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19-6458; rev 0; 9/12 ordering information/selector guide typical operating circuit general description the max14575a/max14575al/max14575b/MAX14575C programmable current-limit switches feature internal current limiting to prevent damage to host devices due to faulty load conditions. these current-limit switches feature a low 32m i (typ) on-resistance and operate from a +2.3v to +5.5v input voltage range. the current limit is adjustable from 250ma to 2.5a, making these devices ideal for charging a large load capacitor as well as for high-current load switching applications. each device in the family handles an overcurrent event differently depending on the option selected. the max14575a/max14575al feature an autoretry mode, the max14575a has active high, and the max14575al has active-low en polarity. the max14575b has latch- off mode, and the MAX14575C features a continuous current-limit mode. additional safety features include thermal shutdown protection to prevent overheating and reverse current blocking to prevent current from being driven back into the source (see the selector guide ). the max14575a/max14575al/max14575b/MAX14575C are available in a small 8-pin, 2mm x 2mm tdfn pack - age and operate over the -40 n c to +85 n c extended temperature range. features s adjustable current limit (250ma to 2500ma) s accurate 10% overload current limit (500ma to 2.5a) s 32m i (typ) low r on s +2.3v to +5.5v supply voltage range s reverse current protection s short-circuit protection s thermal shutdown protection s 130a (typ) low supply current s 1a (max) shutdown reverse current s small, 8-pin, 2mm x 2mm tdfn package applications + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. * ep = exposed pad. rf power amplifier in cell phones usb ports data modem cards portable media players utca/atca platforms sdxc card power-supply protection load power suppl y p in out seti gnd 1f 1f r seti v pullup flag en(en)* *() for the max14575al onl y 10k charge pump bias vol t age control logic current reference max14575a/max14575al* max14575b/MAX14575C part pin-package temp range en polarity overcurrent response top mark max14575a eta+t 8 tdfn-ep* -40 c to +85 c active-high autoretry bmv max14575al eta+t 8 tdfn-ep* -40 c to +85 c active-low autoretry bmw max14575b eta+t 8 tdfn-ep* -40 c to +85 c active-high latch-off bmx MAX14575C eta+t 8 tdfn-ep* -40 c to +85 c active-high continuous bmy for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maximintegrated.com. 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
2 stresses beyond those listed under absolute 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. (voltages referenced to gnd.) in, en, en , flag , out, and seti to gnd ............ -0.3v to +6v current into any pin (except in, out) ........................... q 20ma out short circuit to gnd ................................ internally limited continuous power dissipation (t a = +70 n c) tdfn (derate 11.9mw/ n c above +70 n c) .................... 954mw operating temperature range .......................... -40 n c to +85 n c storage temperature range ............................ -65 n c to +150 n c junction temperature ..................................................... +150 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c tdfn junction-to-ambient thermal resistance ( b ja ) ..... +83.9 n c/w junction-to-case thermal resistance ( b jc ) ............. +37 n c/w electrical characteristics (v in = +2.3v to +5.5v and t a = -40 n c to +85 n c, unless otherwise noted. typical values are at v in = +3.3v, c in = 1 f f, c out = 1 f f, r seti = 100k i ., t a = +25c.) (note 2) absolute maximum ratings package thermal characteristics (note 1) note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-lay - er board. for detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial . parameter symbol conditions min typ max units supply operation operating voltage v in 2.3 5.5 v quiescent current i q i out = 0a, switch on, v in = 3.3v , r seti = 560k i 130 275 f a latchoff current i latch i out = 0a , after an overcurrent fault (max14575b) 6 20 f a shutdown forward current i shdn v en = 0v, v en = 5.5v, v in = 5.5v, v out = 0v 0.1 3.5 f a shutdown reverse current i rshdn v en = 0v, v en = 5.5v, v in = 0v, v out = 5.5v (current into out) 0.07 1 f a internal fet switch on-resistance r on v in = 5.5v, t a = +25 c, i out = 100ma, i out < i lim 32 50 m i forward current limit i lim r seti = 52.65k i 2250 2500 2750 ma r seti = 268.7k i 450 500 550 r seti = 538.7k i 200 250 300 r seti coefficient p i lim = 0.5a to 2.5a 135 kv r seti constant c i lim = 0.5a to 2.5a 1.35 k i r seti o i lim product i lim = 250ma to 2500ma, v in - v out = 1v 172 215 258 kv reverse blocking current v out > v in + 145mv, after reverse current-limit shutdown 2 f a reverse blocking threshold v out - v in v out - v in = 300mv, out falling until switch turns on, while measuring v out - v in 25 100 145 mv flag assertion drop voltage threshold v fa increase (v in - v out ) drop until flag asserts, in current-limit mode, v in = 3.3v, r seti = unconnected 345 mv maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
