set-top boxes computers and con- trollers embedded controllers intelligent instruments critical p monitoring portable/battery- powered equipment general description the max6821Cmax6825 are low-voltage microproces - sor (p) supervisory circuits that combine voltage mon - itoring, watchdog timer, and manual reset input func - tions in a 5-pin sot23 package. microprocessor super - visory circuits significantly improve system reliability and accuracy compared to separate ics or discrete compo - nents. these devices assert a reset signal whenever the monitored voltage drops below its preset threshold, keep - ing it asserted for a minimum timeout period after v cc rises above the threshold. in addition, a watchdog timer monitors against code execution errors. a debounced manual reset is also available. the max6821Cmax6825 monitor voltag - es from +1.8v to +5.0v. these outputs are guaranteed to be in the correct state for v cc down to +1.0v. nine preprogrammed reset threshold voltages are available (see the threshold suffix guide ). the max6821, max6822, and max6823 all have a manual reset input and a watchdog timer. the max6821 has push-pull reset, the max6822 has open-drain reset , and the max6823 has push-pull reset . the max6824 has a watchdog timer and both push-pull reset and push-pull reset. the max6825 has a manual reset input and both push-pull reset and push-pull reset. the selector guide explains the functions offered in this series of parts. features monitors +1.8v, +2.5v, +3.0v, +3.3v, +5.0v supplies 140ms (min) reset timeout delay 1.6s watchdog timeout period (max6821/max6822/ max6823/max6824) manual reset input (max6821/max6822/max6823/max6825) three reset output options push-pull reset push-pull reset open-drain reset guaranteed reset valid to v cc = +1.0v immune to short negative v cc transients no external components small 5-pin sot23 packages applications 19-1868; rev 3; 7/14 note: bold indicates standard versions. samples are typically available for standard versions only. all parts require a 2.5k minimum order increment. contact factory for availability. *insert the desired suffix letter (from the table below) into the blank to complete the part number devices are available in both leaded and lead(pb)-free packag - ing.specify lead-free by replacing -t with +t when ordering. suffix reset threshold (v) l 4.63 m 4.38 t 3.08 s 2.93 r 2.63 z 2.32 y 2.19 w 1.67 v 1.58 part* temp range pin-package max6821 _uk-t -40c to +125c 5 sot23-5 max6822 _uk-t -40c to +125c 5 sot23-5 max6823 _uk-t -40c to +125c 5 sot23-5 max6824 _uk-t -40c to +125c 5 sot23-5 max6825 _uk-t -40c to +125c 5 sot23-5 gnd wdi mr 1 5 v cc reset (reset) (reset) max6821 only max6821max6822 max6823 sot23-5 top view 2 3 4 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer selector guide appears at end of data sheet. threshold sufix guide ordering information typical operating circuit appears at end of data sheet. pin configurations continued at end of data sheet. pin conigurations downloaded from: http:///
v cc to gnd ......................................................... -0.3v to +6.0v open-drain reset .............................................. -0.3v to +6.0v push-pull reset , reset, mr , wdi ....... -0.3v to (v cc + 0.3v) input current (v cc ) ............................................................ 20ma output current ( reset , reset) ...................................... 20ma continuous power dissipation (t a = +70c) 5-pin sot23 (derate 7.1mw/c above +70c) .......... 571mw operating temperature range ......................... -40c to +125c junction temperature ...................................................... +150c storage temperature range ............................ -65c to +150c lead temperature (soldering, 10s) ................................. +300c (v cc = +4.5v to +5.5v for max682_l/m, v cc = +2.7v to +3.6v for max682_t/s/r, v cc = +2.1v to +2.75v for max682_z/y, v cc = +1.53v to +2.0v for max682_w/v, t a = -40c to +125c, unless otherwise specified. typical values are at t a = +25c.) (note 1) parameter symbol conditions min typ max units operating voltage range v cc t a = 0c to +85c 1.0 5.5 v t a = -40c to +125c 1.2 5.5 v cc supply current ( mr and wdi unconnected) i cc v cc = +5.5v, no load t a = -40c to +85c 10 20 a t a = -40c to +125c 30 v cc = +3.6v, no load t a = -40c to +85c 7 16 t a = -40c to +125c 25 v cc = +3.6v, no load (max6825 only) t a = -40c to +85c 5 12 t a = -40c to +125c 20 v cc reset threshold ( v cc falling) v th max682_l ta = -40c to +85c 4.50 