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general description the max6736?ax6745 are low-power dual-/triple- voltage microprocessor (?) supervisors. these devices assert a reset if any monitored supply falls below its factory-trimmed or adjustable threshold and maintain reset for a minimum timeout period after all supplies rise above their thresholds. the integrated dual/triple supervisory circuits significantly reduce size and power compared to separate ics or discrete com- ponents. the low supply current of 6? makes these devices ideal for portable equipment. the max6736/max6737 are dual fixed-voltage ? supervisors with a manual reset input. the max6738/ max6739 have one fixed and one adjustable reset threshold and a manual reset input. the max6740/ max6743 are triple-voltage ? supervisors with two fixed and one user-adjustable reset threshold inputs. the max6741/max6744 are dual-voltage ? supervi- sors with a power-ok (pok) output ideal for power- supply sequencing. the max6742/max6745 monitor the primary v cc supply and have an independent power-fail comparator. the max6736?ax6745 monitor i/o supply voltages (v cc 1) from 1.8v to 5.0v and core supply voltages (v cc 2) from 0.9v to 3.3v with factory-trimmed reset threshold voltage options (table 1). an external adjustable rstin input option allows monitoring volt- ages down to 0.5v. a variety of push-pull or open-drain reset outputs along with manual reset input and power-fail input/output fea- tures are available (see the selector guide ). the max6736?ax6745 are offered in a space-saving 5-pin sc70 package and operate over the -40? to +85? temperature range. applications features dual-/triple-supply reset voltage monitors precision factory-set reset thresholds for monitoring from 0.9v to 5.0v adjustable reset input down to 0.488v 150ms and 1200ms (min) reset timeout period options v cc 1 power-ok output for power-supply sequencing applications (max6741/max6744) power-fail input/power-fail output (max6742/max6745) 6? supply current tiny sc70 package max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits ________________________________________________________________ maxim integrated products 1 part voltage monitors open-drain reset push-pull reset manual reset power-fail input/ output pok output rstin input max6736 2 fixed x x max6737 2 fixed xx max6738 1 fixed, 1 adj x x x selector guide ordering information 19-2531; rev 0; 10/02 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. part temp range pin-package max6736 xk_ _d_-t -40 c to +85 c 5 sc70-5 max6737 xk_ _d_-t* -40 c to +85 c 5 sc70-5 note: the first ? _?or ??are placeholders for the threshold voltage levels of the devices. desired threshold levels are set by the part number suffix found in tables 1 and 2. the ??after the d is a placeholder for the reset timeout period suffix found in table 3. for example, the max6736xkltd3-t is a dual-volt- age supervisor v th 1 = 4.625v, v th 2 = 3.075v, and a 150ms minimum reset timeout period. all devices are available in tape-and-reel only. there is a 2500-piece minimum order increment for standard versions (see table 1). sample stock is typically held on standard versions only. nonstandard versions require a minimum order increment of 10,000 pieces. contact factory for availability. portable/battery- powered equipment multivoltage systems notebook computers controllers pdas gps equipment pos equipment ordering information continued at end of data sheet. selector guide continued at end of data sheet. pin configurations appear at end of data sheet. typical application circuits appear at end of data sheet. functional diagram appears at end of data sheet. * manual reset detect on reset output. * future product contact factory for availability.
