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low voltage supervisory circuits with watchdog in 4-lead sc70 adm8616/adm8617 rev. b 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 ?2007 analog devices, inc. all rights reserved. features precision 1.8 v to 5 v power supply monitoring 9 reset threshold options 1.58 v to 4.63 v 4 reset timeout options 1 ms, 20 ms, 140 ms, 1120 ms 3 watchdog timeout options 6.3 ms, 102 ms, 1.6 sec reset output stages push-pull active-low (adm8616) open-drain active-low (adm8617) low power consumption (5 a) guaranteed reset output valid to v cc = 1 v power supply glitch immunity specified over ? 40c to +85c temperature range 4-lead sc70 package applications microprocessor systems computers controllers intelligent instruments portable equipment functional block diagram adm8616 v cc v cc gnd wdi reset reset generator watchdog detector v ref 0 4795-001 figure 1. general description the adm8616/adm8617 are supervisory circuits that monitor power supply voltage levels and code execution integrity in microprocessor-based systems. a power-on reset signal is generated when the supply voltage rises to a preset threshold level. the adm8616/adm8617 have an on-chip watchdog timer that can reset the microprocessor if it fails to strobe within a preset timeout period. each part is available in the following nine reset threshold options: 1.58 v, 1.67 v, 2.19 v, 2.32 v, 2.63 v, 2.93 v, 3.08 v, 4.38 v, and 4.63 v. there are four reset timeout options: 1 ms, 20 ms, 140 ms, and 1120 ms. there are also three possible watchdog timeouts available: 6.3 ms, 102 ms, and 1.6 sec. the parts differ in terms of reset output configuration. the adm8616 is active-low with a push-pull output, while the adm8617 is active-low with an open-drain output. the adm8616/adm8617 are available in 4-lead sc70 packages and typically consume only 5 a, making them suitable for use in low power, portable applications.
adm8616/adm8617 rev. b | 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............................................................ 4 esd caution.................................................................................. 4 pin configuration and function descriptions............................. 5 typical performance characteristics ............................................. 6 circuit description............................................................................8 reset output ...............................................................................8 watchdog input .............................................................................8 application information...................................................................9 watchdog input current ..............................................................9 negative-going v cc transients ...................................................9 ensuring reset valid to v cc = 0 v ...........................................9 watchdog software considerations............................................9 outline dimensions ....................................................................... 10 ordering guide .......................................................................... 10 revision history 1/07rev. a to rev. b changes to functional block diagram.......................................... 1 11/06rev. 0 to rev. a changes to ordering guide .......................................................... 10 6/05revision 0: initial version
adm8616/adm8617 rev. b | page 3 of 12 specifications v cc = full operating range, t a = ?40 o c to +85 o c, unless otherwise noted. table 1. parameter min typ max unit test conditions/comments supply v cc operating voltage range 1 5.5 v supply current 10 20 a v cc = 5.5 v 5 12 a v cc = 3.6 v reset threshold voltage adm861xl 4.50 4.63 4.75 v adm861xm 4.25 4.38 4.50 v adm861xt 3.00 3.08 3.15 v adm861xs 2.85 2.93 3.00 v adm861xr 2.55 2.63 2.70 v adm861xz 2.25 2.32 2.38 v adm861xy 2.12 2.19 2.25 v adm861xw 1.62 1.67 1.71 v adm861xv 1.52 1.58 1.62 v reset threshold temperature coefficient 40 ppm/c reset threshold hysteresis 2 v th mv reset timeout period adm861xxa 1 1.4 2 ms adm861xxb 20 28 40 ms adm861xxc 140 200 280 ms adm861xxd 1120 1600 2240 ms v cc to reset delay 40 s v cc falling at 1 mv/s reset output voltage vol (open-drain and push-pull) 0.3 v v cc 1.0 v, i sink = 50 a 0.3 v v cc 1.2 v, i sink = 100 a 0.3 v v cc 2.7 v, i sink = 1.2 ma 0.4 v v cc 4.5 v, i sink = 3.2 ma voh (push-pull only) 0.8 v cc v v cc 2.7 v, i source = 500 a v cc ? 1.5 v v cc 4.5 v, i source = 800 a reset rise time 5 25 ns from 10% to 90% v cc , c l = 5 pf, v cc = 3.3 v open-drain reset output leakage current 1 a watchdog input watchdog timeout period adm861xxxw 4.3 6.3 9.3 ms adm861xxxx 71 102 153 ms adm861xxxy 1.12 1.6 2.4 sec wdi pulse width 50 ns v il = 0.3 v cc , v ih = 0.7 v cc wdi input threshold v vil 0.3 v cc vih 0.7 v cc v wdi input current 120 160 a v wdi = v cc ?20 ?15 a v wdi = 0
