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general description the max6715aCmax6729a/max6797a are ultra-low- voltage microprocessor (p) supervisory circuits designed to monitor two or three system power-supply voltages. these devices assert a system reset if any monitored supply falls below its factory-trimmed or adjustable threshold and main - tain reset for a minimum timeout period after all supplies rise above their thresholds. the integrated dual/triple superviso - ry circuits significantly improve system reliability and reduce size compared to separate ics or discrete components. these devices monitor primary supply voltages (v cc1 ) from 1.8v to 5.0v and secondary supply voltages (v cc 2) from 0.9v to 3.3v with factory-trimmed reset threshold voltage options (see the reset voltage threshold suffix guide ). an externally adjustable rstin input option allows customers to monitor a third supply voltage down to 0.62v. these devices are guaranteed to be in the cor - rect reset output logic state when either v cc1 or v cc2 remains greater than 0.8v. a variety of push-pull or open-drain reset outputs along with watchdog input, manual-reset input, and power-fail input/output features are available (see the selector guide). select reset timeout periods from 1.1ms to 1120ms (min) (see the reset timeout period suffix guide ). the max6715aCmax6729a/max6797a are available in small 5-, 6-, and 8-pin sot23 packages and operate over the -40c to +125c temperature range. applications multivoltage systems telecom/networking equipment computers/servers portable/battery- operated equipment industrial equipment printers/fax machines set-top boxes features v cc1 (primary supply) reset threshold voltages from 1.58v to 4.63v v cc2 (secondary supply) reset threshold voltages from 0.79v to 3.08v externally adjustable rstin threshold for auxiliary/ triple-voltage monitoring (0.62v internal reference) watchdog timer option ? 35s (min) long startup period ? 1.12s (min) normal timeout period manual-reset input option power-fail input/power-fail output option (push-pull and open-drain active-low) guaranteed reset valid down to v cc1 or v cc2 = 0.8v reset output logic options immune to short v cc transients low supply current 14a (typ) at 3.6v watchdog disable feature small 5-, 6-, and 8-pin sot23 packages ordering information continued at end of data sheet. pin configurations and selector guide appear at end of data sheet. 19-0536; rev 4; 3/14 note: the first _ _ are placeholders for the threshold voltage levels of the devices. desired threshold levels are set by the part number suffix found in the reset voltage threshold suffix guide. the _ after the d is a placeholder for the reset timeout delay time. desired delay time is set using the timeout period suffix found in the reset timeout period suffix guide. for example, the max6716autltd3-t is a dual-voltage supervisor v th1 = 4.625v, v th2 = 3.075v, and 210ms (typ) timeout period. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. /v denotes an automotive qualified part. * future productcontact factory for availability. part temp range pin- package max6715a ut_ _d_+t -40c to +125c 6 sot23 max6716a ut_ _d_+t -40c to +125c 6 sot23 max6717a uk_ _d_+t -40c to +125c 5 sot23 max6718a uk_ _d_+t -40c to +125c 5 sot23 max6719a ut_ _d_+t -40c to +125c 6 sot23 max6719aut_ _d_/v+t* -40c to +125c 6 sot23 in out2out1 dc-dc converter unregulated dc r1r2 v cc1 v cc2 rstin/pfimr rst wdi pfo max67_ _ pushbutton switch i/o supply core supply reset i/onmi p 1.8v 0.9v max6715a- max6729a/ max6797a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits typical operating circuit ordering information downloaded from: http:///
