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general description the max4826?ax4831 family of switches has internalcurrent limiting to prevent host devices from being damaged due to faulty load conditions. these analog switches have a low 0.7 on-resistance and operate from a +2.3v to +5.5v input voltage range. thesedevices are available with guaranteed 50ma and 100ma current limits, making them ideal for load- switching applications. in addition to the current-limit fault flag ( fflg ), an open-drain no-load flag indicator ( nold) notifies the system when the current through the switch is less than 10ma (max4826?ax4829), or5ma (max4830/max4831). 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 max4826/max4828/max4830 enter a latchoff state where the switch is turned off, and fflg is issued to the microprocessor. the switch can be turned on againby cycling the power or on. the max4827/max4829/max4831 have an autoretry feature where the switch turns off after the blanking time, and then continuously checks to see if the over- load condition is present. the current-limit fault flag ( fflg ) is issued and remains low until after the fault condition is removed. the switch remains on after theoverload condition disappears. the max4826?ax4831 operate over the extended -40? to +85? temperature range, and are available in a tiny space-saving, 1mm x 1.5mm, 6-pin ?fn package. features ? guaranteed current limit: 50ma, 100ma ? thermal shutdown protection ? reverse-current protection ? 0.7 on-resistance (max4826Cmax4831) ? 14ms guaranteed blanking time ? fault flag ( fflg ) ? no-load flag ( nold ) ? 65 a supply current ? 8 a latchoff current ? 0.01 a shutdown current ? +2.3v to +5.5v supply range ? undervoltage lockout ? fast current-limit response time ? 6-pin dfn package (1mm x 1.5mm) applications gps systemscell phones digital still cameras pdas and palmtop devices mp3 players max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn ___________________________________________________ _____________ maxim integrated products 1 ordering information/selector guide 19-3672; rev 1; 8/09 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part pin-package min full-load limit (a) max no-load limit (a) on-resistance ( ) t a = +25 c mode top mark max4826 elt+t 6 dfn 50 10 1 latchoff ak max4827 elt+t* 6 dfn 50 10 1 autoretry al max4828 elt+t* 6 dfn 100 10 1 latchoff am max4829 elt+t 6 dfn 100 10 1 autoretry an max4830 elt+t 6 dfn 50 5 2 latchoff ao max4830elt/v+t 6 dfn 50 5 2 latchoff ox max4831 elt+t* 6 dfn 50 5 2 autoretry ap note: all devices operate over the -40? to +85? operating range. t = tape and reel. *future product?ontact factory for availability. /v denotes an automotive qualified part. pin configuration appears at end of data sheet. downloaded from: http:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn 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, fflg , nold , out to gnd .........................-0.3v to +6v out short circuit to gnd .................................internally limited continuous power dissipation (t a = +70?) 6-pin ?fn (derate 2.1mw/? above +70?) .............168mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? 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) parameter symbol conditions min typ max units operating voltage v in 2.3 5.5 v v in = +2.3v to +5.0v 65 100 quiescent current i q v on = v in , i out = 0, switch on v in = +5.0v to +5.5v 120 ? latchoff current (note 2) i latch v on = v in = 3.3v, after an overcurrent fault (max4826/max4828/max4830) 81 5 a shutdown current i shdn v on = 0, i out = 0ma 0.01 1 a shutdown reverse leakage i shdnrv v on = 0, v in = +2.3v, v out = +5.5v 0.01 1 a (max4826/max4827/max4830/max4831)r l = 10 50 120 forward-current limit i fwd (max4828/max4829) r l = 5 100 240 ma v out - v in < 0.5v (max4826/max4827/max4830/max4831) 120 reverse-current limit i rev v out - v in < 0.5v (max4828/max4829) 240 ma max4826?ax4829 1.0 10.0 no-load threshold i nlth max4830/max4831 0.5 5.0 ma on input leakage i onlk v on = v in or gnd -1 +1 ? off-switch leakage i swlk v in = +5.5v, v on = 0, v out = 0 0.01 1 a undervoltage lockout uvlo rising edge 1.8 2.2 v undervoltage lockout hysteresis uvlo hys 100 mv (max4826?ax4829) 0.7 1.0 t a = +25?, i out = 20ma (max4830/max4831) 1.4 2.0 (max4826?ax4829) 1.3 on-resistance r on t a = -40? to +85?,i out = 20ma (max4830/max4831) 2.6 on input-logic-high voltage v ih 2.0 v on input-logic-low voltage v il 0.8 v fflg , nold output-logic-low voltage i sink = 1ma 0.4 v downloaded from: http:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn ___________________________________________________ ____________________________________ 3 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 fflg , nold output-high leakage current v in = v fflg = v nold = +5.5v 1 a thermal shutdown +150 ? thermal-shutdown hysterisis 15 ? dynamic turn-on time on from low to high; i out = 10ma, c l = 0.1? (note 3) 50 ? turn-off time on from high to low; i out =10ma, c l = 0.1? (note 3) 30 ns blanking time t blank overcurrent fault 14 60 ms short-circuit current-limitresponse time v on = v in = +3.3v, short circuit applied to out 5 s no-load-detection responsetime i out falling step signal from 15ma to 0ma, c l = 0.1? 