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max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset product data supersedes data of 2003 aug 08 2003 oct 15 integrated circuits
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2 2003 oct 15 description the max708r/s/t are microprocessor supervisory circuits used to monitor +3 v power supply levels in +3 v to +5 v microprocessor and other logic systems. the r, s, t suffixes have reset thresholds of 2.63 v, 2.93 v and 3.08 v, respectively. they reduce the number of circuit components, and improve reliability and accuracy compared to using separate ics or discrete components. the max708r/s/t features make the max708r/s/t ideal for use in portable, battery operated equipment. the low supply current, typically 50 m a, minimizes battery load. both reset and reset are active during power-up, power-down and brownout conditions an active-low manual reset input is also available. a 1.25 v threshold detector provides power-fail warning. this independent comparator can be used to monitor a second voltage supply and provide an early warning to the microprocessor that voltage is falling. this allows for an orderly shutdown, transmitting an alert to an operator, or activation of an alternate power source before the device asserts the reset signals. the device is available in the 8-pin so package (sop005). features ? reset and reset signals ? independent comparator with 1.25 v threshold for power failure or low battery warning ? manual reset input ? 50 m a quiescent current ? reset thresholds of 2.63, 2.93, and 3.08 v ? guaranteed reset assertion to v cc = 1 v applications ? battery powered devices ? critical microprocessor monitoring ? controllers ? portable instruments simplified system diagram sl01640 v cc reset input interrupt gnd microprocessor v cc pfi gnd max708 pfo reset reset regulated dc supply (v cc ) mr push-button switch unregulated dc supply r1 1% r2 1% figure 1. simplified system diagram.
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 3 ordering information type number package temperature type number name description version range max708 x d so8 plastic small outline package; 8 leads (see dimensional drawing) sop005 45 c to +85 c note: the device has 3 voltage output options, indicated by the `x' on the `type number'. part number threshold voltage (typical) max708rd 2.63 v max708sd 2.93 v MAX708TD 3.08 v marking code each device is marked with a four letter code. the first three letters designate the product. the fourth, represented by an `x', designates the date tracking code. part marking max708rd anex max708sd andx MAX708TD ancx pin configuration sl01639 1 2 3 4 8 7 6 5 top view so8 mr v cc gnd pfi reset reset nc pfo figure 2. pin configuration. pin description pin symbol description 1 mr manual reset input (active-low). triggers a reset pulse when pulled below 0.6 v. connect to v cc or leave floating if not used. 2 v cc supply voltage input. 3 gnd ground. 4 pfi power fail comparator input. when pfi is less than 1.25 v, pfo goes low, otherwise pfo remains high. connect to ground if not used. 5 pfo power fail comparator output (active-low). when voltage at pfi is less than 1.25 v, pfo goes low and sinks current. do not connect if not used. 6 nc no connection. 7 reset active-low reset output. reset is low if v cc is below the threshold voltage or if mr is held low. reset is maintained for 200 ms after the reset conditions are terminated. 8 reset active-high reset output. reset is high if v cc is below the threshold voltage or if mr is held low. reset is maintained for 200 ms after the reset conditions are terminated. maximum ratings symbol parameter conditions min. max. unit v cc supply voltage 0.3 6.0 v v n other input pin voltage note 1 0.3 v cc + 0.3 v input current at v cc or gnd 20 ma output current, all outputs 20 ma rate of rise at v cc 100 v/ m s t amb ambient temperature 40 +85 c t stg storage temperature 65 +160 c p power dissipation, so8 package t amb = 70 c; note 2 470 mw notes: 1. input voltage limits on pfi and mr can be exceeded provided the input current is less than 10 ma. 2. derate the dissipation 5.88 mw/ c above 70 c.