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 1.2v to 5.5v, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (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. v cc 1 , v cc 2, pok1 to gnd ......................................-0.3v to +6v open-drain reset , pfo to gnd.............................-0.3v to +6v push-pull reset to gnd..........................-0.3v to (v cc 1 + 0.3v) mr , rstin, pfi to gnd............................-0.3v to (v cc 1 + 0.3v) input/output current, all pins .............................................20ma continuous power dissipation (t a = +70 c) 5-pin sc70 (derate 3.1mw/ c above +70 c) ..............247mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units t a = -40 c to 0 c 1.2 5.5 operating voltage range v cc 1, v cc 2 t a = 0 c to +85 c 1.0 5.5 v v cc 1 = 3.3v, v cc 1 > v cc 2, no load, reset not asserted 510 v cc 1 supply current i cc 1 v cc 1 = 1.8v, v cc 1 < v cc 2, no load, reset not asserted 510 a v cc 2 = 1.8v, v cc 2 < v cc 1, no load, reset not asserted 12 v cc 2 supply current i cc 2 v cc 2 = 3.3v, v cc 2 > v cc 1, no load, reset not asserted 10 20 a t a = 0 c to +85 c 4.500 4.625 4.750 max67_ _l t a = -40 c to +85 c 4.425 4.825 t a = 0 c to +85 c 4.250 4.375 4.500 max67_ _m t a = -40 c to +85 c 4.175 4.575 t a = 0 c to +85 c 3.000 3.075 3.150 max67_ _t t a = -40 c to +85 c 2.950 3.200 t a = 0 c to +85 c 2.850 2.925 3.000 max67_ _s t a = -40 c to +85 c 2.800 3.050 t a = 0 c to +85 c 2.550 2.625 2.700 max67_ _r t a = -40 c to +85 c 2.505 2.745 t a = 0 c to +85 c 2.250 2.313 2.375 max67_ _z t a = -40 c to +85 c 2.213 2.413 t a = 0 c to +85 c 2.125 2.188 2.250 max67_ _y t a = -40 c to +85 c 2.088 2.288 t a = 0 c to +85 c 1.620 1.665 1.710 max67_ _w t a = -40 c to +85 c 1.593 1.737 t a = 0 c to +85 c 1.530 1.575 1.620 reset threshold for v cc 1v th 1 max67_ _v t a = -40 c to +85 c 1.503 1.647 v
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = 1.2v to 5.5v, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units t a = 0 c to +85 c 3.000 3.075 3.150 max67_ _t t a = -40 c to +85 c 2.905 3.050 t a = 0 c to +85 c 2.850 2.925 3.000 max67_ _s t a = -40 c to +85 c 2.800 3.050 t a = 0 c to +85 c 2.550 2.625 2.700 max67_ _r t a = -40 c to +85 c 2.505 2.745 t a = 0 c to +85 c 2.250 2.313 2.375 max67_ _z t a = -40 c to +85 c 2.213 2.413 t a = 0 c to +85 c 2.125 2.188 2.250 max67_ _y t a = -40 c to +85 c 2.088 2.288 t a = 0 c to +85 c 1.620 1.665 1.710 max67_ _w t a = -40 c to +85 c 1.593 1.737 t a = 0 c to +85 c 1.530 1.575 1.620 max67_ _v t a = -40 c to +85 c 1.503 1.647 t a = 0 c to +85 c 1.350 1.388 1.425 max67_ _i t a = -40 c to +85 c 1.328 1.448 t a = 0 c to +85 c 1.275 1.313 1.350 max67_ _h t a = -40 c to +85 c 1.253 1.373 t a = 0 c to +85 c 1.080 1.110 1.140 max67_ _g t a = -40 c to +85 c 1.062 1.158 t a = 0 c to +85 c 1.020 1.050 1.080 max67_ _f t a = -40 c to +85 c 1.002 1.098 t a = 0 c to +85 c 0.810 0.833 0.855 max67_ _e t a = -40 c to +85 c 0.797 0.869 t a = 0 c to + 85 c 0.765 0.788 0.810 reset threshold for v cc 2v th 2 max67_ _d t a = -40 c to +85 c 0.752 0.824 v t a = 0 c to +85 c 0.476 0.488 0.500 rstin threshold (max6738/ max6739/max6740/max6743) v th-rstin t a = -40 c to +85 c 0.468 0.507 v rstin input current v rstin 0.1v (note 2) -10 +10 na reset threshold hysteresis v th 1, v th 2, rstin, pfi 0.5 % v cc 1 1.0v, i sink = 50a, t a = 0 c to +85 c 0.3 v cc 1 1.2v, i sink = 100a 0.3 v cc 1 2.13v, i sink = 1.2ma 0.3 reset , pok1 output low v ol v cc 1 4.25v, i sink = 3.2ma, 0.4 v v cc 1 2.38v, i source = 500a, output deasserted 0.8 v cc reset output high (push-pull) v oh v cc 1 4.75v, i source = 800a, output deasserted 0.8 v cc v
