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supervisory circuits with watchdog and manual reset in 5-lead sc70 and sot-23 adm823/ADM824/adm825 rev. c information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2004C2010 analog devices, inc. all rights reserved. features precision 2.5 v to 5 v power supply monitor 7 reset threshold options: 2.19 v to 4.63 v 140 ms (minimum) reset timeout watchdog timer with 1.6 sec timeout (adm823, ADM824) manual reset input (adm823, adm825) push-pull output stages reset (adm823) reset , reset (ADM824/adm825) low power consumption: 5 a guaranteed reset output valid to v cc = 1 v power supply glitch immunity specified over automotive temperature range 5-lead sc70 and sot-23 packages applications microprocessor systems computers controllers intelligent instruments portable equipment functional block diagram adm823 v cc v cc mr gnd wdi reset reset generator watchdog detector debounce v ref 04534-001 figure 1. general description the adm823/ADM824/adm825 are supervisory circuits that monitor power supply voltage levels and code execution integrity in microprocessor-based system s. in addition to providing power-on reset signals, an on-chip watchdog timer can reset the microprocessor if it fails to strobe within a preset timeout period. a reset signal can also be asserted by an external push- button, through a manual reset input. the three parts feature different combinations of watchdog input, manual reset input, and output stage configuration, as shown in table 1 . these parts are available in a choice of seven reset threshold options ranging from 2.19 v to 4.63 v. the reset and watchdog timeout periods are fixed at 140 ms (minimum) and 1.6 sec (typical), respectively. the adm823/ADM824/adm825 are available in 5-lead sc70 and sot-23 packages and typically consume only 5 a, making them suitable for use in low power, portable applications. table 1. selection table output stage part no. watchdog timer manual reset reset reset adm823 yes yes push-pull C ADM824 yes C push-pull push-pull adm825 C yes push-pull push-pull
adm823/ADM824/adm825 rev. c | page 2 of 12 table of contents features .............................................................................................. 1 applications....................................................................................... 1 functional block diagram .............................................................. 1 general description ......................................................................... 1 revision history ............................................................................... 2 specifications..................................................................................... 3 absolute maximum ratings............................................................ 5 esd caution.................................................................................. 5 pin configurations and function descriptions ........................... 6 typical performance characteristics ............................................. 7 circuit description........................................................................... 9 reset output ..................................................................................9 manual reset input .......................................................................9 watchdog input .............................................................................9 applications information .............................................................. 10 watchdog input current ........................................................... 10 negative-going v cc transients ................................................ 10 ensuring reset valid to v cc = 0 v ........................................... 10 watchdog software considerations......................................... 10 outline dimensions ....................................................................... 11 ordering guide .......................................................................... 11 revision history 10/10rev. b to rev. c updated outline dimensions ....................................................... 11 changes to ordering guide .......................................................... 11 5/08rev. a to rev. b changes to general description section ...................................... 1 changes to table 4............................................................................ 6 changes to ordering guide .......................................................... 11 2/07rev. 0 to rev. a updated format..................................................................universal changes to ordering guide .......................................................... 11 10/04revision 0: initial version
