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________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 1 / 15 u m706xs/um708xs supply voltage supervisor w/ watchdog input and manual reset u m 70 6 x s so p 8 u m708 x s so p 8 general description the um 706 xs / um 708 xs series are cost effective system power supply supervi sory circuits designed to monitor the power supplies in digital systems. the um 70 6 xs provide s power - supply monitoring circuitry that generate s a reset output during power - up, power - down, and brownout conditions. the reset output remains operational with v cc as low as 1v. independent watchdog monitoring circuitry is also provided. this is activated if the watchdog input has not been toggled within 1.6 seconds. i n addition, there is a 1.25v threshold detector for power - fail warning, low battery detection, or to monitor an additional power supply. a n active low debounced manual reset input is also include d. the um 708 xs is the same as the um 706 xs , except an active - high reset is substituted for t he watchdog timer. all parts are available in a small outline sop8 package. applications features ? applications using dsps, microcontroller s or microproc e ssors ? p rogrammable c ontrols ? computers ? embedded s ystem ? industrial e quipments ? intelligent i nstrument ? wireless c ommunications s ystems ? wide o peration v oltage r ang e of 1v to 5.5 v ? correct l ogic o utput g uaranteed to v cc =1.0v ? precision supply - voltage monitor : 2. 63 v , 2.93v, 3.08 v ,4.38v,4. 6 3v ? 20 0 ms reset pulse width ? independent watchdog timer - 1.6s timeout (UM706 xs ) ? a ctive - high reset o utput (um708 xs ) ? voltage monitor for power - fail or low - battery warning ? temperature r ange: - 40 c to + 85 c ? supply current of 80a (typ.) pin configurations top view UM706x s ( )* for um708x s xx : week code ( )* for u m708 xs 1 2 3 4 5 6 7 8 m r v c c g n d p f i p f o w d i ( n c ) * r e s e t w d o ( r e s e t ) * 1 2 3 4 5 6 7 8 u m 7 0 6 ( 7 0 8 ) * x s x x
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 2 / 15 u m706xs/um708xs ordering information part number top marking reset threshold (v) timeout period (ms) package type UM706l s UM706l s 4.63 240 sop8 UM706m s UM706m s 4.38 240 UM706t s UM706t s 3.08 240 UM706s s UM706s s 2.93 240 UM706r s UM706r s 2.63 240 um708 l s um708l s 4.63 240 um708m s um708m s 4.38 240 um708t s um708t s 3.08 240 um708s s um708s s 2.93 240 um708r s um708r s 2.63 240 typical application circuit figure 1 . UM706x s application circuit figure 2 . um708 x s applicatio n circuit u m 7 0 6 v c c p f i p f o m r w d o w d i r e s e t i n t n m i i / o r e s e t v c c p u s h b u t t o n s w i t c h v c c p u m 7 0 8 v c c p f i p f o m r r e s e t i n t r e s e t v c c p u s h b u t t o n s w i t c h v c c p r e s e t r e s e t
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 3 / 15 u m706xs/um708xs pin des cr iption pin number pin name function 1 mr _______ manual - reset input triggers a reset pulse when pulled below 0.8v. this active - low input has an internal 250 a pull - up cu rrent. i t can be driven from a ttl or cmos logic line as well as shorted to ground with a switch. 2 v cc supply input 3 gnd ground reference for all signals. 4 pfi power - fail voltage monitor input. when pfi is less than 1.25v, pfo ________ goe s low. connect pfi to gnd or v cc when not used. 5 pfo ________ power - fail output goes low and sinks current when pfi is less than 1.25v; oth erwise pfo ________ stays high. 6 UM706 wdi watchdog input. if wdi remains either high or low for longer than the watchdog timeout period, the wdo __________ goes low. the timer resets with each transition at the wdi input. either a high - to - low or a low - to - high transition clears the counter. the internal timer is also cleared whenever reset is asserted. um708 nc no connect 7 reset ______________ active - low reset output pulses low for 20 0 ms when tri gged, and stays low whenever v cc is below the reset threshold. it remains low for 20 0 ms after v cc rises above the reset threshold or mr _______ goes from low to high. 8 UM706 wdo ___________ watchdog output pulls low when the internal watchdog tim er finishes its 1.6sec count and does not go high again until the watchdog is cleared. wdo ___________ also goes low during low - line conditions. whenever v cc is below the reset threshold, wdo ___________ stays low; however, unlike reset ______________ , wdo ______ _____ does not have a minimum pulse width. as soon as v cc rises above the reset threshold, wdo ___________ goes high with no delay. um708 reset active - high reset output is the inverse of reset ____________ . whenever reset is high, reset ____________ is low, and vice versa.
