_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, pl ease contact maxim direct at 1-888-629-4642, or visit maxim?s website at www.maxim-ic.com. 28v-capable, i lim v bus accessory switch max14544/max14545 general description the max14544/max14545 are overcurrent detection switches that can provide power to external accesso- ries while preventing the host device from damage due to faulty overload conditions. these analog switches feature a 270m (typ) on-resistance and operate from a +2.3v to +5.5v input voltage range. the selectable current limit of 200ma or 400ma makes them ideal for load-switching applications. the max14544 has an autoretry feature, whereas the max14545 has a latchoff feature. when the switch is off, out can withstand 28v maximum. when the switch is on and a load is connected to the port, a blanking time of 10.5ms ensures that the transient voltage settles down. after this blanking time, if the voltage across the switch is greater than the flag assertion voltage, the switch turns off and then a flag is issued to the microprocessor. after the retry time, the device recloses for the duration of the blanking time to check if the load current is lower than the limit. the max14544 repeats this cycle if the overload condition is present. during the cycle, flag remains asserted. the max14544 remains on after the overload condition is removed and flag deasserts. for the max14545, after the blanking time, the switch turns off and then a flag is issued to the microprocessor. the switch can be turned on again by cycling the power or the en input. the max14544/max14545 have additional safety fea- tures that include thermal shutdown protection, reverse- current blocking, and overvoltage protection. the max14544/max14545 are offered in a space-sav- ing, 8-pin, 2mm x 2mm tdfn package, and operate over the -40 n c to +85 n c extended temperature range. applications cell phones mp3 players pdas digital cameras ebook mid features s 200ma or 400ma selectable current limit s output capable of withstanding +28v s reverse-current shutdown protection s +2.3v to +5.5v input operation range s undervoltage lockout s autoretry or latchoff option s thermal shutdown protection s 0.1a (typ) shutdown current s 5s fast current-limit detect s 8-pin tdfn (2mm x 2mm) package s -40 n c to +85 n c operating temperature range 19-5037; rev 0; 1/10 pin configuration ordering information/ selector guide note: all devices are specified over the -40c to +85c tem- perature range. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. * ep = exposed pad. typical operating circuit appears at end of data sheet. 1 + *ep *connect exposed pad to gnd. 34 86 5 out 2 7 out in iset gnd in tdfn max14544max14545 top view enflag part pin-package top mark retry/ latchoff max14544 eta+t 8 tdfn-ep* acy autoretry max14545 eta+t 8 tdfn-ep* acz latchoff downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 2 stresses beyond those listed under ?absolute maximu m ratings? may cause permanent damage to the device . these are stress ratings only, and functional operation of the device at these or any other condi tions beyond those indicated in the operational sec tions of the specifications is not implied. exposur e to absolute maximum rating conditions for extended periods may affect device reliability. (voltages referenced to gnd.) out .......................................................................-0.3v to +30v in, flag , en, iset ..............................................-0.3v to +6.0v continuous power dissipation (t a = +70 n c) 8-pin tdfn (derate 11.9mw/ n c above +70 n c) ...........953mw junction-to-ambient thermal resistance b ja (note 1) ..............................................................83.9 n c/w junction-to-case thermal resistance b jc (note 1) .................................................................37 n c/w operating temperature range .......................... -40 n c to +85 n c storage temperature range ............................ -65 n c to +150 n c junction temperature ..................................... -40 n c to +150 n c lead temperature (soldering, 10s) ................................+300 n c soldering temperature (reflow) ......................................+260 n c electrical characteristics (v in = +2.3v to +5.5v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at v in = +3.3v, t a = +25 n c.) (note 2) absolute maximum ratings note 1: package thermal resistances were obtained using the method described in jedec specifications. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . parameter symbol conditions min typ max units operating voltage range v in 2.3 5.5 v undervoltage lockout v uvlo v in falling 1.8 2.2 v undervoltage lockout hysteresis 100 mv in overvoltage trip level v ovlo v in rising 5.5 6.0 v in overvoltage hysteresis 1 % quiescent current i q v en = v in = 3.3v, i out = 0a 225 380 f a out voltage v out switch off 28 v out leakage current i outl v en = v in = 5v, v out = 5v after an overcur- rent fault 0.2 1 f a v en = v in = 5v, v out = 10v after an overcur- rent fault 3.5 in shutdown current i shdn v en = 0v, v in = 5v, v out = 0v, v iset = 0v 0.1 1.1 f a v en = 0v, v in = 5v, v out = 10v, v iset = 0v 0.1 1.1 switch on-resistance r on i out = 100ma, v in = 2.3v 370 600 m i i out = 100ma, v in > 3.3v 270 450 current limit i lim v iset = 0v, v in - v out = 1v 200 250 300 ma v iset = v in , v in - v out = 1v 400 500 600 flag assertion voltage v fa v fa = v in - v out , where overcurrent is detected and flag asserted 0.30 0.45 0.60 v reverse-current detection threshold i det v en = v in = 3.3v, v out rising until reverse- current shutdown protection trips 0 155 350 ma reverse-current detection hysteresis after a reverse overcurrent event, v out falls below v in until switch turns on, measure v in - v out 100 200 300 mv downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 3 electrical characteristics (continued) (v in = +2.3v to +5.5v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at v in = +3.3v, t a = +25 n c.) (note 2) note 2: all devices are production tested at t a = +25 n c. specifications over temperature limits are guaranteed by design. note 3: all timing characteristics are measured using 20% and 80% levels. parameter symbol conditions min typ max units input logic-high voltage v ih 1.4 v input logic-low voltage v il 0.4 v input leakage i in v en = v iset = 0v or 5v -1 +1 f a output logic-low voltage v ol i sink = 1ma 0.4 v output high leakage current v flag = 5v 1 f a thermal shutdown v in = 5v 150 n c thermal shutdown hysteresis v in = 5v 15 n c timing characteristics (note 3) turn-on time t on v en from low to high, v in = 3.3v, r l = 100 i 0.3 ms turn-off time t off v en from high to low, v in = 3.3v, r l = 100 i 1 ms current-limit reaction time t lim v en = v in = 3.3v, output high and then short circuit applied, c in = 10 f f ceramic, c out = 1 f f ceramic 5 f s blanking time t blank v en = v in = 3.3v, figures 1 and 2 4 10.5 30 ms autoretry time t retry max14544, figure 1 252 661.5 1890 ms reverse-current detection time t det v in = 3.3v, i reverse = 250ma, c in = 10 f f ceramic, c out = 1 f f ceramic 5 f s reverse-current recovery time t rec v out = v in + 500mv to v out = v in - 500mv 0.1 ms downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 4 figure 1. max14544 timing diagram (waveforms not to scale) figure 2. max14545 timing diagram (waveforms not to scale) t blank t blank t blank t blank t retry t retry current limit load current on off en on off switch flag current limit load current on off en on off switch flag t blank t blank downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 5 typical operating characteristics (v in = +3.3v, c in = 10 f f, c out = 1 f f, t a = +25 n c, unless otherwise noted.) normalized on-resistance vs. temperature max14544/5 toc09 temperature (c) normalized on-resistance 60 35 10 -15 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.50.5 -40 85 i out = 100ma normalized on-resistance vs. supply voltage max14544/5 toc08 supply voltage (v) normalized on-resistance 5.1 4.7 3.9 4.3 3.1 3.5 2.7 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.50.5 2.3 5.5 i out = 100ma shutdown reverse current vs. temperature max14544/5 toc07 temperature (c) shutdown reverse current (na) 60 35 10 -15 750 800 850 900 950 1000 700 -40 85 v in = 2.3v v out = 5v shutdown forward current vs. temperature max14544/5 toc06 temperature (c) shutdown forward current (na) 60 35 10 -15 100 200 300 400 500 600 700 800 900 0 -40 85 v out = 0v v in = 5v v in = 2.3v shutdown supply current vs. temperature max14544/5 toc05 temperature (c) shutdown supply current (na) 60 35 10 -15 100 200 300 400 500 600 700 800 900 0 -40 85 v out = 5v v in = 5v v in = 2.3v normalized current limit vs. temperature max14544/5 toc04 temperature (c) normalized current limit 60 35 10 -15 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.050.95 -40 85 normalized current limit vs. supply voltage max14544/5 toc03 supply voltage (v) normalized current limit 5.1 4.7 3.9 4.3 3.1 3.5 2.7 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.050.95 2.3 5.5 quiescent supply current vs. temperature max14544/5 toc02 temperature (c) supply current (a) 60 35 10 -15 50 100 150 200 250 300 350 400 450 0 -40 85 v en = v in v in = 5v v in = 3.3v quiescent supply current vs. supply voltage max14544/5 toc01 supply voltage (v) supply current (a) 5.1 4.7 3.9 4.3 3.1 3.5 2.7 50 100 150 200 250 300 350 400 450 0 2.3 5.5 v en = v in downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 6 blanking time max14544/5 toc18 10ms/div v out 2v/div i out 200ma/divv flag 2v/div max14544 iset high overcurrent duration time max14544/5 toc17 200ms/div v out 2v/div i out 200ma/divv flag 2v/div max14544 iset high current limit response max14544/5 toc16 100ms/div v out 2v/div i out 200ma/divv flag 2v/div iset high current limit response max14544/5 toc15 20ms/div v out 2v/div i out 200ma/divv flag 2v/div iset high flag response max14544/5 toc14 100ms/div v out 5v/div i out 200ma/divv flag 5v/div v in = 5v r l = 100 ? iset high reverse overvoltage protection max14544/5 toc13 10s/div 10v 5v0v 0v 3.3v v out 2v/divv in 2v/div v en = 0v power-up response max14544/5 toc12 200s/div v in 5v/divv out 5v/divi out 50ma/div switch turn-off time vs. temperature max14544/5 toc11 temperature (c) switch turn-off time (s) 60 35 -15 10 930 940 950 960 980970 990 1000 920 -40 85 v in = 5v r l = 100 ? switch turn-on time vs. temperature max14544/5 toc10 temperature (c) switch turn-on time (s) 60 35 10 -15 86 87 88 89 90 91 92 93 94 9585 -40 85 v in = 5v r l = 100 ? typical operating characteristics (continued) (v in = +3.3v, c in = 10 f f, c out = 1 f f, t a = +25 n c, unless otherwise noted.) downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 7 pin description functional diagram control ovlo en in iset charge pump out gnd forward current reverse current max14544max14545 flag uvlo pin name function 1, 2 in input voltage. connect in pins 1 and 2 together and bypass in to gnd with a 10 f f ceramic capacitor as close to the device as possible. 3 iset current-limit setting. drive iset low to have a 200ma current limit. drive iset high to have a 400ma current limit. 4 gnd ground 5 flag active-low fault open-drain output. flag goes low when the forward output current limit is exceeded for longer than the blanking time, the reverse current limit is exceeded, the ovp threshold on in is reached, or the part goes into thermal shutdown. flag is high impedance when en is low or a fault is not present. 6 en active-high switch-enable input. drive en high to turn on the device. drive en low to turn off the device. 7, 8 out output voltage. connect out pins 7 and 8 together and bypass out to gnd with a 1 f f ceramic capacitor as close to the device as possible. ? ep exposed pad. connect ep to gnd. for enhanced thermal dissipation, connect ep to a large copper ground plane. do not use ep as the sole ground connection. downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 8 detailed description the max14544/max14545 are overcurrent detection switches that prevent host devices from being damaged due to faulty load conditions. the switch opens if current exceeds the current limit for longer than the blanking time or if a reverse-current condition is detected. the switch also disconnects if v in exceeds ovlo, v in falls below uvlo, thermal shutdown occurs, or en is driven low. current limit can be set to either 200ma or 400ma. when the switch is open, the output (out) can withstand 28v maximum. when the switch is on and a load is connected to the port, a blanking time of 10.5ms ensures that the inrush current settles down. after this blanking time, if the volt- age across the switch is greater than the flag asser- tion voltage, the part is turned off and issues a flag to the microprocessor. after the retry time elapses, the max14544 switch is closed for the duration of the blank- ing time to check if the load current is lower than the limit. cycle the power or en input to turn the max14545 switch back on. current-limit threshold the max14544/max14545 iset logic input sets the desired minimum current-limit threshold to 200ma or 400ma. connect iset low for a 200ma current limit and high for a 400ma current limit. if 400ma is selected as the current limit, the input supply current at shutdown can be reduced by connecting iset to en. this is due to the fact that the device consumes the lower supply current in iset = low mode than in iset = high mode. reverse-current protection the max14544/max14545 monitor the reverse current (v out to v in ) from exceeding the maximum i det value. if the reverse-current detection threshold is exceeded, the switch turns off and flag is asserted without waiting for t blank to elapse. this feature prevents excessive reverse currents from flowing through the device. flag indicator the max14544/max14545 feature a fault output ( flag ). whenever v in - v out > v fa , the max14544 asserts flag low after the blanking time and keeps it low until the condition is removed. during this time, the switch cycles on and off in the autoretry mode. when the condi- tion is removed, flag deasserts and the switch turns on (figure 1). the max14545 asserts flag low after the blanking time and turns the switch off when flag asser- tion voltage is exceeded (figure 2). flag is an open-drain output and requires an external pullup resistor. during shutdown (en is low), the pull- down on flag output is released to limit power dissipa- tion. flag goes low when one of the following occurs: 1) the temperature exceeds the thermal shutdown tem- perature, +150 n c (typ). 2) the device is in current limit for more than the fault blanking period. 3) the switch is in autoretry. 4) the reverse current limit is exceeded. 