3 electrical characteristics (continued) (v in = +2.3v to +5.5v and t a = -40 n c to +85 n c, unless otherwise noted. typical values are at v in = +3.3v, c in = 1 f f, c out = 1 f f, r seti = 100k i , t a = +25c.) (note 2) note 2: all devices are 100% production tested at t a = +25 n c. limits over the operating temperature range are guaranteed by design; not production tested. note 3: blanking time and retry time are generated by the same internal oscillator. the ratio of retry blank t t is a constant value of 32. figure 1. timing diagram for measuring turn-on time (t ss ) and turn-off time (t off ). t ss t off v out 10% v in 90% v in en(en)* *() the polarity of the signal is reversed for the max14575al only. parameter symbol conditions min typ max units en, en input en, en input leakage i leak en, en = in or gnd -1 +1 f a en, en input logic-high voltage v ih 1.6 v en, en input logic-low voltage v il 0.4 v flag output flag output logic-low voltage i sink = 1ma 0.4 v flag output leakage current v in = v flag = 5.5v, flag deasserted 1 f a timing characteristics turn-on time t ss time from enable signal to v out = 90% of v in , figure 1 600 f s turn-off time t off time from disable signal to v out = 10% of v in , r l = 1k i , c out = 0 , figure 1 100 f s current-limit reaction time t lim output high and then short circuit applied 3 f s blanking time t blank figures 2 and 3 (note 3) 10 15 25 ms retry time t retry max14575a/max14575al figure 2 (note 3) 320 500 875 ms thermal protection thermal shutdown +160 n c thermal shutdown hysteresis 20 n c maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
4 figure 2. autoretry fault diagram figure 3. latchoff fault diagram t retry t blank t blank t blank t blank t retry flag out current limit load current the device goes to thermal-shutdown mode t blank t blank flag out current limit load current the device goes to thermal-shutdown mode maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
5 typical operating characteristics (v in = +3.3v, c in = 1 f f, c out = 1 f f, r seti = 94.2k i , t a = +25 n c, unless otherwise noted.) current limit vs. supply voltage max14575a toc01 supply voltage (v) current limit (a) 5.0 4.0 4.5 3.0 3.5 2.5 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 1.0 2.0 5.5 normalized current limit vs. temperature max14575a toc02 temperature (c) normalized current limit 60 35 10 -15 0.8 0.9 1.0 1.1 1.2 1.3 0.7 -40 85 quiescent supply current vs. supply voltage max14575a toc03 supply voltage (v) quiescent supply current (a) 5.0 4.5 4.0 3.5 3.0 2.5 110 120 130 140 150 170 160 180 190 200 100 2.0 5.5 v en = v in i out = 0a quiescent supply current vs. temperature max14575a toc04 temperature (c) quiescent supply current (a) 60 35 10 -15 120 140 160 180 200 220 100 -40 85 v en = v in i out = 0a v in = +3.3v v in = +5v shutdown supply current vs. temperature max14575a toc05 temperature (c) shutdown supply current (a) 60 35 10 -15 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 -40 85 v en = 0v i out = 0a v in = +3.3v v in = +5v shutdown forward current vs. temperature max14575a toc06 temperature (c) shutdown forward current (a) 60 35 10 -15 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 -40 85 v en = 0v v out = 0v v in = +2.3v v in = +5.5v shutdown reverse current vs. temperature max14575a toc07 temperature (c) shutdown reverse current (a) 60 35 10 -15 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 -40 85 v en = 0v v out = 5.5v v in = 2.3v latchoff current vs. temperature max14575a toc08 temperature (c) i latch (a) 60 35 10 -15 1 2 3 4 5 6 7 8 9 10 0 -40 85 max14575b v en = v in v in = +3.3v v in = +5v normalized on-resistance vs. supply voltage max14575a toc09 supply voltage (v) normalized (r on ) 5.0 4.5 4.0 3.5 3.0 2.5 0.5 1.0 1.5 2.0 2.5 0 2.0 6.5 t a = +25c t a = +40c t a = +85c v en = v in i out = 100ma normalized to v in = 5.5v at +25c maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
6 typical operating characteristics (continued) (v in = +3.3v, c in = 1 f f, c out = 1 f f, r seti = 94.2k i , t a = +25 n c, unless otherwise noted.) switch turn-on time vs. temperature max14575a toc10 temperature (c) t ss (ms) 60 35 10 -15 0.4 0.8 1.2 1.6 2.0 0 0.6 1.0 1.4 1.8 0.2 -40 85 i out = 10ma v in = 3.3v v in = +5v switch turn-off time vs. temperature max14575a toc11 temperature (c) t off (s) 60 35 10 -15 20 40 60 80 100 0 30 50 70 90 10 -40 85 r l = 1ki no output capacitor v in = 3.3v v in = +5v 4ms/div current-limit response max14575a toc12 suddent short applied at output v en = v in = +3.3v v out 2v/div i out 1a/div 20ms/div current-limit response max14575a toc13 i out = 200ma to short applied v en = v in = +3.3v v out 2v/div i out 1a/div 4ms/div flag response (overload condition) max14575a toc14 short to ground applied v en = v in = +3.3v i out 1a/div v flag 2v/div maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
