general description the max1792 low-dropout linear regulator operates from a +2.5v to +5.5v supply and delivers a guaran- teed 500ma load current with low 130mv dropout. the high-accuracy (1%) 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 80a 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 with a 4ms timeout period that indicates when the output is out of regulation, a 0.1a shutdown mode, short-circuit protection, and thermal shutdown protec- tion. the device is available in a miniature 1.3w, 8-pin power-max package with a metal pad on the under- side of the package. ________________________applications notebook computers cellular and cordless telephones personal digital assistants (pdas) palmtop computers base stations usb hubs docking stations features ? guaranteed 500ma output current ? low 130mv dropout at 500ma ? up to 1% output voltage accuracy preset at 1.5v, 1.8v, 2.5v, 3.3v, or 5.0v adjustable from 1.25v to 5.0v ? reset output with 4ms timeout period ? low 80 a ground current ? 0.1 a shutdown current ? thermal overload protection ? output current limit ? tiny 1.3w power- max package max1792 500ma low-dropout linear regulator in max ________________________________________________________________ maxim integrated products 1 power- max set gnd + ep shdn 1 2 8 7 out out in rst in top view 3 4 6 5 max1792 pin configuration nc max1792 in in c in 1 f c out 3.3 f r rst 100k v in = +2.5v to +5.5v on off shdn out v out out rst gnd set to c typical operating circuit 19-1699; rev 2; 11/11 ordering information selector guide part and suffix v out max top mark max1792eua15+ 1.5v or adj. aaae max1792eua18+ 1.8v or adj. aaaa max1792eua25+ 2.5v or adj. aaab max1792eua33+ 3.3v or adj. aaac max1792eua50+ 5.0v or adj. aaad max1792eua33/v+ 3.3v or adj. aacp part* temp range pin-package max1792eua_ _+ -40 c to +85 c 8 power-max max1792eua_ _/v+ -40 c to +85 c 8 power-max * insert the desired two-digit suffix (see selector guide) into the blanks to complete the part number. + denotes a lead(pb)-free/rohs-compliant package. /v denotes an automotive qualified part. contact factory for other preset output voltages. 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.
max1792 500ma low-dropout linear regulator in max 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = v out(nom) + 500mv, 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 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 , rst , set to gnd ....................................-0.3v to +6v out to gnd ................................................-0.3v to (v in + 0.3v) output short-circuit duration ........................................indefinite continuous power dissipation (t a = +70?) 8-pin power-?ax (derate 17mw/? above +70?) .......1.3w operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? dual mode is a trademark of maxim integrated products. parameter symbol conditions min typ max units input voltage v in 2.5 5.5 v input undervoltage lockout v uvlo rising, 75mv hysteresis 2.0 2.15 2.3 v preset v out 2.5v -1 +1 i out = 100ma, t a = +85 c preset v out < 2.5v -1.5 +1.5 % i out = 100ma, t a = 0 c to +85 c -2 +2 output voltage accuracy (preset mode) v out i out = 1ma to 500ma, v in > v out + 0.5v, t a = 0 c to +85 c -3 +3 % adjustable output voltage range 1.25 5 v t a = +85 c 1.229 1.250 1.271 set voltage threshold (adjustable mode) v set v in = +2.7v, v out set to 2.0v, i out = 100ma t a = 0 c to +85 c 1.219 1.281 v maximum output current i out v in 2.7v 500 ma rms short-circuit current limit i lim v out = 0v, 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 = 1ma 80 250 ground-pin current i q i out = 500ma 110 a v out = 5.0v 120 225 v out = 3.3v 130 250 dropout voltage (note 1) 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 load regulation v ldr i out = 1ma to 500ma 0.4 1.0 % output voltage noise 10hz to 1mhz, c out = 3.3f (esr < 0.1 ) 115 v rms shutdown shutdown supply current i off shdn = gnd, v in = 5.5v 0.1 15 a 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 input bias current shdn = in or gnd 10 100 na
