View MAX882_5844772.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

general description t he MAX882/max883/max884 linear regulators maxi- mize battery life by combining ultra-low supply currents and low dropout voltages. they feature 200ma output current capability at up to +125? junction temperature and come in a 1.5w soic package. the 1.5w package (compared to 0.47w for standard soic packages) allows a wider operating range for the input voltage and output current. the MAX882/max883/max884 use a p- channel mosfet pass transistor to maintain a low 11? (15? max) supply current from no-load to the full 200ma output. unlike earlier bipolar regulators, there are no pnp base current losses that increase with output current. in dropout, the mosfet does not suffer from excessive base currents that occur when pnp transistors go into saturation. typical dropout voltages are 220mv at 5v and 200ma, or 320mv at 3.3v and 200ma. the MAX882 features a 7? standby mode that disables the output but keeps the reference, low-battery compara- tor, and biasing circuitry alive. the max883/max884 fea- ture a shutdown (off) mode that turns off all circuitry, reducing supply current to less than 1?. all three devices include a low-battery-detection comparator, fold- back current limiting, reverse-current protection, and thermal-overload protection. the output is preset at 3.3v for the MAX882/max884 and 5v for the max883. in addition, all devices employ dual mode operation, allowing user-adjustable outputs from 1.25v to 11v using external resistors. the input volt- age supply range is 2.7v to 11.5v. for low-dropout linear regulators with output currents up to 500ma, refer to the max603/max604 data sheet. applications pagers and cellular phones 3.3v and 5v regulators 1.25v to 11v adjustable regulators high-efficiency linear regulators battery-powered devices portable instruments solar-powered instruments features guaranteed 200ma output current at t j = +125?, with foldback current limiting high-power (1.5w) 8-pin so package dual mode operation: fixed or adjustable output from 1.25v to 11v large input range (2.7v to 11.5v) internal 1.1 ? p-channel pass transistor draws no base current low 220mv dropout voltage at 200ma output current 11a (typ) quiescent current 1a (max) shutdown mode or 7a (typ) standby mode low-battery detection comparator reverse-current protection thermal-overload protection ordering information MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators ________________________________________________________________ maxim integrated products 1 pin configuration typical operating circuit 19-0275; rev 1; 7/99 part MAX882 cpa MAX882csa MAX882c/d 0? to +70? 0? to +70? 0? to +70? temp. range pin-package 8 plastic dip 8 so dice* ordering information continued at end of data sheet. * dice are tested at t j = +25?, dc parameters only. ** contact factory for availability. MAX882epa -40? to +85? 8 plastic dip MAX882esa -40? to +85? 8 so MAX882mja -55? to +125? 8 cerdip** dual mode is a trademark of maxim integrated products. MAX882 max883 max884 c in o.1 f c out 2.2 f output voltage input voltage battery lbi off (stby) ( ) are for MAX882. in out gnd set on/off lbi off (stby) ( ) are for MAX882. gnd in out gnd set lbo dip/so top view 1 2 3 4 8 7 6 5 MAX882 max883 max884 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.
