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general description the max4995a/max4995af/max4995al/max4995b/max4995c programmable current-limit switches fea- ture internal current limiting to prevent damage to host devices due to faulty load conditions. these analog switches feature a low 130m (typ) on-resistance and operate from a +1.7v to +5.5v input voltage range. thecurrent limit is adjustable from 50ma to 600ma, making these devices ideal for sdio (secure digital input/out- put) and other load-switching applications. each device in the family handles an overcurrent event differently depending on the option selected. the max4995a/max4995af/max4995al go into an autoretry mode, the max4995b latches off the switch, and the max4995c places the device in a continuous current-limit mode. additional safety features include thermal shutdown to prevent overheating and reverse- current blocking to prevent current from being driven back into the source. the max4995a/max4995af/max4995al/max4995b/ max4995c are available in a tiny 10-pin, 1.4mm x 1.8mm utqfn, a 6-pin sot23, or an 8-pin, 2mm x 2mm tdfn package and operate over the -40? to +125? extended temperature range. features ? 50ma to 600ma programmable current limit ? ?0% accurate current limit ? overload flag threshold ? low dropout voltage ? short-circuit protection ? thermal shutdown ? reverse-current protection ? 170? (typ) supply current ? +1.7v to +5.5v supply voltage range ? tiny 10-pin, 1.4mm x 1.8mm utqfn package applications max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches ________________________________________________________________ maxim integrated products 1 ordering information/selector guide 19-4363; rev 2; 2/10 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. all devices operate over the -40? to +125? temperature range. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. * future product. contact factory for availability. ** ep = exposed pad. part pin-package on polarity overcurrent response short-circuit response top mark max4995a aut+t* 6 sot23 active-high autoretry normal +acnz max4995aavb+t 10 utqfn active-high autoretry normal +aam max4995aata+t 8 tdfn-ep** active-high autoretry normal +abl max4995af aut+t* 6 sot23 active-high autoretry fast +acoe max4995afavb+t 10 utqfn active-high autoretry fast +aar max4995afata+t* 8 tdfn-ep** active-high autoretry fast +aco max4995al aut+t* 6 sot23 active-low autoretry normal +acda max4995alavb+t 10 utqfn active-low autoretry normal +aan max4995alata+t* 8 tdfn-ep** active-low autoretry normal +abm max4995b aut+t* 6 sot23 active-high latchoff normal +acdb max4995bavb+t 10 utqfn active-high latchoff normal +aao max4995bata+t* 8 tdfn-ep** active-high latchoff normal +abn max4995c aut+t* 6 sot23 active-high continuous normal +acod max4995cavb+t 10 utqfn active-high continuous normal +aaq max4995cata+t* 8 tdfn-ep** active-high continuous normal +abp typical operating circuit appears at end of data sheet. sdio portsusb ports notebook vga ports gps cell phonesmp3 players utca/atca platforms downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, on, on , flag , out, and seti to gnd .............-0.3v to +6v current into any pin (except in, out)................................20ma out short circuit to gnd .................................................800ma continuous power dissipation (t a = +70?) (note 1) 10-pin utqfn (derate 6.99mw/ ? above t a = +70?) ..559mw 6-pin sot23 (derate 13.4mw/ ? above t a = +70?)...1072.4mw 8-pin tdfn (derate 11.9mw/ ? above t a = +70?) ....953.5mw junction-to-ambient thermal resistance ( ja ) (note 2).....................................................................143.1?/w operating temperature range .........................-40? to +125? storage temperature range .............................-65? to +150? junction temperature ......................................................+150? lead temperature (soldering, 10s) .................................