7 pin configuration pin description tdfn (2mm 2mm) top view ep* *connect exposed pad to gnd **parentheses are for the max14575al only max14575a max14575al max14575b MAX14575C 1 + 8 gnd flag 2 7 en(en)** seti 4 5 in out 3 6 in out pin name function max14575al max14575_ 1 1 flag open-drain overcurrent indicator output. flag goes low when the overload fault duration exceeds the blanking time, reverse current is detected, thermal shutdown mode is active, or seti is connected to ground. 2 2 seti forward current-limit adjust input. connect a resistor from seti to gnd to program the overcurrent limit. if seti is connected to gnd, the switch turns off and flag is asserted. do not leave seti unconnected or connect any capacitor larger than 20pf to seti. 3, 4 3, 4 out switch output. connect out pins 3 and 4 together and bypass out to gnd with a 1 f f ceramic capacitor as close to the device as possible. 5, 6 5, 6 in power input. connect in pins 5 and 6 together and bypass in to gnd with a 1 f f ceramic capacitor as close to the device as possible. if necessary, use higher capacitance to prevent large load transients from pulling down the supply voltage. 7 en active-low enable input. drive en low to turn on the switch. drive en high to turn off the switch. 7 en active-high enable input. drive en high to turn on the switch. drive en low to turn off the switch. 8 8 gnd ground ep exposed pad. internally connected to gnd. connect to a large ground plane to maximize thermal performance. not intended as an electrical connection point. maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
8 detailed description the max14575a/max14575al/max14575b/MAX14575C programmable current-limit switches operate from +2.3v to +5.5v and provide internal current limiting adjust - able from 250ma to 2.5a. these devices feature a fixed blanking time and a flag output that notifies the proces - sor when a fault condition is present. programmable current-limit threshold a resistor from seti to gnd sets the current-limit thresh - old for the switch (see the setting the current-limit threshold section). if the output current is limited at the current threshold value for a time equal to or longer than t blank with v in - v out higher than the flag assertion drop voltage threshold ( v fa.), then the flag asserts, and the max14575a/max14575al enter the autoretry mode, the max14575b latches off the switch, and the MAX14575C enters the continuous current-limit mode. autoretry (max14575a/max14575al) when the forward current reaches the current thresh - old, the t blank timer begins counting (figure 2). flag asserts if the overcurrent condition is present for t blank . the timer resets if the overcurrent condition disappears before the blanking time (t blank ) has elapsed. a retry time delay (t retry ) starts immediately after the blanking time has elapsed and during that time, the switch latches off. at the end of t retry , the switch turns on again. if the fault still exists, the cycle repeats. if the fault has been removed, the switch stays on. during this cycle, flag stays low. in autoretry, if the die temperature exceeds +160 n c (typ) due to self-heating, the max14575a/ max14575al go into thermal-shutdown mode until the die temperature drops by approximately 20 n c. the autoretry feature saves system power in case of an overcurrent or short-circuit condition. during t blank time, when the switch is on, the supply current is held at the current limit. during time t retry , when the switch is off, the current through the switch is zero. thus, the aver - age output current is much less than the programmed current limit. calculate the average output current using the following equation: = + blank load lim blank retry t ii tt for example, if t blank = 15ms and t retry = 500ms, the duty cycle is 3%, resulting in a 97% power savings over the switch being on the entire time. functional diagram max14575a max14575al max14575b MAX14575C buffer control logic current limit bandgap reference timing circuitry buffer thermal shutdown out in en(en)* *parentheses are for the max14575al only flag seti reverse-current protection maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
9 latchoff (max14575b) when the forward current reaches the current thresh - old, the t blank timer begins counting (figure 3). flag asserts if an overcurrent condition is present for greater than t blank time. the timer resets if the overcurrent con - dition disappears before t blank has elapsed. the switch turns off if the overcurrent condition continues beyond the blanking time. reset the switch by either toggling the control logic (en) or cycling the input voltage. if the die temperature exceeds +160 n c (typ) due to self-heating, the max14575b goes into thermal-shutdown mode until the die temperature drops by approximately 20 n c. continuous current limit (MAX14575C) when the forward current reaches the forward-current threshold, the MAX14575C limits the output current to the programmed current limit. flag asserts if the cur - rent limit is present for t blank and deasserts when