max1792 500ma low-dropout linear regulator in max _______________________________________________________________________________________ 3 electrical characteristics (v in = v out(nom) + 500mv, or v in = +2.5v (whichever is greater), shdn = in, t a = -40c to +85c , unless otherwise noted.) (note 2) electrical characteristics (continued) (v in = v out(nom) + 500mv, 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?.) parameter symbol conditions min typ max units reset output reset output low voltage v ol rst sinking 1ma 0.01 0.1 v operating voltage range for valid reset rst sinking 100a 1.0 5.5 v rst output high leakage current v rst = +5.5v 100 na rst threshold rising edge, referred to v out(nominal) 90 93 96 % rst release delay t rp rising edge of out to rising edge of rst 1.5 4.5 8 ms thermal protection thermal shutdown temperature t shdn 170 c thermal shutdown hysteresis t shdn 20 c parameter symbol conditions min max units input voltage v in 2.5 5.5 v input undervoltage lockout v uvlo rising or falling 2.0 2.3 v i out = 100ma -2 +2 output voltage accuracy (preset mode) v out i out = 1ma to 500ma -3 +3 % adjustable output voltage range 1.25 5 v set voltage threshold (adjustable mode) v set i out = 100ma 1.212 1.288 v maximum output current i out 500 ma rms short-circuit current limit i lim v out = 0v 0.55 1.8 a set dual mode threshold 50 150 mv set input bias current i set v set = 1.25v -100 +100 na ground-pin current i q i out = 1ma 250 a v out = 5.0v 225 v out = 3.3v 250 dropout voltage (note 1) v in - v out i out = 500ma v out = 2.5v 360 mv line regulation v lnr v in from (v out + 100mv) to 5.5v, i load = 5ma -0.15 +0.15 %/v load regulation v ldr i out = 1ma to 500ma 1.0 % shutdown shutdown supply current i off shdn = gnd, v in = +5.5v 15 a 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 input bias current i shdn shdn = in or gnd 100 na
0 1.0 0.5 2.0 1.5 3.0 2.5 3.5 2.0 3.0 3.5 2.5 4.0 4.5 5.0 5.5 output voltage vs. input voltage max1792-01 input voltage (v) output voltage (v) i out = 0a i out = 500ma 3.27 3.28 3.29 3.30 3.31 3.32 3.33 0 200 100 300 400 500 600 700 800 output voltage vs. load current max1792-02 load current (ma) output voltage (v) 3.27 3.29 3.28 3.31 3.30 3.32 3.33 -40 10 -15 35 60 85 output voltage vs. temperature max1792-03 temperature ( c) output voltage (v) v in = v out + 500mv i out = 0a 0 50 150 100 200 250 0 200 300 100 400 500 600 700 800 dropout voltage vs. load current max1792-04 load current (ma) dropout voltage (mv) t a = +85 c t a = -40 c t a = +25 c 0 40 20 80 60 120 100 140 0 1.0 1.5 2.0 0.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 ground-pin current vs. input voltage max1792-05 input voltage (v) ground-pin current ( a) i out = 500ma i out = 0a 60 80 70 100 90 110 120 130 140 0 200 300 100 400 500 600 700 800 ground-pin current vs. load current max1792-06 load current (ma) ground-pin current ( a) v in = 5.5v v in = 3.8v typical operating characteristics (max1792eua33, v in = v out + 500mv, shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.) max1792 500ma low-dropout linear regulator in max 4 _______________________________________________________________________________________ electrical characteristics (continued) (v in = v out(nom) + 500mv, 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 