________________general description the max811/max812 are low-power microprocessor (?) supervisory circuits used to monitor power sup- plies in ? and digital systems. they provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with 5v- powered or 3v-powered circuits. the max811/max812 also provide a debounced manual reset input. these devices perform a single function: they assert a reset signal whenever the v cc supply voltage falls below a preset threshold, keeping it asserted for at least 140ms after v cc has risen above the reset thresh- old. the only difference between the two devices is that the max811 has an active-low reset output (which is guaranteed to be in the correct state for v cc down to 1v), while the max812 has an active-high reset out- put. the reset comparator is designed to ignore fast transients on v cc . reset thresholds are available for operation with a variety of supply voltages. low supply current makes the max811/max812 ideal for use in portable equipment. the devices come in a 4-pin sot143 package. ________________________applications computers controllers intelligent instruments critical ? and ? power monitoring portable/battery-powered equipment ____________________________features precision monitoring of 3v, 3.3v, and 5v power-supply voltages 6 a supply current 140ms min power-on reset pulse width; r r e e s s e e t t output (max811), reset output (max812) guaranteed over temperature guaranteed r r e e s s e e t t valid to v cc = 1v (max811) power-supply transient immunity no external components 4-pin sot143 package max811/max812 4-pin p voltage monitors with manual reset input ________________________________________________________________ maxim integrated products 1 1 2 4 3 v cc mr (reset) reset gnd max811 max812 sot143 top view ( ) are for max812 note: see last page for marking information. ___________________pin configuration max811 max812 v cc v cc reset (reset) reset input gnd v cc gnd p ( ) are for max812 pushbutton switch mr ___________typical operating circuit 19-0411; rev 3; 3/99 part * max811_eus-t max812_eus-t -40? to +85? -40? to +85? temp. range pin-package 4 sot143 4 sot143 _______________ordering information * this part offers a choice of five different reset threshold voltages. select the letter corresponding to the desired nominal reset threshold voltage, and insert it into the blank to complete the part number. reset threshold suffix voltage (v) l 4.63 m 4.38 t 3.08 s 2.93 r 2.63 for free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. for small orders, phone 1-800-835-8769.
max811/max812 4-pin p voltage monitors with manual reset input 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 5v for l/m versions, v cc = 3.3v for t/s versions, v cc = 3v for r version, t a = -40? to +85?, unless otherwise noted. typical values are at 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. terminal voltage (with respect to gnd) v cc ......................................................................-0.3v to 6.0v all other inputs.......................................-0.3v to (v cc + 0.3v) input current, v cc, mr .......................................................20ma output current, reset or reset .......................................20ma continuous power dissipation (t a = +70?) sot143 (derate 4mw/? above +70?) 320mw operating temperature range ...........................-40? to +85? storage temperature range .............................-65? to +160? lead temperature (soldering, 10sec) .............................+300? i source = 150?, 1.8v < v cc < v th(min) max81_r/s/t, v cc = 3.6v, i out = 0 max81_l/m, v cc = 5.5v, i out = 0 t a = -40? to +85? v od = 125mv, max81_r/s/t v od = 125mv, max81_l/m max81_s max81_l max81_m v cc = v th(max) conditions 0.8v cc 2.3 v ih ? 0.5 t md mr to reset propagation delay (note 2) ns 100 mr glitch immunity (note 3) ? 10 t mr mr minimum pulse width ms 140 560 t rp reset active timeout period ? 2.7 10 i cc supply current 615 v 1.2 v cc operating voltage range ? 20 v cc to reset delay (note 2) 40 2.88 2.93 2.98 3.03 3.08 3.14 reset threshold 4.54 4.63 4.72 4.50 4.75 4.30 4.38 4.46 4.25 4.50 units min typ max symbol parameter max812l/m only, i sink = 3.2ma, v cc = v th(max) max812r/s/t only, i sink = 1.2ma, v cc = v th(max) v 0.4 v ol reset output voltage (max812) 0.3 v oh v cc > v th(max) , max81_l/m 0.8 v il v cc > v th(max) , max81_r/s/t v 0.25 x v cc v il mr input threshold 0.7 x v cc v ih k ? 10 20 30 mr pull-up resistance t a = 0? to +70? 1.0 5.5 3.00 3.15 2.85 3.00 ppm/? 30 reset threshold tempco max81_r 2.58 2.63 2.68 2.55 2.70 t a = +25? t a = -40? to +85? t a = +25? t a = -40? to +85? max81_t t a = +25? t a = -40? to +85? t a = +25? t a = -40? to +85? t a = +25? t a = -40? to +85? v th v