mv MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 6v (max883) or v in = 4.3v (MAX882/max884), c out = 2.2?, stby or off = v in , set = gnd, lbi = v in , t j = t min to t max , unless otherwise noted. typical values are at t j = +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. supply voltage (in or out to gnd).......................-0.3v to +12v output short-circuit duration ...............................................1min continuous output current ...............................................300ma lbo output current ............................................................50ma lbo output voltage and lbi, set, stby, off input voltages ............-0.3v to the greater of (in + 0.3v) or (out + 0.3v) continuous power dissipation (t j = +70?) plastic dip (derate 9.09mw/? above +70?) ............727mw high-power so (derate 18.75mw/? above +70?) .......1.5w cerdip (derate 8.00mw/? above +70?) .................640mw operating temperature ranges max88_c_a ........................................................0? to +70? max88_e_a .....................................................-40? to +85? max88_mja ..................................................-55? to +125? junction temperature .....................................................+150? storage temperature range .............................-65? to +160? lead temperature (soldering, 10s) .................................+300? v in = 11.5v set = out, v in = 6v set = out, r l = 1k ? MAX882/max884 max883 (v out + 0.5v) < v in < 11.5v, i out = 10ma conditions 40 i q quiescent current 15 25 30 11 15 mv 320 640 ? v do dropout voltage (note 3) 160 320 220 440 110 220 mv 10 40 ? v lnr line regulation v 3.0 11.5 v in input voltage range 2.9 11.5 2.7 11.5 units min typ max symbol parameter max88_c_a max88_mja max88_e_a i out = 10??00ma, t j +125? i out = 10??50ma, t j +85? i out = 100ma i out = 100ma max88_c_a/e_a max88_c_a/e_a i out = 200ma i out = 200ma max88_mja max88_mja ? i out = 1ma to 150ma max883c_a/e_a i out = 1ma to 200ma mv 30 100 ? v ldr load regulation max883mja MAX882, max884 150 60 100 MAX882/max884, 4.3v v in 11.5v v 3.15 3.30 3.45 v out output voltage (note 2) i out = 10??00ma, t j +85? i out = 10??00ma, t j +70? max883, 6.0v v in 11.5v i out = 10??50ma, t j +70? i out = 10??50ma, t j +125? 4.75 5.00 5.25
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators _______________________________________________________________________________________ 3 v in = 9v, r l = 33 ? , off from 0 to v in , 0% to 95% of v out MAX882: v in = 0, stby = 0, v out = 3.0v stby = 0, v in = 6v, set = out v out = 3.0v v out < 0.8v v in = 11.5v, set = out v out = 4.5v stby = 0, v in =11.5v, set = out off = 0, r l = 1k ? , v in = 11.5v (max883/max884) v out > 0.8v and v in - v out > 0.7v conditions ? 200 t start time required to exit off or stby modes i rvl reverse leakage current % of v out 1 ? 7 mv 620 ? v rth reverse-current-protection threshold (note 6) 620 ? 10 ? t sd thermal shutdown hysteresis ? 160 t sd thermal shutdown temperature ma 430 i lim foldback current limit (note 5) 10 25 30 715 170 ? 10 i out(min) minimum load current 3 1 ? 40 i q stby stby quiescent current (note 4) 0.01 1 5 ? 10 i q off off quiescent current units min typ max symbol parameter 65 30 dual mode set threshold v set th for internal feedback 150 65 set = out, r l = 1k ? 1.16 1.20 1.24 mv set reference voltage v set v set = 1.5v or 0 ?.01 ?0 na lbi threshold voltage v lbi lbi signal falling 1.15 1.20 1.25 v lbi hysteresis ? v lbi 7 mv lbi input leakage current i lbi v lbi = 1.5v ?.01 ?0 na lbo output low voltage v lbo l i lbo sink = 1.2ma, v lbi =1v, 3v < v in < 11.5v, set = out 90 250 mv lbo output leakage current i lbo lkg v lbi = v in , v lbo = v in 0.01 0.1 ? 0.01 1 3 out leakage current i out lkg v in = 11.5v, v out = 2v, set = out 10 ? MAX882c_a/e_a MAX882mja MAX882c_a/e_a MAX882mja max88_c_a max88_e_a max88_mja max88_c_a max88_e_a max88_mja MAX882_a, max884_a max883_a r l = 1k ? , c out = 2.2? v osh startup overshoot for external feedback v set input leakage current i set max88_c_a max88_mja max88_e_a electrical characteristics (continued) (v in = 6v (max883) or v in = 4.3v (MAX882/max884), c out = 2.2?, stby or off = v in , set = gnd, lbi = v in , t j = t min to t max , unless otherwise noted. typical values are at t j = +25?.) (note 1) max883/max884: v in = 0, off = 0, v out = 3.0v 0.01