the overload condition is removed. in this mode, if the die temperature exceeds +160 n c (typ) due to self-heating, the MAX14575C goes into thermal-shutdown mode until the die temperature drops by approximately 20 n c. switch enable control (en/ en ) the en input for the max14575a/b/c and en input for the max14575al control the internal switch. see table 1. reverse current protection the max14575a/max14575al/max14575b/MAX14575C feature a reverse current protection circuit that limits the backflow current to 2 f a when the reverse current protec - tion circuitry has tripped. the switch turns off and flag asserts without waiting for t blank to elapse. the switch turns back on and flag deasserts when v out - v in drops below the reverse blocking threshold. flag indicator flag is an open-drain fault indicator output and requires an external pullup resistor to a dc supply. flag goes low when any of the following conditions occur: ? an overcurrent condition after the blanking time has elapsed and v in - v out > v fa ? the reverse current protection has tripped ? the die temperature exceeds +160 n c ? seti is connected to ground thermal shutdown thermal shutdown circuitry protects the devices from overheating. the switch turns off and flag goes low immediately when the junction temperature exceeds +160 n c (typ). the max14575a/al/c switches turn on again after the device temperature drops by approxi - mately 20 n c (typ). applications information setting the current-limit threshold connect a resistor between seti and ground to program the current-limit threshold value for the max14575a/ max14575al/max14575b/MAX14575C. table 2 shows current-limit thresholds for different resistor values at seti. connecting seti to ground asserts flag . use the following formula to calculate the current limit: seti(k ) lim p(kv) r c(k ) i (ma) ? = ?? do not use an r seti value smaller than 40k i . note: connecting any capacitor larger than 20pf to seti can cause instability. table 1. switch truth table table 2. current-limit threshold vs. resistor values max14575a/b/c max14575al switch status en en 0 1 off 1 0 on r seti (k ) current limit (a) 510 0.26 470 0.28 402 0.33 301 0.45 261 0.51 200 0.625 150 0.86 100 1.32 90 1.45 85 1.55 75 1.75 64 2.02 57.6 2.26 53 2.5 maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
10 in bypass capacitor connect a minimum 1 f f capacitor from in to gnd to limit the input-voltage drop during momentary output short-circuit conditions. if the power supply cannot support the required short-circuit current, then a larger capacitor should be used to maintain the input voltage above 2.3v. if the supply is not strong enough and the user does not want to use a larger capacitor at the input, then the fol - lowing circuitry can be used (figure 4.) out bypass capacitor for stable operation over the full temperature range and over the full programmable current-limit range, use a 1 f f ceramic capacitor from out to ground. excessive output capacitance can cause a false over - current condition due to decreased dv/dt across the capacitor. use the following formula to calculate the maximum capacitive load (c max ) on out: = lim blank(min) max in i (ma) t (ms) c ( f) v (v) for example, for v in = 5.0v, t blank = 10ms, and i lim = 1000ma, c max equals 2000 f f. layout and thermal dissipation to optimize the switch response time to output short- circuit conditions, it is very important to keep all traces as short as possible to reduce the effect of undesirable parasitic inductance. place input and output capacitors as close as possible to the device (should be no more than 5mm). in and out must be connected with wide short traces to the power bus. during normal operation, the power dissipation is small and the package tem - perature change is minimal. if the output is continuously shorted to ground at the maximum supply voltage, the operation of the switches with the autoretry option does not cause problems because the total power dissipated during the short is scaled by the duty cycle: = + in(max) out(max) blank (max) retry blank vi t p tt attention must be given to the MAX14575C continuous current-limit version when the power dissipation during a fault condition causes the device to reach the thermal- shutdown threshold. chip information process: bicmos figure 4. optional protection for weak supply r set i en(en) in ou t flag gn d set i ep ~100 i* 1 f parentheses for the max14575al only *if v in > 3v, a diode can be used in place of the resistor . load max14575a max14575al max14575b MAX14575C package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. 8 tdfn-ep t822+2 21-0168 90-0065 maxim integrated 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 11 ? 2012 maxim integrated products, inc. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. revision history revision number revision date description pages changed 0 9/12 initial release 250ma to 2.5a adjustable current-limit switches max14575a/max14575al/ max14575b/MAX14575C

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