terminal voltage (with respect to gnd) v cc1 , v cc2 .........................................................-0.3v to +6v open-drain rst , rst1 , rst2 , pfo , rst ............-0.3v to +6v push-pull rst, rst1 , pfo , rst .......... -0.3v to (v cc1 + 0.3v) push-pull rst2 ...................................... -0.3v to (v cc2 + 0.3v) rstin, pfi, mr , wdi .............................................-0.3v to +6v input current/output current (all pins) ...............................20ma continuous power dissipation (t a = +70c) 5-pin sot23-5 (derate 7.1mw/c above +70c) ....... 571mw 6-pin sot23-6 (derate 8.7mw/c above +70c) ....... 696mw 8-pin sot23-8 (derate 8.9mw/c above +70c) ....... 714mw operating temperature range ......................... -40c to +125c storage temperature range ............................ -65c to +150c junction temperature ......................................................+150c lead temperature (soldering, 10s) ................................. +300c (v cc1 = 0.8v to 5.5v, v cc2 = 0.8v to 5.5v, gnd = 0v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c.) (note 1) parameter symbol conditions min typ max units supply voltage v cc 0.8 5.5 v supply current i cc1 v cc1 < 5.5v all i/o connections open, outputs not asserted 15 39 a v cc1 < 3.6v all i/o connections open, outputs not asserted 10 28 i cc2 v cc2 < 3.6v all i/o connections open, outputs not asserted 4 11 v cc2 < 2.75v all i/o connections open, outputs not asserted 3 9 v cc1 reset threshold v th1 l (falling) 4.500 4.625 4.750 v m (falling) 4.250 4.375 4.500 t (falling) 3.000 3.075 3.150 s (falling) 2.850 2.925 3.000 r (falling) 2.550 2.625 2.700 z (falling) 2.250 2.313 2.375 y (falling) 2.125 2.188 2.250 w (falling) 1.620 1.665 1.710 v (falling) 1.530 1.575 1.620 v cc2 reset threshold v th2 t (falling) 3.000 3.075 3.150 v s (falling) 2.850 2.925 3.000 r (falling) 2.550 2.625 2.700 z (falling) 2.250 2.313 2.375 y (falling) 2.125 2.188 2.250 w (falling) 1.620 1.665 1.710 v (falling) 1.530 1.575 1.620 i (falling) 1.350 1.388 1.425 h (falling) 1.275 1.313 1.350 g (falling) 1.080 1.110 1.140 f (falling) 1.020 1.050 1.080 e (falling) 0.810 0.833 0.855 d (falling) 0.765 0.788 0.810 max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 2 absolute maximum ratings stresses beyond those listed under absolute 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. electrical characteristics downloaded from: http:///
(v cc1 = 0.8v to 5.5v, v cc2 = 0.8v to 5.5v, gnd = 0v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c.) (note 1) parameter symbol conditions min typ max units reset threshold tempco v th /c 20 ppm/c reset threshold hysteresis v hyst referenced to v th typical 0.5 % v cc to reset output delay t rd v cc1 = (v th1 + 100mv) to (v th1 - 100mv) or v cc2 = (v th2 + 75mv) to (v th2 - 75mv) 20 s reset timeout period t rp d1 1.1 1.65 2.2 ms d2 8.8 13.2 17.6 d7 (max6797a only) 17.5 26.25 35 d8 (max6797a only) 35 52.5 70 d3 140 210 280 d5 280 420 560 d6 560 840 1120 d4 1120 1680 2240 adjustable reset comparator input (max6719a/max6720a/max6723aCmax6727a) rstin input threshold v rstin 611 626.5 642 mv rstin input current i rstin -100 +100 na rstin hysteresis 3 mv rstin to reset output delay t rstind v rstin to (v rstin - 30mv) 22 s power-fail input (max6728a/max6729a) pfi input threshold v pfi 611 626.5 642 mv pfi input current i pfi -100 +100 na pfi hysteresis v pfh 3 mv pfi to pfo delay t dpf (v pfi + 30mv) to (v pfi - 30mv) 2 s manual-reset input (max6715aCmax6722a/max6725aCmax6729a) mr input voltage v il 0.3 x v cc1 v v ih 0.7 x v cc1 mr minimum pulse width 1 s mr glitch rejection 100 ns mr to reset delay t mr 200 ns mr pullup resistance 25 50 80 k? watchdog input (max6721aCmax6729a) watchdog timeout period t wd first watchdog period after reset timeout period 35 54 72 s normal mode 1.12 1.68 2.24 wdi pulse width t wdi (note 2) 50 ns wdi input voltage v il 0.3 x v cc1 v v ih 0.7 x v cc1 wdi input current i wdi v wdi = 0v or v cc1 -1 +1 a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 3 electrical characteristics (continued) downloaded from: http:///