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 4 electrical characteristics t amb = 40 c to +85 c; v cc = (v rst(max) + 0.7 v) to 5.5 v, unless otherwise specified. symbol parameter conditions min. typ. max. unit v cc operating voltage range 1.2 5.5 v i sup supply current v cc < 3.6 v 50 300 m a v cc < 5.5 v 65 500 m a v rst reset threshold (note 1) max708r 2.55 2.63 2.70 v max708s 2.85 2.93 3.00 v max708t 3.00 3.08 3.15 v reset threshold hysteresis 20 mv t rst reset delay time (note 1) max708r; v cc = 3.0 v 140 200 280 ms max708s, max708t; v cc = 3.3 v 140 200 280 ms max708r, max708s, max708t; v cc = 5.0 v 200 ms v oh high-level output voltage reset v rst(max) < v cc < 3.6v; i source = 500 m a v cc 0.8 v 4.5 v < v cc < 5.5 v; i source = 800 m a v cc 1.5 v reset v rst(max) < v cc < 3.6v; i source = 500 m a v cc 0.8 v 4.5 v < v cc < 5.5 v; i source = 800 m a v cc 1.5 v pfo v rst(max) < v cc < 3.6v; i source = 500 m a v cc 0.8 v 4.5 v < v cc < 5.5 v; i source = 800 m a v cc 1.5 v v ol low-level output voltage reset v rst(max) < v cc < 3.6 v; i sink = 1.2 ma 0.3 v 4.5 v < v cc < 5.5 v; i sink = 3.2 ma 0.4 v v cc = 1.2 v; i sink = 100 m a 0.3 v reset v rst(max) < v cc < 3.6 v; i sink = 500 m a 0.3 v 4.5 v < v cc < 5.5 v; i sink = 1.2 ma 0.4 v pfo v rst(max) < v cc < 3.6 v; i sink = 1.2 ma 0.3 v 4.5 v < v cc < 5.5 v; i sink = 3.2 ma 0.4 v mr pull-up current v rst(max) < v cc < 3.6 v; mr = 0 v 25 70 250 m a 4.5 v < v cc < 5.5 v; mr = 0 v 100 250 600 m a t mr mr pulse width v rst(max) < v cc < 3.6 v 500 ns 4.5 v < v cc < 5.5 v 150 ns v il mr low-level input threshold v rst(max) < v cc < 3.6 v 0.6 v 4.5 v < v cc < 5.5 v 0.8 v v ih mr high-level input threshold v rst(max) < v cc < 3.6 v v cc 0.7 v 4.5 v < v cc < 5.5 v 2.0 v t md mr to reset out delay (note 1) v rst(max) < v cc < 3.6 v 750 ns 4.5 v < v cc < 5.5 v 250 ns pfi input threshold pfi falling; max708r: v cc = 3.0 v; max708s/t: v cc = 3.3 v 1.2 1.25 1.3 v pfi input current 25 0.01 +25 na note: 1. applies to reset and reset .
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 5 timing diagram on power-up, when v cc reaches 1 v, reset is guaranteed to be a logic low and reset is guaranteed to be a logic high. event a: v cc rises to the reset threshold voltage, v rst . at this time, the internal reset delay timer is initiated. reset and reset will remain asserted for the reset delay time, t rst of typically 200 ms after the supply voltage rises above the reset threshold, v rst . event b: at this time, the resets are released. reset goes high; while reset goes low. the reset delay time helps to ensure valid reset signals despite erratic changes in supply voltage. events ce: at event c, under brown-out conditions, v cc falls below the reset threshold minus the hysteresis voltage (typically 20 mv), and the reset signal is asserted. as power recovers and v cc rises above the reset threshold (event d), it once again initiates the reset delay time. at event e, v cc falls below the reset threshold before the reset delay time has elapsed and reset remains asserted. event f: the v cc rises above the reset threshold again and remains above the reset threshold for typically 200 ms. at g, the reset is once again released. event h: the mr is externally pulled low for longer than 150 ns (minimum mr pulse width, t mr for v cc = +5 v). event i: the manual reset is asserted within 250 ns (maximum mr to reset out delay time, t md for v cc = +5v). event j: the mr pin returns high. at this point, reset delay timer is initiated and in typically 200 ms, (at event k), the reset condition is released. event l: on power-down, when v cc falls below v rst 20 mv, reset and reset are guaranteed to be asserted until v cc falls below 1 v. time reset v rst v rst v cc v rst 20 mv t rst t rst t rst reset mr sl01812 t md t mr abcdef ghij kl figure 3. timing diagram.