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 4 _______________________________________________________________________________________ v stby = v in or 0 stby signal falling v off = v in or 0 in on mode, set = out, 6v < v in < 11.5v in off mode in on mode, set = out, v in <6v 10hz to 10khz, set = out, r l = 1k ? , c out = 2.2? conditions ? rms 250 e n output noise (note 7) na ?.01 ?0 i stby stby input leakage current mv 7 ? v stby v 1.15 1.20 1.25 v stby stby threshold voltage stby hysteresis na ?.01 ?0 i off off input leakage current v 3.0 off threshold voltage 0.4 v il off 2.0 v ih off units min typ max symbol parameter note 1: electrical specifications are measured by pulse testing and are guaranteed for a junction temperature (t j ) within the operat- ing temperature range, unless otherwise noted. when operating c- and e-grade parts up to a t j of +125?, expect perfor- mance similar to m-grade specifications. for t j between +125? and +150?, the output voltage may drift more. note 2: (v in - v out ) is limited to keep the product (i out x (v in - v out )) from exceeding the package power dissipation limits. see figure 5. therefore, the combination of high output current and high supply voltage is not tested. output current at t j = +125? is guaranteed by guard banding tests at t j = +85? and +70?. note 3: dropout voltage is (v in - v out ) when v out falls to 100mv below its nominal value at v in = (v out + 2v). for example, the max883 is tested by measuring the v out at v in = 7v, then v in is lowered until v out falls 100mv below the measured value. the difference (v in - v out ) is then measured and defined as ? v do . note 4: since standby mode inhibits the output but keeps all biasing circuitry alive, the standby quiescent current is similar to the normal operating quiescent current. note 5: foldback current limit was characterized by pulse testing to remain below the maximum junction temperature (not production tested). note 6: the reverse-current protection threshold is the output/input differential voltage (v out - v in ) at which reverse-current protection switchover occurs and the pass transistor is turned off. see the section reverse-current protection in the detailed description. note 7: noise is tested using a bandpass amplifier with two poles at 10hz and two poles at 10khz. MAX882_a MAX882_a MAX882_a max883_a, max884_a max883_a, max884_a max883_a, max884_a electrical characteristics (continued) (v in = 6v (max883) or v in = 4.3v (MAX882/max884), c out = 2.2?, stby or off = v in , set = gnd, lbi = v in , t j = t min to t max , unless otherwise noted. typical values are at t j = +25?.) (note 1)
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators _______________________________________________________________________________________ 5 typical operating characteristics (v in = 7v for max883, v in = 5.3v for MAX882/max884, off or stby = v in , set = gnd, lbi = v in , lbo = open, c in = c out = 2.2?, r l = 1k ? , t a = +25?, unless otherwise noted.) 95 101 100 99 98 97 96 0.01 0.1 1 100 10 250 output voltage and quiescent current vs. load current MAX882/4-01 load current (ma) normalized output voltage (%) v out = 5v (max883) v out = 3.3v (MAX882/max884) output voltage normalized to output voltage at 1ma 0 5 10 15 20 25 30 quiescent current ( a) i q 0 2 3 4 5 6 4 6 8 10 12 14 16 output voltage and quiescent current vs. supply voltage MAX882/4-03 supply voltage (v) output voltage (v) quiescent current ( a) 2 3 4 5 6 7 8 9 10 11 12 v out = 5v (max883) v out = 3.3v (MAX882/max884) i q (MAX882/max884) i q (max883) 1 0 0.1 0.2 0.3 0.4 0.5 0.6 dropout voltage vs. load current MAX882/4-05 load current (ma) dropout voltage (v) 0 50 100 150 200 250 300 v out = 3.3v (MAX882/max884) v out = 5v (max883) 0 15 12 9 6 3 quiescent current vs. temperature MAX882/4-04 temperature (?) quiescent current ( a) -55 -35 -15 5 25 45 65 85 105 125 10hz to 10khz output noise 10ms/div output noise (1mv/div) max883 v out = 5v MAX882/4-06 96 97 98 99 100 101 102 103 104 output voltage vs. temperature MAX882/4-04a temperature ( c) normalized output voltage (%) -55 -35 -15 5 25 45 65 85 105 125
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 6 _______________________________________________________________________________________ line-transient response 500 s/div max883: v out = 5v, c in = 0 f, t r = 15 s, t f = 13 s a: v in = 8v (high) / v in = 7v (low) b: output voltage (100mv/div) b a load-transient response 1ms/div max883: v out = 5v, t r = 24 s, t f = 44 s a: output voltage (100mv/div) b: i out = 250ma (high) / i out = 50ma (low) b a overshoot and time exiting shutdown mode r l = 100 ? 500 s/div a: off pin voltage (1v/div): rise time = 9 s b: max883 output voltage (1v/div): delay = 135 s, rise time = 67 s, overshoot = 0% 0v 5v a b 0 1 2 3 4 5 0.1 1 10 50 lbo low voltage vs. sink current MAX882/4-10 sink current (ma) lbo low voltage (v) MAX882/max884 max883 typical operating characteristics (continued) (v in = 7v for max883, v in = 5.3v for MAX882/max884, off or stby = v in , set = gnd, lbi = v in , lbo = open, c in = c out = 2.2?, r l = 1k ? , t a = +25?, unless otherwise noted.)