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 4 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = 1.2v to 5.5v, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units reset output open-drain leakage current (max6736/max6738) i lkg output not asserted low (note 2) 500 na pok1 output open-drain leakage output not asserted low (note 2) 500 na v cc reset delay t rd v cc 1, v cc 2, or rstin falling at 10mv/s from v th + 100mv to v th - 100mv 35 s max67_ _ _ _ xk_ _d3 150 225 300 v cc reset timeout period (note 3) t rp max67_ _ _ _ xk_ _ d7 1200 1800 2400 ms manual reset (max6736?ax6739 only) mr to v cc 1 internal pullup impedance 0.75 1.5 3.00 k ? mr timeout period t mrp both d3 and d7 timing options 150 225 300 ms mr minimum input pulse width t mpw 1s mr glitch rejection 100 ns v il 0.3 v cc 1 mr input voltage v ih 0.8 v cc 1 v mr to reset delay 300 ns v cc 1 power-ok output (max6741/max6744 only) pok1 timeout period t pokp 37.5 56.25 75.0 ms pushbutton reset (max6740/max6741/max6742 only) reset to v cc 1 internal pullup impedance 25 50 100 k ? manual reset detect debounce period t deb (note 4) 37.5 56.25 75.0 ms max67_ _ _ _ xk_ _d3 150 225 300 manual reset timeout period (note 3) t mrp max67_ _ _ _ xk_ _ d7 1200 1800 2400 ms manual reset minimum input pulse width t mpw (note 4) 1 s manual reset release detect threshold (note 4) 0.5 v cc 1 v manual reset glitch rejection (note 4) 100 ns manual reset to reset delay 300 ns
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits _______________________________________________________________________________________ 5 electrical characteristics (continued) (v cc = 1.2v to 5.5v, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units power-fail comparator (max6742/max6745 only) t a = 0 c to +85 c 0.476 0.488 0.500 power fail in threshold (note 5) v th-pfi t a = -40 c to +85 c 0.468 0.507 v power fail in current i pfi v pfi 0.1v (note 2) -10 +10 na v cc 1 1.53v, i sink = 500a 0.3 v cc 1 2.03v, i sink = 1.2ma 0.3 pfo output low v ol v cc 1 4.25v, i sink = 3.2ma 0.4 v pfi to pfo propagation delay t p pfi falling at 10mv/s from v th-pfi + 100mv to v th-pfi - 100mv or rising at 10mv/s from v th-pfi - 100mv to v th-pfi + 100mv (note 5) 35 s pfo startup delay to output valid (note 5) 5 ms note 1: all devices are 100% tested at t a = +25 c. all temperature limits are guaranteed by design. note 2: guaranteed by design. note 3: t rd timeout period begins after pok1 timeout period (t pokp ) and v cc 2 v th 2 (max) (max6741/max6744). note 4: refers to the manual reset function obtained by forcing the reset output low. note 5: v cc 1 1.6v. typical operating characteristics (t a = +25 c, unless otherwise noted.) supply current vs. temperature max6736-45 toc01 temperature ( c) supply current ( a) 60 40 20 0 -20 1 2 3 4 5 6 7 8 9 10 0 -40 80 v cc 1 = 3.3v, v cc 2 = 2.5v total i cc 1 i cc 2 supply current vs. temperature max6736-45 toc02 temperature ( c) supply current ( a) 60 40 20 0 -20 1 2 3 4 5 6 7 8 9 10 0 -40 80 v cc 1 = 2.5v, v cc 2 = 1.8v total i cc 1 i cc 2 supply current vs. temperature max6736-45 toc03 temperature ( c) supply current ( a) 60 40 20 0 -20 1 2 3 4 5 6 7 8 9 10 0 -40 80 v cc 1 = 1.8v, v cc 2 = 1.2v total i cc 1 i cc 2
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 6 _______________________________________________________________________________________ normalized v cc /pok1/mr timeout period vs. temperature max6736-45 toc04 temperature ( c) normalized v cc /pok1/mr reset timeout period 60 40 20 0 -20 0.989 0.994 0.999 1.004 1.009 1.014 1.019 0.984 -40 80 maximum v cc 1/v cc 2 transient duration vs. reset threshold overdrive max6736-45 toc05 reset threshold overdrive (mv) maximum v cc 1/v cc 2 transient duration ( s) 100 10 100 1000 10,000 0 10 1000 v cc 1 v cc 2 reset occurs above these lines normalized v cc reset threshold vs. temperature max6736-45 toc06 temperature ( c) normalized v cc reset threshold 60 40 20 0 -20 0.993 0.998 1.003 1.008 0.988 -40 80 normalized to +25 c v cc to reset output delay vs. temperature max6736-45 toc07 temperature ( c) v cc to reset output delay ( s) 60 40 20 0 -20 33.5 38.5 43.5 48.5 28.5 -40 80 100mv overdrive reset input to reset output delay vs. temperature max6736-45 toc08 temperature ( c) rstin to reset output delay ( s) 60 40 20 0 -20 25 30 35 20 -40 80 100mv overdrive power-fail input to power-fail output delay vs. temperature max6736-45 toc09 temperature ( c) pfi to pfo delay ( s) 60 40 20 0 -20 29 39 44 49 24 -40 80 100mv overdrive rising edge falling edge 34 typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.)