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 4 / 15 u m706xs/um708xs absolute maximum ratings (no te 1) symbol parameter v alue u nit v cc supply voltage - 0.3 to + 6.0 v reset, reset ____________ (push - pull) - 0.3 to v cc +0.3 v i cc input current , v cc 20 ma i o output current , reset, reset ____________ 20 ma rate of rise, v cc 100 v/ d continuous power dissipation 471 mw t j operating junction temperature - 40 to +1 05 c t stg storage temperature range - 65 to +1 50 c le ad temperature (soldering, 10s) 300 c note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. electrical characteristics v cc = full range, t a = - 40c to + 8 5c, unless otherwise noted. typical valu es are at t a =+25c, v cc = 5v for l/m versions, v cc = 3.3v for t/s versions, and v cc = 3v for r version . (note 2 ) symbol parameter conditions min. typ. max. unit v cc v cc range t a =0 to + 70 1.0 5.5 v t a = - 40 to + 8 5 1.2 5.5 i cc supply current t a = - 40 to + 8 5 80 150 a v th reset threshold um 70 6 l / um708l t a =+25 4.56 4.63 4.70 v t a = - 40 to + 85 4.50 4.75 um70 6 m / um708m t a =+25 4.31 4.38 4.45 t a = - 40 to + 85 4.25 4.50 um 70 6 t / um708t t a =+25 3.04 3.08 3.11 t a = - 40 to + 85 3.00 3.15 um 70 6 s / um708s t a =+25 2.89 2.93 2.96 t a = - 40 to + 85 2.85 3.00 um70 6 r / um708r t a =+25 2.59 2.63 2.66 t a = - 40 to + 85 2.55 2.70 reset thresh old hysteresis 40 mv t rs r eset pulse width 140 200 280 ms note 2 : production testing done at t a = +25c; limits over temperature guaranteed by design only.
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 5 / 15 u m706xs/um708xs electrical characteristics (continued) v cc = full range, t a = - 40c to + 8 5c, unless other wise noted. typical values are at t a =+25c, v cc = 5v for l/m versions, v cc = 3.3v for t/s versions, and v cc = 3v for r version . (note 2 ) symbol parameter conditions min. typ. max. unit v ol reset / reset ______________ output voltage low i sink =1.2ma, (for r/s/t versions) 0.3 v i sink = 3 .2ma, (for l/m ve r sions) 0.4 v cc = 1.2v, i sink = 100 a 0.3 v oh reset / reset ______________ output voltage high i source = 800 a v cc - 1.5 v mr _______ pull - up current mr _______ =0v 100 250 600 a t mr mr _______ pulse width 150 ns mr _______ input threshold, low 0.8 v mr _ ______ input threshold, high 2.0 v t md mr _______ to reset out delay 250 ns pfi input threshold v cc =5v 1.20 1.25 1.30 v pfi input current - 25 0.01 +25 na pfo ________ output voltage i s o u r c e =800 a vcc - 1.5 v i s i n k =3.2ma 0.4 watchdog function for UM706 t wd watchdog timeout period 1.0 1.6 2.25 s t w p wdi pulse width v il =0.4v,v ih =0.8vcc 50 ns wdi input t hreshold low v cc =5v 0.8 v wdi input threshold high v cc =5v 3.5 v wdi input current wdi=v c c 50 150 a wdi=0v - 150 - 50 wdo output voltage high i source =800 a vcc - 1.5 v wdo output voltage low i sink =1.2ma 0.4 v note 2 : production testing done at t a = +25c; limits over temperature guaranteed by design only.