(v cc1 = 0.8v to 5.5v, v cc2 = 0.8v to 5.5v, gnd = 0v, t a = -40c to +125c, unless otherwise noted. typical values are at t a = +25c.) (note 1) note 1: devices tested at t a = +25c. overtemperature limits are guaranteed by design and not production tested. note 2: parameter guaranteed by design. parameter symbol conditions min typ max units reset/power-fail outputs rst/rst1/rst2/pfo output low (push-pull or open-drain) v ol v cc1 or v cc2 0.8v, i sink = 1a, output asserted 0.3 v v cc1 or v cc2 1.0v, i sink = 50a, output asserted 0.3 v cc1 or v cc2 1.2v, i sink = 100a, output asserted 0.3 v cc1 or v cc2 2.7v, i sink = 1.2ma, output asserted 0.3 v cc1 or v cc2 4.5v, i sink = 3.2ma, output asserted 0.4 rst/rst1/pfo output high (push-pull only) v oh v cc1 1.8v, i source = 200a, output not asserted 0.8 x v cc1 v v cc1 2.7v, i source = 500a, output not asserted 0.8 x v cc1 v cc1 4.5v, i source = 800a, output not asserted 0.8 x v cc1 rst2 output high (push-pull only) v oh v cc1 1.8v, i source = 200a, output not asserted 0.8 x v cc2 v v cc1 2.7v, i source = 500a, output not asserted 0.8 x v cc2 v cc1 4.5v, i source = 800a, output not asserted 0.8 x v cc2 rstoutput high (push-pull only) v oh v cc1 1.0v, i source = 1a, reset asserted 0.8 x v cc1 v v cc1 1.8v, i source = 150a, reset asserted 0.8 x v cc1 v cc1 2.7v, i source = 500a, reset asserted 0.8 x v cc1 v cc1 4.5v, i source = 800a, reset asserted 0.8 x v cc1 rstoutput low (push-pull or open drain) v ol v cc1 or v cc2 1.8v, i sink = 500a, reset not asserted 0.3 v v cc1 or v cc2 2.7v, i sink = 1.2ma, reset not asserted 0.3 v cc1 or v cc2 4.5v, i sink = 3.2ma, reset not asserted 0.4 rst/rst1/rst2/pfo output open-drain leakage current output not asserted 0.5 a rst output open-drain leakage current output asserted 0.5 a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 4 electrical characteristics (continued) downloaded from: http:///
(v cc1 = 5v, v cc2 = 3.3v, t a = +25c, unless otherwise noted.) 0 42 10 86 1816 14 12 20 supply current vs. temperature (v cc 1 = +3.3v, v cc 2 = +2.5v) max6715a-29a toc02 temperature (c) supply current (a) -40 20 -10 50 80 5 -25 35 65 110 95 125 total i cc 1 i cc 2 0 2 64 1210 8 1816 14 20 -40 20 -10 50 80 5 -25 35 65 110 95 125 supply current vs. temperature (v cc 1 = +2.5v, v cc 2 = +1.8v) max6715a-29a toc03 temperature (c) supply current (a) total i cc 1 i cc 2 0 2 64 1210 8 1816 14 20 -40 20 -10 50 80 5 -25 35 65 110 95 125 supply current vs. temperature (v cc 1 = +1.8v, v cc 2 = +1.2v) max6715a-29a toc04 temperature (c) supply current (a) total i cc 1 i cc 2 0.980 0.984 0.9920.988 1.0041.000 0.996 1.0161.012 1.008 1.020 -40 20 -10 50 80 5 -25 35 65 110 95 125 normalized/ reset watchdog timeout period vs. temperature max6715a-29a toc05 temperature (c) reset/watchdog timeout period 10,000 1000 100 10 1 100 10 1000 maximum v cc transient duration vs. reset threshold overdrive max6715a-29a toc06 reset threshold overdrive (mv) maximum v cc transient duration (s) reset occurs above this line 0.998 0.999 1.0011.000 1.0041.003 1.002 1.0071.006 1.005 1.008 -40 20 -10 50 80 5 -25 35 65 110 95 125 normalized v cc reset threshold vs. temperature max6715a-29a toc07 temperature (c) reset threshold 0 2 64 1210 8 1816 14 20 -40 20 -10 50 80 5 -25 35 65 110 95 125 supply current vs. temperature (v cc 1 = +5v, v cc 2 = +3.3v) max6715a-29a toc01 temperature (c) supply current (a) total i cc 1 i cc 2 628 630629 633632 631 637636 634 635 638 -40 20 -10 50 80 5 -25 35 65 110 95 125 reset input and power-fail input threshold vs. temperature max6715a-29a toc08 temperature (c) reset threshold 10 11 1312 1615 14 1918 17 20 -40 20 -10 50 80 5 -25 35 65 110 95 125 v cc to reset delay vs. temperature max6715a-29a toc09 temperature (c) v cc to reset delay (s) 75mv overdrive max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits maxim integrated 5 www.maximintegrated.com typical operating characteristics downloaded from: http:///