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators _______________________________________________________________________________________ 7 _______________detailed description the MAX882/max883/max884 are micropower, low- dropout linear regulators designed primarily for battery- powered applications. they feature dual mode operation, allowing a fixed output of 5v for the max883 and 3.3v for the MAX882/max884, or an adjustable output from 1.25v to 11v. these devices supply up to 200ma while requiring less than 15? quiescent current. as illustrated in figure 1, they consist of a 1.20v reference, error amplifier, mos- fet driver, p-channel pass transistor, dual-mode com- parator, and feedback voltage-divider. the 1.20v reference is connected to the error amplifier? inverting input. the error amplifier compares this refer- ence 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 pass transistor. if the feedback voltage is lower than the refer- ence, the pass transistor? gate is pulled lower, allowing more current to pass and increasing 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 resistor voltage-divider connected to the out pin, or an external resistor network connected to the set pin. the dual-mode comparator examines the set pin voltage and selects the feedback path used. if the set pin is below 65mv, internal feedback is used and the output voltage is regulated to 5v for the max883 or 3.3v for the MAX882/max884. additional blocks include a foldback current limiter, reverse-current pro- tection, a thermal sensor, shutdown or standby logic, and a low-battery-detection comparator. internal p-channel pass transistor the MAX882/max883/max884 feature a 200ma p- channel mosfet pass transistor. this provides several advantages over similar designs using pnp pass tran- sistors, including longer battery life. the p-channel mosfet requires no base drive, which reduces quiescent current considerably. pnp-based reg- ulators waste large amounts of current in dropout when the pass transistor saturates. they also use high base- drive currents under large loads. the MAX882/max883/ max884 do not suffer from these problems and consume only 11? of quiescent current during light loads, heavy loads, and dropout. output voltage selection the MAX882/max883/max884 feature dual mode operation. in preset voltage mode, the max883? out- put is set to 5v and the MAX882/max884? output is set to 3.3v, using internal trimmed feedback resistors. select this mode by connecting set to ground. in preset voltage mode, impedances between set and ground should be less than 100k ? . otherwise, spurious conditions could cause the voltage at set to exceed the 65mv dual-mode threshold. pin description lbo set gnd out lbi off stby in 1 1 low-battery output is an open-drain output that goes low when lbi is less than 1.2v. connect to in or out through a pull-up resistor. lbo is undefined during shutdown mode (max883/max884). 2 2 feedback for setting the output voltage. connect to gnd to set the output voltage to the prese- lected 3.3v or 5v. connect to an external resistor network for adjustable-output operation. 3, 6 3, 6 ground pins?lso function as heatsinks in the so package. all gnd pins must be soldered to the pc board for proper power dissipation. connect to large copper pads or planes to channel heat from the ic. 4 4 regulator output. fixed or adjustable from 1.25v to 11.0v. sources up to 200ma. bypass with a 2.2? capacitor. 8 8 low-battery comparator input. tie to in when not used. 7 shutdown. active-low logic input. in off mode, supply current is reduced below 1? and v out = 0. 7 standby. active-low comparator input. connect to gnd to disable the output or to in for normal operation. a resistor network (from in) can be used to set a standby mode threshold. 5 5 regulator input. supply voltage can range from 2.7v to 11.5v. name pin function max883/ max884 MAX882