+300? note 1: these power limits are defined by the thermal characteristics of the package, maximum function temperature (+150?), andthe jedec51-7 defined setup. maximum power dissipation could be lower, limited by the thermal-shutdown protection included in this ic. note 2: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . electrical characteristics(v in = +1.7v to +5.5v, r seti = 94.3k , c in = 1?, and t a = t j = -40? to +125?, unless otherwise noted. typical values are at v in = +3.3v, t a = +25?.) parameter symbol conditions min typ max units supply operation operating voltage v in 1.7 5.5 v quiescent current i q i out = 0, switch on, v in = 3.3v 170 300 a latchoff current i latch v in = 3.3v, i out = 0 after an overcurrent fault (max4995b) 8 15 a shutdown forward current i shdn v on = 0, v on = v in , v in = 5.5v, v out = 0 0.01 5 a shutdown reverse current i rshdn v on = 0, v on = v in , v in = 1.7v, v out = 5.5v (current into out) 0.01 1 a internal fet switch-on resistance r on v in = 3.3v, i out lower than i lim 130 350 m normalized current-limit accuracy i lim = 50ma to 600ma, v in - v out = 1v, v in = 3.3v (note 3) 0.9 1 1.1 (r seti + 2.48) x i lim product i lim = 50ma to 600ma, v in - v out = 1v, v in = 3.3v 26138 29042 31946 v reverse blocking current v out > v in + 300mv after reverse-current- limit shutdown 10 a reverse blocking threshold v out = v in + 300mv, out falling until switch turns on 35 110 210 mv flag assertion drop voltage threshold v fa increase (v in - v out ) drop until flag asserts, i out limiting, v in = 3.3v 650 mv on, on input on, on input leakage i leak v on , v on = v in or gnd -1 +1 a on, on input logic-high voltage v ih 1.6 v on, on input logic-low voltage v il 0.4 v downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches _______________________________________________________________________________________ 3 note 3: i lim is forward current limit. note 4: turn-on time and turn-off time are defined as the difference in the time between when the output crosses 10% and 90%of the final output voltage. note 5: blanking time and retry time are generated by the same oscillator. therefore, the ratio of is a constant value of 32. see figures 2 and 3. t t retry blank i (ma) 2 r(k 2.48k lim seti = + 9042( ) )( ) v ? electrical characteristics (continued)(v in = +1.7v to +5.5v, r seti = 94.3k , c in = 1?, and t a = t j = -40? to +125?, unless otherwise noted. typical values are at v in = +3.3v, t a = +25?.) parameter symbol conditions min typ max units flag o u t p u t flag output logic-low voltage i sink = 1ma 0.4 v flag output leakage current v in = v flag = 5.5v, flag deasserted 1 a dynamic turn-on time t ss v in = 3.3v, c out = 1f, r l = 20 , figure 1, (note 4) 120 s turn-off time t off switch from on to off, v in = 3.3v, c out = 1f, r l = 20 , figure 1 (note 4) 120 s max4995a/al/b/c 5 current-limit reaction time t lim v in = 3.3v, r seti = 578k , output high and then short-circuit applied max4995af 1.5 s blanking time t blank (note 5) 10 16.3 22.6 ms retry time t retry max4995a/max4995af/max4995al (note 5) 320 723.2 ms thermal protection thermal shutdown +150 c thermal-shutdown hysteresis 15 c t ss 10% 90% 10% 90% t off v out figure 1. timing diagram for measuring turn-on time (t ss ) and turn-off time (t off ). downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 4 _______________________________________________________________________________________ current limit vs. supply voltage max4995a toc01 supply voltage (v) current limit (ma) 2.0 3.0 2.5 4.5 5.0 3.5 4.0 290 295 300 305 310 315285 1.5 5.5 max4995al normalized current limit vs. temperature max4995a toc02 temperature ( c) normalized current limit -25 5 -10 20 0.950 0.975 1.000 1.0500.925 1.025 1.075 1.1000.900 -40 50 80 65 95 110 35 125 max4995al current-limit response (max4995a) max4995a toc03 i out (10a/div) v out (2v/div) 10 s/div sudden short applied at output current-limit response max4995a toc05 i out (100ma/div) v out (2v/div) 4ms/div r load = 8 current-limit response (max4995af) max4995a toc04 i out (10a/div) v out (2v/div) 10 s/div sudden short applied at output quiescent supply current vs. supply voltage max4995a toc06 supply voltage (v) quiescent supply current ( a) 2.0 3.0 2.5 4.5 5.0 3.5 4.0 160 180 200 260 280120 140 220 240 300100 1.5 5.5 max4995a typical operating characteristics (v in = +3.3v, c in = 1?, c out = 1?, r seti = 94.2k , t a = +25?, unless otherwise noted.) downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches _______________________________________________________________________________________ 5 typical operating characteristics (continued) (v in = +3.3v, c in = 1?, c out = 1?, r seti = 94.2k , t a = +25?, unless otherwise noted.) quiescent supply limit vs. temperature max4995a toc07 quiescent supply current ( a) 180 190 200 240170 230160 220150 210 250 260140 v in = 5v max4995al v in = 3.3v temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 shutdown supply current vs. temperature max4995a toc08 shutdown supply current ( a) 1.000.50 1.500.75 1.75 2.00 2.250.25 1.25 2.50 0 v in = 5v v in = 3.3v max4995al temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 shutdown forward current vs. temperature max4995a toc09 shutdown forward current (na) 50 7040 30 20 10 60 80 0 v in = 5v v in = 1.7v max4995c temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 shutdown reverse current vs. temperature max4995a toc10 shutdown reverse current (na) 150100 125 200 7550 25 175 225 0 v in = 5v max4995cv out = 5.5v v in = 1.7v temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 normalized on-resistance vs. temperature max4995a toc13 normalized on-resistance 0.9 1.1 1.2 1.3 1.40.8 0.7 0.6 1.0 1.50.5 max4995cv in = 3.3v temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 latchoff current vs. temperature max4995a toc11 latchoff current ( a) 1814 1612 10 8 20 6 v in = 5v max4995b v in = 3.3v temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 normalized on-resistance vs. supply voltage max4995a toc12 supply voltage (v) normalized on-resistance 2.2 4.7 2.7 3.7 4.2 3.2 1.0101.000 1.0201.005 1.025 1.030 1.0350.995 0.990 0.985 1.015 1.0400.980 1.7 5.2 max4995ci out < i lim switch turn-on time vs. temperature max4995a toc14 switch turn-on time ( s) 140130 120 170160 150 110 180100 v in = 5v v in = 3.3v max4995ci load = 10ma temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 switch turn-off time vs. temperature max4995a toc15 switch turn-off time (ms) 1.0 1.4 1.50.9 0.8 1.31.2 1.1 0.7 1.60.6 v in = 5v v in = 3.3v max4995ci load = 10ma temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 6 _______________________________________________________________________________________ switch turn-on time response max4995a toc16 v on (5v/div)v out (2v/div) 200 s/div switch turn-off time response max4995a toc17 v on (5v/div)v out (2v/div) 200 s/div flag response (overload) condition max4995a toc18 v out (2v/div) i out (200ma/div)v flag (2v/div) 100ms/div switch dropout voltage vs. temperature max4995a toc19 switch dropout voltage (mv) 1412 11 1713 1816 15 10 19 9 v in = 3.3v max4995ai load = 100ma temperature ( c) -25 5 -10 20 -40 50 80 65 95 110 35 125 i out /flag vs. v drop (v in - v out ) max4995a toc20 i out (ma) 250150 100 200 300 50 350 0 v in = 5.5v max4995b v drop (mv) flag (logic-level status) 70 490 560 420 0 0 1 210 630 140 280 350 700 typical operating characteristics (continued) (v in = +3.3v, c in = 1?, c out = 1?, r seti = 94.2k , t a = +25?, unless otherwise noted.) downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches _______________________________________________________________________________________ 7 pin description pin (utqfn) pin (tdfn-ep) pin (sot23) max4995al max4995 max4995al max4995 max4995al max4995 name function 1, 10 1, 10 1, 2 1, 2 5 5 in power input. bypass in with a 1f ceramic capacitor to ground. use higher capacitance to prevent large load transients from pulling down the supply voltage if necessary. connect both power inputs (in) together. 2 2 3 3 6 6 flag open-drain, overload 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. 3 4 4 on active-low, switch-on input. drive on low to turn on the switch. 3 4 4 on active-high, switch-on input. drive on high to turn on the switch. 4 4 5 5 2 2 gnd ground 5 5 6 6 3 3 seti overload current limit adjust. connect a resistor from seti to ground to program the overcurrent limit. do not connect any capacitance larger than 20pf to seti. pin configurations 35 10 8 in *( ) for the max4995al only.**exposed pad. connect ep to gnd. out max4995a/max4995afmax4995al/max4995b max4995c 4 9 n.c. on (on)* gnd utqfn (1.4mm 1.8mm) top views seti on (on)* 7 out 1 in 6 n.c. 2 flag max4995a/max4995afmax4995al/max4995b max4995c max4995a/max4995afmax4995al/max4995b max4995c sot23 (1.6mm 2.9mm) 4 on (on)* 3 seti 5in 2 gnd 6 flag 1 out 1 + 34 86 5 out gnd 2 7 n.c. in flag in tdfn (2mm 2mm) seti *ep downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 8 _______________________________________________________________________________________ out seti in max4995a/max4995af/max4995al/max4995b/ max4995c control logic reverse- current protection thermal shutdown current limit bandgap reference buffer timing circuitry buffer n.c. flag soft-start on (on)* uvlo *( ) for the max4995al only. gnd functional diagram pin description (continued) pin (utqfn) pin (tdfn-ep) pin (sot23) max4995al max4995 max4995al max4995 max4995al max4995 name function 6, 9 6, 9 7 7 n.c. no connect. not internally connected. 