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 6 / 15 u m706xs/um708xs block diagram figure 3 . UM706 xs block diagram figure 4 . um708 xs block diagram - + - + r e s e t g e n e r a t o r t i m e b a s e f o r r e s e t a n d w a t c h d o g w a t c h d o g t i m e r w a t c h d o g t r a n s i t i o n d e t e c t o r v c c 1 . 2 5 v 2 5 0 a 6 1 2 4 3 5 7 8 w d o r e s e t p f o g n d p f i v c c m r w d i v r e f - + - + r e s e t g e n e r a t o r v c c 1 . 2 5 v 2 5 0 a 1 2 4 3 5 7 r e s e t r e s e t p f o g n d p f i v c c m r 8 v r e f
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 7 / 15 u m706xs/um708xs ty pi cal operating char acteristics reset ______________ output voltage vs. supply voltage reset ______________ resp onse time power - fail compara tor assertion power - fail comparator de - assertion response time response time (a) (b) (c) (d) v cc reset _____________ 2v/div 2v/div 500ms/div pfo _________ pfi 2v/div 1v/div 200ns/div pfo _________ pfi 2v/div 1v/div 200ns/div v cc reset _____________ 2v/div 2v/div 1s/div - + 1 k 30 pf pfi + 5 v pfo + 1 . 25 v v cc gnd reset 2 k 330 pf v cc reset v cc gnd reset 10 k 30 pf v cc reset - + 1 k 30 pf pfi + 5 v pfo + 1 . 25 v
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 8 / 15 u m706xs/um708xs typi cal operating char acteristics reset output voltage vs. supply voltage reset response time reset, reset ______________ assertion reset, reset ______________ de - assertion (e) (f) v cc reset 500ms/div reset reset ______________ 200ns/div reset reset _____________ 200ns/div v cc reset 2 s/div v cc gnd reset 10 k 330 pf v cc gnd reset 10 k 330 pf reset 10 k 330 pf
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 9 / 15 u m706xs/um708xs detailed description p ower - f ail reset the rese t output provides a reset signal to the microprocessor whenever the v cc input is below the threshold. an internal timer holds the reset output active for 200ms after the voltage on v cc rises above the threshold. this is intended as a power - on reset signal for the microprocessor. it allows time for both the power supply and the microprocessor to stabilize after power - up. if a power supply brownout or interruption occurs, the reset line is similarly activated and re mains active for 200ms after the supply recovers. if another interruption occurs during an active reset period, the reset timeout period continues for an additional 200ms. the reset output is guaranteed to remain valid wit h v cc as low as 1v. this ensures that the microprocessor is held in a stable shutdown condition as the power supply starts up. the UM706 xs provides an active low reset ______________ signal wh ile the um708 xs provides an active high reset signal as well as active low reset ______________ signal . power - fail comparator t he power - fail comparator can be used for various purposes becaus e its output and non - i nverting input are not internally connected. t he inverting input is internally connected to a 1.25v reference. t o build an early - warning circuit for power failure, connect the pfi pin to a voltage driver, choose the voltage divider rat io so that the voltage at pfi falls below 1.25v just before the regulator drops out. use pfo ________ to interrupt the p so it can prepare for an orderly power - down. manual reset t he manual - reset input ( mr _______ ) allows reset to be trigged by a pushbutton switch. t he switch is effectively d ebounced by the 140 ms minimum reset pulse width. mr _______ is ttl/cmos logic compatible, so it can be driven by an external logic line. if unused , mr _______ input can be tied high or left floating. watchdog timer t he um 706 xs watchdog timer circuit is used to monitor the activity of the microprocessor to check that it is not stalled in an indefinite loop . an output line on the processor is used to toggle the watchdog input (wdi) . if this line is not toggled within 1. 6sec, wdo __________ goes low. wdo __________ is connected to the non - maskable interrupt input (nmi) of a p . therefore, if the watchdog timer times out, an interrupt is generated. the interrupt service routine is used to rectify the problem. the watchdog timer is cleared either by a high - to - low or by a low - to - high transition on wdi . pulses as narrow as 50ns are detected. the timer is also cleared by reset/ reset _____________ going active. therefore, the watchdog timeout period begins after reset goes inactive. when v cc falls below the reset threshold, wdo __________ is forced low whether or not the watchdog timer has timed out. normally, this generates an interrupt, but it is overridden by reset/ reset _____________ going active.