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 6 technical discussion general discussion the max708r/s/t microprocessor supervisor circuits are comprised of both reset and reset outputs, a mr manual reset input, and a comparator which may be used for power-failure detection (see figure 4). the reset threshold voltages are guaranteed within 3% of the nominal reset threshold. the max708r/s/t are designed to monitor +3 v to +3.3 v power supplies in +3 v to +5 v microprocessor and other logic systems. with a threshold voltage range between 5% to 10% of the nominal supply voltage, the max708r/s/t will assert an output within predictable range of power supply voltage. 8 +1.25 v power-fail comparator v rst reset generator v cc 7 5 6 1 2 4 3 reset reset nc pfo mr v cc gnd pfi sl01813 max708r/s/t figure 4. max708r/s/t internal block diagram. reset and reset outputs the max708r/s/t reset and reset outputs are push-pull outputs and do not require an external pull-up resistor. the reset output is active-low logic, while the reset output is active-high logic. manual reset the manual reset input, mr is active-low logic. it allows the reset and reset to be asserted by a pushbutton switch. a mechanical pushbutton switch is effectively debounced by the 140 ms minimum reset time delay. mr may be driven from an external logic circuit because it is ttl/cmos compatible. the minimum mr input pulse is 500 ns for v cc = +3 v and 150 ns for v cc = +5 v. if manual reset will not be used, leave the pin left floating or tie it to v cc . power-fail comparator the power-fail comparator has many useful purposes, such as monitoring upstream or secondary power supplies. the power-fail output (pfo ) and the non-inverting power-fail input (pfi) are pinned out. the inverting input of the power-fail comparator is internally connected to a 1.25 v reference. the comparator has 10 mv of hysteresis which prevents repeated triggering of the output (pfo ).
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 7 application information operating with a +3 v or +5 v supply when powered from either +3.0 v or +5.0 v, the max708r/s/t provides voltage monitoring at the reset threshold. the max708r/s/t are ideal for portable applications that are powered from a +3 v battery or an ac-dc wall adapter that generates +5 v. power-fail comparator an early warning power-fail circuit uses the power-fail input to monitor the upstream, unregulated dc supply that powers the +3 v/+3.3 v regulator powering the max708r/s/t. figure 1, asimplified system diagramo, shows the resistor divider network that is connected to pfi. the network resistors r1 and r2 are chosen so that the voltage at pfi will fall below 1.25 v before the regulator voltage drops out. the pfo signal may be used to interrupt the microprocessor so it can perform an orderly shutdown. any unregulated or regulated supply can be monitored by adjusting the resistive divider for the desired power supply trip voltage. table 1 shows examples for nominal trip voltages of 3.7 v and 10.9 v. the desired trip voltage, v t is calculated by the following equation: v t 1.25 v (r1 r2) r2 table 1. power-fail detection circuit of 3.7 v and 10.9 v r1 1% r2 1% v t 5 v unregulated power supply 1 m w 510 k w 3.7 v 12 v unregulated power supply 1 m w 130 k w 10.9 v adding hysteresis to the power-fail comparator hysteresis adds noise margin to the power-fail comparator and prevents repeated triggering of pfo when v in is varying around the comparator trip point. in figure 5, aadding hysteresis to the power-fail comparatoro, r1 and r2 are the divider resistors that set the desired trip point. r3 is added from the comparator input to the output to increase hysteresis; it is typically an order of magnitude greater than r1 and r2. the current through r1 and r2 should be at least 1 ma to ensure that the 25 na max pfi input current does significantly shift the trip point. capacitor c1 provides noise rejection. r1 gnd pfi r2 c1 r3 v cc v cc2 max708r/s/t pfo to microprocessor v in sl01814 figure 5. adding hysteresis to the power-fail comparator. pfo v cc2 0 v 0 v v l v t v h v in v t 1.25 v (r1 r2) r2 the hysteresis of v h and v l voltages are calculated by: v h 1.25 v 1 (r3 r2) (r2 r3) r1 v l 1.25 v r1 1.25 r2 1.25 v cc r3 thus, v hys v h v l r1 v cc2 r3
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 8 monitoring a negative voltage the power-fail comparator can be used to monitor a negative voltage using the circuit shown in figure 6. when the negative supply is operating in tolerance, pfo is low. however, when the negative supply drops (goes positive) pfo goes high. r1 gnd pfi r2 v cc max708r/s/t pfo sl01815 v +3 v to +3.3 v to m p interrupt figure 6. circuit for monitoring a negative voltage. when monitoring a negative supply, the trip voltage, v t is a negative voltage. use the following ratio to determine the divider resistors: v cc 1.25 r1 1.25 v t r2 solving for v t : v t 1.25 r2 r1 v cc 1.25 v in 0 v v t 0 v +3 v to +3.3 v pfo ensuring a valid reset down to v cc = 0 v when v cc falls below 1 v, the max708r/s/t reset no longer sinks current (i.e., it becomes open circuit). a high impedance cmos logic input connected to reset can drift to undetermined voltages. in most applications in which the microprocessor circuitry is inoperative below 1 v this will not present a problem. however, in applications in which reset must be valid down to 0 v, use a relatively large pull-down resistor from reset to ground (figure 7). 100 k w is small enough to provide a path for any stray leakage currents to flow to ground (holding reset low), while it is large enough not to load reset. sl01816 v cc reset max708r/s/t gnd 100 k w v cc v cc microprocessor gnd reset figure 7. reset valid to v cc = ground circuit. interfacing to a microprocessor with bi-directional reset pins microprocessors with bi-directional reset pins, such as the motorola 68hc11 series, can be connected to the max708r/s/t reset output. the bi-directional reset of the microprocessor functions both as a driven reset input and as an active reset driver. to ensure a correct output on the max708r/s/t even when the microprocessor reset pin is in the opposite state, connect a 4.7 k w resistor between the reset pins as shown in figure 8. this allows the microprocessor to issue commands to the system regardless of the state of the reset pin. sl01817 v cc reset max708r/s/t gnd 4.7 k w v cc v cc motorola 68hcxx gnd reset figure 8. interfacing to a microprocessor with bi-directional reset i/o
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 9 packing method the max708r/s/t are packed in reels, as shown in figure 9. sl01305 tape detail cover tape carrier tape reel assembly tape guard band barcode label box figure 9. tape and reel packing method.
