general description the MAX6841?ax6845 microprocessor (?) supervi- sory circuits monitor ultra-low-voltage power supplies in ? and digital systems. they provide excellent circuit reliability at low cost by eliminating external compo- nents and adjustments when used with +0.9v to +1.5v systems. factory-trimmed reset thresholds are avail- able for the MAX6841/max6842. the max6843/ max6844/max6845 provide a reset in input, allowing the user to externally adjust the reset threshold. the MAX6841?ax6845 family features a debounced man- ual reset input ( mr ). the reset comparator is designed to ignore fast transients on v cc . the MAX6841?ax6845 assert a reset signal whenev- er the v cc supply voltage declines below a preset or adjustable threshold or whenever manual reset ( mr ) is asserted. reset remains asserted for a fixed timeout delay after v cc has risen above the reset threshold and when manual reset is deasserted. five timeout periods are available for each part: 150? (voltage detector ver- sion), 1.5ms, 30ms, 210ms, and 1.68s (typ). the MAX6841/max6843 have an active-low push-pull reset output. the MAX6841/max6842/max6844 have an active-high push-pull reset output, and the max6842/max6845 have an active-low open-drain reset output. the active-low open-drain reset output requires a pullup resistor that can be connected to a voltage from 0 to v cc . the low supply current (5.7?) and small package (sot23-5) make the MAX6841?ax6845 ideal for use in portable equipment. applications computers controllers intelligent instruments critical ? and ? power monitoring portable/battery-powered equipment telecom/networking equipment basestations servers/workstations features factory-set reset threshold voltages for monitoring supplies from 0.9v to 1.5v (MAX6841/max6842) adjustable threshold reset in (max6843/max6844/max6845) low power consumption: 5.7a (typ) 2.5% reset threshold accuracy over temperature five timeout periods: 150s (voltage detector version), 1.5ms, 30ms, 210ms, and 1.68s available in three output configurations push-pull reset push-pull reset open-drain reset guaranteed reset valid to v cc = 0.55v (active low) manual reset input immune to short v cc transients space-saving 5-pin sot23 package MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors ________________________________________________________________ maxim integrated products 1 ordering information 19-2625; rev 1; 2/03 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. selector guide and typical operating circuit appear at end of data sheet. part temp range pin-package MAX6841 _ukd_-t -40 c to +85 c 5 sot23-5 max6842 _ukd_-t -40 c to +85 c 5 sot23-5 max6843 ukd_-t -40 c to +85 c 5 sot23-5 max6844 ukd_-t -40 c to +85 c 5 sot23-5 max6845 ukd_-t -40 c to +85 c 5 sot23-5 gnd reset 15v cc MAX6841 max6842 sot23-5 top view 2 34 reset mr ( ) are for 6844 gnd reset in 15v cc max6843 max6844 max6845 sot23-5 2 34 reset (reset) mr pin configurations note: insert desired suffix letter (from the threshold suffix guide and the active timeout period tables) into the blanks to com- plete the part number. for example, the max6842gukd1 has a reset threshold of 1.11v and a typical reset timeout period of 1.5ms. sample stock is generally available on standard versions only (see the standard versions table). standard versions require a minimum order increment of 2.5k units. nonstandard versions must be ordered in 10k-unit increments. contact factory for availability. all parts are offered in tape-and-reel only.
MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +0.55v to +1.8v, 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. terminal voltage (with respect to gnd) v cc .......................................................................-0.3v to +6v mr , reset in, reset (open-drain).........................-0.3v to +6v push-pull reset and reset .....................-0.3v to (v cc + 0.3v) input current (all pins) ........................................................20ma output current (reset, reset ).........................................20ma continuous power dissipation (t a = +70 c) 5-pin sot23 (derate 7.1mw/ c above +70 c)............571mw 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 max6843/max6845 0.55 1.80 supply voltage range v cc MAX6841/max6842/max6844 (note 2) 0.75 1.80 v v cc = 0.9v, no load, reset not asserted 5.7 20 v cc = 1.5v, no load, reset not asserted 7.3 20 supply current i cc v cc = 1.8v, no load, reset not asserted 8.1 20 a i 1.350 1.388 1.425 h 1.275 1.313 1.350 g 1.080 1.110 1.140 f 1.020 1.050 1.080 e 0.810 0.833 0.855 reset threshold (v cc falling) v th d, t a = 0 c to +85 c 0.765 0.788 0.810 v reset in threshold v rstin max6843/max6844/max6845 (note 3) 181.2 187.4 191.5 mv reset in leakage current i rstin -25 +25 na reset threshold hysteresis v hys 0.75 %v th v cc or reset in to reset delay v cc falling, step signal from (v th + 10%) to (v th - 10%) within 1s 150 s d0 (voltage detector) 0.15 d1 1 1.5 2 d2 20 30 40 d3 140 210 280 reset active timeout period t rp d4 1120 1680 2240 ms v il 0.3 v cc mr input voltage (note 3) v ih 0.7 v cc v mr minimum input pulse width mr driven from v cc to 0 (note 3) 1 s mr glitch rejection mr driven from v cc to 0 (note 3) 150 ns mr to reset delay mr driven from v cc to 0 (note 3) 500 ns mr pullup resistance to v cc 10 20 26 k ?
MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors _______________________________________________________________________________________ 3 note 1: 100% production tested at +25 c. overtemperature limits are guaranteed by design. note 2: the active-low output reset has v cc(min) = 0.55v (MAX6841/max6842). note 3: for v cc > 0.788v, t a = 0 c to +85 c, and for v cc > 0.833v, t a = -40 c to +85 c. electrical characteristics (continued) (v cc = +0.55v to +1.8v, 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 v cc 0.55v, i sink = 10a, reset asserted 0.2 v cc open-drain reset output voltage v ol v cc 0.83v, i sink = 80a, reset asserted 0.2 v cc v open-drain reset output leakage current i lkg v cc > v th , reset not asserted 1 a v cc 0.55v, i sink = 10a, reset asserted 0.2 v cc v ol v cc 0.83v, i sink = 80a, reset asserted 0.2 v cc push-pull reset output voltage v oh v cc 0.83v, i source = 40a, reset not asserted 0.8 v cc v v cc 0.75v, i source = 10a, reset asserted 0.8 v cc v oh v cc 0.83v, i source = 40a, reset asserted 0.8 v cc push-pull reset output voltage v ol v cc 0.83v, i sink = 80a, reset not asserted 0.2 v cc v typical operating characteristics (v cc = 1.5v, t a = +25 c, unless otherwise noted.) supply current vs. temperature MAX6841-45 toc01 temperature ( c) supply current ( a) 60 40 20 0 -20 1 2 3 4 5 6 7 8 9 0 -40 80 v cc = 1.8v v cc = 1.5v v cc = 0.9v power-down reset delay vs. temperature MAX6841-45 toc02 temperature ( c) power-down reset delay ( s) 60 40 20 0 -20 50 100 150 200 250 300 350 0 -40 80 v od = 10mv v od = 20mv v od = 100mv v od = overdrive (mv) normalized reset timeout period vs. temperature MAX6841-45 toc03 temperature ( c) normalized reset timeout period 60 40 20 0 -20 0.96 0.98 1.00 1.02 1.04 1.06 0.94 -40 80 d2 option d3 option d4 option
MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors 4 _______________________________________________________________________________________ pin description typical operating characteristics (continued) (v cc = 1.5v, t a = +25 c, unless otherwise noted.) normalized v cc reset threshold vs. temperature MAX6841-45 toc04 temperature ( c) normalized v cc reset threshold 60 40 20 0 -20 0.990 0.995 1.000 1.005 1.010 1.015 0.985 -40 80 v th = 0.833v normalized reset in threshold vs. temperature MAX6841-45 toc05 temperature ( c) normalized reset in threshold 60 40 20 0 -20 0.990 0.995 1.000 1.005 1.010 1.015 0.985 -40 80 power-up/power-down characteristics (max6843aukd3) MAX6841-45 toc06 200ms/div v cc 1v/div reset 1v/div pin MAX6841 max6842 max6843 max6845 max6844 name function 1 push-pull (MAX6841) or open-drain (max6842) active-low reset output. reset changes from high to low when v cc drops below the selected reset threshold or mr is pulled low. reset remains low for the reset timeout period after v cc exceeds the device reset threshold and mr is released high. 1 reset push-pull (max6843) or open-drain (max6845) active-low reset output. reset changes from high to low when reset in drops below the 187.4mv reset threshold (referenced to v cc ) or mr is pulled low. reset remains low for the reset timeout period after reset in exceeds the reset threshold and mr is released high. 2 2 2 gnd ground 3 push-pull active-high reset output. reset changes from low to high when v cc input drops below the selected reset threshold or mr is pulled low. reset remains high for the reset timeout period after v cc exceeds the device reset threshold and mr is released high. 1 reset push-pull active-high reset output. reset changes from low to high when the reset in input drops below the 187.4mv reset threshold (referenced to v cc ). reset remains high for the reset timeout period after reset in exceeds the reset threshold. 3 3 reset in adjustable reset input. high-impedance input for reset comparator. connect this pin to an external resistive-divider network to set the reset threshold voltage; the typical threshold is 187.4mv (referenced to v cc ). the max6843/max6844/ max6845 assert a reset signal when the v cc to reset in differential falls below its threshold voltage. 444 mr active-low manual reset input. internal 20k ? pullup to v cc . pull low to force a reset. 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. 555v cc supply voltage. monitored supply for the MAX6841/max6842.