adm8616/adm8617 rev. b | page 4 of 12 absolute maximum ratings t a = 25c, unless otherwise noted. table 2. parameter rating v cc ? 0.3 v to +6 v reset ? 0.3 v to +6 v output current ( reset ) 20 ma operating temperature range ? 40c to +85c storage temperature range ?65c to +150c ja thermal impedance, sc70 146c/w soldering temperature sn/pb 240c, 30 sec pb-free 260c, 40 sec stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; 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
adm8616/adm8617 rev. b | page 5 of 12 pin configuration and fu nction descriptions gnd 1 reset 2 v cc 4 wdi 3 adm8616/ adm8617 top view (not to scale) 04795-002 figure 2. pin configuration table 3. pin function descriptions pin no. mnemonic description 1 gnd ground. 2 reset active-low reset output. asserted whenever v cc is below the reset threshold (v th ). push-pull output stage for adm8616. open-drain output stage for adm8617. 3 wdi watchdog input. generates a reset if the logic level on the pin remains low or high for the duration of the watchdog timeout. the timer is cleared if a logic transition occurs on this pin, or if a reset is generated. leave floating to disable the watchdog timer. 4 v cc power supply voltage being monitored.
adm8616/adm8617 rev. b | page 6 of 12 typical performance characteristics temperature (c) 120 ?40 ?20 0 20 40 60 80 100 i cc (a) 10.0 9.5 7.5 7.0 6.5 9.0 8.5 8.0 6.0 5.5 5.0 4.5 4.0 3.5 v cc = 5v v cc = 3.3v v cc = 1.5v 04795-003 figure 3. supply current vs. temperature temperature (c) 120 ?40 0?20 4020 1008060 normalized reset timeout 1.20 1.15 1.10 1.05 0.95 1.00 0.90 0.85 0.80 04795-004 figure 4. normalized reset timeout period vs. temperature temperature (c) 120 ?40 0?20 4020 1008060 v cc to reset delay (s) 100 90 80 60 70 40 50 20 10 30 0 04795-005 figure 5. v cc to reset output delay vs. temperature temperature (c) 120 ?40 0?20 4020 1008060 normalized watchdog timeout 1.20 1.15 1.10 1.05 1.00 0.95 0.90 04795-006 figure 6. normalized watchdog timeout period vs. temperature temperature (c) 120 ?40 0?20 4020 1008060 normalized reset threshold 1.05 1.03 1.04 1.01 1.02 0.99 1.00 0.97 0.98 0.95 0.96 04795-007 figure 7. normalized reset threshold vs. temperature reset threshold overdrive (mv) 1000 10 100 minimum pulse width (s) 160 120 140 100 60 80 20 40 0 v cc = 4.63v v cc = 2.93v 04795-008 figure 8. maximum v cc transient duration vs. reset threshold overdrive
adm8616/adm8617 rev. b | page 7 of 12 i sink (ma) 7 56 03 4 12 v out (v) 0.20 0.15 0.10 0.05 0 v cc = 2.9v 04795-009 figure 9. voltage output low vs. i sink i source (ma) 1.0 00 . 6 0 . 0.2 0.4 v out (v) 2.92 2.90 2.88 2.86 2.84 2.82 8 v cc = 2.9v 04795-010 figure 10. voltage output high vs. i source
adm8616/adm8617 rev. b | page 8 of 12 circuit description the adm8616/adm8617 provide microprocessor supply voltage supervision by controlling the microprocessors reset input. 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 and by allowing supply voltage stabilization with a fixed timeout reset after the supply voltage rises above the threshold. in addition, problems with microprocessor code execution can be monitored and corrected with a watchdog timer. by including watchdog strobe instructions in microprocessor code, a watch- dog timer can detect if 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. reset output the adm8616 features an active-low, push-pull reset output, while the adm8617 features an active-low, open-drain reset output. the reset signal is guaranteed to be logic low and logic high, respectively, for v cc down to 1 v. the reset output is asserted when v cc is below the reset threshold (v th ), 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 or after the watchdog timer times out. figure 11 illustrates the behavior of the reset outputs. v cc 1v v cc 0v v th v th 0v v cc reset t rd t rp 04795-011 figure 11. reset timing diagram watchdog input the adm8616/adm8617 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 watch- dog 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 micro- processor 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 condition on v cc . when reset is asserted, the watchdog timer is cleared and does not begin counting again until reset deas- serts. 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 04795-012 figure 12. watchdog timing diagram