(v cc1 = 5v, v cc2 = 3.3v, t a = +25c, unless otherwise noted.) pin name function max6715a/ max6716a max6717a/ max6718a max6719a/ max6720a max6721a/ max6722a max6723a/ max6724a max6725a/ max6726a max6727a max6728a/max6729a/ max6797a 1 1 1 1 1 1 1, 4 1 rst / rst1 active-low reset output, open-drain or push-pull. rst/rst1 changes from high to low when v cc1 or v cc2 drops below the selected reset thresholds, rstin is below threshold, mr is pulled low, or the watchdog triggers a reset. rst/rst1 remains low for the reset timeout period after v cc1 /v cc2 /rstin exceed the device reset thresholds, mr goes low to high, or the watchdog triggers a reset. open- drain outputs require an external pullup resistor. push-pull outputs are referenced to v cc1 . 12 1614 2220 18 24 -40 20 -10 50 80 5 -25 35 65 110 95 125 rstin input to reset output delay vs. temperature max6715a-29a toc10 temperature (c) rstin to reset delay (s) 30mv overdrive 1.0 1.2 1.81.6 1.4 1.3 1.1 1.91.7 1.5 2.0 -40 20 -10 50 80 5 -25 35 65 110 95 125 power-fail input to power-fail output delay vs. temperature max6715a-29a toc11 temperature (c) power-fail delay (s) 30mv overdrive 0v 0v v rst 2v/div max6715a-29a toc12 50ns/div mr to reset output delay v mr 2v/div max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 6 pin description typical operating characteristics (continued) downloaded from: http:///
pin name function max6715a/ max6716a max6717a/ max6718a max6719a/ max6720a max6721a/ max6722a max6723a/ max6724a max6725a/ max6726a max6727a max6728a/max6729a/ max6797a 5 rst2 active-low reset output, open-drain or push-pull. rst2 changes from high to low when v cc1 or v cc2 drops below the selected reset thresholds or mr is pulled low. rst2 remains low for the reset timeout period after v cc1 /v cc2 exceed the device reset thresholds or mr goes low to high. open-drain outputs require an external pullup resistor. push-pull outputs are referenced to v cc2 . 2 2 2 2 2 2 2 2 gnd ground 3 3 3 3 5 5 5 mr active-low manual-reset input. internal 50k? pullup to v cc1 . 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 cc1 if unused. 4 4 4 4 4 6 6 6 v cc2 secondary supply voltage input. powers the device when it is above v cc1 and input for secondary reset threshold monitor. 6 5 6 6 6 8 8 8 v cc1 primary supply voltage input. powers the device when it is above v cc2 and input for primary reset threshold monitor. max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 7 pin description (continued) downloaded from: http:///
pin name function max6715a/ max6716a max6717a/ max6718a max6719a/ max6720a max6721a/ max6722a max6723a/ max6724a max6725a/ max6726a max6727a max6728a/max6729a/ max6797a 5 3 3 3 3 wdi watchdog input. if wdi remains high or low for longer than the watchdog timeout period, the internal watchdog timer runs out and the reset output asserts for the reset timeout period. the internal watchdog timer clears whenever a reset is asserted or wdi sees a rising or falling edge. the watchdog has a long startup period (35s min) after each reset event and a short watchdog timeout period (1.12s min) after the irst valid wdi transition. leave wdi unconnected to disable the watchdog timer. the wdi unconnected-state detector uses a small 200na current source. therefore, do not connect wdi to anything that will source more than 50na. 5 5 7 7 rstin undervoltage reset comparator input. high- impedance input for adjustable reset monitor. the reset output is asserted when rstin falls below the 0.626v internal reference voltage. set the monitored voltage reset threshold with an external resistor-divider network. connect rstin to v cc1 or v cc2 if not used. max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 8 pin description (continued) downloaded from: http:///
pin name function max6715a/ max6716a max6717a/ max6718a max6719a/ max6720a max6721a/ max6722a max6723a/ max6724a max6725a/ max6726a max6727a max6728a/max6729a/ max6797a 7 pfi power-fail voltage monitor input. high- impedance input for internal power-fail monitor comparator. connect pfi to an external resistor- divider network to set the power-fail threshold voltage (0.626v typical internal reference voltage). connect to gnd, v cc1 , or v cc2 if not used. 4 pfo active-low power-fail monitor output, open- drain or push-pull. pfo is asserted low when pfi is less than 0.626v. pfo deasserts without a reset timeout period. open-drain outputs require an external pullup resistor. push-pull outputs are referenced to v cc1 . 