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 8 _______________________________________________________________________________________ in adjustable mode, the user selects an output voltage in the 1.25v to 11v range by connecting two external resistors, used as a voltage-divider, to the set pin (figure 2). the output voltage is set by the following equation: where v set = 1.20v. to simplify resistor selection: since the input bias current at set is nominally zero, large resistance values can be used for r1 and r2 to minimize power consumption without losing accuracy. up to 1.5m ? is acceptable for r2. since the v set toler- ance is less than ?0mv, the output can be set using fixed resistors instead of trim pots. standby mode (MAX882) the MAX882 has a standby feature that disconnects the input from the output when stby is brought low, but keeps all other circuitry awake. in this mode, v out drops to 0, and the internal biasing circuitry (including the low-battery comparator) remains on. the maximum quiescent current during standby is 15?. stby is a comparator input with the other input internally tied to the reference voltage. use a resistor network as shown in figure 3 to set a standby-mode threshold voltage for undervoltage lockout. connect stby to in for normal operation. off mode (max883/max884) a low-logic input on the off pin shuts down the max883/max884. in this mode, the pass transistor, control circuit, reference, and all biases are turned off, and the supply current is reduced to less than 1?. lbo is undefined in off mode. connect off to in for normal operation. r1 r2 v v 1 out set =? ? ? ? ? ? ? vv r r out set =+ ? ? ? ? ? ? 1 1 2 figure 1. MAX882/max883/max884 functional diagram p out set r1 r2 65mv error amp off (stby) gnd lbo lbi n in mosfet driver with foldback current limit reverse- current protection shut- down logic 1.20v reference thermal sensor ( ) are for MAX882. dual-mode comparator low-battery comparator
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators _______________________________________________________________________________________ 9 foldback current limiting the MAX882/max883/max884 also include a foldback current limiter. it monitors and controls the pass transis- tor? gate voltage, estimating the output current and limiting it to 430ma for output voltages above 0.8v and (v in - v out ) > 0.7v. if the output voltage drops below 0.8v, implying a short-circuit condition, the output cur- rent is limited to 170ma. the output can be shorted to ground for 1min without damaging the device if the package can dissipate (v in x 170ma) without exceed- ing t j = +150?. when the output is greater than 0.8v and (v in - v out ) < 0.7v (dropout operation), no current limiting is allowed, to provide maximum load drive. thermal overload protection thermal overload protection limits total power dissipa- tion in the MAX882/max883/max884. when the junc- tion temperature exceeds t j =+160?, the thermal sensor sends a signal to 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 temperature cools by 10?, resulting in a pulsed output during thermal overload conditions. thermal overload protection is designed to protect the MAX882/max883/max884 if fault conditions occur. it is not intended to be used as an operating mode. prolonged operation in thermal-shutdown mode may reduce the ic? reliability. for continual operation, do not exceed the absolute maximum junction temperature rating of t j = +150?. power dissipation and operating region maximum power dissipation of the MAX882/max883/ max884 depends on the thermal resistance of the case and pc board, the temperature difference between the die junction and ambient air, and the rate of air flow. the power dissipation across the device is p = i out (v in - v out ). the resulting power dissipation is as follows: where (t j - t a ) is the temperature difference between the MAX882/max883/max884 die junction and the sur- rounding air, jb (or jc ) is the thermal resistance of the package chosen, and ba is the thermal resistance through the pc board, copper traces, and other materi- als to the surrounding air. the 8-pin small-outline package for the MAX882/ max883/max884 features a special lead frame with a lower thermal resistance and higher allowable power dissipation. this package? thermal resistance package is jb = 53?/w, compared with jb = 110?/w for an 8-pin plastic dip package and jb = 125?/w for an 8- pin ceramic dip package. p (t t ) () ja jb ba = ? + ? figure 2. adjustable output using external feedback resistors figure 3. setting an undervoltage lockout threshold using stby MAX882 max883 max884 c in o.1 f c out 2.2 f output voltage input voltage lbi off (stby) ( ) are for MAX882. in r1 r2 r1 + r2 r2 v out = v set , v set = 1.20v load out gnd set MAX882 c in o.1 f c out 2.2 f output voltage input voltage lbi set stby in r1 r2 r1+ r2 r2 v stby trip = v stby , v stby = 1.20v out gnd