4.63 4.75 v t a = -40c to +125c 4.47 4.63 4.78 max682_m t a = -40c to +85c 4.25 4.38 4.50 t a = -40c to +125c 4.22 4.38 4.53 max682_t t a = -40c to +85c 3.00 3.08 3.15 t a = -40c to +125c 2.97 3.08 3.17 max682_s t a = -40c to +85c 2.85 2.93 3.00 t a = -40c to +125c 2.83 2.93 3.02 max682_r t a = -40c to +85c 2.55 2.63 2.70 t a = -40c to +125c 2.53 2.63 2.72 max682_z t a = -40c to +85c 2.25 2.32 2.38 t a = -40c to +125c 2.24 2.32 2.40 max682_y t a = -40c to +85c 2.12 2.19 2.25 t a = -40c to +125c 2.11 2.19 2.27 max682_w t a = -40c to +85c 1.62 1.67 1.71 t a = -40c to +125c 1.61 1.67 1.72 max682_v t a = -40c to +85c 1.52 1.58 1.62 reset threshold temperature coefficient 60 ppm/c reset threshold hysteresis 2 v th mv v cc to reset output delay t rd v cc = v th to (v th - 100mv) 20 s www.maximintegrated.com maxim integrated 2 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer electrical characteristics 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. absolute maximum ratings downloaded from: http:///
note 1: over-temperature limits are guaranteed by design and not production tested. devices tested at t a = +25c. note 2: guaranteed by design and not production tested. (v cc = +4.5v to +5.5v for max682_l/m, v cc = +2.7v to +3.6v for max682_t/s/r, v cc = +2.1v to +2.75v for max682_z/y, v cc = +1.53v to +2.0v for max682_w/v, t a = -40c to +125c, unless otherwise specified. typical values are at t a = +25c.) (note 1) parameter symbol conditions min typ max units reset timeout period trp t a = -40c to +85c 140 200 280 ms t a = -40c to +125c 100 320 reset output low (push-pull or open-drain) v ol v cc 1.0v, i sink = 50a, reset asserted, t a = 0c to +85c 0.3 v v cc 1.2v, i sink = 100a, reset asserted 0.3 v cc 2.55v, i sink = 1.2ma, reset asserted 0.3 v cc 4.25v, i sink = 3.2ma, reset asserted 0.4 reset output high (push-pull only) v oh v cc 1.8v, i source = 200a, reset not asserted 0.8 v cc v v cc 3.15v, i source = 500a, reset not asserted 0.8 v cc v cc 4.75v, i source = 800a, reset not asserted 0.8 v cc open-drain reset output leakage current (note 1) i lkg v cc > v th , reset not asserted 1.0 a reset output high(push-pull only) v oh v cc 1.0v, i source = 1a, reset asserted, t a = 0 c to +85 c 0.8 v cc v v cc 1.50v, i source = 100a, reset asserted 0.8 v cc v cc 2.55v, i source = 500a, reset asserted 0.8 v cc v cc 4.25v, i source = 800a, reset asserted 0.8 v cc reset output low(push-pull only) v ol v cc 1.8v, i sink = 500a, reset not asserted 0.3 v v cc 3.15v, i sink = 1.2ma, reset not asserted 0.3 v cc 4.75v, i sink = 3.2ma, reset not asserted 0.4 manual reset input (max6821/max6822/max6823/max6825) mr input voltage v il 0.3 v cc v v ih 0.7 v cc mr minimum input pulse 1 s mr glitch rejection 100 ns mr to reset delay 200 ns mr pullup resistance 25 50 75 k? watchdog input (max6821/max6822/max6823/max6824) watchdog timeout period t wd t a = -40c to +85c 1.12 1.60 2.40 s t a = -40c to +125c 0.80 2.60 wdi pulse width (note 2) t wdi 50 ns wdi input voltage v il 0.3 v cc v v ih 0.7 v cc wdi input current i wdi wdi = v cc , time average 120 160 a wdi = 0, time average -20 -15 www.maximintegrated.com maxim integrated 3 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer electrical characteristics (continued) downloaded from: http:///
(t a = +25c, unless otherwise noted.) 2.74 2.782.76 2.822.80 2.84 2.86 2.902.88 2.92 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 voltage output high vs. source current max6821 toc08 i source (ma) v out (v) v cc = +2.9v 0 0.100.05 0.200.15 0.300.25 0.35 0 2 3 1 4 5 6 7 voltage output low vs. sink current max6821 toc07 i sink (ma) v out (v) v cc = +2.9v 0 6040 20 80 100 120 0 80 60 20 40 100 120 140 160 180 200 maximum v cc transient duration vs. reset threshold overdrive max6821 toc06 reset threshold overdrive (mv), v th - v cc transient duration ( s) reset occursabove curve 0.94 0.96 1.000.98 1.041.02 1.06 -40 0 20 -20 40 60 80 100 120 normalized reset threshold delay vs. temperature max6821 toc05 temperature (c) reset threshold (v) 1.0 1.21.1 1.41.3 1.61.5 1.7 1.91.8 2.0 -40 0 20 40 -20 60 80 100 120 watchdog timeout period vs. temperature max6821 toc04 temperature (c) watchdog timeout period (s) 0 10 5 2015 3025 35 -40 0 20 -20 40 60 80 100 120 v cc to reset output delay vs. temperature max6821 toc03 temperature (c) propagation delay ( s) v cc falling, v cc = v th - 100mv temperature (c) 150 170160 190180 210200 220 240230 250 -40 0 20 40 -20 60 80 100 120 reset timeout period vs. temperature max6821 toc02 reset timeout period (ms) 3 54 76 98 10 1211 13 -40 0 20 40 -20 60 80 100 120 supply current vs. temperature max6821 toc01 temperature ( c) supply current ( a) v cc = +5v, l version v cc = +3.3v, s version v cc = +1.8v, v version maxim integrated 4 www.maximintegrated.com max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer typical operating characteristics downloaded from: http:///
