general description the max1725/max1726 are ultra-low supply current, low-dropout linear regulators intended for low-power applications that demand the longest possible battery life. unlike inferior pnp-based designs, the max1725/ max1726s?pmos pass elements maintain an ultra-low 2? supply current throughout their entire operating range and in dropout. despite their ultra-low power consumption, the max1725/max1726 have tight output accuracy (1.5%) and require just 1? output capacitance to achieve good load-transient response. these regulators have a wide input voltage range (+2.5v to +12v), making them excellent choices for systems powered from two lithium-ion (li+) cells and 9v batteries. other features include reverse-battery pro- tection, short-circuit protection, and thermal protection. the max1725 provides an adjustable 1.5v to 5v output using an external resistor-divider. the max1726 pro- vides factory preset 1.8v, 2.5v, 3.3v, or 5v output volt- ages (see ordering information ). both devices are available in a miniature 5-pin sot23 package. ________________________applications smoke detectors remote transmitters smart battery packs industrial control systems microcontroller power real-time clock backup power pdas and handy-terminals battery-powered alarms features 2a supply current reverse-battery protection +2.5v to +12v input voltage range fixed 1.8v, 2.5v, 3.3v, and 5v output voltages (max1726) adjustable 1.5v to 5v output voltages (max1725) 20ma guaranteed output current 1.5% output voltage accuracy small 1f output capacitor short-circuit protection thermal protection tiny 5-pin sot23 package max1725/max1726 12v, ultra-low i q , low-dropout linear regulators ________________________________________________________________ maxim integrated products 1 v in 2.5v to 12v output 1.5v to 5v max1726 off on in out shdn gnd typical operating circuit 19-1680; rev 0; 4/00 ordering information selector guide pin configuration appears at end of data sheet. note: see the selector guide for the max1725/max1726 output options as they relate to the part number suffix. 5 sot23-5 pin- package temp. range -40? to +85? max1725 euk-t part 5 sot23-5 -40? to +85? max1726 euk18-t 5 sot23-5 -40? to +85? max1726euk25-t 5 sot23-5 -40? to +85? max1726euk33-t 5 sot23-5 -40? to +85? max1726euk5-t adnk top mark adnl adnm adnn adno output voltage (v) part adj 1.5 to 5.0 max1725euk-t fixed 1.8 max1726euk18-t fixed 2.5 max1726euk25-t fixed 3.3 max1726euk33-t fixed 5.0 max1726euk50-t 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.
max1725/max1726 12v, ultra-low i q , low-dropout linear regulators 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (circuit of figure 1, v in = v out + 1v, shdn = in, i out = 1ma, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) 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 to gnd ................................................................-14v to +14v shdn to gnd ..............................................-0.3v to (v in + 0.3v) (-0.3v to + 0.3v when v in < 0v) out, fb (max1725 only) to gnd .................................................-0.3v to +6v when v in >5.7v; ............................. -0.3v to (v in + 0.3v) when 0v < v in < 5.7v; ................................................... -0.3v to +0.3v when v in < 0v out continuous current...................................................200ma out short circuit...........................................................indefinite continuous power dissipation (t a = +70?) 5-pin sot23-5 (derate 7.1mw/? above +70?) ......571mw ja ...............................................................................+140?/w junction temperature ......................................................+150? operating temperature range ...........................-40? to +85? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? shdn = 0, v in = 12v, v out = 0 v in = 12v v in = -12v, v shdn = 0 v in = 2.5v to 12v v in = 12v, v out = 0 v fb = 1.25v i out = 20ma for v out 2.5v, i out = 10ma for v out < 2.5v, not applicable for v out < 1.9v v in = (v out + 1v) or 3v max1725 only v in = 2.5v or (v out + 0.5v) to 12v i out = 1ma to 20ma, v in = (v out + 1v) or 3v min v shdn = 0 to 12v conditions ? 15 thermal shutdown hysteresis ? 0.01 10 in reverse leakage current 1.5 na -20 2 +20 i fb fb input bias current (max1725 only) 0.1 na -50 +50 i shdn shdn input bias current ? 0.7 2 i in( shdn ) shutdown supply current ? 24.5 i in v 2.5 12 v in input voltage range (note 2) supply current v 2 v ih ma 40 i sc foldback current limit mv 300 600 ? v do dropout voltage (note 4) ma 20 80 i out maximum out current (note 4) v 1.5 5 v out out voltage range % -1.5 1.5 out voltage accuracy (note 3) %/v 0.01 0.3 ? v lnr line regulation %/ma 0.015 0.15 ? v ldr load regulation units min typ max symbol parameter t a = +25? t a = +85? t a = +25? t a = +85? max1725 v 1.245 v fb fb voltage (note 3) -2 2 -3 3 t a = +25? t a = 0? to +85? t a = -40? to +85? 0.5 v il shdn input threshold temperature rising ? 150 thermal shutdown threshold