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits _______________________________________________________________________________________ 7 typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) mr to reset output delay max6736-45 toc10 100ns/div v mr 2v/div v reset 2v/div power-fail input to power-fail output delay max6736-45 toc11 10 s/div pfi 200mv/div pfo 2v/div v cc to reset output delay max6736-45 toc12 4 s/div v cc 200mv/div ac-coupled v reset 2v/div 0 100 200 300 400 500 045 23 1678910 output low voltage vs. sink current max6736-45 toc13 sink current (ma) output low voltage (mv) v cc = 3.3v 0 1 2 3 4 0 0.50 1.00 1.50 0.25 0.75 1.25 1.75 2.00 output high voltage vs. source current max6736-45 toc14 sourcing current (ma) output high voltage (v) v cc = 3.3v
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 8 _______________________________________________________________________________________ pin description pin max6736 max6737 max6738 max6739 max6740 max6743 max6741 max6744 max6742 max6745 name function 11111 reset reset output, push-pull or open drain active low. reset changes from high to low when any monitored power-supply input (v cc 1, v cc 2, rstin) drops below its selected reset threshold. it remains low until all monitored power-supply inputs exceed their selected reset thresholds for the v cc reset timeout period. reset is forced low if mr is low for at least the mr minimum input pulse width. it remains low for the mr reset timeout period after mr goes high. the push- pull output is referenced to v cc 1. the max6736/max6738 open-drain outputs require an external pullup resistor. the max6740/max6741/max6742 open-drain outputs have an internal 50k ? pullup resistor to v cc 1 and provide a manual reset function. 22222gnd ground 33 mr manual reset, active low. pull low for at least mr minimum input pulse width to force reset low. reset remains active as long as mr is low and for the mr reset timeout period after mr goes high. there is an internal 1.5k ? pullup resistor to v cc 1. 4 44 v cc 2 voltage input 1. power supply and input for the secondary p voltage reset monitor. 43 rstin adjustable reset threshold input. reset is asserted when rstin is below the internal 0.488v reference level. set the adjustable reset threshold with an external resistor-divider network. connect rstin to v cc 1 if unused. 55555v cc 1 voltage input 2. power supply and input for the primary p voltage reset monitor. 4 pfi power-fail comparator input. pfo is asserted when pfi is below 0.488v. pfo is deasserted without any reset timeout period when pfi goes above 0.488v. connect pfi to an external resistor network to set the desired monitor threshold. 3 pfo power-fail comparator output, open drain active low. pfo is asserted when pfi is below 0.488v. 3 pok1 v cc 1 power-ok output, open drain active high. pok1 remains low as long as v cc 1 is below v th 1. pok1 output goes high after v cc 1 exceeds v th 1 for the pok1 timeout period. pok1 logic is independent of the mr or v cc 2 inputs. the output can be used to control v cc 1-to-v cc 2 supply sequencing.
