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general description the max4789?ax4794 family of switches feature internal current limiting to prevent damage to host devices due to faulty load conditions. these analog switches have a low 0.2 ? on-resistance and operate from 2.3v to 5.5v input voltage range. they are avail- able with guaranteed 200ma, 250ma, and 300ma cur- rent limits, making them ideal for sdio and other load switching applications. when the switch is on and a load is connected to the port, a guaranteed blanking time of 14ms ensures that the transient voltages settle down. if after this blanking time the load current is greater than the current limit, the max4789, max4791, and max4793 enter a latch- off state where the switch is turned off and flag is issued to the microprocessor. the switch can be turned on again by cycling the power or the on pin. the max4790, max4792, and MAX4794 have an autoretry feature where the switch turns off after the blanking time and then continuously checks to see if the overload condition is present. the switch remains on after the overload condition disappears. the max4789?ax4794 are available in 6-pin 3mm x 3mm tdfn and tiny space-saving 4-pin sot143 pack- ages. the max4789/max4791/max4793 are also avail- able in a tiny 5-pin sot23 package. for lower current current-limiting switches, refer to the max4785?ax4788 data sheet. applications pdas and palmtop devices cell phones gps systems hand-held devices sdio features ? guaranteed current limit: 200ma, 250ma, 300ma ? thermal-shutdown protection ? reverse current protection ? 0.2 ? on-resistance ? 14ms guaranteed blanking time ? flag function (max4789/max4791/max4793) ? 80? supply current ? 8? latch-off current (max4789/max4791/max4793) ? 0.01? shutdown current ? 2.3v to 5.5v supply range ? undervoltage lockout ? fast current-limit response time (5?) ? tdfn and sot23/sot143 packages max4789?ax4794 200ma/250ma/300ma current-limit switches ________________________________________________________________ maxim integrated products 1 ordering information 2.3v to 5.5v in out flag gnd on p to sdio port max4789 max4791 max4793 typical operating circuit 19-2663; rev 2; 2/05 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. * ep = exposed pad. ordering information continued at end of data sheet. selector guide appears at end of data sheet. part temp range pin-package top mark max4789 eus-t -40? to +85? 4 sot143-4 kafe max4789euk-t -40? to +85? 5 sot23-5 aeac max4789ett -40? to +85? 6 tdfn-ep* abo max4790 eus-t -40? to +85? 4 sot143-4 kaff max4790ett -40? to +85? 6 tdfn-ep abp gnd flag pin configurations continued at end of data sheet. 15 out in max4789 max4791 max4793 sot23 top view 2 34 on on 14 in out max4789 MAX4794 sot143 23 gnd pin configurations
max4789?ax4794 200ma/250ma/300ma current-limit switches 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 2.3v to 5.5v, t a = -40? to +85?, unless otherwise noted. typical values are at v in = 3.3v, t a = +25?.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, on, flag , out to gnd .....................................-0.3v to +6v out short circuit to gnd .................................internally limited continuous power dissipation (t a = +70?) 4-pin sot143 (derate 4.0mw/? above +70?)..........320mw 5-pin sot23 (derate 7.1mw/? above +70?)............571mw 6-pin tdfn (derate 24.4mw/? above +70?).........1951.2mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units operating voltage v in 2.3 5.5 v v in = +2.3v to +5.0v 80 120 quiescent current i q v on = v in , i out = 0, switch on v in = +5.0v to +5.5v 160 ? latch-off current (note 2) i latch v on = v in , after an overcurrent fault (max4789/max4791/max4793) 815a shutdown current i shdn v on = 0v 0.01 1 a max4789/max4790 200 300 max4791/max4792 250 375 forward current limit max4793/MAX4794 300 450 ma max4789/max4790 300 max4791/max4792 375 reverse current limit max4793/MAX4794 450 ma on input leakage v on = v in or gnd -1 +1 ? off switch leakage v on = 0v, v out = 0v 0.01 1 a undervoltage lockout uvlo rising edge 1.8 2.2 v undervoltage lockout hysteresis 100 mv t a = +25?, i out = 100ma 0.2 0.4 on-resistance r on t a = - 40 c to + 85c , i ou t = 100m a 0.5 ? on input logic high voltage v ih 2.0 v on input logic low voltage v il 0.8 v flag output logic low voltage i s in k = 1m a ( m ax 4789/m ax 4791/m ax 4793) 0.4 v flag output high leakage current v in = v flag = 5.5v (max4789/max4791/max4793) 1a thermal shutdown 150 ? thermal-shutdown hysteresis 15 ? dynamic turn-on time (note 3) v on from low to high; i out = 10ma, c l = 0.1? 