adm823/ADM824/adm825 rev. c | page 3 of 12 specifications v cc = 4.75 v to 5.5 v for adm82xl, v cc = 4.5 v to 5.5 v for adm82xm, v cc = 3.15 v to 3.6 v for adm82xt, v cc = 3 v to 3.6 v for adm82xs, v cc = 2.7 v to 3.6 v for adm82xr, v cc = 2.38 v to 2.75 v for adm82xz, v cc = 2.25 v to 2.75 v for adm82xy, t a = t min to t max , unless otherwise noted. table 2. parameter min typ max unit test conditions/comments supply v cc operating voltage range 1 5.5 v t a = 0c to 70c 1.2 v t a = t min to t max supply current 10 24 a wdi and mr unconnected adm82xl/m 5 12 a wdi and mr unconnected adm82xt/s/r/z/y reset threshold voltage adm82xl 4.56 4.63 4.70 v t a = 25c 4.50 4.75 v t a = t min to t max adm82xm 4.31 4.38 4.45 v t a = 25c 4.25 4.50 v t a = t min to t max adm82xt 3.04 3.08 3.11 v t a = 25c 3.00 3.15 v t a = t min to t max adm82xs 2.89 2.93 2.96 v t a = 25c 2.85 3.00 v t a = t min to t max adm82xr 2.59 2.63 2.66 v t a = 25c 2.55 2.70 v t a = t min to t max adm82xz (sc70 only) 2.28 2.32 2.35 v t a = 25c 2.25 2.38 v t a = t min to t max adm82xy (sc70 only) 2.16 2.19 2.22 v t a = 25c 2.13 2.25 v t a = t min to t max reset threshold temperature coefficient 40 ppm/c reset threshold hysteresis 10 mv adm82xl/m 5 mv adm82xt/s/r/z/y reset timeout period 140 200 280 ms v cc to reset delay 40 s v th ? v cc = 100 mv reset /reset reset output voltage 0.4 v v cc = v th min, i sink = 3.2 ma, adm82xl/m 0.3 v v cc = v th min, i sink = 1.2 ma, adm82xt/s/r/z/y 0.3 v t a = 0c to 70c, v cc = 1 v, v cc falling, i sink = 50 a v cc ? 1.5 v v cc = v th max, i source = 120 a, adm82xl/m 0.8 v cc v v cc = v th max, i source = 30 a, adm82xt/s/r/z/y reset output voltage (ADM824, adm825) 0.4 v v cc = v th max, i sink = 3.2 ma, adm82xl/m 0.3 v v cc = v th max, i sink = 1.2 ma, adm82xt/s/r/z/y 0.8 v cc v v cc 1.8 v, i source = 150 a
adm823/ADM824/adm825 rev. c | page 4 of 12 parameter min typ max unit test conditions/comments watchdog input (adm823, ADM824) watchdog timeout period 1.12 1.6 2.40 sec wdi pulse width 50 ns v il = 0.4 v, v ih = 0.8 v cc wdi input threshold, v il 0.7 v cc 0.3 v cc v wdi input current 120 160 a v wdi = v cc , time average ?20 ?15 a v wdi = 0 v, time average manual reset input (adm823, adm825) mr input threshold 0.7 v cc 0.3 v cc v mr input pulse width 1 s mr glitch rejection 100 ns mr pull-up resistance 35 52 75 k mr to reset delay 500 ns
adm823/ADM824/adm825 rev. c | page 5 of 12 absolute maximum ratings t a = 25c, unless otherwise noted. table 3. parameter rating v cc ?0.3 v to +6 v output current (reset, reset ) 20 ma all other pins ?0.3 v to (v cc + 0.3 v) operating temperature range ?40c to +125c storage temperature range ?65c to +150c ja thermal impedance sc70 146c/w sot-23 270c/w lead temperature soldering (10 sec) 300c vapor phase (60 sec) 215c infrared (15 sec) 220c stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. esd caution
adm823/ADM824/adm825 rev. c | page 6 of 12 pin configurations and function descriptions adm823 top view (not to scale) reset 1 gnd 2 mr 3 v cc wdi 5 4 04534-002 reset 1 gnd 2 reset 3 v cc wdi 5 4 04534-003 ADM824 top view (not to scale) adm825 top view (not to scale) reset 1 gnd 2 reset 3 v cc mr 5 4 04534-004 figure 2. adm823 pin configuration figure 3. ADM824 pin configuration figure 4. adm825 pin configuration table 4. pin function descriptions pin no. mnemonic description 1 reset active low, push-pull reset output. asserted whenever v cc is below the reset threshold, v th . 2 gnd ground. 3 mr (adm823) manual reset input. this is an active low input which, when forced low for at least 1 s, generates a reset. it features a 52 k internal pull-up. reset (ADM824/adm825) active high, push-pull reset output. 4 wdi (adm823/ADM824) watchdog input. generates a reset if the voltage on the pin remains low or high for the duration of the watchdog timeout. the timer is cleared if a lo gic transition occurs on this pin or if a reset is generated. mr (adm825) manual reset input. this is an active low input which, when forced low for at least 1 s, generates a reset. it features a 52 k internal pull-up. 5 v cc power supply voltage being monitored.