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits _______________________________________________________________________________________ 9 part no. suffix ( _ _ ) v cc 1 nominal voltage threshold (v) v cc 2 nominal voltage threshold (v) lt 4.625 3.075 ms 4.375 2.925 mr 4.375 2.625 tz 3.075 2.313 tw 3.075 1.665 ti 3.075 1.388 tg 3.075 1.110 te 3.075 0.833 sy 2.925 2.188 sv 2.925 1.575 sh 2.925 1.313 sf 2.925 1.050 sd 2.925 0.788 ry 2.625 2.188 rv 2.625 1.575 rh 2.625 1.313 rf 2.625 1.050 part no. suffix ( _ _ ) v cc 1 nominal voltage threshold (v) v cc 2 nominal voltage threshold (v) rd 2.625 0.788 zw 2.313 1.665 zi 2.313 1.388 zg 2.313 1.110 ze 2.313 0.833 yv 2.188 1.575 yh 2.188 1.313 yf 2.188 1.050 yd 2.188 0.788 wt 1.665 3.075 wi 1.665 1.388 wg 1.665 1.110 we 1.665 0.833 vr 1.575 2.625 vh 1.575 1.313 vf 1.575 1.050 vd 1.575 0.788 table 1. reset voltage threshold suffix guide for max6736/max6737/max6740/ max6741/max6743/max6744 table 2. reset voltage threshold suffix guide for max6738/max6739/max6742/ max6745 note: standard versions, shown in bold, are available in the d3 timeout option only. samples are typically held on standard versions only. there is a 10,000-piece order increment on nonstandard versions. other threshold voltage combinations may be available; contact factory for availability. part no. suffix ( _ ) v cc 1 nominal voltage threshold (v) l 4.625 m 4.375 t 3.075 s 2.925 r 2.625 z 2.313 y 2.188 w 1.665 v 1.575 note: standard versions, shown in bold, are available in the d3 timeout option only. samples are typically held on standard versions only. there is a 10,000-piece order increment on non- standard versions. other threshold voltages may be avail- able; contact factory for availability . table 3. v cc timeout period suffix guide active timeout period timeout period suffix min (ms) max (ms) d3 150 300 d7 1200 2400
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 10 ______________________________________________________________________________________ detailed description supply voltages the max6736 max6745 p supervisory circuits main- tain system integrity by alerting the p to fault condi- tions. these devices are optimized for systems that monitor two or three supply voltages. the reset output state is guaranteed to remain valid while either v cc 1 or v cc 2 is above 1.2v. threshold levels the max6736/max6737/max6740/max6741/max6743/ max6744 input voltage threshold combinations are indi- cated by a two-letter code in table 1. the max6738/ max6739/max6742/max6745 input voltage thresholds are indicated by a one-letter code in table 2. contact the factory for the availability of other voltage thresholds. reset output the max6736 max6745 provide an active-low reset out- put ( reset ). reset is asserted when the voltage at either v cc 1 or v cc 2 falls below the voltage threshold level, rstin drops below the threshold, or mr is pulled low. once reset is asserted, it stays low for the reset time- out period. if v cc 1, v cc 2, or rstin goes below the reset threshold before the reset timeout period is completed, the internal timer restarts. the max6736/max6738/ max6740/max6741/max6742 have open-drain reset out- puts, while the max6737/max6739/max6743/max6744/ max6745 have push-pull reset outputs (figure 1). the max6740/max6741/max6742 include a reset output with a manual reset detect function. the open- drain reset output has an internal 50k ? pullup to v cc 1. the reset output is low while the output is pulled to gnd and remains low for at least the manual reset timeout period after the external gnd pulldown is v th 1 v cc 1 gnd gnd t rp t mrp gnd pok1 gnd v th 2 v cc 2 gnd t pokp mr reset switch bounce switch bounce figure 1. timing diagram
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits ______________________________________________________________________________________ 11 released. the manual reset detect function is internally debounced for the t deb timeout period, so the output can be connected directly to a momentary pushbutton switch, if desired (figure 2). manual reset input many microprocessor-based products require manual reset capability, allowing the operator, a test techni- cian, or external logic circuitry to initiate a reset while the monitored supplies remain above their reset thresh- olds. the max6736 max6739 have a dedicated active-low mr input. the reset is asserted low while mr is held low and remains asserted for the manual reset timeout period after mr returns