f capacitor for output voltages below 2v. typical operating characteristics (continued) (v in = (v out + 500mv) or +2.5v, whichever is greater; shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.) downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 6 __________________________________________________ _____________________________________ additional blocks include an output current limiter, ther-mal sensor, and shutdown logic. internal p-channel pass transistor the max1818 features a 0.25 p-channel mosfet pass transistor. unlike similar designs using pnp passtransistors, 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 max1818 does not suf- fer from these problems and consumes only 125? of quiescent current under heavy loads as well as in dropout. output voltage selection the max1818? dual mode operation allows operationin either a preset voltage mode or an adjustable mode. connect set to gnd to select the preset output volt- age. the two-digit part number suffix identifies the out- put voltage (see selector guide) . for example, the max1818eut33 has a preset 3.3v output voltage.the output voltage may also be adjusted by connecting a voltage-divider from out to set to gnd (figure 2). select r2 in the 25k to 100k range. calculate r1 with the following equation: r1 = r2 [(v out / v set ) ?1] where v set = 1.25v, and v out may range from 1.25v to 5.0v. shutdown pull shdn low to enter shutdown. during shutdown, the output is disconnected from the input and supply cur-rent drops to 0.1?. when in shutdown, pok pulls low and out is high impedance. the capacitance and load at out determine the rate at which v out decays. shdn can be pulled as high as 6v, regardless of the input and output voltage. 100mv shdn inpok on off c in 1 f v in = 2.5v to 5.5v out v out = 1.25v to 5.0v c out 3.3 f thermal sensor set mosfet driver with i lim shutdown logic v ref 1.25v error amplifier gnd r1r2 r pok 100k logic supply voltage (v out ) 93% v ref to c 5k max1818 figure 1. functional diagram downloaded from: http:///
pok output the power ok (pok) output pulls low when out is lessthan 93% of the nominal regulation voltage. once out exceeds 93% of the nominal voltage, pok goes high impedance. pok is an open-drain n-channel output. to obtain a voltage output, connect a pullup resistor from pok to out. a 100k resistor works well for most appli- cations. pok can be used as a power-okay (pok) signal to a microcontroller ( c), or drive an external led to indi- cate power failure. when the max1818 is shut down, pok is held low independent of the output voltage. if unused, leave pok grounded or unconnected. current limit the max1818 monitors and controls the pass transis-tor? gate voltage, limiting the output current to 0.8a (typ). this current limit doubles when the output voltage is within 4% of the nominal value to improve perfor- mance with large load transients. thermal overload protection thermal overload protection limits total power dissipa-tion in the max1818. when the junction temperature exceeds t j = +170?, a thermal sensor turns off the pass transistor, allowing the ic to cool. the thermalsensor turns the pass transistor on again after the junc- tion temperature cools by 20?, resulting in a pulsed output during continuous thermal overload conditions. thermal overload protection protects the max1818 in the event of fault conditions. for continuous operation, do not exceed the absolute maximum junction-temper-ature rating of t j = +150?. operating region and power dissipation the max1818? maximum power dissipation dependson the thermal resistance of the ic package and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. the power dissipated in the device is p = i out (v in - v out ). the maximum allowed power dissipation is 800mw at t a = +70? or: p max = (t j(max) - t a ) / ( jc + ca ) where t j - t a is the temperature difference between the max1818 die junction and the surrounding air, jc is the thermal resistance of the junction to the case,and ca is the thermal resistance from the case through the pc board, copper traces, and other materi-als to the surrounding air. for best heatsinking, the copper area should be equally shared between the in, out, and gnd pins. the max1818 delivers up to 0.5a rms and operates with input voltages up to +5.5v, but not simultaneously. high output currents can only be sustained when input- output differential voltages are low, as shown in figure 3. max1818 500ma low-dropout linear regulator in sot23 ___________________________________________________ ____________________________________ 7 out set gnd in shdn pok c out 3.3 f v out v out c in 1 f on off v in = 2.5v to 5.5v r 2 r1 = r2 - 1 1.25v max1818 r 1 figure 2. adjustable output using external feedback resistors 2.5 3.5 3.0 4.0 4.5 5.0 5.5 6.0 max1818 fig03 input voltage (v) maximum output current (ma) 0 200 400 600 maximum output current vs. input voltage (power dissipation limit) maximum recommendedoutput current v out = 2.5v v out = 1.8v v out = 3.3v t a = +85 c maximum input voltage t a = +70 c figure 3. power operating regions: maximum output vs. supply voltage downloaded from: http:///
applications information capacitor selection and regulator stability capacitors are required at the max1818? input andoutput for stable operation over the full temperature range and with load currents up to 500ma. connect a 1? capacitor between in and ground and a 3.3? low- esr capacitor between out and ground. for output voltages less than 2v, use a 4.7? low-esr output capacitor. the input capacitor (c in ) lowers the source impedance of the input supply. reduce noise andimprove load-transient response, stability, and power- supply rejection by using larger output capacitors, such as 10?. the output capacitor? (c out ) equivalent series resis- tance (esr) affects stability and output noise. use out-put capacitors with an esr of 0.1 or less to ensure stability and optimum transient response. surface-mount ceramic capacitors have very low esr and are commonly available in values up to 10?. connect c in and c out as close to the max1818 as possible to mini- mize the impact of pc board trace inductance. noise, psrr, and transient response the max1818 is designed to operate with low dropoutvoltages and low quiescent currents in battery-powered systems while still maintaining good noise, transient response, and ac rejection. see the t ypical operating characteristics for a plot of power-supply rejection ratio (psrr) versus frequency. when operating from noisysources, improved supply-noise rejection and transient response can be achieved by increasing the values of the input and output bypass capacitors and through passive filtering techniques. the max1818 load-transient response (see t ypical operating characteristics ) shows two components of the output response: a dc shift from the output imped-ance due to the load current change, and the transient response. a typical transient response for a step change in the load current from 100ma to 500ma is 8mv. increasing the output capacitor? value and decreasing the esr attenuates the overshoot. input-output (dropout) voltage a regulator? minimum input-to-output voltage differen-tial (dropout voltage) determines the lowest usable sup- ply voltage. in battery-powered systems, this determines the useful end-of-life battery voltage. because the max1818 uses a p-channel mosfet pass transistor, its dropout voltage is a function of drain-to- source on-resistance (r ds(on) ) multiplied by the load current (see typical operating characteristics ). v dropout = v in - v out = r ds(on) i out the max1818 ground current remains below 150? indropout. max1818 8 __________________________________________________ _____________________________________ 500ma low-dropout linear regulator in sot23 part and suffix v out sot23 top mark sot23 top mark (rohs compliant) max1818eut15 1.5v or adj aaso abzm max1818eut18 1.8v or adj aanu abzg max1818eut20 2.0v or adj aanv abzj max1818eut25 2.5v or adj aanf abzk max1818eut33 3.3v or adj aang abzh max1818eut50 5.0v or adj aanh abzl selector guide chip information transistor count: 845 package information for the latest package outline information and land patterns, goto www.maxim-ic.com/packages . package type package code document no. 6 sot23 u6f-6 21-0058 6 sot23# u6fh-6 21-0058 downloaded from: http:///
max1818 500ma low-dropout linear regulator in sot23 revision history revision number revision date description pages changed 2 6/08 updated ordering information and selector guide with rohs-compliant package 1, 8 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 _____________________ 9 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. downloaded from: http:///
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