adm823/ADM824/adm825 rev. c | page 7 of 12 typical performance characteristics 04534-005 temperature (c) 120 ?40 ?20 0 20 40 60 80 100 i cc (a) 10.0 9.0 9.5 8.0 7.5 8.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 adm823l ADM824y adm825r 04534-008 temperature (c) 120 ?40 4020 0 ?20 60 80 100 v cc to reset del a y (s) 100 80 90 60 50 70 40 30 20 10 0 figure 8. reset comparator propagation delay vs. temperature (v cc falling) figure 5. supply current vs. temperature 04534-006 v cc (v) 5.5 02 . 0 1.51.0 0.5 2.5 3.0 3.5 4.0 4.5 5.0 i cc (a) 80 70 75 60 55 65 50 45 40 35 30 20 10 25 15 5 0 04534-009 temperature (c) 120 ?40 4020 0 ?20 60 80 100 manual rese t to reset del a y (ns) 340 300 320 260 240 280 220 200 180 160 140 120 100 figure 6. supply current vs. supply voltage figure 9. manual reset to reset propagation delay vs. temperature (adm823/adm825) 04534-010 temperature (c) 120 ?40 4020 0 ?20 60 80 100 reset timeout period (ms) 250 230 240 210 200 220 190 180 170 04534-007 temperature (c) 120 ?40 4020 0 ?20 60 80 100 normalized reset threshold (v) 1.05 1.03 1.04 1.01 1.00 1.02 0.99 0.98 0.97 0.96 0.95 figure 10. reset timeout period vs. temperature figure 7. normalized reset threshold vs. temperature
adm823/ADM824/adm825 rev. c | page 8 of 12 04534-011 temperature (c) 120 ?40 ?20 0 20 40 60 80 100 watchdog timeout period (s) 2.0 1.6 1.8 1.4 1.2 0.8 1.0 0.6 0.4 0.2 0 figure 11. watchdog timeout period vs. temperature (adm823/ADM824) 04534-012 overdrive vod (mv) 1000 10 100 maximum v cc transient duration (s) 160 120 140 100 60 80 40 20 0 v th = 4.63v v th = 2.93v reset occurs above graph figure 12. maximum v cc transient duration vs. reset threshold overdrive 04534-013 temperature (c) 100 ?50 0 50 mr minimum pulse width (ns) 190 160 180 170 150 130 140 120 110 100 figure 13. manual reset minimum pulse width vs. temperature (adm823/adm825) 04534-014 temperature (c) 160 ?40 10 110 60 minimum pulse width (ns) 3.8 3.2 3.6 3.4 3.0 2.6 2.8 2.4 2.2 2.0 negative pulse positive pulse figure 14. watchdog input mini mum pulse width vs. temperature (adm823/ADM824)
adm823/ADM824/adm825 rev. c | page 9 of 12 circuit description the adm823/ADM824/adm825 provide microprocessor supply voltage supervision by controlling the reset input of the microprocessor. code execution errors are avoided during power-up, power-down, and brownout conditions by asserting a reset signal when the supply voltage is below a preset threshold. errors are also avoided by allowing supply voltage stabilization with a fixed timeout reset pulse after the supply voltage rises above the threshold. in addition, problems with microprocessor code execution can be monitored and corrected with a watchdog timer (adm823/ADM824). by including watchdog strobe instructions in microprocessor code, a watchdog timer can detect whether the microprocessor code breaks down or becomes stuck in an infinite loop. if this happens, the watchdog timer asserts a reset pulse that restarts the microprocessor in a known state. if the user detects a problem with the systems operation, a manual reset input is available (adm823/adm825) to reset the microprocessor with an external push-button, for example. reset output the adm823 features an active low, push-pull reset output, and the ADM824/adm825 feature dual active low and active high push-pull reset outputs. for active low and active high outputs, the reset signal is guaranteed to be logic low and logic high, respectively, for v cc 1 v. the reset output is asserted when v cc is below the reset threshold (v th ), when mr is driven low, or when wdi is not serviced within the watchdog timeout period (t wd ). reset remains asserted for the duration of the reset active timeout period (t rp ) after v cc rises above the reset threshold, after mr transitions from low to high, or after the watchdog timer times out. illustrates the behavior of the reset outputs. figure 15 v cc 1v v cc 0v v cc 0v v th v th 0v v cc reset reset t rd t rd 1v t