max1725/max1726 12v, ultra-low i q , low-dropout linear regulators _______________________________________________________________________________________ 3 0 1 3 2 4 5 467 5 8 9 101112 supply current vs. input voltage max1725/26 toc01 input voltage (v) supply current ( a) 0 1 3 2 4 5 supply current vs. load current max1725/26 toc02 load current (ma) supply current ( a) 010 51520 v in = 5v 0 3 2 1 4 5 -40 0 20 -20 406080 supply current vs. temperature max1725/26 toc03 temperature ( c) supply current ( a) v in = 5v -1.4 -1.0 -0.4 -0.6 -0.2 0 467 589101112 output voltage vs. input voltage max1725/26 toc04 input voltage (v) output voltage (%deviation) -0.8 -1.2 i load = 20ma i load = 1ma nominal output = 3.3v -0.8 -0.4 0.2 -0.2 0.6 0.8 output voltage vs. load current max1725/26 toc05 load current (ma) output voltage (% deviation) 0 4 26 20 0.4 0 -0.6 8101214 16 18 nominal output = 3.3v v in = 4.5v -0.30 -0.10 0.10 0 0.20 0.30 -40 0 -20 20406080 normalized output voltage vs. temperature max1725/26 toc06 temperature ( c) normalized output voltage (%) -0.20 i out = 1ma typical operating characteristics (v out = +3.3v, i out = 1ma, t a = +25?, unless otherwise noted.) electrical characteristics (continued) (circuit of figure 1, v in = v out + 1v, shdn = in, i out = 1ma, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) note 1: limits are 100% production tested at +25?. all temperature limits are guaranteed by design. note 2: guaranteed by out line-regulation testing. note 3: out accuracy from nominal voltage. the max1725 is tested at v out = 1.5v, 2.5v, and 5v. note 4: when v out falls to 4% below its value at v in = v out + 1v. i out from 1ma to 10ma, t r = t f = 1? ? v in = ?.25v, t r = t f = 5? f = 10hz to 100khz conditions mv 200 out load-transient overshoot/undershoot mv 15 out line-transient overshoot/undershoot ? rms 350 e n out noise units min typ max symbol parameter
detailed description the max1725/max1726 are low-dropout, low-quiescent- current linear regulators designed primarily for battery- powered applications ( figure 1). the max1725 provides an adjustable output voltage from 1.5v to 5v using an external resistor-divider. the max1726 supplies preset output voltages of 1.8v, 2.5v, 3.3v, or 5v. these devices consist of a +1.245v error amplifier, mosfet driver, and p-channel pass transistor (figure 2). max1725/max1726 12v, ultra-low i q , low-dropout linear regulators 4 _______________________________________________________________________________________ typical operating characteristics (continued) (v out = +3.3v, i out = 1ma, t a = +25?, unless otherwise noted.) name max1725 max1726 1 1 in 2 2 gnd 3 3 out 4 gnd 4 fb pin description function supply voltage input ground voltage output ground feedback voltage input 5 5 shdn active-low shutdown input pin v in 1v/div v out 100mv/div 400 s/div load transient max1725/26 toc10 c out = 1 f i out = 1ma - 20ma v shdn 2v/div v out 1v/div 4ms turn-on/turn-off response max1725/26 toc11 c out = 1 f i out = 1ma 0 100 50 200 150 250 300 010 51520 dropout voltage vs. load current max1725/26 toc07 load current (ma) dropout voltage (mv) t a = +85? t a = +25? t a = -40? 80 70 60 50 40 30 20 10 0 0.01 1 10 0.1 100 power-supply rejection ratio vs. frequency max1725/26 toc08 frequency (khz) psrr (db) v in = 5v v out = 3.3v r l = 3.3k ? c out = 1 f v in 200mv/div v out 20mv/div 100 s/div line-transient response max1725/26 toc09 c out = 1 f i out = 1ma
the error amplifier compares 1.245v to the selected feedback voltage and amplifies the difference. if the feedback voltage is lower than 1.245v, the pass-tran- sistor gate is pulled lower, allowing more current to pass, and thus increasing the output voltage. if the feedback voltage is higher than 1.245v, the pass-tran- sistor gate is driven higher, allowing less current to pass to the output. the output voltage is fed back through either an internal resistor voltage-divider con- nected to out (max1726) or an external resistor net- work connected to fb (m ax1725). additional features include an output current lim iter, reverse-battery protec- tion, a thermal sensor, and shutdown logic. internal p-channel pass transistor the max1725/max1726 feature a p-channel mosfet pass transistor. this provides advantages over similar designs using pnp pass transistors, including longer battery life. the p-channel mosfet requires no base drive, which reduces quiescent current considerably. pnp-based regulators waste considerable current in dropout when the pass transistor saturates; they also use high