detailed description reset output a microprocessor s (p s) reset input starts the p in a known state. the MAX6841 max6845 assert a reset dur- ing power-up, power-down, and brownout conditions. when the v cc supply voltage falls below a preset thresh- old (MAX6841/max6842) or reset in falls below the adjustable threshold (max6843/max6844/max6845), reset asserts and stays asserted for a fixed timeout delay (table 2) after v cc or reset in has risen above the reset threshold. the MAX6841 max6845 are available with five typical timeout options for each part: 150s (voltage detector), 1.5ms, 30ms, 210ms, and 1.68s. the MAX6841/max6842 have two reset outputs (reset and reset ); one is the inverse of the other. the MAX6841 has one active-high push-pull output and one active-low push-pull output. the max6842 has one active-high push-pull output and one active-low open- drain output. the max6843 features an active-low push-pull output. the max6844 features an active- high push-pull output, and the max6845 has an active- low open-drain output stage. connect a pullup resistor from the open-drain reset output to any voltage between 0 and 6v. manual reset input many p-based systems require a manual reset capa- bility, allowing the operator, a test technician, or exter- nal logic circuitry to initiate a reset. reset remains asserted while mr is low, and for a fixed timeout delay after mr returns high. this input has an internal 20k ? pullup resistor, so it can be left open if it is not used. mr can be driven with cmos logic level or with open- drain/collector outputs. to create a manual reset func- tion, connect a normally open momentary switch from mr to ground; external debounce circuitry is not required. if mr is driven from long cables or the device is used in a noisy environment, connect a 0.1f capac- itor from mr to ground to provide additional noise immunity. reset in the max6843/max6844/max6845 feature a reset in input, which allows users to adjust the reset threshold voltage. the internal reference voltage is 187.4mv with respect to v cc . an external resistive-divider network can be used to set voltage monitoring thresholds, as shown in figure 1. the resistive-divider network must be referenced to v cc . as v cc falls, the voltage at MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors _______________________________________________________________________________________ 5 v cc reset output reset reset timeout period v ref manual reset detect gnd mr mr pullup reset MAX6841 max6842 functional diagrams v cc reset output reset timeout period v ref = 187.4mv manual reset detect gnd mr mr pullup reset reset reset in max6843 max6844 max6845 max6843 max6844 max6845 v cc gnd reset in mr reset (reset) ( ) are for max6844 r1 = r2 r2 r1 v cc-th v ref - 1 where v ref = 187.4mv (with respect to v cc ) and v cc-th is the v cc threshold. v cc figure 1. setting the adjustable threshold externally
MAX6841?ax6845 reset in decreases. the max6843/max6844/ max6845 assert a reset when the voltage at reset in falls below the reset in threshold (v rstin ). the low- leakage current at reset in allows for relatively large- value resistors to be used, which reduces power consumption. for example, for v cc-th = 0.9v, if r2 = 100k ? , then r1 = 26.3k ? . applications information v cc falling transients the MAX6841 max6845 are relatively immune to short- duration falling v cc transients (glitches). figure 2 shows typical transient duration vs. reset comparator overdrive, for which the MAX6841 max6845 do not generate a reset pulse. the graph was generated using a falling pulse applied to v cc , starting 0.1v above the actual reset threshold and ending below it by the mag- nitude indicated (reset comparator overdrive). the graph indicates the maximum pulse width that a falling v cc transient can have without causing a reset pulse. as the magnitude of the transient increases (goes fur- ther below the reset threshold), the maximum allowable pulse width decreases. a 0.1f 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 when v cc falls