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 10 ______________________________________________________________________________________ the gnd pins of the MAX882/max883/max884 soic package perform the dual function of providing an elect- rical connection to ground and channeling heat away. con- nect all gnd pins to ground using a large pad or ground plane. where this is impossible, place a copper plane on an adjacent layer. for a given power dissipation, the pad should exceed the associated dimensions in figure 4. figure 4 assumes the ic is in an 8-pin small-outline pack- age that has a maximum junction temperature of +125? and is soldered directly to the pad; it also has a +25? ambient air temperature and no other heat sources. use larger pad sizes for other packages, lower junction tem- peratures, higher ambient temperatures, or conditions where the ic is not soldered directly to the heat-sinking ground pad. when operating c- and e-grade parts up to a t j of +125?, expect performance similar to m-grade specifications. for t j between +125? and +150?, the output voltage may drift more. the MAX882/max883/max884 can regulate currents up to 250ma and operate with input voltages up to 11.5v, but not simultaneously. high output currents can only be sus- tained when input-output differential voltages are small, as shown in figure 5. maximum power dissipation depends on packaging, temperature, and air flow. the maximum output current is as follows: where p is derived from figure 4. i p(t t ) (v v )100 c out(max) ja in out = ? ? 1.0 0.9 1.6 1.5 1.4 1.3 1.2 1.1 0.1cm 2 0.0155in 2 1cm 2 0.155in 2 10cm 2 1.55in 2 100cm 2 15.5in 2 MAX882/4-fig04 copper ground pad area power dissipation (w) max883, v out = 5v 8-pin so package 77.4cm 2 , single-sided board 1oz copper glass epoxy, t j = +125 c, t a = +25 c, still air 250 200 150 100 50 0 MAX882/4-05a supply voltage (v) maximum output current (ma) 5 4 3 27 6810 91113 12 maximum power dissipation limit high- power soic plastic dip ceramic dip maximum supply voltage limit typical dropout voltage limit maximum current operating region at t a = +25 c t j = +125 c 250 200 150 100 50 0 MAX882/4-05b supply voltage (v) maximum output current (ma) 5 47 6810 91113 12 maximum power dissipation limit high- power soic plastic dip ceramic dip maximum supply voltage limit typical dropout voltage limit maximum current operating region at t a = +25 c t j = +125 c figure 4. typical maximum power dissipation vs. ground pad area figure 5a. safe operating regions: MAX882/max884 maximum output current vs. supply voltage figure 5b. safe operating regions: max883 maximum output current vs. supply voltage
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators ______________________________________________________________________________________ 11 reverse-current protection the MAX882/max883/max884 have a unique protection scheme that limits reverse currents when the input volt- age falls below the output. it monitors the voltages on in and out and switches the ic? substrate and power bus to the more positive of the two. the control circuitry is then able to remain functioning and turn the pass transis- tor off, limiting reverse currents back through to the input of the device. in this mode, typical current into out to gnd is 15? at v out = 3.3v and 50? at v out = 5v. reverse-current protection activates when the voltage on in falls 6mv (or 20mv max) below the voltage on out. before this happens, currents as high as several milliamperes can flow back through the device. low-battery-detection comparator the MAX882/max883/max884 provide a low-battery com- parator that compares the voltage on the lbi pin to the 1.20v internal reference. lbo , an open-drain output, goes low when lbi is below 1.20v. hysteresis of 7mv has been added to the low-battery comparator to provide noise immunity during switching. lbo remains functional in stand- by mode for the MAX882, but is undefined in off mode for the max883 and max884. tie lbi to in when not used. use a resistor-divider network as shown in figure 6 to set the low-battery trip voltage. current into the lbi input is ?0na (max), so r2 can be as large as 1m ? . add extra noise immunity by connecting a small capacitor from lbi to gnd. additional hysteresis can be added by connect- ing