100 ? turn-off time (note 3) v on from high to low; i out = 10ma, c l = 0.1? 40 ns
max4789?ax4794 200ma/250ma/300ma current-limit switches _______________________________________________________________________________________ 3 quiescent supply current vs. supply voltage max4789 toc01 supply voltage (v) supply current ( a) 5.5 5.0 4.0 4.5 3.0 3.5 2.5 10 20 30 40 50 60 70 80 90 100 0 2.0 v on = v in supply current vs. temperature max4789 toc02 temperature ( c) supply current ( a) 60 35 10 -15 20 40 60 80 100 120 0 -40 85 v on = v in v in = 5v v in = 3.3v latch-off current vs. temperature max4789 toc03 temperature ( c) latch-off ( a) 60 35 10 -15 1 2 3 4 5 6 7 8 9 10 11 12 13 15 14 0 -40 85 v on = v in v in = 5v v in = 3.3v 100 10 0.001 -40 85 shutdown supply current vs. temperature 0.01 0.1 1 max4789 toc04 temperature ( c) shutdown supply current (na) 60 35 10 -15 v cc = 5v v cc = 3.3v 10 -40 85 1 0.1 0.01 0.001 0.0001 shutdown leakage current vs. temperature max4789 toc05 temperature ( c) shutdown leakage current (na) 60 35 10 -15 v in = 5v v in = 3.3v latch-off leakage current vs. temperature max4789 toc06 temperature ( c) latch-off leakage current (na) 60 35 10 -15 0.001 0.01 0.1 1 10 100 0.0001 -40 85 v in = 5v v in = 3.3v typical operating characteristics (v in = 3.3v, t a = +25?, unless otherwise noted.) note 1: all parts are 100% tested at +25?. limits across the full temperature range are guaranteed by design and correlation. note 2: latch-off current does not include the current flowing into flag . note 3: the on time is defined as the time taken for the current through the switch to go from 0ma to full load. the off-time is define d as the time taken for the current through the switch to go from full load to 0ma. note 4: retry time is typically 7 times the blanking time. electrical characteristics (continued) (v in = 2.3v to 5.5v, t a = -40? to +85?, unless otherwise noted. typical values are at v in = 3.3v, t a = +25?.) (note 1) parameter symbol conditions min typ max units blanking time t blank overcurrent fault (figures 2, 3) 14 60 ms short-circuit current-limit response time v on = v in = 3.3v, short circuit applied to out 5s retry time (note 4) t retry max4790/max4792/MAX4794 (figure 2) 98 420 ms
max4789?ax4794 200ma/250ma/300ma current-limit switches 4 _______________________________________________________________________________________ normalized on-resistance vs. temperature max4789 toc07 temperature ( c) normalized r on 60 35 10 -15 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 -40 85 v cc = 5v output current vs. output voltage max4789 toc08 v in - v out (v) output current (ma) 3.0 2.7 2.1 2.4 0.6 0.9 1.2 1.5 1.8 0.3 50 100 150 200 250 300 350 400 450 500 0 0 3.3 max4793/MAX4794 max4789/max4790 max4791/max4792 switch turn-on/off times vs. temperature max4789 toc09 temperature ( c) turn-on/off times ( s) 60 35 10 -15 0.01 0.1 1 10 100 1000 0.001 -40 85 i load = 10ma off on v cc = 3.3v v cc = 5v flag-blanking timeout vs. temperature max4789 toc10 temperature ( c) flag-blanking time (ms) 60 35 10 -15 25 30 35 40 45 50 20 -40 85 current-limit response max4789 toc11 40 s/div v in 2v/div v on 2v/div i out 100ma/div v in = 3.3v c in = 1 f c out = 1 f current-limit response max4789 toc12 20 s/div v in = v on 1v/div i out 100ma/div v in = v on c in = 1 f c out = 1 f typical operating characteristics (continued) (v in = 3.3v, t a = +25?, unless otherwise noted.)