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 10 / 15 u m706xs/um708xs figure 5 . watchdog and reset timing figure 6 . reset, manual reset and watchdog timing w d i w d o r e s e t 0 v + 5 v 0 v + 5 v 0 v + 5 v t w p t w d t w d t r s t w d r e s e t e x t e r n a l l y t r i g g e r e d b y m r v c c 0 v + 5 v 0 v + 5 v 0 v + 5 v r e s e t m r w d o m r e x t e r n a l l y d r i v e n l o w v r t v r t t r s t r s t m d t m r
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 11 / 15 u m706xs/um708xs ap plications information valid reset ______________ below 1v v c c the UM706 xs /um708 xs are guaranteed to provide a valid reset level with v cc as low as 1v. when v cc falls below 1v, the internal t ransistor does not have sufficient drive to hold it on so the voltage on reset _____________ is no longer held at 0v. if a pull - down resistor is added to the reset _____________ pin as shown in figure 7 , any stray charge or leakage current will be drained to ground, holding reset _____________ low. resistor value (r1) is not critical. it should be about 100k, large enough not to load reset _____________ and small enough to pull res et _____________ to ground. monitoring additional supply levels it is possible to use the power - fail comparator to monitor a second supply as shown in figure 8. the two sensing resistors, r1 and r2, are selected such that the voltage on pfi drops below 1.25v at the m inimum acceptable input supply. the pfo _________ output can be connected to the mr ________ input so that a reset is generated when the supply drops out of tolerance. in this case, if either supply drops out of tolerance, a reset is generated. monitoring a negative voltage the power - fail comparator can also monitor a negative supply rail (figure 9 ). when the negative rail is good (a negative voltage of large magnitude), pfo ________ is low, and when the negative rail is degraded (a negative voltage of lesser magnitude), pfo ________ is high. by adding the resistors and transistor as shown, a high pfo ________ triggers reset . as long as pfo ________ remains high, theum 706 xs /um 708 xs will keep reset asserted ( reset _____________ = low, reset = high). note that this circuits accuracy depends on the pfi threshold tolerance , the v cc line, and the resistors. microprocessor with bidirectional reset to prevent contention for microprocessors with a bidirectional reset line, a current limiting resistor is to be inserted between the reset _____________ output pin and the microprocessor reset pin. this limits the current to a safe level if there are conflicting output reset levels. a suitable resistor value is 4.7k . i f the reset output is required for other uses, it should be buffered as shown in figure 10.
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 12 / 15 u m706xs/um708xs figure 7 . reset v alid to ground circuit figure 8 . monitoring an additional supply v x figure 9 . monitoring a negative voltage figure 10 . bidirectional reset i/o v x + 5 v v c c p f i g n d p f o m r r e s e t r 1 r 2 t o p + 5 v p f i v c c g n d m r p f o r e s e t r 1 r 2 t o p v - 1 0 0 k 1 0 0 k 2 n 3 9 0 4 m r p f o + 5 v + 5 v 0 v 0 v 0 v v - v t r i p 5 - 1 . 2 5 r 1 = 1 . 2 5 - v t r i p r 2 , v t r i p 0 v cc gnd reset v cc gnd reset p 4 . 7 k buffered reset to other system components v cc gnd reset r 1
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 13 / 15 u m706xs/um708xs package information um70 6 x s so p 8 outline drawing dimensions symbol millimeters inches min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.33 0.51 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.100 0.185 0.200 e 3.800 4.000 0.150 0.157 e1 5.800 6.200 0.228 0.244 e 1.270 (bsc) 0.050 (bsc) l 0.400 1.270 0.016 0.050 0 8 0 8 land pattern notes: 1. compound dimension: 4.90 3.90 2. unit: mm; 3. general tolerance 0.0 5 mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation d e 1 e e 1 2 t o p v i e w l c e n d v i e w a 2 b a 1 a s i d e v i e w 4 . 9 5 1 . 3 0 1 . 2 7 0 . 5 0 u m 7 0 6 x s x x
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 14 / 15 u m706xs/um708xs um70 8 xs sop8 outline drawing dimensions symbol millimeters inches min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.33 0.51 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.100 0.185 0.200 e 3.800 4.000 0.150 0.157 e1 5. 800 6.200 0.228 0.244 e 1.270 (bsc) 0.050 (bsc) l 0.400 1.270 0.016 0.050 0 8 0 8 land pattern notes: 1. compound dimension: 4.90 3.90 2. unit: mm; 3. general tolerance 0.0 5 mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation d e 1 e e 1 2 t o p v i e w l c e n d v i e w a 2 b a 1 a s i d e v i e w 4 . 9 5 1 . 3 0 1 . 2 7 0 . 5 0 u m 7 0 8 x s x x
________________________________________________________________________ http://www.union - ic.com rev.0 2 may .20 1 4 15 / 15 u m706xs/um708xs important notice the informa tion in this document has been carefully reviewed and is believed to be accurate. nonetheless, this document is subject to change without notice. union assumes no responsibility for any inaccuracies that may be contained in this document, and makes no comm itment to update or to keep current the contained information, or to notify a person or organization of any update. union reserves the right to make changes, at any time, in order to improve reliability, function or design and to attempt to supply the best product possible. union semiconductor, inc add : 2 f, no. 3 , lane647 songtao road, shanghai 201203 tel: 021 - 5109 3966 fax: 021 - 51026018 website: www.union - ic.com

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