4 rst active-high reset output, open-drain or push-pull. rst changes from low to high when v cc1 or v cc2 drops below selectedreset thresholds, rstin is below threshold, mr is pulled low, or the watchdog triggers a reset. rst remains high for the reset timeout period after v cc1 /v cc2 /rstin exceed the device reset thresholds, mr goes low to high, or the watchdog triggers a reset. open- drain outputs require an external pullup resistor. push-pull outputs are referenced to v cc1 . max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 9 pin description (continued) downloaded from: http:///
detailed description supply voltages the max6715aCmax6729a/max6797a p supervisory circuits maintain system integrity by alerting the p to fault conditions. these ics are optimized for systems that monitor two or three supply voltages. the output reset state is guaranteed to remain valid while either v cc1 or v cc2 is above 0.8v. threshold levels input-voltage threshold level combinations are indicated by a two-letter code in the reset voltage threshold suffix guide (table 1). contact factory for availability of other voltage threshold combinations. reset outputs the max6715aCmax6729a/max6797a provide an active-low reset output ( rst ) and the max6725a/ max6726a also provide an active-high ( rst ) output. rst, rst , rst1 , and rst2 are asserted when the voltage at either v cc1 or v cc2 falls below the voltage threshold level, rstin drops below threshold, or mr is pulled low. once reset is asserted, it stays low for the reset timeout period (see table 2). if v cc1 , v cc2 , or rstin goes below the reset threshold before the reset timeout period is completed, the internal timer restarts. the max6715a/max6717a/max6719a/max6721a/ max6723a/max6725a/max6727a/max6728a con - tain open-drain reset outputs, while the max6716a/ max6718a/max6720a/max6722a/max6724a/ max6726a/max6729a/max6797a contain push-pull reset outputs. the max6727a provides two separate open-drain rst outputs driven by the same internal logic. manual-reset input many p-based products require manual-reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. a logic-low on mr asserts the reset output. reset remains asserted while mr is low for the reset timeout period (t rp ) after mr returns high. this input has an internal 50k pullup resistor to v cc1 and can be left unconnected if not used. mr can be driven with cmos logic levels, or with open-drain/collector out - puts. 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, connect a 0.1f capacitor from mr to gnd to provide additional noise immunity. adjustable input voltage the max6719a/max6720a and max6723aCmax6727a provide an additional input to monitor a third system volt - age. the threshold voltage at rstin is typically 626mv. connect a resistor-divider network to the circuit as shown in figure 1 to establish an externally controlled threshold voltage, v ext_th . v ext_th = 626mv((r1 + r2)/r2) low-leakage current at rstin allows the use of large- val ued resistors resulting in reduced power consumption of the system. watchdog input the watchdog monitors p activity through the watchdog input (wdi). to use the watchdog function, connect wdi to a bus line or p i/o line. when wdi remains high or low for longer than the watchdog timeout period, the reset output asserts. the max6721aCmax6729a/max6797a include a dual - mode watchdog timer to monitor p activity. the flexible timeout architecture provides a long period initial watch - dog mode, allowing complicated systems to complete lengthy boots, and a short period normal watchdog mode, allowing the supervisor to provide quick alerts when pro - cessor activity fails. after each reset event (v cc power- up/brownout, manual reset, or watchdog reset), there is a long initial watchdog period of 35s minimum. the long watchdog period mode provides an extended time for the system to power-up and fully initialize all p and system components before assuming responsibility for routine watchdog updates. figure 1. monitoring a third voltage v ext_th r1r2 rstin gnd max6719a/max6720a/ max6723aC max6727a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 10 downloaded from: http:///