below 0.55v, the MAX6841/max6843 push-pull reset output no longer sinks current; it becomes an open circuit. therefore, high-impedance cmos-logic inputs connected to reset can drift to undetermined voltages. this presents no problem in most applications, because most p and other circuitry are inoperative with v cc lower than 0.55v. however, in applications in which reset must be valid down to 0, adding a pulldown resistor to reset causes any stray leakage currents to flow to ground, holding reset low (figure 3). r3 s value is not critical; 200k ? is large enough not to load reset and small enough to pull reset to ground. a 200k ? pullup resistor to v cc is also recommended for the MAX6841/max6842/max6844 if push-pull reset is required to remain valid for v cc 0.75v. interfacing to ?s with bidirectional reset pins because the reset output on the max6842/max6845 is open drain, these devices interface easily with ps that have bidirectional reset pins. connecting the p supervisor s reset output directly to the p s reset pin with a single pullup resistor allows either device to assert reset (figure 4). ultra-low-voltage ? reset circuits and voltage detectors 6 _______________________________________________________________________________________ maximum transient duration vs. overdrive overdrive v th - v cc (mv) maximum transient duration ( s) 10 150 200 250 300 350 400 450 500 550 600 100 1 100 reset occurs above this line figure 2. maximum transient duration vs. overdrive MAX6841 max6843 v cc reset gnd r3 figure 3. reset valid to v cc = 0 max6842 max6845 v cc v cc reset gnd v cc reset input gnd p figure 4. interfacing to microprocessors with bidirectional reset i/0
using the max6842/max6845 open-drain reset output with multiple supplies generally, the pullup connected to the max6842/ max6845 connects to the supply voltage being moni- tored at the ic s v cc pin. however, some systems use the open-drain output to level-shift from the monitored supply to reset circuitry powered by some other supply (figure 5). note that as the max6842/max6845 s v cc decreases, so does the ic s ability to sink current at reset . also, with any pullup, reset is pulled high as v cc decays toward 0. the voltage where this occurs depends on the pullup resistor value and the voltage to which it is connected. chip information transistor count: 788 process: bicmos MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors _______________________________________________________________________________________ 7 table 1. threshold suffix guide max6842 max6845 v cc reset gnd v cc reset gnd r pullup 0.9v p +5.0v figure 5. using the max6842/max6845 open-drain reset output with multiple supplies suffix reset threshold (v) i 1.388 h 1.313 g 1.110 f 1.050 e 0.833 d 0.788 table 2. active timeout period guide reset active timeout period (ms) suffix min typ max d0 0.15 d1 1 1.5 2 d2 20 30 40 d3 140 210 280 d4 1120 1680 2240 table 3. standard versions device top mark MAX6841 hukd0 aedr MAX6841hukd3 aeds MAX6841fukd0 aedp MAX6841fukd3 aedq MAX6841dukd0 aedn MAX6841dukd3 aedo max6842 hukd0 aedx max6842hukd3 aedy max6842fukd0 aedv max6842fukd3 aedw max6842dukd0 aedt max6842dukd3 aedu max6843 ukd0 aedz max6843ukd3 aeav max6844 ukd0 aeeb max6844ukd3 aeec max6845 ukd0 aeax max6845ukd3 aeay
MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors 8 _______________________________________________________________________________________ selector guide part manual reset adjustable reset input push-pull reset push-pull reset open-drain reset MAX6841 ? ?? max6842 ? ?? max6843 ??? max6844 ?? ? max6845 ?? ? core supply p i/o supply v cc gnd gnd 0.9v reset v in 3.3v dc/dc converter max6842d/e mr reset reset pushbutton switch typical operating circuit
MAX6841?ax6845 ultra-low-voltage ? reset circuits and voltage detectors 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 _____________________ 9 ? 2003 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 information, go to www.maxim-ic.com/packages .) sot5l.eps
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