max4789?ax4794 200ma/250ma/300ma current-limit switches _______________________________________________________________________________________ 5 pin description switch turn-on time response max4789 toc14 100 s/div v on 1v/div i out 10ma/div current-limit response (out shorted to gnd) max4789 toc13 40 s/div v in 2v/div v out 2v/div i out 5a/div c in = 1 f c out = 1 f typical operating characteristics (continued) (v in = 3.3v, t a = +25?, unless otherwise noted.) pin tdfn max4789 max4791 max4793 tdfn max4790 max4792 MAX4794 5-sot23 max4789 max4791 max4793 4-sot143 max4789 MAX4794 name function 14 flag fault output. this open-drain output goes low when the device stays in forward or reverse current limit for more than the blanking time period. flag is high impedance when a fault is not present or when on is low. 2 2 2 2 gnd ground 3 3 3 3 on active-high switch on input. a logic high turns the switch on. 4 1, 4 n.c. no connection. not internally connected. 5 5 1 4 in input. bypass with a 0.1? ceramic capacitor to ground. 6 6 5 1 out switch output. bypass with a 0.1? ceramic capacitor to ground. flag-blanking response max4789 toc16 4ms/div flag 2v/div i out 100ma/div v in 2v/div v on 2v/div switch turn-off time response max4789 toc15 200ns/div v on 2v/div i out 10ma/div
max4789?ax4794 detailed description the max4789?ax4794 are forward/reverse current- limited switches that operate from a 2.3v to 5.5v input voltage range and guarantee a 200ma, 250ma, and 300ma minimum current-limit threshold for different options. the voltage drop across an internal sense resistor is compared to two reference voltages to indi- cate a forward or reverse current-limit fault. when the load current exceeds the preset current limit for greater than the fault-blanking time, the switch opens. the max4790, max4792, and MAX4794 have an autoretry function that turns on the switch again after an internal retry time expires. if the faulty load condition is still present after the blanking time, the switch turns off again and the cycle is repeated. if the faulty load con- dition is not present, the switch remains on. the max4789, max4791, and max4793 do not have the autoretry option and the switch remains in latch-off mode until the on pin or the input power is cycled from high to low and then high again. the undervoltage lockout (uvlo) circuit prevents erro- neous switch operation when the input voltage goes too low during startup conditions. reverse current protection the max4789?ax4794 limit the reverse current (v out to v in ) from exceeding the maximum i rev value. the switch is shut off and flag is asserted (max4789/ max4791/max4793) if the reverse current-limit condition persists for more than the blanking time. this feature pre- vents excessive reverse currents from flowing through the device. switch-on/off control toggle on high to enable the current-limited switches. the switches are continuously on, only if v in exceeds the uvlo threshold (typically 2v) and there is no fault. when a forward/reverse current fault is present or the die exceeds the thermal-shutdown temperature of +150?, out is internally disconnected from in and the supply current decreases to 8? (latch off). the switch is now operating in one of its off states. the switch-off state also occurs when driving on low, thus reducing the supply current (shutdown) to 0.01?. table 1 illustrates the on/off state of the max4789?ax4794 current-limit switches. flag indicator the max4789, max4791, and max4793 feature a latched fault output, flag . whenever a fault is activat- ed, it latches flag output low and also turns the switch 200ma/250ma/300ma current-limit switches 6 _______________________________________________________________________________________ n blanking time circuitry reverse current detector forward current detector n +2.0v flag out in on gnd max4789/max4791/ max4793 only logic auto- retry max4789?ax4794 undervoltage lockout figure 1. functional diagram