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 10 so8: plastic small outline package; 8 leads; body width 3.9 mm sop005
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 11 revision history rev date description _4 20031015 product data (9397 750 12055); ecn 8532354 30312 of 08 september 2003; supersedes data of 08 aug 2003 (9397 750 11882). modifications: ? change package outline drawing from so8 (non-standard drawing) to sop005 (offical drawing). _3 20030808 product data (9397 750 11882); ecn 8532354 30185 of 04 august 2003; supersedes data of 13 feb 2003 (9397 750 10514). _2 20030213 product data (9397 750 10514); ecn 8532354 29010 of 02 october 2002; supersedes data of 20 jun 2002 (9397 750 10023). _1 20020620 product data (9397 750 10023); ecn 8532354 28505 of 20 june 2002.
philips semiconductors product data max708r/s/t 3 v microprocessor supervisor circuit with power fail comparator and manual reset 2003 oct 15 12 definitions short-form specification e the data in a short-form specification is extracted from a full data sheet with the same type number and title. for detailed i nformation see the relevant data sheet or data handbook. limiting values definition e limiting values given are in accordance with the absolute maximum rating system (iec 60134). stress above one or more of the l imiting values may cause permanent damage to the device. these are stress ratings only and operation of the device at these or at any o ther conditions above those given in the characteristics sections of the specification is not implied. exposure to limiting values for extended periods may affec t device reliability. application information e applications that are described herein for any of these products are for illustrative purposes only. philips semiconductors ma ke no representation or warranty that such applications will be suitable for the specified use without further testing or modificatio n. disclaimers life support e these products are not designed for use in life support appliances, devices, or systems where malfunction of these products ca n reasonably be expected to result in personal injury. philips semiconductors customers using or selling these products for use in such applica tions do so at their own risk and agree to fully indemnify philips semiconductors for any damages resulting from such application. right to make changes e philips semiconductors reserves the right to make changes in the productseincluding circuits, standard cells, and/or softwaree described or contained herein in order to improve design and/or performance. when the product is in full production (status `production') , relevant changes will be communicated via a customer product/process change notification (cpcn). philips semiconductors assumes no responsibility or liability for th e use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these products, and makes no representations or warranti es that these products are free from patent, copyright, or mask work right infringement, unless otherwise specified. contact information for additional information please visit http://www.semiconductors.philips.com . fax: +31 40 27 24825 for sales offices addresses send e-mail to: sales.addresses@www.semiconductors.philips.com . ? koninklijke philips electronics n.v. 2003 all rights reserved. printed in u.s.a. date of release: 10-03 document order number: 9397 750 12055

data sheet status [1] objective data preliminary data product data product status [2] [3] development qualification production definitions this data sheet contains data from the objective specification for product development. philips semiconductors reserves the right to change the specification in any manner without notice. this data sheet contains data from the preliminary specification. supplementary data will be published at a later date. philips semiconductors reserves the right to change the specification without notice, in order to improve the design and supply the best possible product. this data sheet contains data from the product specification. philips semiconductors reserves the right to make changes at any time in order to improve the design, manufacturing and supply. relevant changes will be communicated via a customer product/process change notification (cpcn). data sheet status [1] please consult the most recently issued data sheet before initiating or completing a design. [2] the product status of the device(s) described in this data sheet may have changed since this data sheet was published. the l atest information is available on the internet at url http://www.semiconductors.philips.com. [3] for data sheets describing multiple type numbers, the highest-level product status determines the data sheet status. level i ii iii

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