60 ? retry time t retry overcurrent fault (figure 2) (note 4) 196 840 ms note 1: all parts are 100% tested at t a = +25?. limits at t a = -40? to +85? are guaranteed by design. note 2: latchoff current does not include the current flowing into fflg and nold . note 3: turn-on time is defined as the time taken for the current through the switch to go from 0ma to full load. turn-off time isdefined as the time taken for the current through the switch to go from full load to 0ma. note 4: retry time is typically 14x the blanking time. typical operating characteristics (v in = +3.3v, t a = +25?, unless otherwise noted.) quiescent supply current vs. supply voltage max4826 toc01 supply voltage (v) supply current ( a) 5.1 4.7 3.9 4.3 3.1 3.5 2.7 10 20 30 40 50 60 70 80 90 0 2.3 5.5 v on = v in v in = +2.3v to +5.5v temperature ( c) 60 35 10 -15 -40 85 quiescent supply current vs. temperature max4826 toc02 supply current ( a) 10 20 30 40 50 60 70 80 90 0 v on = v in v in = 5v v in = 3.3v 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 temperature ( c) 60 35 10 -15 -40 85 latchoff current vs. temperature max4826 toc03 latchoff current ( a) v in = 5v v in = 3.3v v on = v in downloaded from: http:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn 4 __________________________________________________ _____________________________________ typical operating characteristics (continued) (v in = +3.3v, t a = +25?, unless otherwise noted.) shutdown supply current vs. temperature max4826 toc04 temperature ( c) shutdown supply current (na) 0.001 0.01 0.1 1 10 0.0001 v in = 5v v in = 3.3v 60 35 10 -15 -40 85 shutdown leakage current vs. temperature max4826 toc05 temperature ( c) shutdown leakage current (na) 0.001 0.01 0.1 1 10 0.0001 v in = 5v v in = 3.3v 60 35 10 -15 -40 85 shutdown reverse leakage current vs. temperature max4826 toc06 temperature ( c) reverse leakage current (na) 0.001 0.01 0.1 1 10 0.0001 60 35 10 -15 -40 85 v on = v in = ov v out = 5v latchoff-leakage current vs. temperature max4826 toc07 temperature ( c) latchoff-leakage current (na) 0.001 0.01 0.1 1 10 0.0001 v in = 5v v in = 3.3v 60 35 10 -15 -40 85 temperature ( c) 60 35 10 -15 -40 85 normalized on-resistance vs. temperature max4826 toc08 normalized r on 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 v on = v in = 3.3v 0 100 50 200150 250 300 0 0.6 0.9 1.2 0.3 1.5 1.8 2.1 2.4 2.7 3.0 3.3 output current vs. output voltage max4826 toc09 v in - v out (v) output current (ma) max4828/max4829 max4826/max4827/max4830/max4831 switch turn-on/off times vs. temperature max4826 toc10 temperature ( c) turn-on/off times ( s) 0.01 0.1 1 10 100 0.001 60 35 10 -15 -40 85 i load = -10ma on off v in = 3.3v v in = 5v fflg-blanking timeout vs. temperature fflg-blanking time (ms) 15 20 25 30 35 4010 max4826 toc11 temperature ( c) 60 35 10 -15 -40 85 downloaded from: http:///
max4826?ax4831 typical operating characteristics (continued) (v in = +3.3v, t a = +25?, unless otherwise noted.) 50ma/100ma current-limit switches with no-load flag in ?fn _______________________________________________________________________________________ 5 current-limit response max4826 toc12 40 s/div v on = 3.3v v out = gnd c in = 1 f c out = 1 f v in 2v/div v on 2v/divi out 100ma/div current-limit response (out shorted to gnd) max4826 toc14 40 s/div v in 2v/divv out 2v/divi out 2a/div current-limit response max4826 toc13 20 s/div v on = 3.3v v out = gnd c in = 1 f c out = 1 f v in = v on 1v/divi out 100ma/div switch turn-on-time response max4826 toc15 100 s/div v in = 3.3v i load = 10ma v on 2v/divi out 100ma/div switch turn-off-time response max4826 toc16 100ns/div v on 2v/divi out 10ma/div v in = 3.3v i load = 10ma fflg-blanking response max4826 toc17 4ms/div v in 2v/div v on 2v/divi out 100ma/div fflg 2v/div downloaded from: http:///