off. flag is an open-drain output transistor and requires an external pullup resistor from flag to in. during shut- down (on is low), the pulldown on flag output is released in order to limit power dissipation. flag goes low when any of the following conditions occur: the die temperature exceeds the thermal-shutdown temperature limit of +150?. the device is in current limit for more than the fault- blanking period. ? in is below uvlo threshold. autoretry (max4790/max4792/MAX4794) when the forward or reverse current-limit threshold is exceeded, t blank timer begins counting (figure 2). the timer resets if the overcurrent 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 latched off. at the end of t retry , the switch is turned on again. if the fault still exists, the cycle is repeated. if the fault has been removed, the switch stays on. the autoretry feature saves system power in the case of an 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 switch sees the equivalent load current times duty cycle or i supply = i load ? t blank /(t blank + t retry ). with a typical t blank = 37ms and typical t retry = 259ms, the duty cycle is 12%, which results in an 88% power savings over the switch being on the entire time. the duty cycle is consistent across the process and devices. latch off (max4789/max4791/max4793) when the forward or reverse current-limit threshold is exceeded, t blank timer begins counting. the timer resets if the overcurrent condition disappears before t blank has elapsed. the switch is shut off if the over- current condition continues up to the end of the blank- ing time. reset the switch by either toggling on (figure 3a) or cycling the input voltage below uvlo, typically 2v (figure 3b). fault blanking the max4789?ax4794 feature 14ms (min) fault blank- ing. fault blanking allows current-limit faults, including momentary short-circuit faults that occur when hot swapping 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 counter starts. if the load-transient fault persists beyond the fault-blanking timeout, the max4789/max4791/ max4793 flag asserts low. load-transient faults less than t blank do not cause a flag output assertion. only current-limit faults are blanked. a thermal fault and input voltage drops below the uvlo threshold cause flag to assert immediately and do not wait for the blanking time. thermal shutdown the max4789?ax4794 have a thermal shutdown fea- ture to protect the devices from overheating. the switch turns off and flag goes low immediately (no fault blank- ing) when the junction temperature exceeds +150?. the switch turns back on when the device temperature drops approximately 15?. max4789?ax4794 200ma/250ma/300ma current-limit switches _______________________________________________________________________________________ 7 on fault switch on/off supply current mode low x off shutdown high undervoltage lockout off shutdown high thermal off immediately (t blank period does not apply) latch off off after t blank period has elapsed latch off high current limit on during t blank period, off during t retry period for the max4790, max4792, and MAX4794; cycle repeats until fault is removed see the autoretry section table 1. max4789?ax4794 switch truth table load current switch status t blank off on t retry current limit short condition removed t blank t blank figure 2. max4790/max4792/MAX4794 autoretry fault blanking diagram
max4789?ax4794 applications information input capacitor to limit the input voltage drop during momentary output short-circuit conditions, connect a capacitor from in to gnd. a 0.1? 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 capacitance connect a 0.1? capacitor from out to gnd. this capacitor helps prevent inductive parasitics from pulling out negative during turn-off, thus preventing the max4789?ax4794 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 a faulty load condition. the maximum capacitive load value that can be driven from out is obtained by the following formula: 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 (no more than 5mm). in and out pins 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 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: where v in = 5.5v, i out = 450ma, t blank = 14ms, and t retry = 98ms. attention must be given to the max4789, max4791, and max4793 where the latch-off condition must be manually reset by toggling on from high to low. if the latch-off time duration is not sufficiently high, it is possi- ble for the device to reach the thermal-shutdown threshold and never be able to turn the device on until it cools down. chip information transistor count: 1408 process: bicmos p vi t tt mw max in max out max blank retry blank = + = __ 302 c it v max fwd min blank min in < __ 200ma/250ma/300ma current-limit switches 8 _______________________________________________________________________________________ load current switch status on pin voltage t blank t blank off on (a) (b) uvlo load current switch status in pin voltage off on t blank t blank flag pin status flag pin status figure 3. max4789/max4791/max4793 latch-off fault blanking
max4789?ax4794 200ma/250ma/300ma current-limit switches _______________________________________________________________________________________ 9 selector guide part pin- package c u r r en t l im it ( m a ) f l a g f u n c t io n auto- retry max4789eus 4 sot143 200 no no max4789euk 5 sot23 200 yes no max4789ett 6 tdfn 200 yes no max4790eus 4 sot143 200 no yes max4790ett 6 tdfn 200 no yes max4791eus 4 sot143 250 no no max4791euk 5 sot23 250 yes no max4791ett 6 tdfn 250 yes no max4792eus 4 sot143 250 no yes max4792ett 6 tdfn 250 no yes max4793eus 4 sot143 300 no no max4793euk 5 sot23 300 yes no max4793ett 6 tdfn 300 yes no MAX4794eus 4 sot143 300 no yes MAX4794ett 6 tdfn 300 no yes gnd n.c. 1 out *( ) for the max4790, max4792, and MAX4794. in flag (n.c.) max4789 MAX4794 3mm x 3mm tdfn top view 2 3 6 5 4 on pin configurations (continued) ordering information (continued) part temp range pin-package top mark max4791 eus-t -40? to +85? 4 sot143-4 kafg max4791euk-t -40? to +85? 5 sot23-5 aeae max4791ett -40? to +85? 6 tdfn-ep* abq max4792 eus-t -40? to +85? 4 sot143-4 kafh max4792ett -40? to +85? 6 tdfn-ep* abr max4793 eus-t -40? to +85? 4 sot143-4 kafi max4793euk-t -40? to +85? 5 sot23-5 aeag max4793ett -40? to +85? 6 tdfn-ep* abs MAX4794 eus-t -40? to +85? 4 sot143-4 kafj MAX4794ett -40? to +85? 6 tdfn-ep* abt * ep = exposed pad.
max4789?ax4794 200ma/250ma/300ma current-limit switches 10 ______________________________________________________________________________________ sot-143 4l.eps e 1 1 21-0052 package outline, sot-143, 4l package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)
max4789?ax4794 200ma/250ma/300ma current-limit switches ______________________________________________________________________________________ 11 package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) sot-23 5l .eps e 1 1 21-0057 package outline, sot-23, 5l
max4789?ax4794 200ma/250ma/300ma current-limit switches 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. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2005 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) 6, 8, &10l, dfn thin.eps l c l c pin 1 index area d e l e l a e e2 n g 1 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm -drawing not to scale- k e [(n/2)-1] x e ref. pin 1 id 0.35x0.35 detail a b d2 a2 a1 common dimensions symbol min. max. a 0.70 0.80 d 2.90 3.10 e 2.90 3.10 a1 0.00 0.05 l 0.20 0.40 pkg. code n d2 e2 e jedec spec b [(n/2)-1] x e package variations 0.25 min. k a2 0.20 ref. 2.300.10 1.500.10 6 t633-1 0.95 bsc mo229 / weea 1.90 ref 0.400.05 1.95 ref 0.300.05 0.65 bsc 2.300.10 8 t833-1 2.00 ref 0.250.05 0.50 bsc 2.300.10 10 t1033-1 2.40 ref 0.200.05 - - - - 0.40 bsc 1.700.10 2.300.10 14 t1433-1 1.500.10 1.500.10 mo229 / weec mo229 / weed-3 0.40 bsc - - - - 0.200.05 2.40 ref t1433-2 14 2.300.10 1.700.10 t633-2 6 1.500.10 2.300.10 0.95 bsc mo229 / weea 0.400.05 1.90 ref t833-2 8 1.500.10 2.300.10 0.65 bsc mo229 / weec 0.300.05 1.95 ref t833-3 8 1.500.10 2.300.10 0.65 bsc mo229 / weec 0.300.05 1.95 ref -drawing not to scale- g 2 2 21-0137 package outline, 6,8,10 & 14l, tdfn, exposed pad, 3x3x0.80 mm downbonds allowed no no no no yes no yes no

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