the normal watchdog timeout period (1.12s min) begins after the first transition on wdi before the conclusion of the long initial watchdog period (figure 2). during the normal operating mode, the supervisor will issue a reset pulse for the reset timeout period if the p does not update the wdi with a valid transition (high-to-low or low- to-high) within the standard timeout period (1.12s min). leave wdi unconnected to disable the watchdog timer. the wdi unconnected-state detector uses a small (200na typ) current source. therefore, do not connect wdi to anything that will source more than 50na. power-fail comparator pfi is the noninverting input to a comparator. if pfi is less than v pfi (626.5mv), pfo goes low. common uses for the power-fail comparator include monitoring preregulated input of the power supply (such as a battery) or providing an early power-fail warning so software can conduct an orderly system shutdown. it can also be used to monitor supplies other than v cc1 or v cc2 by setting the power- fail threshold with a resistor-divider, as shown in figure 3. pfi is the input to the power-fail comparator. the typical comparator delay is 2s from pfi to pfo . connect pfi to ground of v cc1 if unused. ensuring a valid reset output down to v cc = 0v the max6715aCmax6729a/max6797a are guaranteed to operate properly down to v cc = 0.8v. in applica - tions that require valid reset levels down to v cc = 0v, use a pulldown resistor at rst to ground. the resistor value used is not critical, 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. this configuration does not work for the open-drain outputs of the max6715a/max6717a/max6719a/max6721a/ max6723a/max6725a/max6727a/max6728a. for push-pull, active-high rst output connect the external resistor as a pullup from rst to v cc1 . figure 2. normal watchdog startup sequence figure 3. using power-fail input to monitor an additional power-supply a) v in is positive b) v in is negative 1.12s max t wdi-normal 1.12s max t wdi-startup 35s max v th v cc wdi rst t rp r1r2 pfi gnd v in pfo v trip = v pfi r1 + r2 r2 ( ) r1r2 pfi gnd v cc v in pfo v trip = r2 (v pfi ) 1 r1 1 r2 + - v cc r1 [ ] ( ) v pfi = 626.5mv a)b) max6728a/max6729a/ max6797a max6728a/max6729a/ max6797a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 11 downloaded from: http:///
applications information interfacing to ps with bidirectional reset pins most ps with bidirectional reset pins can interface directly to open-drain rst output options. systems simultane - ously requiring a push-pull rst output and a bidirectional reset interface can be in logic contention. to prevent con - tention, connect a 4.7k resistor between rst and the ps reset i/o port, as shown in figure 4. adding hysteresis to the power-fail comparator the power-fail comparator has a typical input hysteresis of 3mv. this is sufficient for most applications where a power-supply line is being monitored through an external voltage-divider (see the power-fail comparator section). if additional noise margin is desired, connect a resistor between pfo and pfi as shown in figure 5. select the values of r1, r2, and r3 so pfi sees v pfi (626mv) when v ext falls to its power-fail trip point (v fail ) and when v in rises to its power-good trip point (v good ). the hysteresis window extends between the specified v fail and v good thresholds. r3 adds the additional hysteresis by sinking current from the r1/r2 divider network when pfo is logic-low and sourcing current into the network when pfo is logic-high. r3 is typically an order of magni - tude greater than r1 or r2. the current through r2 should be at least 2.5a to ensure that the 100na (max) pfi input current does not signifi - cantly shift the trip points. therefore, r2 < v pfi /10a < 62k for most applications. r3 will provide additional hysteresis for pfo push-pull (v oh = v cc1 ) or open-drain (v oh = v pullup ) applications. monitoring