rp t rp 04534-018 figure 15. reset timing diagram manual reset input the adm823/adm825 feature a manual reset input ( mr ) which, when driven low, asserts the reset output. when mr transitions from low to high, reset remains asserted for the duration of the reset active timeout period before deasserting. the mr input has a 52 k internal pull-up so that the input is always high when unconnected. an external push-button switch can be connected between mr and ground so that the user can generate a reset. debounce circuitry for this purpose is integrated on chip. noise immunity is provided on the mr input and fast, negative-going transients of up to 100 ns (typical) are ignored. a 0.1 f capacitor between mr and ground provides additional noise immunity. watchdog input the adm823/ADM824 feature a watchdog timer that monitors microprocessor activity. a timer circuit is cleared with every low-to-high or high-to-low logic transition on the watchdog input pin (wdi), which detects pulses as short as 50 ns. if the timer counts through the preset watchdog timeout period (t wd ), reset is asserted. the microprocessor is required to toggle the wdi pin to avoid being reset. failure of the microprocessor to toggle wdi within the timeout period, therefore, indicates a code execution error, and the reset pulse generated restarts the microprocessor in a known state. in addition to logic transitions on wdi, the watchdog timer is also cleared by a reset assertion due to an undervoltage condi- tion on v cc or by mr being pulled low. when reset is asserted, the watchdog timer is cleared and does not begin counting again until reset is deasserted. the watchdog timer can be disabled by leaving wdi floating or by three-stating the wdi driver. v cc 1v v cc 0v v cc 0v v th 0v v cc wdi reset t rp t rd t wd 04534-021 figure 16. watchdog timing diagram
adm823/ADM824/adm825 rev. c | page 10 of 12 applications information watchdog input current to minimize the watchdog input current (and minimize overall power consumption), leave wdi low for the majority of the watchdog timeout period. when driven high, wdi can draw as much as 160 a. pulsing wdi low-high-low at a low duty cycle reduces the effect of the large input current. when wdi is unconnected, a window comparator disconnects the watchdog timer from the reset output circuitry so that reset is not asserted when the watchdog timer times out. negative-going v cc transients to avoid unnecessary resets caused by fast power supply transients, the adm823/ADM824/adm825 are equipped with glitch rejection circuitry. the typical performance characteristic in figure 12 plots v cc transient duration vs. the transient mag- nitude. the curves show combinations of transient magnitude and duration for which a reset is not generated for 4.63 v and 2.93 v reset threshold parts. for example, with the 2.93 v threshold, a transient that goes 100 mv below the threshold and lasts 8 s typically does not cause a reset, but if the transient is any larger in magnitude or duration, a reset is generated. an optional 0.1 f bypass capacitor mounted close to v cc provides additional glitch rejection. ensuring reset valid to v cc = 0 v both active low and active high reset outputs are guaranteed to be valid for v cc as low as 1 v. however, by using an external resistor with push-pull configured reset outputs, valid outputs for v cc as low as 0 v are possible. for an active low reset output, a resistor connected between reset and ground pulls the output low when it is unable to sink current. for an active high reset output, a resistor connected between reset and v cc pulls the output high when it is unable to source current. a large resist- ance such as 100 k should be used so that the reset output is not overloaded when v cc is above 1 v. adm823/ ADM824/ adm825 v cc reset 100k ? ADM824/ adm825 v cc reset 100k ? 