detailed description reset /reset output a ps reset input starts the p in a known state. the max6821Cmax6825 p supervisory circuits assert a reset to prevent code-execution errors during power-up, power-down, and brownout conditions. whenever v cc falls below the reset threshold, the reset output asserts low for reset and high for reset. once v cc exceeds the reset threshold, an internal timer keeps the reset out - put asserted for the specified reset timeout period (t rp ); after this interval, reset output returns to its original state (see figure 2). manual reset input many p-based products require manual reset capabili- ty, allowing the operator, a test technician, or external logic circuitry to initiate a reset. on the max6821/max6822/max6823/max6825, a logic low on mr asserts a reset. reset remains asserted while mr is low, and for the timeout period (140ms min) after it returns high. mr has an internal 50k ? pullup resistor, so it can be left open if not used. this input can be dri- ven with 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 dri- ven from long cables or the device is used in a noisy environment, connect a 0.1f capacitor from mr to gnd to provide additional noise immunity. watchdog input in the max6821Cmax6824, the watchdog circuit moni- tors the ps activity. if the p does not toggle (low to high or high to low) the watchdog input (wdi) within the watchdog timeout period (1.6s nominal), reset asserts for the reset timoeout period. the internal 1.6s timer can be cleared by either a reset pulse or by toggling wdi. the wdi can detect pulses as short as 50ns. while reset is asserted, the timer remains cleared and does not count. as soon as reset is released, the timer starts counting (see figure 3). pin numbers pin name function max6821 max6822 max6823 max6824 max6825 1 1 1 1 reset active-low open-drain or push-pull reset output. reset changes from high to low when the v cc input drops below the selected reset threshold, mr is pulled low, or the watchdog triggers a reset. reset remains low for the reset timeout period after v cc exceeds the device reset threshold, mr goes low to high, or the watchdog triggers a reset. 1 3 3 reset active-high push-pull reset output. reset changes from low to high when the v cc input drops below the selected reset threshold, mr is pulled low, or the watchdog triggers a reset. reset remains high for the reset timeout period after v cc exceeds the device reset threshold, mr goes low to high, or the watchdog triggers a reset. 2 2 2 2 2 gnd ground 3 3 3 4 mr active-low manual reset input. internal 50k ? 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. 4 4 4 4 wdi watchdog input. if wdi remains high or low for longer than the watchdog timeout period, the internal watchdog timer runs out and a reset is triggered for the reset timeout period. the internal watchdog timer clears whenever reset is asserted, the manual reset is asserted, or wdi sees a rising or falling edge. if wdi is left unconnected or is connected to a three-stated buffer output, the watchdog feature is disabled. 5 5 5 5 5 v cc supply voltage and input for reset threshold monitor www.maximintegrated.com maxim integrated 5 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer pin description downloaded from: http:///
disable the watchdog function by leaving wdi uncon - nected or by three-stating the driver connected to wdi. the watchdog input is internally driven low during the first 7/8 of the watchdog timeout period and high for the last 1/8 of the watchdog timeout period. when wdi is left unconnected, this internal driver clears the 1.6s timer every 1.4s. when wdi is three-stated or unconnected, the maximum allowable leakage current is 10a and the maximum allowable load capacitance is 200pf. applications information watchdog input current the max6821/max6822/max6823/max6824 wdi inputs are internally driven through a buffer and series resistor from the watchdog timer (figure 1). when wdi is left unconnected, the watchdog timer is serviced within the watchdog timeout period by a low-high-low pulse from the counter chain. for minimum watchdog input current (minimum overall power