7, 8 7, 8 8 8 1 1 out switch output. bypass out with a 1f capacitor to ground. connect both outputs (out) together. ep exposed pad. connect ep to gnd. for tdfn package only. downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches _______________________________________________________________________________________ 9 detailed description the max4995a/max4995af/max4995al/max4995b/max4995c programmable current-limit switches oper- ate from +1.7v to +5.5v and provide internal current limiting adjustable from 50ma to 600ma. these devices feature a fixed blanking time and a flag output that notifies the processor when a fault condition is present. programmable current limit a resistor from seti to gnd programs the current limitfor the switch (see the setting the current limit sec- tion). if the output current exceeds the current limit for atime equal to or longer than t blank , the output flag asserts and the max4995a/max4995af/max4995alenter the autoretry mode. the max4995b latches off the switch, and the max4995c enters the continuous current-limit mode. autoretry (max4995a/max4995af/ max4995al) when the forward current reaches the current-limitthreshold, the t blank timer begins counting (figure 2). flag asserts if the overcurrent-limit condition is pre- sent for t blank . the timer resets if the overcurrent con- dition 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 cyclerepeats. if the fault has been removed, the switch stays on. during this cycle, flag stays low. in autoretry if the thermal power rating of the package is exceeded,the max4995a/max4995af/max4995al go into ther- mal shutdown. 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 atthe current limit. during time t retry when the switch is off, the current through the switch is zero. thus, theaverage output current is much less than the pro- grammed current limit. calculate the average output current using the following equation: i load = i lim [t blank /(t blank + t retry )] with a typical t blank = 16.3ms and typical t retry = 524ms, the duty cycle is 3%, resulting in a 97% powersavings over the switch being on the entire time. latchoff (max4995b) when the forward current reaches the current-limitthreshold, the t blank timer begins counting (figure 3). flag asserts if an overcurrent-limit condition is present for greater than t blank time. the timer resets if the over- current condition disappears before t blank has elapsed. the switch turns off if the overcurrent conditioncontinues beyond the blanking time. reset the switch by either toggling the control logic (on) or cycling theinput voltage. if the thermal power rating of the pack- age is exceeded during t blank , the max4995b goes into thermal shutdown. continuous current limit (max4995c) when the forward current reaches the forward current-limit threshold, the max4995c limits the output current to the programmed current limit. flag asserts if the current limit is present for t blank and deasserts when the overload condition is removed. in this mode, if thethermal power rating of the package is exceeded, the max4995c goes into thermal shutdown. switch-on/off control the on input for the max4995_/max4995af and on input for the max4995al control the switch; see table1. toggle on for the max4995b to reset the fault condi- tion once the short current is detected and the device shuts down. reverse-current protection the max4995 features a reverse-current protection cir-cuit that limits the backflow current to 10? when the output voltage exceeds the input voltage by 110mv (typ). the switch turns off and flag asserts without waiting for t blank to elapse. the switch turns back on and flag deasserts when the output voltage drops below the detecting threshold by 10mv (typ). max4995_/ max4995af max4995al on on switch status 0 1 off 10o n table 1. switch truth table downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 10 ______________________________________________________________________________________ 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 occurs: the device is in current-limit mode. the out voltage is above the in voltage by more than 110mv (typ). the die temperature exceeds the thermal-shutdown temperature limit of +150?. seti is connected to