general description the max6342?ax6345 family of microprocessor (?) supervisory circuits monitors power supplies in digital sys- tems. these devices significantly improve system reliabili- ty and accuracy compared to separate ics or discrete components. the max6342?ax6345 provide factory-trimmed v cc reset threshold voltages from 2.33v to 4.63v and operatewith supply voltages between +1v and +5.5v. a +1.25v threshold detector allows for a power-fail warning, for low-battery detection, or for monitoring another power supply. the max6342 contains an mr input and an active-low push-pull reset. the max6343 and max6344are identical to the max6342 except they provide an active-low, open-drain reset and an active-high, push- pull reset, respectively. the max6345 provides a second reset output in place of the mr input to give it an active- high push-pull reset and an active-low push-pull reset.all of the devices are packaged in a miniature 6-pin sot23. applications portable computerstelecom equipment networking equipment portable/battery-powered equipment multivoltage systems embedded control systems features ? small 6-pin sot23 package ? precision factory-set v cc reset thresholds between 2.33v and 4.63v ? guaranteed reset valid to v cc = +1v ? 100ms min reset pulse width ? debounced cmos-compatible manual-resetinput ? voltage monitor for power-fail or low-batterywarning max6342?ax6345 6-pin ? reset circuit with power-fail comparator ________________________________________________________________ maxim integrated products 1 gnd pfi 16 5 v cc ( ) are for max6344 only. top view 234 reset (reset) pfo mr max6342max6343 max6344 sot23-6 selector guide 1 selector guide 2 19-1568; rev 2; 12/05 part max6342 _ut-t max6343 _ut-t max6344 _ut-t -40? to +125? -40? to +125? -40? to +125? temp range pin-package 6 sot23-66 sot23-6 6 sot23-6 note: the max6342?ax6345 are available with factory-set reset thresholds from 2.33v to 4.63v (see selector guides 1, 2).insert the letter corresponding to the desired nominal reset threshold into the blank following the part number. there is a 2500 piece order increment required for the sot package. sot top marks table appears at end of data sheet. devices are available in both leaded and lead-free packaging. specify lead-free by replacing ?t?with ?t?when ordering. pin configurations ordering information max6345 _ut-t -40? to +125? 6 sot23-6 part push-pull reset output open-drain reset output push-pull reset output max6342 ? max6343 ? max6344 ? max6345 ? ? manual-reset input ? ? ? typical operating circuit appears at end of data sheet. pin configurations continued at end of data sheet. suffix reset threshold (v) l 4.63 m 4.38 t 3.08 s 2.93 r 2.63 z 2.33 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. downloaded from: http:///
? max6342?ax6345 6-pin ? reset circuit with power-fail comparator 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics(v cc = +1.0v to +5.5v, t a = -40? to +125?, unless otherwise noted. typical values are at t a = +25? and v cc = +3v.) (note 1) 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. v cc to gnd ..............................................................-0.3v to +6v reset, reset (max6342/max6344/max6345) ......... -0.3v to (v cc + 0.3v) reset (max6343)................................................... -0.3v to +6v mr , pfi, pfo ..............................................-0.3v to (v cc + 0.3v) input current, v cc ..............................................................50ma output current, reset, reset ..........................................50ma continuous power dissipation (t a = +70?) 6-pin sot23 (derate 4mw/? above +70?).............320mw operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature range (soldering, 10s)..................... +300? v v cc > 1.2v, i sink = 100? 0.4 v ol reset and reset outputs drivecapability (note 2) t a = -40? to +85? 2.25 2.38 t a = -40? to +125? 2.21 2.45 max634_z max634_s max634_t max634_m t a = +25? t a = -40? to +125? t a = -40? to +85? t a = +25? 