a high-value resistor from lbi to lbo . applications information the MAX882/max883/max884 are series linear regula- tors designed primarily for battery-powered systems. figure 7 shows a typical application. standby mode vs. off mode stby is a comparator input that allows the user to set the standby-mode threshold voltage, while off is a logic-level input. when in standby mode, the output is disconnected from the input, but the biasing circuitry (including the low-battery comparator) is kept alive, causing the device to draw approximately 7?. standby mode is useful in applications where a low- battery comparator function is still needed in shutdown. a logic low at the off pin turns off all biasing circuitry, including the lbi/ lbo comparator, and reduces supply current to less than 1?. off mode is useful for maxi- mizing battery life. there is little difference in the time it takes to exit standby mode or off mode. output capacitor selection and regulator stability an output filter capacitor is required at the MAX882/ max883/max884 out pin. the minimum output capacitance required for stability is 2.2?. MAX882 max883 max884 c in o.1 f c out 2.2 f output voltage battery lbo lbi off (stby) ( ) are for MAX882. in power- fail indication r3 r1 + r2 r2 v lbi trip = v lbi , v lbi = 1.20v out gnd set r1 r2 MAX882 max883 max884 c in o.1 f c out 2.2 f output voltage input voltage battery off (stby) on/off * * optional reverse battery protection ( ) are for MAX882. in out gnd set lbi figure 6. using the low-battery comparator to monitor battery voltage figure 7. typical 3.3v or 5v linear regulator circuit
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 12 ______________________________________________________________________________________ the filter capacitor? size depends primarily on the desired power-up time and load-transient responses. load-transient response is improved by using larger output capacitors. the output capacitor? equivalent series resistance (esr) will not affect stability as long as the minimum capacitance requirement is observed. the type of capacitor selected is not critical, but it must remain above the minimum value over the full operating temper- ature range. input bypass capacitor normally, use 0.1? to 10? capacitors on the MAX882/ max883/max884 input. the best value depends pri- marily on the power-up slew rate of v in , and on load and line transients. larger input capacitor values pro- vide better supply-noise rejection and line-transient response, as well as improved performance, when the supply has a high ac impedance. the type of input bypass capacitor used is not critical. noise the MAX882/max883/max884 exhibit up to 4mv p-p of noise during normal operation. this is negligible in most applications. when using the MAX882/max883/ max884 for applications that include analog-to-digital converters (adcs) with resolutions greater than 12 bits, consider the adc? power-supply rejection specifica- tions. see the output noise plot in the typical operating characteristics section. psrr and operation from sources other than batteries the MAX882/max883/max884 are designed to achieve low dropout voltages and low quiescent cur- rents in battery-powered systems. however, to gain these benefits, the devices must trade away power- supply noise rejection, as well as swift response to sup- ply variations and load transients. for a 1ma load current, power-supply rejection ranges from 60db down to 20db at 2khz. at higher frequencies, the cir- cuit depends primarily on the characteristics of the out- put capacitor, and the psrr increases (figure 8). 0 60 50 40 30 20 10 10 1 10 2 10 3 10 4 10 5 10 6 MAX882/4-8b frequency (hz) psrr (db) a: c out = 1 f b: c out = 10 f c: c out = 100 f a b c max883 ? v in = 1v p-p c in = 0 f i out = 100ma 0 80 70 60 50 40 30 20 10 10 0 10 1 10 2 10 3 10 4 10 5 10 6 MAX882/4-8a frequency (hz) psrr (db) i out = 1ma i out = 100ma max884 ? v in = 1v p-p c in = 0 f c out = 2.2 f figure 8b. power-supply rejection ratio vs. ripple frequency for various output capacitances figure 8a. power-supply rejection ratio vs. ripple frequency for light and heavy loads