high. the mr input has an internal 1.5k ? pullup resistor to v cc 1 and can be left unconnected if not used. mr can be driven with cmos logic levels, open-drain/open-collector out- puts, or a momentary pushbutton switch to gnd to cre- ate a manual reset function. adjustable input voltage the max6738/max6739 and max6740/max6743 pro- vide an additional input to monitor a second or third system voltage. the threshold voltage at rstin is typi- cally 488mv. connect a resistor-divider network to the circuit as shown in figure 3 to establish an externally controlled threshold voltage, v ext_th . v ext_th = 0.488v((r1 + r2) / r2) low leakage current at rstin allows the use of large- valued resistors, resulting in reduced power consump- tion of the system. power-fail comparator pfi is the noninverting input to an auxiliary comparator. a 488mv internal reference (v th - pfi ) is connected to the inverting input of the comparator. if pfi is less than 488mv, pfo is asserted low. pfo deasserts without a timeout period when pfi rises above the externally set threshold. common uses for the power-fail comparator include monitoring for low battery conditions or a failing dc-dc converter input voltage (see the typical application circuits ). the asserted pfo output can place a system in a low-power suspend mode or support an orderly system shutdown before monitored v cc voltages drop below the reset thresholds. connect pfi to an exter- nal resistor-divider network as shown in figure 4 to set the desired trip threshold. connect pfi to v cc 1 if unused. applications information interfacing to the ? with bidirectional reset pins most microprocessors with bidirectional reset pins can interface directly to open-drain reset output options. systems simultaneously requiring a push-pull reset output and a bidirectional reset interface can be in logic contention. to prevent contention, connect a 4.7k ? resistor between reset and the p s reset i/o port as shown in figure 5. figure 2. max6740/max6741/max6742 manual reset timing diagram open closed t deb gnd t mrp t mrp t deb v cc 1 reset pushbutton switch switch bounce switch bounce switch bounce switch bounce max6738 max6739 max6740 max6743 rstin gnd v ext_th r1 r2 figure 3. monitoring an additional voltage
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 12 ______________________________________________________________________________________ adding hysteresis to the power-fail comparator the power-fail comparator has a typical input hystere- sis of 2.5mv. this is sufficient for most applications in which a power-supply line is being monitored through an external voltage-divider. if additional noise margin is desired, connect a resistor between pfo and pfi, as shown in figure 6. select the values of r1, r2, and r3 such that pfi sees v th-pfi (488mv) when v ext falls to its power-fail trip point (v fail ) and when v ext rises to its power-good trip point (v good ). the hysteresis win- dow extends between the specified v fail and v good thresholds. r3 adds the additional hysteresis by sink- ing current from the r1/r2 divider network when the pfo output is logic low and sourcing current into the network when pfo is logic high. r3 is typically an order of magnitude greater than r1 or r2. the current through r2 should be at least 1a to ensure that the 10na (max) pfi input current does not significant- ly shift the trip points. therefore, for most applications: r2 < v th-pfi / 1ma < 0.488v / 1ma < 488k ? pfo is an open-drain output requiring an external pullup resistor, r4. select r4 to be less than 1% of r3. v good = desired v ext good voltage threshold v fail = desired v ext fail voltage threshold v pu = v pullup (for open-drain pfo ) r2 = 488k ? (for >1a r2 current) r3 = (r1 x v pu ) / (v good - v fail ) r4 0.01 x r3 power sequencing applications many dual-voltage processors/asics require specific power-up/power-down sequences for the i/o and core supplies. rr vv vv v v v good th pfi th pfi good fail pu th pfi 12 = () () ? ? - - - - ( max6742 max6745 pfi gnd v ext_th a) v in is positive r1 r2 pfo v ext_th = v th-pfi r1 + r2 r2 () max6742 max6745 pfi gnd v ext_th v cc b) v in is negative r1 r2 pfo v ext_th = r 2 1 r 1 1 r 2 v cc r 1 + ( () ) - (v th-pfi ) v pfi = 488mv figure 4. using power-fail input to monitor an additional power supply max6737 max6739 max6743 max6744 max6745 gnd gnd v cc 1v cc 2 v cc 2 v cc 1 reset reset to other system components reset p 4.7k ? figure 5. interfacing to ?s with bidirectional reset i/o max6742 max6745 v ext r1 r4 r3 r2 pfi gnd pfo v good = desired v ext good voltage threshold v fail = desired v ext fail voltage threshold v oh = v cc 1 (for push-pull pfo) r2 = 200k ? (for > 2.5 a r2 current) r1 = r2 ((v good - v th-pfi ) - (v th-pfi )(v good - v fail ) / v pu ) / v th-pfi r3 = (r1 x v oh ) / (v good - v fail ) v good v fail v in pfo v pullup figure 6. adding hysteresis to power fail for push-pull pfo