2.50 2.76 max634_r 2.59 2.63 2.67 2.55 2.70 2.30 2.33 2.36 t a = -40? to +125? t a = -40? to +85? t a = +25? t a = -40? to +125? 2.85 3.00 2.92 3.23 2.89 2.93 2.97 2.78 3.08 t a = -40? to +85? t a = +25? t a = -40? to +125? t a = -40? to +85? 3.03 3.08 3.13 4.25 4.50 4.16 4.56 3.00 3.15 t a = +25? t a = -40? to +125? t a = -40? to +85? t a = +25? 4.40 4.86 v max634_l 4.56 4.63 4.70 v th reset threshold 4.50 4.75 4.31 4.38 4.45 30 60 v cc = 5.5v, ta = -40 to +125? v cc = 3v, ta = -40 to +125? v cc = 5.5v, ta = -40 to +85? v cc = 3v, ta = -40 to +85? 25 50 t a = -40? to +125? t a = 0? to +70? v cc = v th to (v th - 100mv) ? no load conditions ? 20 v cc to reset delay 25 40 i cc supply current 1.2 5.5 v 1.0 5.5 v cc supply voltage range 30 50 units min typ max symbol parameter v cc > 2.7v, i sink = 1.2ma v cc > 4.5v, i sink = 3.2ma 0.4 0.3 v 0.8 ? v cc v cc > 1.2v, i source = 50? 0.8 ? v cc v cc > 2.7v, i source = 500? (max6342/max6345 only) 0.8 ? v cc v cc > 4.5v, i source = 800? (max6342/max6345 only) v oh downloaded from: http:///
max6342?ax6345 6-pin ? reset circuit with power-fail comparator _______________________________________________________________________________________ 3 electrical characteristics (continued)(v cc = +1.0v to +5.5v, t a = -40? to +125?, unless otherwise noted. typical values are at t a = +25? and v cc = +3v.) (note 1) t ypical operating characteristics (v pfi = v cc = +5v, t a = +25?, unless otherwise noted.) 0 10 5 2015 25 30 -40 10 -15 35 60 85 supply current vs. supply voltage and temperature max6342-01 temperature (?) supply current ( a) v cc = 5v v cc = 3.3v v cc = 2.5v v cc = 1v 0 0 1sec/div max6342-02 max6344l/max6345l reset output voltage vs. supply voltage v cc reset 1v/div 0 0 1sec/div max6342-03 max6342m/max6345m reset output voltage vs. supply voltage v cc reset 1v/div note 1: overtemperature limits are guaranteed by design and not production tested. note 2: apply to each part in accordance with threshold voltage, output configuration, and manual reset status selected. note 3: leakage parameters are guaranteed by design and not production tested. v ? 3 v overdrive = 15mv pfi to pfo delay 5 output source current ma 20 output sink current pfo output short-circuit current 0.8 ? v cc v cc = 4.5v, i source = 800? v oh pfo output voltage v 0.4 v cc = 4.5v, i sink = 3.2ma v ol pfo output voltage pfi input threshold ? 0.2 mr to reset delay ? 0.1 mr glitch rejection ? 1 mr minimum pulse width k ? 60 open-drain reset output leakage current (note 3) i lkg 1 ? mr input low v il 0.3 ? v cc v mr input high v ih 0.7 ? v cc v mr pull-up resistance max6343 only, v cc > v th(max) parameter symbol min typ max units conditions pfi leakage current (note 3) 1.2 1.25 1.3 t a = -40? to +85? t a = -40? to +125? ?.01 ?5 t a = -40? to +85? t a = -85? to +125? v 1.15 1.35 na ?00 reset timeout period t rp 100 180 280 ms t a = -40? to +85? t a = -40? to +125? 80 360 downloaded from: http:///
max6342?ax6345 6-pin ? reset circuit with power-fail comparator 4 _______________________________________________________________________________________ 0 21 43 5 6 02 13 4 5 6 max6342-04 supply voltage (v) pfo output-voltage high vs. supply voltage pfo (v) r l = 10k ? 0.20 0.30 0.35 0.25 0.450.40 0.50 0.55 0.60 02 13 4 5 6 max6342-05 supply voltage (v) pfo output-voltage low vs. supply voltage pfo (v) r l = 1k ? 10 s/div max6342-06 max6344/max6345 reset response time v cc reset 0 4v 5v 4v 2 s/div max6342-07 max6342/max6345 reset response time v cc 0 4v 5v 4v reset 5v t ypical operating characteristics (continued) (v pfi = v cc = +5v, t a = +25?, unless otherwise noted.) pin description max6344 1 1 supply voltage 2 2 ground max6342 3 3 power-fail voltage monitor input. when pfi is < 1.25v, pfo goes low. connect pfi to gnd or v cc when not used. 4 4 power-fail voltage monitor output function pin name 1 2 max6343 3 4 max6345 1 2 3 4 v cc gnd pfi pfo downloaded from: http:///