5) the input is over the ovlo. autoretry (max14544) when the flag assertion voltage is exceeded, the t blank timer begins counting (figure 1). the timer resets if the condition disappears before t blank has elapsed. a retry time delay (t retry ) is started immediately after t blank has elapsed and during that time the switch is turned off and flag is asserted. at the end of t retry , the device is turned on again. if the fault still exists, the cycle is repeated. if the fault is removed, the device stays on and flag deasserts. the autoretry feature saves system power in the case of a continuous overcurrent or short-circuit condition. during t blank , when the switch is on, the supply current is at the current limit. during t retry , when the switch is off, the current through the switch is zero. instead of observing the full load current, the device sees the equivalent load current times duty cycle or: i supply = i load x t blank /(t blank + t retry ) with a typical t blank = 10.5ms and typical t retry = 661.5ms, the duty cycle is 1.6%, resulting in a 98.4% power savings over the switch being on the entire time. latchoff (max14545) when the flag assertion voltage is exceeded, the t blank timer begins counting. the device turns off after the blanking time. the timer resets if the condition is removed before the end of the blanking time. reset the device by toggling en (figure 2). fault blanking the max14544/max14545 feature a 10.5ms (typ) fault blanking. fault blanking allows current-limit fault s, including momentary short-circuit faults that occur when plugging a capacitive load, and also ensures that no fault is issued during power-up. when a load transient causes the device to enter current limit, an internal coun- ter starts. if the load-transient fault persists beyond the downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 9 fault-blanking timeout, flag asserts low. flag is not asserted when load-transient fault is less than t blank . the fault blanking time only applies to forward current- limit faults. a reverse current-limit fault, thermal fault, or ovp fault causes flag to assert immediately and does not wait for the blanking time. thermal shutdown the max14544/max14545 have a thermal-shutdown feature to protect the devices from overheating. the device turns off and flag goes low immediately (no fault blanking) when the junction temperature exceeds +150 n c. the max14544/max14545 turns back on when the device temperature drops approximately 15 n c. ovlo and uvlo the max14544/max14545 feature an overvoltage pro- tection. when in goes above v ovlo (6.0v max), the switch turns off and flag goes low immediately with no fault-blanking time. when in drops below v uvlo (1.8v min), the switch turns off but flag stays high. the max14544/max14545 turns back on when in is in the operating range. applications information input capacitor to limit the input-voltage drop during momentary output short-circuit conditions, connect a capacitor from in to gnd. a 10 f f ceramic capacitor is adequate for most applications; however, higher capacitor values further reduce the voltage drop at the input and are recom- mended for lower voltage applications. output capacitor connect a 1 f f ceramic capacitor from out to gnd. this capacitor helps prevent inductive parasitics from pulling out negative during turn-off, thus preventing the max14544/max14545 from tripping erroneously. if the load capacitance is too large, then current may not have enough time to charge the capacitance and the device assumes that there is faulty load condition. the maximum capacitive load value that can be driven from out is obtained by the following formula: < fwd_min blank_min max in i t c v 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. in and out must be connected with short traces to the power bus. during normal operation, the power dissipation is small and the package temperature 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 v i t p 51.6mw t t = = + where v in_max = 5.5v, i out_max = 600ma, t blank = 10.5ms, and t retry = 661.5ms. attention must be given to the max14545 where the latchoff condition can be manually reset by toggling en from high to low. if the latchoff time duration is not suf- ficiently high, it is possible for the device to reach the thermal-shutdown threshold and never be able to turn the device on until it cools down. downloaded from: http:///
28v-capable, i lim v bus accessory switch max14544/max14545 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. 10 maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2010 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. chip information process: bicmos package information for the latest package outline information and land pat- terns, 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 suf- fix character, but the drawing pertains to the package regardless of rohs status. li+ battery charger note: drive iset high to have a 400ma current limit. drive iset low to have a 200ma current limit. mini-b usb jack outout iset in batt 10k i v cc inen gnd vbus current or current d+ gnd d- max14544 max14545 c charger power source peripheral device v cc flag package type package code document no. 8 tdfn-ep t822+2 21-0168 downloaded from: http:/// typical operating circuit
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