an additional power supply these p supervisors can monitor either positive or nega - tive supplies using a resistor voltage-divider to pfi. pfo can be used to generate an interrupt to the p or cause reset to assert (figure 3). monitoring a negative voltage the power-fail comparator can be used to monitor a neg - ative supply voltage using the circuit shown in figure 3. when the negative supply is valid, pfo is low. when the negative supply voltage drops, pfo goes high. the cir - cuits accuracy is affected by the pfi threshold tolerance, v cc , r1, and r2. negative-going v cc transients the max6715aCmax6729a/max6797a supervisors are relatively immune to short-duration negative-going v cc transients (glitches). it is usually undesirable to reset the p when v cc experiences only small glitches. the typical operating characteristics show maximum transient duration vs. reset threshold overdrive, for which reset pulses are not generated. the graph was produced using negative-going v cc pulses, starting above v th and ending below the reset threshold by the figure 4. interfacing to ps with bidirectional reset i/o figure 5. adding hysteresis to power-fail for push-pull pfo gnd gnd v cc1 v cc2 v cc2 v cc1 rst reset to other system components reset p 4.7k ? max6715aC max6729a/ max6797a v ext r1 r3 r2 pfi gnd pfo a v good = desired v ext good voltage threshold v fail = desired v ext fail voltage threshold v oh = v cc1 (for push-pull pfo ) r2 = 50k ? (for > 10a r2 current) r1 = r2 ((v good - v pfi ) - (v pfi )(v good - v fail )/v oh )/v pfi r3 = (r1 x v oh )/(v good - v fail ) v good v fail v in pfo max6729a max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 12 downloaded from: http:///
magnitude indicated (reset threshold overdrive). the graph shows the maximum pulse width that a negative - going v cc transient may typically have without causing a reset pulse to be issued. as the amplitude of the transient increases (i.e., goes farther below the reset threshold), the maximum allowable pulse width decreases. a 0.1f bypass capacitor mounted close to the v cc pin provides additional transient immunity. watchdog software considerations setting and resetting the watchdog input at different points in the program, rather than pulsing the watchdog input high-low-high or low-high-low, helps the watchdog timer to closely monitor software execution. this technique avoids a stuck loop where the watchdog timer continues to be reset within the loop, keeping the watchdog from timing out. figure 6 shows an example flow diagram where the i/o driving the watchdog input is set high at the begin - ning of the program, set low at the beginning of every subroutine or loop, then set high again when the program returns to the beginning. if the program should hang in any subroutine, the i/o is continually set low and the watchdog timer is allowed to time out, causing a reset or interrupt to be issued. figure 6. watchdog flow diagram start set wdi high program code subroutine or program loop set wdi low return subroutine completed hang in subroutine max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 13 downloaded from: http:///
v cc1 v ref v cc2 rstin/pfi v ref v cc1 mr v cc1 v cc1 v cc1 reset timeout period v cc2 rstrst pfo watchdog timer wdi v cc1 mr pullup reset output driver v ref/2 max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 14 functional diagram downloaded from: http:///
note: the first _ _ are placeholders for the threshold voltage levels of the devices. desired threshold levels are set by the part number suffix found in the reset voltage threshold suffix guide. the _ after the d is a placeholder for the reset timeout delay time. desired delay time is set using the timeout period suffix found in the reset timeout period suffix guide. for example, the max6716autltd3-t is a dual-voltage supervisor v th1 = 4.625v, v th2 = 3.075v, and 210ms (typ) timeout period. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. part number number of voltage monitors open- drain reset open- drain reset push- pull reset push- pull reset manual reset watch- dog input power-fail input/ output max6715a 2 2 max6716a 2 2 max6717a 2 1 max6718a 2 1 max6719a 3 1 max6720a 3 1 max6721a 2 1 max6722a 2 1 max6723a 3 1 max6724a 3 1 max6725a 3 1 1 max6726a 3 1 1 max6727a 3 2 max6728a 2 1 (open drain) max6729a 2 1 (push-pull) max6797a 2 1 (open drain) part temp range pin- package max6720a ut_ _d_+t -40c to +125c 6 sot23 max6721a ut_ _d_+t -40c to +125c 6 sot23 max6722a ut_ _d_+t -40c to +125c 6 sot23 max6723a ut_ _d_+t -40c to +125c 6 sot23 max6724a ut_ _d_+t -40c to +125c 6 sot23 max6725a ka_ _d_+t -40c to +125c 8 sot23 max6726a ka_ _d_+t -40c to +125c 8 sot23 max6727a ka_ _d_+t -40c to +125c 8 sot23 max6728a ka_ _d_+t -40c to +125c 8 sot23 max6729a ka_ _d_+t -40c to +125c 8 sot23 max6797a ka_ _d_+t -40c to +125c 8 sot23 max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 15 selector guideordering information (continued) downloaded from: http:///
table 1. reset voltage threshold suffix guide** table 2. reset timeout period suffix guide ? d7 and d8 timeout periods are only available for the max6797a. note: standard versions are shown in bold and are available in a d3 timeout option only. standard versions require 2500-piece- order increments and are typically held in sample stock. there is a 10,000 order increment on nonstandard versions. other thresh - old voltages may be available; contact factory for availability. part number suffix (_ _) v cc1 nominal voltage threshold (v) v cc2 nominal voltage threshold (v) lt 4.625 3.075 ms 4.375 2.925 mr 4.375 2.625 tz 3.075 2.313 sy 2.925 2.188 ry 2.625 2.188 tw 3.075 1.665 sv 2.925 1.575 rv 2.625 1.575 ti 3.075 1.388 sh 2.925 1.313 rh 2.625 1.313 tg 3.075 1.110 sf 2.925 1.050 rf 2.625 1.050 te 3.075 0.833 sd 2.925 0.788 rd 2.625 0.788 zw 2.313 1.665 yv 2.188 1.575 zi 2.313 1.388 yh 2.188 1.313 zg 2.313 1.110 yf 2.188 1.050 ze 2.313 0.833 yd 2.188 0.788 wi 1.665 1.388 vh 1.575 1.313 wg 1.665 1.110 vf 1.575 1.050 we 1.665 0.833 vd 1.575 0.788 timeout period suffix active timeout period min (ms) max (ms) d1 1.1 2.2 d2 8.8 17.6 d7 ? 17.5 35.0 d8 ? 35.0 70.0 d3 140 280 d5 280 560 d6 560 1120 d4 1120 2240 max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 16 downloaded from: http:///
package type package code outline no. land pattern no. 5 sot23 u5+1 21-0057 90-0174 6 sot23 u6+1 21-0058 90-0175 8 sot23 k8sn+1 21-0078 90-0176 gnd v cc2 1 + 6 v cc1 5 sot23 top view 2 3 4 rst1 mr rst2 gnd v cc2 1 6 v cc1 5 sot23 2 3 4 rst mr wdi gnd v cc2 1 6 v cc1 5 sot23 2 3 4 rst wdi rstin 5 rstin gnd v cc2 1 5 v cc1 sot23 2 3 4 rst mr gnd v cc2 1 6 v cc1 sot23 2 3 4 rst mr v cc2 mr rst 12 8 7 v cc1 rstin gnd wdi rst sot23 3 4 6 5 v cc2 mr 12 8 7 v cc1 rstin gnd wdi rst sot23 3 4 6 5 rst v cc2 mr 12 8 7 v cc1 pfi gnd wdi rst sot23 3 4 6 5 pfo max6715a/ max6716a max6721a/ max6722a max6723a/ max6724a max6717a/ max6718a max6719a/ max6720a max6725a/ max6726a max6727a max6728a/ max6729a/ max6797a + + + + + + + max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits www.maximintegrated.com maxim integrated 17 pin conigurationschip information process: bicmos package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. downloaded from: http:///
revision number revision date description pages changed 0 4/06 initial release 1 7/06 updated ordering information 1, 15 2 6/08 added the max6797a to ordering information, electrical characteristics, pin description, detailed description , figures 4 and 5, selector guide, table 2, pin conigurations 1, 2, 6C11, 12, 15C17 3 9/08 updated selector guide 15 4 3/14 added automotive part to the ordering information table 1 maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and speciications without n otice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. max6715aCmax6729a/max6797a dual/triple, ultra-low-voltage, sot23 p supervisory circuits ? 2014 maxim integrated products, inc. 18 revision history for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com. downloaded from: http:///

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