max4826?ax4831 detailed description the max4826?ax4831 are forward-/reverse-current-limited switches that operate from a +2.3v to +5.5v input voltage range and guarantee a 50ma and 100ma minimum current-limit threshold for different options. the voltage drop across an internal sense resistor is compared to two reference voltages to indicate a for- ward- or reverse-current-limit fault. when the load cur- rent exceeds the preset current limit for greater than the fault-blanking time, the switch opens. the max4827/max4829/max4831 have an autoretry function that turns on the switch again after an internal retry time expires. if the faulty load condition is still pre- sent after the blanking time, the switch turns off again and the cycle is repeated. if the faulty load condition is not present, the switch remains on. the max4826/max4828/max4830 do not have the autoretry option, and the switch remains in latchoff mode until on 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 max4826?ax4831 limit the reverse current (v out to v in ) from exceeding the maximum i rev value. the switch is shut off and fflg is asserted if the reverse- current-limit condition persists for more than the blank-ing time. this feature prevents excessive reverse cur- rents 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? (latchoff). 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 max4826 max4831 current-limit switches. 50ma/100ma current-limit switches with no-load flag in ?fn 6 __________________________________________________ _____________________________________ pin description pin name function 1 in input. bypass in with a 0.1? ceramic capacitor to ground. 2 gnd ground 3 out switch output. bypass out with a 0.1? capacitor to ground 4 fflg current-limit fault output. fflg is an open-drain output. fflg goes low when the device stays in forward- or reverse-current limit for more than the blanking time period. fflg is high impedance when a fault is not present or when on is low. 5 nold no-load flag output. nold is an open-drain output. nold goes low when a load of less than 10ma (max4826?ax4829) or 5ma (max4830/max4831) is delivered to the output. nold is high impedance when a fault is not present or when on is low. 6 on active-high switch-on input. drive on high to turn the switch on. on fault switch on/off supply current mode low x off shutdown high undervoltage lockout off latchoff high thermal off immediately (t blank period does not apply). latchoff off after t blank period has elapsed. latchoff high current limit on during t blank period, off during t retry period for the max4827/max4829/max4831. cycle repeats until fault is removed. see the autoretr (max4827/ max4829/max4831) section table 1. max4826Cmax4831 switch truth table downloaded from: http:///
fflg indicator the max4826?ax4831 feature a current-limit faultoutput, fflg . whenever a current-limit fault is activat- ed, fflg goes low and the switch turns off. fflg is an open-drain output transistor and requires an externalpullup resistor from fflg to in. during shutdown (on is low), the pulldown on the fflg output is released to limit power dissipation. fflg goes low when any of the following conditions occur: ?the die temperature exceeds the thermal shut- down temperature limit of +150?. ?the device is in current limit for more than the fault-blanking period. ?v in is below the uvlo threshold. nold indicator the max4826?ax4831 feature a no-load flag output,nold (figure 1). this output is pulled low every time the current coming out of the switch is less than 10ma(max4826?ax4829), or 5ma (max4830/max4831). nold is an open-drain output transistor and requires an external pullup resistor from nold to a supply up to +5.5v. current through the switch is intended to bepositive (from in to out), and for currents that are large in magnitude but negative in sign (out to in), nold asserts low. for options with the autoretry fea- ture (max4827/max4829/max4831), the nold output is high impedance during the t retry period when a for- ward-current-limit condition is present. however, nold is pulled low if a reverse current-limit condition is pre-sent during the t retry period. a constant time filter is present at the output of nold that gives a 60? delay when a no-load condition is asserted. deassertion ofnold is not delayed. during shutdown (on is low), the pulldown on nold is released to limit power dissipation. autoretry (max4827/max4829/max4831) when the forward- or reverse-current-limit threshold isexceeded, the t blank timer begins counting (figure 2). the timer resets if the overcurrent condition disappears max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn ___________________________________________________ ____________________________________ 7 load current switch status t blank t blank off on on pin voltage (a) (b) uvlo fflg pin status load current switch status off on in pin voltage fflg pin status t blank t blank figure 3. max4826/max4828/max4830 latchoff fault blanking figure 2. max4827/max4829/max4831 autoretry fault blanking diagram load current switch status t blank off on t retry current limit short condition removed t blank t blank v in v on load current nold status no-load threshold current limit 60 s 60 s figure 1. max4826?ax4831 no-load flag response downloaded from: http:///