max6342?ax6345 6-pin ? reset circuit with power-fail comparator _______________________________________________________________________________________ 5 max6344 max6342 6 active-high push-pull reset output. it remains high for 180msafter v cc rises above the reset threshold or mr goes from low to high. 6 active-low reset output. push-pull for max6342/max6345.open-drain for max6343. it remains low for 180ms after v cc rises above the reset threshold or mr goes from low to high. 5 5 manual-reset input. pull low to force a reset. reset or reset remains active as long as mr is low and for the reset timeout period after mr goes high. leave unconnected or connect to v cc if unused. pin description (continued) max6343 6 5 max6345 6 5 reset reset mr function pin name _______________detailed description reset output a ?? reset input starts the ? in a known state. these? supervisory circuits assert reset to prevent code- execution errors during power-up, power-down, or brownout conditions. reset and reset are guaranteed to be asserted at a valid logic level for v cc > +1v (see the electrical char- acteristics table). once reset asserts, it remains asserted for at least 100ms (t rp ) after v cc rises above its threshold value or after mr returns high (figures 1 and 2). open-drain reset output the max6343 has an active-low, open-drain reset out-put. this output sinks current when reset is asserted. connect a pull-up resistor from reset to any positive supply voltage up to +5.5v (figure 3). select a resistorvalue large enough to register a logic low (see the elec- trical characteristics table), and small enough to regis- ter a logic high while supplying all input current andleakage paths connected to the reset line. a 10k ? pull-up is sufficient in most applications. manual reset the max6342/max6343/max6344s?manual-reset input( mr ) allows reset to be triggered by a pushbutton switch. the switch is effectively debounced by the 1 s min reset pulse width. mr is cmos-logic compatible. reset generator v cc 6 (reset) 5 reset 4 pfo 1.25v gnd 100k ? v th ( ) are for max6344 only. 1 mr 2 v cc 3 pfi max6342max6343 max6344 reset generator 6 reset 5 reset 4 pfo 1.25v gnd v th 1 2 v cc 3 pfi max6345 figure 1. max6342/max6343/max6344 functional diagram figure 2. max6345 functional diagram downloaded from: http:///
max6342?ax6345 power-fail comparator the power-fail comparator is useful for various purpos-es because the power-fail output ( pfo ) is independent of the reset output. the inverting input is internally con-nected to a +1.25v reference. to build an early-warning circuit for power failure, con- nect the pfi pin to a voltage divider (see the typical oper-ating circuit ). choose the voltage-divider ratio so that the voltage at pfi falls below +1.25v just before the+5v regulator drops out. use pfo to interrupt the ? to prepare for an orderly shutdown. applications information negative-going v cc transients the max6342?ax6345 supervisors are immune toshort-duration, negative-going v cc transients (glitches) that usually do not require the entire system to shut down. figure 4 shows typical transient duration vs. reset com- parator overdrive, for which the max6342?ax6345 do not generate a reset pulse. the graph was generated using a negative-going pulse applied to v cc , starting 0.5v above the actual reset threshold and ending belowit by the magnitude indicated (reset comparator over- drive). the graph indicates the maximum pulse width a negative-going v cc transient can have without causing a reset pulse. as the magnitude of the transient increas- es (goes further below the reset threshold), the maxi- mum allowable pulse width decreases. typically, a v cc transient that goes 100mv below the reset threshold and lasts 12? or less will not cause a reset pulse. a 1 f bypass capacitor mounted as close as possible to the v cc pin provides additional transient immunity. ensuring a valid reset output down to v cc = 0 the max6342?ax6345 are guaranteed to operateproperly down to v cc = +1v. in applications that require valid reset levels down to v cc = 0, a pulldown resistor to active-low outputs (max6342/max6345) and a pullupresistor to active-high outputs (max6344/max6345) ensure that the reset line is valid when the reset output is no longer sinking or sourcing current ( figures 5 and 6). 