max811/max812 4-pin p voltage monitors with manual reset input _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = 5v for l/m versions, v cc = 3.3v for t/s versions, v cc = 3v for r version, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) note 1: production testing done at t a = +25?, over temperature limits guaranteed by design using six sigma design limits. note 2: reset output for max811, reset output for max812. note 3: ?litches?of 100ns or less typically will not generate a reset pulse. max811r/s/t only, i sink = 1.2ma, v cc = v th(min) max811l/m only, i source = 800?, v cc > v th(max) max811l/m only, i sink = 3.2ma, v cc = v th(min) i sink = 50?, v cc > 1.0v max811r/s/t only, i source = 500?, v cc > v th(max) conditions 0.3 v v cc - 1.5 v oh reset output voltage (max811) 0.4 0.3 v ol 0.8v cc units min typ max symbol parameter
max811/max812 4-pin p voltage monitors with manual reset input 4 _______________________________________________________________________________________ 190 power-up reset timeout vs. temperature 230 max811/12-toc5 temperature (?) power-up reset timeout (ms) 210 200 220 -40 85 35 -15 10 60 max81_r/s/t max81_l/m reset threshold deviation vs. temperature 0.9995 1.0000 1.0005 max811/12-toc6 temperature ( c) normalized threshold (v) 0.9985 0.9980 0.9990 -40 85 35 -15 10 60 0 power-down reset delay vs. temperature (max81_l/m) 200 max811/12-toc4 temperature ( c) power-down reset delay ( s) 100 50 150 -40 85 10 -15 60 35 v od = v th - v cc v od = 125mv v od = 200mv v od = 20mv __________________________________________typical operating characteristics (t a = +25?, unless otherwise noted.) 0 -40 85 supply current vs. temperature (max81_r/s/t) 2.0 2.5 3.0 max811/12-toc1 temperature ( c) supply current (a) 10 1.0 0.5 -15 60 1.5 35 v cc = 3.6v v cc = 3.3v v cc = 1v 0 supply current vs. temperature (max81_l/m) 8 max811/12-toc2 temperature ( c) supply current (a) 4 2 6 -40 85 10 -15 60 35 v cc = 5.5v v cc = 3v v cc = 1v 0 power-down reset delay vs. temperature (max81_r/s/t) 80 100 max811/12-toc3 temperature ( c) power-down reset delay ( s) 40 20 60 -40 85 10 -15 60 35 v od = v th - v cc v od = 20mv v od = 200mv v od = 125mv
max811/max812 4-pin p voltage monitors with manual reset input _______________________________________________________________________________________ 5 ______________________________________________________________ pin description _______________ detailed description reset output a microprocessor? (??) 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 is guaranteed to be a logic low for v cc > 1v. once v cc exceeds the reset threshold, an internal timer keeps reset low for the reset timeout period; after this interval, reset goes high. if a brownout condition occurs (v cc dips below the reset threshold), reset goes low. any time v cc goes below the reset threshold, the internal timer resets to zero, and reset goes low. the internal timer starts after v cc returns above the reset threshold, and reset remains low for the reset timeout period. the manual reset input ( mr ) can also initiate a reset. see the manual reset input section. the max812 has an active-high reset output that is the inverse of the max811? reset output. manual reset input many ?-based products require manual reset capabil- ity, allowing the operator, a test technician, or external logic circuitry to initiate a reset. a logic low on mr asserts reset. reset remains asserted while mr is low, and for the reset active timeout period (t rp ) after mr returns high. this input has an internal 20k ? pull-up resistor, so it can be left open if it is not used. mr can be driven with ttl or cmos-logic levels, or with open- drain/collector outputs. connect a normally open momentary switch from mr to gnd to create a manual- reset function; external debounce circuitry is not required. if mr is driven from long cables or if the device is used in a noisy environment, connecting a 0.1? capacitor from mr to ground provides additional noise immunity. reset threshold accuracy the max811/max812 are ideal for systems using a 5v ?% or 3v ?% power supply with ics specified for 5v ?0% or 3v ?0%, respectively. they are designed to meet worst-case specifications over temperature. the reset is guaranteed to assert after the power supply falls out of regulation, but before power drops below the minimum specified operating voltage range for the system ics. the thresholds are pre-trimmed and exhibit tight distribution, reducing the range over which an undesirable reset may occur. manual reset input. a logic low on mr asserts reset. reset remains asserted as long as mr is low and for 180ms after mr returns high. this active-low input has an internal 20k ? pull-up resistor. it can be driven from a ttl or cmos-logic line, or shorted to ground with a switch. leave open if unused. 