max4826?ax4831 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 oft retry , the switch is turned on again. if the fault still exists, the cycle is repeated. if the fault has beenremoved, 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 cur-rent limit. during t retry , when the switch is off, no cur- rent flows through the switch. instead of observing thefull load current, the switch sees the equivalent load current, multiplied by the duty cycle or i supply = i load x t blank / (t blank + t retry ). with a typical t blank = 37ms and typical t retry = 518ms, the duty cycle is 6% which results in a 94% power savings, as opposed tothe switch being on the entire time. the duty cycle is consistent across the process and devices. latchoff (max4826/max4828/max4830) when the forward- or reverse-current-limit threshold isexceeded, the t blank timer begins counting. the timer resets if the overcurrent condition disappears beforet 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 max4826?ax4831 feature 14ms (min) fault blank-ing. fault blanking allows current-limit faults, including momentary short-circuit faults that occur when hot swap- ping a capacitive load. fault blanking also ensures that no fault is issued during power-up. when a load transient causes the device to enter the current limit, an internal counter starts. if the load-transient fault persists beyond the fault-blanking timeout, fflg asserts low. load-tran- sient faults less than t blank do not cause fflg asser- tion. only current-limit faults are blanked. a thermal fault and input voltage drops below the uvlo threshold cause fflg to assert immediately. these faults do not wait for the blanking time. thermal shutdown the max4826?ax4831 have a thermal-shutdown fea-ture to protect the devices from overheating. the switch turns off and fflg goes low immediately (no fault blanking) when the junction temperature exceeds+150?. the switches with the autoretry feature turn back on when the device temperature drops approxi- mately 15?. the switches with the latchoff feature require on cycling. applications information input capacitor to limit the input voltage drop during momentary outputshort-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. thiscapacitor helps prevent inductive parasitics from pulling out negative during turn-off, thus preventing the max4826?ax4831 from tripping erroneously. if the load capacitance is too large, current may not have enough time to charge the capacitance, and the device assumes that there is a faulty load condition. the maxi- mum 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_max = 5.5v, i out_max = 240ma, t blank = 37ms, and t retry = 518ms. attention must be given to the max4826/max4828/max4830 where the latchoff condition must be manually reset by toggling on from high to low. if the latchoff time duration is not sufficiently 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. p vi t tt mw max in max out max blank retry blank < + = __ 88 c it v max fwd min blank min in < __ 50ma/100ma current-limit switches with no-load flag in ?fn 8 __________________________________________________ _____________________________________ downloaded from: http:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn ___________________________________________________ ____________________________________ 9 6 on 5 nold 4 fflg 12 gnd 3 out max4826 max4831 in dfn top view of bottom leads pin configuration +2.3v to +5.5v in fflg gnd on p to external port max4826max4831 out nold typical operating circuit n blanking-time circuitry reverse-current detector forward-current detector n +2.0v fflg out in on gnd logic auto- retry max4826?ax4831 undervoltage lockout nold gnd n gnd current < 5ma detector (max4830/max4831)current < 10ma detector (max4826?ax4829) functional diagram downloaded from: http:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn 10 _________________________________________________ _____________________________________ chip information process: bicmos package type package code document no. 6 ?fn l611+1 21-0147 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:///
max4826?ax4831 50ma/100ma current-limit switches with no-load flag in ?fn 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 ____________________ 11 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 5/05 initial release. 1 8/09 ? added new automotive part max4830elt/v+t to the ordering information/selector guide table. ? added +t to all the part numbers in the ordering information/selector guide table. 1 downloaded from: http:///

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