6-pin ? reset circuit with power-fail comparator 6 _______________________________________________________________________________________ max6343 v cc gnd reset reset p +5.0v +3.3v 10k ? v cc 160 100 120 140 0 1 100 1000 6040 20 80 reset comparator overdrive, v th - v cc (mv) maximum transient duration ( s) 10 max634_l/m max634_t/s/r/z figure 4. maximum transient duration magnitude rejection figure 3. open-drain reset output allows use with multiple supplies v cc v cc gnd 100k ? reset max6342max6345 v cc v cc gnd 100k ? reset max6344max6345 figure 5. ensuring reset valid to v cc = 0 on active-low push-pull outputs figure 6. ensuring reset valid to v cc = 0 on active-high push-pull outputs downloaded from: http:///
note that this method does not work with the open-drain output of the max6343. the resistor value used is notcritical, but it must be large enough not to load the reset output when v cc is above the reset threshold. for most applications, 100k ? is adequate. monitoring two supplies monitor another voltage by connecting a resistor- divider to pfi as shown in figure 7. the threshold voltage willthen be given by: v th(pfi) = 1.25[(r1 + r2) / r2] where v th(pfi) is the threshold at which the monitored voltage will trip pfo . a good rule of thumb for selecting the resistors is tochoose r2 between 250k ? and 500k ? and solve for r1. connect pfo to mr in applications that require reset to assert when the second voltage falls below its threshold. monitoring a negative voltage connect the circuit as shown in figure 8 to use thepower-fail comparator to monitor a negative supply rail. pfo stays low when v- is good. when v- rises to cause pfi to be above +1.25v, pfo goes high. by adding the resistors and transistor as shown, a high pfo triggers reset. as long as pfo remains high, the max6342/ max6343/max6344 will keep reset asserted. note thatthe accuracy of this circuit depends on the pfi thresh- old tolerance, the v cc line voltage, and the resistors. also, ensure that the voltage at pfi remains abovegnd. interfacing to ?s with bidirectional reset pins max6342?ax6345 6-pin ? reset circuit with power-fail comparator _______________________________________________________________________________________ 7 v cc v cc r1 r2 v+ gnd ( ) are for max6344 only. to p pfi mr pfo reset (reset) max6342max6343 max6344 figure 7. monitoring two supplies v cc v cc r1 r1 r2 r2 v- gnd ( ) are for max6344 only. v cc - 1.25v = 1.25v - v trip 100k ? 100k ? pfi mr pfo reset (reset) max6342max6343 max6344 v trip < 0 figure 8. monitoring a negative voltage v cc gnd buffered reset toother system components 4.7k ? reset max6342max6345 v cc gnd p reset figure 9. interfacing to ?s with bidirectional reset i/o sot top marks part sot top mark part sot top mark max6342lut-t aacp max6344lut-t aadq max6342mut-t aacq max6344mut-t aadr max6342tut-t aacr max6344tut-t aads MAX6342SUT-t aacs max6344sut-t aadt max6342rut-t aact max6344rut-t aadu max6342zut-t aacu max6344zut-t aadv max6343lut-t aacv max6345lut-t aadw max6343mut-t aacw max6345mut-t aadx max6343tut-t aacx max6345tut-t aady max6343sut-t aacy max6345sut-t aadz max6343rut-t aacz max6345rut-t aaea max6343zut-t aada max6345zut-t aaeb downloaded from: http:///
max6342?ax6345 6-pin ? reset circuit with power-fail comparator 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. 8 _____________________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. v cc pfimr pfo p reset unregulated dc pushbutton switch interrupt max6342 linear regulator reset v cc gnd pfi 16 5 v cc top view 234 reset reset pfo max6345 sot23-6 t ypical operating circuit pin configurations (continued) transistor count: 403 chip information 6lsot.eps package outline, sot 6l body 21-0058 1 1 g package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) downloaded from: http:///
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