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) + 704mv. for v out(nom) 3.5v: typical dropout = 120mv; guaranteed maximum dropout = 225mv. note 2: specifications to -40? are guaranteed by design, not production tested. parameter symbol conditions min max units reset output reset output low voltage v ol rst sinking 1ma 0.1 v operating voltage range for valid reset rst sinking 100a 1.0 5.5 v rst output high leakage current v rst = +5.5v 100 na rst threshold rising edge, referred to v out(nominal) 90 96 % rst release delay t rp rising edge of out to rising edge of rst 1.5 8 ms
max1792 500ma low-dropout linear regulator in max _______________________________________________________________________________________ 5 output noise dc to 1mhz max1792-10 20ms/div v out 200 v/div v out = 3.3v r out = 66 (50ma) 100 0.01 0 200 100 400 600 region of stable c out esr vs. load current 0.1 1 10 max1792-11 load current (ma) c out esr ( ) 300 500 700 800 stable region c out = 3.3 f c out = 10 f load-transient response max1792-12 10 s/div i out 500ma/div v out 20mv/div v in = v out + 500mv c in = 10 f r out = 660 to 6.6 (5ma to 500ma) 60 70 65 80 75 90 85 95 -40 10 -15 35 60 85 ground-pin current vs. temperature max1792-07 temperature ( c) ground-pin current ( a) v in = v out + 500 mv i out = 0a -80 0 0.01 0.1 1000 power-supply rejection ratio vs. frequency -10 -30 -60 -70 max1792-08 frequency (khz) psrr (db) 110 -50 -40 -20 100 c out = 3.3 f i out = 50ma 0.1 1 10 100 1000 output spectral noise density vs. frequency max1792-09 frequency (khz) output spectral noise density ( v/ hz) 10 0.001 0.01 0.1 1 c out = 3.3 f i out = 50ma typical operating characteristics (continued) (max1792eua33, v in = v out + 500mv, shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.)
500ma low-dropout linear regulator in max 6 _______________________________________________________________________________________ shutdown waveform max1792-15 20 s/div v shdn 1v/div v out 1v/div 0v 0v 2v 3v r out = 6.6 (500ma) rst waveform max1792-16 20ms/div v in 2.5v/div v out 2v/div 0v 5v 0v 0v r out = 66 (50ma) v rst 2v/div max1792 pin description line-transient response max1792-14 100 s/div v in 1v/div v out 10mv/div 6v 3v load-transient response near dropout max1792-13 20 s/div i out 500ma/div v out 50mv/div v in = v out + 100mv c in = 10 f r out = 660 to 6.6 (5ma to 500ma) typical operating characteristics (continued) (max1792eua33, v in = v out + 500mv, shdn = in, c in = 1?, c out = 3.3?, t a = +25?, unless otherwise noted.) pin name function 1, 2 in regulator input. supply voltage can range from +2.5v to +5.5v. bypass with a 1? capacitor to gnd (see capacitor selection and regulator stability ). connect both input pins together externally. 3 rst open-drain active-low reset output. 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 resistor to out to obtain an output voltage. 4 shdn active-low shutdown input. a logic low reduces supply current to 0.1?. in shutdown, the rst output is low and out is pulled low through an internal 5k resistor. connect to in for normal operation. 5 gnd ground. this pin and the exposed pad also function as a heatsink. solder both to a large pad or to the circuit-board ground plane to maximize power dissipation. 6 set voltage-setting input. connect to gnd for preset output. connect to a resistive divider between out and gnd to set the output voltage between 1.25v and 5.0v. 7, 8 out regulator output. sources up to 500ma. bypass with a 3.3? low-esr capacitor to gnd. use a 4.7? capacitor for output voltages below 2v. connect both output pins together externally. ?p exposed pad. solder to ground plane to maximize thermal performance. not internally connected to ground.