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits ______________________________________________________________________________________ 13 functional diagram v cc 1 v cc 2 rstin/pfi v cc 1 v cc 1 v cc 1 reset timeout period v cc 2 pok1 reset reset output 0.488v 1.23v mr pullup mr max6736 max6745 pfo delay the max6741/max6744 offer a v cc 1 pok (pok1) ideal for v cc 1-to-v cc 2 sequencing. pok1 remains low as long as v cc 1 is below its v th 1 threshold. when v cc 1 exceeds v th 1 for the pok1 timeout period (t pokp ), the open-drain pok1 output is deasserted. the pok1 output can then enable the v cc 2 power supply (use an external pok1 pullup resistor). reset is deasserted when both v cc 1 and v cc 2 remain above their selected thresholds for the reset timeout period (t rp ). the pok1 output can be used for i/o before core or core before i/o sequenc- ing, depending on the selected v cc 1/v cc 2 thresholds. see the typical application circuit and figure 1. monitoring a negative voltage the power-fail comparator can be used to monitor a negative supply voltage using the circuit shown in figure 4. when the negative supply is valid, pfo is low. when the negative supply voltage drops, pfo goes high. the circuit s accuracy is affected by the pfi threshold tolerance, v cc , r1, and r2. transient immunity the max6736 max6745 supervisors are relatively immune to short-duration falling v cc transients (glitch- es). it is usually undesirable to reset the p when v cc experiences only small glitches. the typical operating characteristics show maximum v cc 1/v cc 2 transient duration vs. reset threshold overdrive, for which reset pulses are not generated. the graph shows the maxi- mum pulse width that a falling v cc transient might typi- cally have without causing a reset pulse to be issued. as the amplitude of the transient increases, the maxi- mum allowable pulse width decreases. a 0.1f bypass capacitor mounted close to the v cc pin provides addi- tional transient immunity. chip information transistor count: 249 process: bicmos
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 14 ______________________________________________________________________________________ part voltage monitors open-drain reset push-pull reset manual reset power-fail input/ output pok output rstin input max6739 1 fixed, 1 adj xx x max6740 2 fixed, 1 adj x* x* x max6741 2 fixed x* x* x max6742 1 fixed x* x* x max6743 2 fixed, 1adj x x max6744 2 fixed x x max6745 1 fixed x x selector guide (continued) * manual reset detect on reset output. max6741 v cc 2 in unregulated dc out dc/dc converter in out shdn dc/dc converter pok1 gnd p reset v cc 1 core supply i/o supply reset pushbutton switch gnd max6742 v cc 1 in out dc/dc converter pfi gnd p reset pfo v batt pushbutton switch reset gnd v cc typical application circuits
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits ______________________________________________________________________________________ 15 pin configurations top view gnd rstin mr 15 v cc 1 reset max6738 max6739 sc70 2 34 gnd v cc 2 rstin 15 v cc 1 reset max6740 max6743 sc70 2 34 gnd v cc 2 mr 15 v cc 1 reset max6736 max6737 sc70 2 34 gnd v cc 2 pok1 15 v cc 1 reset max6741 max6744 sc70 2 34 gnd pfi pfo 15 v cc 1 reset max6742 max6745 sc70 2 34 ordering information (continued) part temp range pin-package max6738 xk_d_-t* -40 c to +85 c 5 sc70-5 max6739 xk_d_-t -40 c to +85 c 5 sc70-5 max6740 xk_ _d_-t -40 c to +85 c 5 sc70-5 max6741 xk_ _d_-t -40 c to +85 c 5 sc70-5 max6742 xk_d_-t -40 c to +85 c 5 sc70-5 max6743 xk_ _d_-t* -40 c to +85 c 5 sc70-5 max6744 xk_ _d_-t* -40 c to +85 c 5 sc70-5 max6745 xk_d_-t -40 c to +85 c 5 sc70-5 * future product contact factory for availability.
max6736?ax6745 low-power dual-/triple-voltage sc70 ? supervisory circuits 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. 16 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. 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 .) sc70, 5l.eps

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