3 3 +5v, +3.3v, or +3v supply voltage 4 4 active-high reset output. reset remains high while v cc is below the reset threshold or while mr is held low. reset remains high for reset active timeout period (t rp ) after the reset condi- tions are terminated. 2 active-low reset output. reset remains low while v cc is below the reset threshold or while mr is held low. reset remains low for the reset active timeout period (t rp ) after the reset conditions are terminated. 2 ground 1 1 function pin mr v cc reset reset gnd name max811 max812
max811/max812 __________ applications information negative-going v cc transients in addition to issuing a reset to the ? during power-up, power-down, and brownout conditions, the max811/ max812 are relatively immune to short duration nega- tive-going v cc transients (glitches). figure 1 shows typical transient durations vs. reset comparator overdrive, for which the max811/max812 do not generate a reset pulse. this graph was generat- ed using a negative-going pulse applied to v cc , start- ing above the actual reset threshold and ending below it by the magnitude indicated (reset comparator over- drive). the graph indicates the typical maximum pulse width a negative-going v cc transient may have without causing a reset pulse to be issued. as the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. typically, a v cc transient that goes 125mv below the reset threshold and lasts 40? or less (max81_l/m) or 20? or less (max81_t/s/r) will not cause a reset pulse to be issued. a 0.1? capacitor mounted as close as possible to v cc provides addi- tional transient immunity. ensuring a valid reset output down to v cc = 0v when v cc falls below 1v, the max811 reset output no longer sinks current?t becomes an open circuit. therefore, high-impedance cmos-logic inputs con- nected to the reset output can drift to undetermined voltages. this presents no problem in most applica- tions, since most ? and other circuitry is inoperative with v cc below 1v. however, in applications where the reset output must be valid down to 0v, adding a pull- down resistor to the reset pin will cause any stray leakage currents to flow to ground, holding reset low (figure 2). r1? value is not critical; 100k ? is large enough not to load reset and small enough to pull reset to ground. a 100k ? pull-up resistor to v cc is also recommended for the max812 if reset is required to remain valid for v cc < 1v. 4-pin p voltage monitors with manual reset input 6 _______________________________________________________________________________________ 5 6 7 8 4 0 1 100 1000 2 1 3 reset comparator overdrive , v th - v cc (mv) maximum transient duration (ms) 10 t a = +25 c max81 _l/m max81 _r/s/t r1 v cc gnd max811 reset figure 1. maximum transient duration without causing a reset pulse vs. comparator overdrive figure 2. reset valid to v cc = ground circuit
interfacing to ps with bidirectional reset pins ?s with bidirectional reset pins (such as the motorola 68hc11 series) can contend with the max811/max812 reset outputs. if, for example, the max811 reset out- put is asserted high and the ? wants to pull it low, indeterminate logic levels may result. to correct such cases, connect a 4.7k ? resistor between the max811 reset (or max812 reset) output and the ? reset i/o (figure 3). buffer the reset output to other system com- ponents. max811/max812 4-pin p voltage monitors with manual reset input _______________________________________________________________________________________ 7 4.7k v cc gnd reset max811 reset v cc gnd p buffer buffered reset to other system components figure 3. interfacing to ?s with bidirectional reset i/o transistor count: 341 ___________________chip information
max811/max812 4-pin p voltage monitors with manual reset input ________________________________________________________package information 4.0 ?.1 4.0 ?.1 2.0 ?.05 1.75 ?.1 ?.5 ?.1 ?.1 ?.1 8.0 ?.2 3.5 ?.05 x x x x lot specific code marking information note: dimensions are in mm. and follow eia481-1 standard. ics may also be marked with full part name: 811l, 811m_ ? ? amaa or kabb = max811l anaa or kabc = max811m apaa or kabd = max811t aqaa or kabe = max811s araa or kabf = max811r asaa or kabg = max812l ataa or kabh = max812m avaa or kabi = max812t awaa or kabj = max812s axaa or kabk = max812r sot1434.eps 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. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products.
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