adm8616/adm8617 rev. b | page 9 of 12 application information watchdog input current to minimize 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 adm8616/adm8617 are equipped with glitch rejection circuitry. the typical performance characteristic in figure 8 plots v cc transient duration vs. transient magnitude. the curve shows 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 bigger 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 the active-low reset output is guaranteed to be valid for v cc as low as 1 v. however, by using an external resistor, valid outputs for v cc as low as 0 v are possible. the resistor, connected between reset and ground, pulls the output low when it is unable to sink current. a large resistance, such as 100 k, should be used so that it does not overload the reset output when v cc is above 1 v. adm8616/ adm8617 v cc reset 100k ? 0 4795-013 figure 13. ensuring reset valid to v cc = 0 v watchdog software considerations in implementing the microprocessors 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 from timing out. however, if the subroutine becomes stuck in an infinite loop, the watchdog does not detect this 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. 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 watch- dog times out, and the microprocessor is reset. start set wdi high program code subroutine set wdi low return infinite loop: watchdog times out reset 04795-014 figure 14. watchdog flow diagram reset reset wdi i/o adm8616/ adm8617 v cc p 04795-015 figure 15. typical application circuit
adm8616/adm8617 rev. b | page 10 of 12 outline dimensions * package outline corresponds in full to eiaj sc82 except for width of pin 2 as shown. 0.30 0.15 0.10 max 1.00 0.80 seating plane 0.18 0.10 0.30 0.10 0.10 coplanarity 2 4 3 1 2.20 1.80 pin 1 0.50 bsc * 0.70 0.50 1.35 1.15 2.40 1.80 1.10 0.80 0.65 bsc 0.40 0.10 12 8 figure 16. 4-lead thin shrink small outline transistor package [sc70] (ks-4) dimensions shown in millimeters adm861 ks -rl 7 ordering quantity rl7: 3,000 piece reel generic number (6/7) package code ks: 4-lead sc70 z: lead free watchdog timeout period w: 6.3ms (typ) x: 102ms (typ) y: 1.6s (typ) reset threshold l: 4.63v m: 4.38v t: 3.08v s: 2.93v r: 2.63v z: 2.32v y: 2.19v w: 1.67v v: 1.58v reset timeout period a: 1ms (min) b: 20ms (min) c: 140ms (min) d: 1120ms (min) temperature range a: ?40c to +85c xxxxx x 04795-016 figure 17. ordering code structure ordering guide model 1 reset threshold (v) temperature range quantity package description package option branding adm8616lcyaksz-rl7 2 4.63 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616mcyaksz-rl7 2 4.38 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616tcyaksz-rl7 2 3.08 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616scyaksz-rl7 2 2.93 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616rcyaksz-rl7 2 2.63 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616zcyaksz-rl7 2 2.32 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616ycyaksz-rl7 2 2.19 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f ADM8616WCYAKSZ-RL7 2 1.67 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8616vcyaksz-rl7 2 1.58 ? 40c to +85c 3,000 4-lead sc70 ks-4 n0f adm8617sayaksz-rl7 2 2.93 ? 40c to +85c 3,000 4-lead sc70 ks-4 m4x adm8617rcyaksz-rl7 2 2.63 ? 40c to +85c 3,000 4-lead sc70 ks-4 m4x 1 if ordering nonstandard models, complete the ordering code sh own in figure 17 by inserting reset threshold, reset timeout, and watchdog timeout suffixes. contact sales for availability of nonstandard models. 2 z = pb-free part.
adm8616/adm8617 rev. b | page 11 of 12 notes
adm8616/adm8617 rev. b | page 12 of 12 notes ?2007 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d04795-0-1/07(b)

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