detailed description the max1792 is a low-dropout, low-quiescent-current linear 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 max1792 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 more current 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-preset voltage. additional blocks include an output current limiter, ther- mal sensor, and shutdown logic. internal p-channel pass transistor the max1792 features a 0.25 p-channel mosfet pass transistor. unlike similar designs using pnp pass transistors, 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. max1792 500ma low-dropout linear regulator in max _______________________________________________________________________________________ 7 100mv shdn in in rst on off c in 1 f v in = +2.5v to +5.5v out out v out = 1.25v to 5.0v c out 3.3 f thermal sensor set mosfet driver with i lim delay timer shutdown logic v ref 1.25v error amplifier gnd r1 r2 r rst 100k logic supply voltage (v out ) 93% v ref to c 5k max1792 figure 1. functional diagram
max1792 the max1792 does not suffer from these problems and consumes only 110? of quiescent current under heavy loads as well as in dropout. output voltage selection the max1792? dual mode operation allows operation in 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 max1792eua33 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 current drops to 0.1?. when in shutdown, rst pulls low and out is discharged through an internal 5k resistor. 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. reset output the reset output ( rst ) pulls low when out is less than 93% of the nominal regulation voltage. once out exceeds 93% of the nominal voltage, rst goes high impedance after 4ms. rst is an open-drain n-channel output. to obtain a voltage output, connect a pullup resistor from rst to out. a 100k resistor works well for most applications. rst can be used as a power-on-reset (por) signal to a microcontroller (?), or drive an exter- nal led to indicate power failure. when the max1792 is shut down, rst is held low independent of the output voltage. if unused, leave rst grounded or unconnected. current limit the max1792 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. the output can be shorted to ground for an indefinite period of time with- out damaging the part. thermal overload protection thermal overload protection limits total power dissipa- tion in the max1792. when the junction temperature exceeds t j = +170?, a thermal sensor turns off the pass transistor, allowing the device to cool. the thermal sensor 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 max1792 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 max1792? maximum power dissipation depends on the thermal resistance of the ic package and circuit board, the temperature difference between the die junc- tion and ambient air, and the rate of air flow. the power dissipated in the device is p = i out x (v in - v out ). the maximum allowed power dissipation is 1.3w or: p max = (t j(max) - t a ) / ( jc + ca ) where t j - t a is the temperature difference between the max1792 die junction and the surrounding air, jc is the thermal resistance from 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. the max1792 package features an exposed thermal pad on its underside. this pad lowers the thermal resis- tance of the package by providing a direct heat con- 500ma low-dropout linear regulator in max 8 _______________________________________________________________________________________ out out set gnd in in shdn rst 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 max1792 r 1 figure 2. adjustable output using external feedback resistors
duction path from the die to the pc board. additionally, the max1792? ground pin (gnd) performs the dual function of providing an electrical connection to system ground and channeling heat away. connect the exposed backside pad and gnd to the system ground using a large pad or ground plane, or multiple vias to the ground plane layer. the max1792 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. applications information capacitor selection and regulator stability capacitors are required at the max1792? input and output 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 equivalent series resistance (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 and improve load-transient response, stability, and power-supply rejection by using larger output capacitors such as 10?. the output capacitor? (c out ) esr affects stability and output noise. use output 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 max1792 as possible to minimize the impact of pc board trace inductance. noise, psrr, and transient response the max1792 is designed to operate with low dropout voltages and low quiescent currents in battery-powered systems 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 noisy sources, 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 max1792 load-transient response graphs (see typical operating characteristics ) show two compo- nents of the output response: a dc shift from the output impedance due to the load current change, and the transient response. a typical transient response for a step change in the load current from 5ma to 500ma is 18mv. 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 max1792 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) x i out the max1792 ground current remains below 150? in dropout. note: the max1792 has an exposed thermal pad on the bottom side of the package. max1792 500ma low-dropout linear regulator in max _______________________________________________________________________________________ 9 figure 3. power operating regions: maximum output current vs. supply voltage 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 maximum output current (a) 4.0 4.5 0 0.5 3.5 3.0 2.5 2.0 1.5 1.0 input-output voltage differential (v) maximum supply voltage limit (v out = 1.25v) power- max package operating region at t j(max) = +150 c t a = +50 c t a = +70 c t a = +85 c continuous current limit typical v dropout limit 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. ?ax-ep u8e+2 21-0107 90-0145
max1792 500ma low-dropout linear regulator in max 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. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 1 8/08 updated pin description and package information 6, 10 2 11/11 updated the ordering information and selector guide to include lead(pb)-free and automotive qualified parts; added the soldering information to the absolute maximum ratings section; added the package information table 1, 2, 9
|