consumption), leave wdi low for the majority of the watchdog timeout period, pulsing it low- high-low once within the first 7/8 of the watchdog timeout period to reset the watchdog timer. if wdi is externally driven high for the majority of the timeout period, up to 160a can flow into wdi. interfacing to ps with bidirectional reset pins since the reset output on the max6822 is open drain, it interfaces easily with ps that have bidirectional reset pins, such as the motorola 68hc11. connecting the p supervisors reset output directly to the microcon- trollers reset pin with a single pullup resistor allows either device to assert reset (see figure 4).negative-going v cc transients these supervisors are relatively immune to short-dura- tion, negative-going v cc transients (glitches), which usually do not require the entire system to shut down. figure 2. reset timing diagram figure 1. functional diagram v cc 1v 1v t rd v th v th t rd reset gnd reset t rp t rp max6821Cmax6825 v cc v cc wdi (max6821Cmax6824) 1.26v gnd reset(max6821/max6824 / max6825) reset (max6822 C max6825) mr (max6821Cmax6823, max6825) reset generator watchdog timer watchdog transition detector www.maximintegrated.com maxim integrated 6 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer downloaded from: http:///
resets are issued to the p during power-up, pow - er-down, and brownout conditions. the typical operating characteristics show a graph of the max6821Cmax6825s maximum v cc transient duration vs. reset threshold overdrive, for which reset pulses are not generated. the graph was produced using negative-going v cc pulses, starting at the standard monitored voltage and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). the graph shows the max - imum pulse width that a negative-going v cc transient can typically have without triggering a reset pulse. as the amplitude of the transient increases (i.e., goes farther below the reset threshold), the maximum allowable pulse width decreases. typically, a v cc transient that goes 100mv below the reset threshold and lasts for 20s or less will not trigger a reset pulse. watchdog software considerations one way to help the watchdog timer monitor software execution more closely is to set and reset the watchdog input at different points in the program, rather than pulsing the watchdog input high-low-high or low-high-low. this technique avoids a stuck loop, in which the watchdog timer would continue to be reset inside the loop, keeping the watchdog from timing out. figure 5 shows an example of a 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 problem would quickly be corrected, since the i/o is continually set low and the watchdog timer is allowed to time out, causing a reset or interrupt to be issued. as described in the watchdog input current section, this scheme results in higher time average wdi input current than does leaving wdi low for the majority of the timeout period and periodically pulsing it low-high-low. figure 5. watchdog flow diagram figure 4. interfacing open-drain reset to ps with bidirectional reset i/o figure 3. watchdog timing relationship max6823 p v cc v cc v cc gnd manual reset reseti/o reset mr wdi start set wdi high program code subroutine or program loop set wdi low return max6822 reset generator gnd gnd v cc v cc reset reset p v cc t wd t rp t rp t rst wdi reset * *reset is the inverse of reset . www.maximintegrated.com maxim integrated 7 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer typical operating circuit downloaded from: http:///
function active-low reset active-high reset open-drain reset watchdog input manual reset input max6821 ? ? ? max6822 ? ? ? max6823 ? ? ? max6824 ? ? ? max6825 ? ? ? package type package code outline no. land pattern no. 5 sot23 u5-1 21-0057 gnd wdi reset 1 5 v cc reset max6824 sot23-5 top view 2 3 4 gnd mr reset 1 5 v cc reset max6825 sot23-5 2 3 4 www.maximintegrated.com maxim integrated 8 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer 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. chip information transistor count: 750 process: bicmos pin conigurations (continued) selector guide downloaded from: http:///
revision number revision date description pages changed 3 7/14 no /v opns; removed automotive reference from applications section 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. ? 2014 maxim integrated products, inc. 9 max6821/max6825 low-voltage sot23 p supervisors with manual reset and watchdog timer 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:///
|