base-drive currents under large loads. the max1725/max1726 do not suffer from these problems, and consume only 2? of quiescent current throughout their load range (see typical operating characteristics ). shutdown to enter shutdown, drive the shdn pin below 0.5v. when the max1725/max1726 are shut down, the output pass transistor shuts off, the output falls to ground, and max1725/max1726 12v, ultra-low i q , low-dropout linear regulators _______________________________________________________________________________________ 5 input 2.5v to 12v output 1.5v to 5v max1725 off on in out fb shdn gnd r1 r2 1.2m ? c out 1 f c in 1 f in out fb (max1725 only) (max1726 only) shdn bias circuitry thermal shutdown gnd 1.245v max1725 max1726 figure 1. typical application circuit figure 2. functional diagram
max1725/max1726 supply current drops from 2? to 0.7?. connect shdn to in for normal operation. if reverse-battery protection is needed, drive shdn through a 100k ? resistor. thermal-overload protection thermal-overload protection limits total power dissipa- tion in the max1725/max1726. when the junction tem- perature exceeds t j = +150?, the thermal sensor signals the shutdown logic, turning off the pass transistor and allowing the ic to cool. the thermal sensor turns the pass transistor on again after the ic? junction tem- perature cools by 15?, resulting in a pulsed output during continuous thermal-overload conditions. thermal-overload protection is designed to protect the devices in the event of fault conditions. for continuous operation, do not exceed the absolute maximum junction temperature rating of t j = +150?. foldback current limiting the max1725/max1726 also include a foldback current limiter. when the output is shorted to ground, the output pmos drive is limited so that the output current does not exceed 40ma (typ). the output can be shorted to ground indefinitely without damaging the part. reverse-battery protection the max1725/max1726 have a unique protection scheme that limits the reverse supply current to less than 10? when v in is forced below ground. the cir- cuitry monitors the polarity of the input, disconnecting the internal circuitry and parasitic diodes when the battery is reversed. this feature prevents the device, battery, and load from overheating and electrical stress. for reverse-battery protection, drive shdn through a 100k ? resistor. applications information capacitor selection and regulator stability for general purposes, use a 1? capacitor on the max1725/max1726 input and output. larger input capacitor values and lower esr provide better supply- noise rejection and transient response. a higher-value input capacitor (10?) may be necessary if large, fast transients are anticipated and the device is located sev- eral inches from the power source. for stable operation over the full temperature range, use a minimum of 1? on the output. output voltage selection for fixed 1.8v, 2.5v, 3.3v, or 5v output voltages, use the max1726. the max1725 features an adjustable output voltage from 1.5v to 5v, using two external resistors connected as a voltage-divider to fb (figure 1). the max1725 is optimized for operation with r2 = 1.2m ? . the output voltage is set by the following equation: where typically v fb = 1.245v. to simplify resistor selec- tion: choose r2 = 1.2m ? for best accuracy. power-supply rejection and operation from sources other than batteries the max1725/max1726 are designed to deliver low dropout voltages and low quiescent currents in battery- powered systems. power-supply rejection is 60db at low frequencies and rolls off above 100hz. at high frequen- cies, the output capacitor is the major contributor to the rejection of power-supply noise (see the power-supply rejection ratio vs. frequency graph in the typical operating characteristics ). when operating from sources other than batteries, improve supply-noise rejection and transient response by increasing the value of the input and output capaci- tors, and by using passive filtering techniques (see the supply and load transient response graph in the typical operating characteristics ). 12v, ultra-low i q , low-dropout linear regulators 6 _______________________________________________________________________________________ chip information transistor count: 112 vv r r out fb =+ ? ? ? ? ? ? 1 1 2 rr v v out fb 12 1 =? ? ? ? ? ? ?
max1725/max1726 12v, ultra-low i q , low-dropout linear regulators _______________________________________________________________________________________ 7 sot5l.eps package information gnd fb (gnd) out 15 shdn in max1725 max1726 sot23-5 top view 2 34 ( ) are for max1726 only. pin configuration
max1725/max1726 12v, ultra-low i q , low-dropout linear regulators 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. notes
|