ground. thermal shutdown thermal-shutdown circuitry protects the devices fromoverheating. the switch turns off and flag goes low immediately when the junction temperature exceeds+150? (typ). the switch turns on again after the device temperature drops by approximately 15? (typ). t retry t blank t blank t blank t blank t retry flag out current limit load current the device goes tothermal-shutdown mode figure 2. autoretry fault diagram t blank t blank flag out current limit load current the device goes to thermal-shutdown mode figure 3. latchoff fault diagram downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches ______________________________________________________________________________________ 11 applications information setting the current limit a resistor from seti to ground programs the current-limitvalue for the max4995. table 2 lists various current lim- its set by different resistor values at seti. shorting seti to ground asserts flag . use the following formula to calculate the current limit:using an r seti with a value smaller than 45.8k results in a higher current limit. a programmed output currentgreater than 660ma can damage the device. connecting any capacitance larger than 20pf to seti can cause instability. input capacitor connect a capacitor from in to gnd to limit the inputvoltage drop during momentary output short-circuit conditions. use a 1? minimum ceramic capacitor for proper device operation. larger capacitor values reduce the voltage undershoot at the input. due to the very fast current-limit reaction time of the max4995af, a larger input capacitance might need to be connected at the input to dampen oscillation due to long wires. choose a value large enough to ensure in doesn? exceed the absolute maximum ratings. output capacitor for stable operation over the full temperature rangeand over the full programmable current-limit range, use a 1? ceramic capacitor from out to ground. 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 a faulty load condition. calculate the maximum capacitive load (c max ) value that can be connected to out using the following formula:for example, for v in = 3.3v, t blank(min) = 10ms, and i lim = 300ma, c max equals 909?. due to the very fast current-limit reaction time of themax4995af, a larger output capacitance might need to be connected at the output to dampen oscillation due to long wires. choose a value large enough to ensure out doesn? exceed the absolute maximum ratings. 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 wide, 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 maxi- mum 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: attention must be given to the max4995c continuous current-limit version when the power dissipation during a fault condition may cause the device to reach thermal shutdown threshold. p vi t tt max in(max) out(max) blank retry blank = + c(f ) i (ma) t (ms ) v( max lim blank(min) in = v) r( k) 2 i(a 2.48 k seti lim ? = 9042( ) ) () v m r seti (k ) typical current limit (ma) 45.8 602 55.6 500 70.6 397 94.2 300 143 200 191 150 287 100 576 50 (open) 0 table 2. current limit vs. resistor values downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 12 ______________________________________________________________________________________ max4995a/ max4995af/max4995al/ max4995b/ max4995c load out flag on(on*) p gnd v io n.c. seti r seti *( ) for the max4995al only. in v cc 1 f 1 f typical operating circuit chip information process: bicmos package type package code document no. 10 utqfn v101a1cn+1 21-0028 6 sot23 u6sn+1 21-0058 8 tdfn t822+1 21-0168 package information for the latest package outline information and land patterns,go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. packagedrawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. downloaded from: http:///
max4995a/af/al/max4995b/max4995c 50ma to 600ma programmable current-limit switches 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 13 2010 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 11/08 initial release. 1 6/09 corrected the ordering information/selector guide . 1, 11 2 2/10 ? added tdfn package information to the ordering information/selector guide , absolute maimum ratings , pin description , and package information sections. ? added the tdfn pin configuration drawing to the pin configurations section. 1, 2, 7, 12 downloaded from: http:///

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