04534-017 figure 17. ensuring reset valid to v cc = 0 v watchdog software considerations in implementing the microprocessor watchdog strobe code, quickly switching wdi low-to-high and then high-to-low (minimizing wdi high time) is desirable for current consumption reasons. however, a more effective way of using the watchdog function can be considered. a low-high-low wdi pulse within a given subroutine prevents the watchdog timing out. however, if the subroutine becomes stuck in an infinite loop, the watchdog cannot detect this cond- ition because the subroutine continues to toggle wdi. a more effective coding scheme for detecting this error involves using a slightly longer watchdog timeout. in the program that calls the subroutine, wdi is set high (see figure 18 ). the subroutine sets wdi low when it is called. if the program executes without error, wdi is toggled high and low with every loop of the program. if the subroutine enters an infinite loop, wdi is kept low, the watchdog times out, and the microprocessor is reset. start set wdi high program code subroutine set wdi low return infinite loop: watchdog times out reset 04534-020 figure 18. watchdog flow diagram reset reset wdi i/o mr adm823 v cc microprocessor 04534-019 figure 19. typical application circuit
adm823/ADM824/adm825 rev. c | page 11 of 12 outline dimensions compliant to jedec standards mo-203-aa 1.00 0.90 0.70 0.46 0.36 0.26 2.20 2.00 1.80 2.40 2.10 1.80 1.35 1.25 1.15 072809-a 0.10 max 1.10 0.80 0.40 0.10 0.22 0.08 3 12 4 5 0.65 bsc coplanarity 0.10 seating plane 0.30 0.15 figure 20. 5-lead thin shrink small outline transistor package [sc70] (ks-5) dimensions shown in millimeters compliant to jedec standards mo-178-aa 121608-a 10 5 0 seating plane 1.90 bsc 0.95 bsc 0.20 bsc 5 123 4 3.00 2.90 2.80 3.00 2.80 2.60 1.70 1.60 1.50 1.30 1.15 0.90 0 .15 max 0 .05 min 1.45 max 0.95 min 0.20 max 0.08 min 0.50 max 0.35 min 0.55 0.45 0.35 figure 21. 5-lead small outline transistor package [sot-23] (rj-5) dimensions shown in millimeters ordering guide model 1 reset threshold (v) temperature range quantity package description package option branding adm823lyksz-r7 4.63 ?40c to +125c 3k 5-lead sc70 ks-5 m4l adm823lyrj-r7 4.63 ?40c to +125c 3k 5-lead sot-23 rj-5 n07 adm823lyrjz-r7 4.63 ?40c to +125c 3k 5-lead sot-23 rj-5 m4l adm823myksz-r7 4.38 ?40c to +125c 3k 5-lead sc70 ks-5 m4l adm823myrjz-r7 4.38 ?40c to +125c 3k 5-lead sot-23 rj-5 m4l adm823tyksz-r7 3.08 ?40c to +125c 3k 5-lead sc70 ks-5 m4l adm823tyrj-r7 3.08 ?40c to +125c 3k 5-lead sot-23 rj-5 n07 adm823tyrjz-r7 3.08 ?40c to +125c 3k 5-lead sot-23 rj-5 m4l adm823syksz-r7 2.93 ?40c to +125c 3k 5-lead sc70 ks-5 m4l adm823syrj-r7 2.93 ?40c to +125c 3k 5-lead sot-23 rj-5 n07 adm823syrjz-r7 2.93 ?40c to +125c 3k 5-lead sot-23 rj-5 m4l
adm823/ADM824/adm825 rev. c | page 12 of 12 model 1 reset threshold (v) temperature range quantity package description package option branding adm823ryrjz-r7 2.63 ?40c to +125c 3k 5-lead sot-23 rj-5 m4l adm823zyksz-r7 2.32 ?40c to +125c 3k 5-lead sc70 ks-5 m4l adm823yyksz-r7 2.19 ?40c to +125c 3k 5-lead sc70 ks-5 m4l ADM824lyrjz-reel7 4.63 ?40c to +125c 3k 5-lead sot-23 rj-5 l9m ADM824syksz-reel7 2.93 ?40c to +125c 3k 5-lead sc70 ks-5 m8g adm825lyrj-r7 4.63 ?40c to +125c 3k 5-lead sot-23 rj-5 n09 adm825lyrjz-r7 4.63 ?40c to +125c 3k 5-lead sot-23 rj-5 m8h adm825myrj-r7 4.38 ?40c to +125c 3k 5-lead sot-23 rj-5 n09 adm825tyksz-r7 3.08 ?40c to +125c 3k 5-lead sc70 ks-5 m8h adm825tyrj-r7 3.08 ?40c to +125c 3k 5-lead sot-23 rj-5 n09 adm825tyrjz-r7 3.08 ?40c to +125c 3k 5-lead sot-23 rj-5 m8h adm825syksz-r7 2.93 ?40c to +125c 3k 5-lead sc70 ks-5 m8h adm825syrj-r7 2.93 ?40c to +125c 3k 5-lead sot-23 rj-5 n09 adm825syrjz-r7 2.93 ?40c to +125c 3k 5-lead sot-23 rj-5 m8h adm825ryrj-r7 2.63 ?40c to +125c 3k 5-lead sot-23 rj-5 n09 adm825ryrjz-r7 2.63 ?40c to +125c 3k 5-lead sot-23 rj-5 m8h adm825zyksz-r7 2.32 ?40c to +125c 3k 5-lead sc70 ks-5 m8h 1 z = rohs compliant part. ?2004C2010 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d04534-0-10/10(c)

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