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators ______________________________________________________________________________________ 13 when operating from sources other than batteries, sup- ply-noise rejection and transient response can be improved by increasing the values of the input and out- put capacitors and employing passive filtering tech- niques. do not use power supplies with ripple voltage exceeding 200mv at 100khz. overshoot and transient considerations the typical operating characteristics section shows power-up, supply, and load-transient response graphs. on the load-transient graphs, two components of the output response can be observed: a dc shift from the output impedance due to the different load currents, and the transient response. typical transients for step changes in the load current from 50ma to 250ma are 200mv. increasing the output capacitor? value attenu- ates transient spikes. during recovery from shutdown, overshoot is negligible if the output voltage has been given time to decay ade- quately. during power-up from v in = 0, overshoot is typically less than 1% of v out . input-output (dropout) voltage a regulator? minimum input-output voltage differential (or dropout voltage) determines the lowest usable sup- ply voltage. in battery-powered systems, this deter- mines the useful end-of-life battery voltage. because the MAX882/max883/max884 use a p-channel mos- fet pass transistor, their dropout voltage is a function of r ds(on) multiplied by the load current (see electrical characteristics ). quickly stepping up the input voltage from the dropout voltage can result in overshoot. short-term battery backup using the MAX882 figure 9 illustrates a scheme for implementing battery backup for 3.3v circuits using the MAX882. when the supply voltage drops below some user-specified value based on resistors r1 and r2, the standby function activates, turning off the MAX882? output. under these conditions, the backup battery supplies power to the load. reverse current protection prevents the bat- tery from draining back through the regulator to the input. this application is limited to short-term battery backup for 3.3v circuits. the current drawn by the MAX882? out pin at 3.3v during reverse-current protection is typically 8?. it should not be used with the max883 and max884, since the off pin is a logic input, and indeterminate inputs can cause the regulator to turn on intermittently, draining the battery. reverse battery protection reverse battery protection can be added by including an inexpensive schottky diode between the battery input and the regulator circuit, as shown in figure 7. however, the dropout voltage of the regulator will be increased by the forward voltage drop of the diode. for example, the forward voltage of a standard 1n5817 schottky diode is typically 0.29v at 200ma. backup battery MAX882 c in o.1 f c out 2.2 f output voltage input voltage lbi set stby in d2 r1 r2 out gnd figure 9. short-term battery backup using the MAX882
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators 14 ______________________________________________________________________________________ ordering information (continued) ___________________chip topography * dice are tested at t j = +25?, dc parameters only. ** contact factory for availability. set out in 0.085" (2.159mm) 0.080" (2.032mm) out lbi off (max883/4) stby (MAX882) gnd lb0 transistor count: 151 no direct substrate connection. the n-sub- strate is internally switched between the more positive of in or out. part max883 cpa max883csa max883c/d 0? to +70? 0? to +70? 0? to +70? temp. range pin-package 8 plastic dip 8 so dice* max883epa -40? to +85? 8 plastic dip max883esa -40? to +85? 8 so max883mja -55? to +125? 8 cerdip** max884 cpa max884csa max884c/d 0? to +70? 0? to +70? 0? to +70? 8 plastic dip 8 so dice* max884epa -40? to +85? 8 plastic dip max884esa -40? to +85? 8 so max884mja -55? to +125? 8 cerdip**
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators ______________________________________________________________________________________ 15 ________________________________________________________package information soicn.eps pdipn.eps
MAX882/max883/max884 5v/3.3v or adjustable, low-dropout, low i q , 200ma linear regulators ___________________________________________package information (continued) cdips.eps 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. 16 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products.

▲Up To Search▲

Price & Availability of MAX882

	To Download MAX882 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .