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ltc1727/ltc1728 1 17278fb typical a pplica t ion descrip t ion micropower precision triple supply monitors in 8-lead msop and 5-lead sot-23 packages the ltc ? 1727 is a triple supply monitor intended for systems with multiple supply voltages. each supply moni- tor has its own open-drain output for individual supply monitoring. a common open-drain reset output remains low until all three supplies have been in compliance for 200ms. tight 1.5% accuracy specifcations and glitch immunity ensure reliable reset operation without false triggering. the ltc1728 is functionally identical to the ltc1727 without the individual monitor outputs. the rst output is guaranteed to be in the correct state for v cc5 /v cc25 /v cc18 or v cc3 down to 1v. the ltc1727/ ltc1728 may also be confgured to monitor any one or two v cc inputs instead of three, depending on system requirements. very low (10a typical) supply current makes the ltc1727/ ltc1728 ideal for power conscious systems. the ltc1727 is available in an 8-lead msop or so pack - age and the ltc1728 is available in a 5-lead sot-23 package. triple supply monitor with power good output (3.3v, 2.5v and adjustable) l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. fea t ures a pplica t ions n monitors three inputs simultaneously ltc1727-5: 5v , 3.3v and adj ltc1727-2.5: 2.5v , 3.3v and adj ltc1728-5: 5v , 3.3v and adj ltc1728-2.5: 2.5v , 3.3v and adj ltc1728-1.8: 3v , 1.8v and adj ltc1728-3.3: 3.3v , 1.8v and adj n 1.5% threshold accuracy over temperature n very low supply current: 10a typ n 200ms reset time delay n active low reset output n power supply glitch immunity n guaranteed reset for v cc3 1v or v cc5 /v cc25 /v cc18 1v n ltc1727 includes monitor output for each supply n ltc1727: 8-lead msop and so packages n ltc1728: 5-lead sot-23 package n desktop computers n notebook computers n intelligent instruments n portable battery-powered equipment n network servers v cc3 v cc5 v cca rst gnd ltc1728-5 1727/28 ta01 3.3v 5v 1.8v 0.1f 5 1 2 r1 61.9k 1% r2 100k 1% 4 3 dc/dc converter system logic 0.1f 1 2 3 4 8 7 6 5 ltc1727-2.5 r2 1727/28 ta08 r1 adjustable supply 3.3v 2.5v r3 10k power good system reset r4 10k v cc3 v cc25 v cca gnd comp3 comp25 rst compa
ltc1727/ltc1728 2 17278fb a bsolu t e maxi m u m r a t ings v cc3 , v cc5 /v cc25 /v cc18 , v cca ........................ C 0.3v to 7v rst ............................................................. C 0.3v to 7v compa, comp3, comp25/comp5 (ms8 and so-8 only) ............................. C 0.3v to 7v (notes 1. 2) 1 2 3 4 v cc3 v cc5 /v cc25 v cca gnd 8 7 6 5 comp3 comp25/comp5 rst compa top view ms8 package 8-lead plastic msop t jmax = 125c, ja = 200c/w 1 2 3 4 8 7 6 5 top view comp3 rst compa v cc3 v cca gnd s8 package 8-lead plastic so comp25/ comp5 v cc5 / v cc25 t jmax = 125c, ja = 150c/w rst 1 gnd 2 top view s5 package 5-lead plastic sot-23 v cca 3 5 v cc3 4 v cc5 / v cc25 / v cc18 t jmax = 125c, ja = 250c/w order part number ms8 part marking order part number s8 part marking order part number s5 part marking ltc1727ems8-2.5 ltc1727ems8-5 lthy lthx ltc1727es8-2.5 ltc1727is8-2.5 ltc1727es8-5 ltc1727is8-5 172725 727i25 17275 172715 ltc1728es5-1.8 ltc1728es5-2.5 ltc1728es5-3.3 ltc1728es5-5 LTC1728HS5-5 ltph ltia lty p lthz lthz order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/ consult ltc marketing for parts specifed with wider operating temperature ranges. p in c on f igura t ion elec t rical c h arac t eris t ics operating temperature range ltc1727/l tc1728e (note 3) ............... C 40c to 85c l tc1728h .......................................... C 40c to 125c l tc1727i ..............................................C 40c to 85c storage temperature range .................. C 65c to 150c lead temperature (soldering, 10 sec) ................. 300c symbol parameter conditions min typ max units v rt3 reset threshold v cc3 v cc3 input threshold l 3.036 3.086 3.135 v v rt5 reset threshold v cc5 v cc5 input threshold (5v version) l 4.600 4.675 4.750 v v rt25 reset threshold v cc25 v cc25 input threshold (2.5v version) l 2.300 2.338 2.375 v v rta reset threshold v cca v cca input threshold l 0.985 1.000 1.015 v v ccop v cc3 , v cc5 /v cc25 operating voltage rst, comp3, comp5, comp25 in correct logic state l 1 7 v v ccopa v cc3 , v cc5 /v cc25 operating voltage minimum supply voltage to guarantee compa in correct logic state l 2 2.3 v all except ltc1728-1.8/l tc1728-3.3. the l denotes specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc3 = 3.3v, v cc5 = 5v, v cc25 = 2.5v, v cca = v cc3 unless otherwise noted.
ltc1727/ltc1728 3 17278fb e lec t rical ch arac t eris t ics all except ltc1728-1.8/l tc1728-3.3. the l denotes specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc3 = 3.3v, v cc5 = 5v, v cc25 = 2.5v, v cca = v cc3 unless otherwise noted. symbol parameter conditions min typ max units i vcc3 v cc3 supply current v cc5 /v cc25 > v cc3 v cc5 /v cc25 < v cc3 , v cc3 = 3.3v (note 4) l l 1 10 2 20 a a i vcc25 v cc25 supply current v cc25 < v cc3 , v cc25 = 2.5v (note 4) l 1 2 a i vcc5 v cc5 supply current v cc5 = 5v, v cc3 < v cc5 l 10 20 a i vcca v cca input current v cca = 1v C40c < t a < 125c l l C15 C20 0 0 15 50 na na t rst reset pulse width rst low with 10k pull-up to v cc3 (note 5) C40c < t a < 125c l l 140 140 200 280 350 ms ms t uv v cc undervoltage detect to rst or compx v cc5 , v cc25 , v cc3 or v cca less than reset threshold v rt by more than 1% (note 5) 110 s v ol output voltage low, rst , compx i sink = 2.5ma, v cc3 = 3v, v cc5 /v cc25 = 0v i sink = 100a, v cc3 = 1v, v cc5 /v cc25 = 0v i sink = 100a, v cc3 = 0v, v cc5 /v cc25 = 1v i sink = 100a, v cc3 = 1v, v cc5 /v cc25 = 1v l l l l 0.15 0.05 0.05 0.05 0.4 0.3 0.3 0.3 v v v v v oh output voltage high, rst , compx (note 6) i source = 1a l v cc3 C 1 v ltc1727-5/ltc1728-5 only v ovr v cc5 reset override voltage (note 7) override v cc5 ability to assert rst v cc3 0.025 v symbol parameter conditions min typ max units v rt3 reset threshold v cc3 v cc3 input threshold l 2.760 2.805 2.850 v v rt18 reset threshold v cc18 v cc18 input threshold l 1.656 1.683 1.710 v v rta reset threshold v cca v cca input threshold l 0.985 1.000 1.015 v v ccop v cc3 , v cc18 operating voltage rst in correct logic state l 1 7 v i vcc3 v cc3 supply current v cc18 > v cc3 v cc18 < v cc3 , v cc3 = 3v (note 4) l l 1 10 2 20 a a i vcc18 v cc18 supply current v cc18 < v cc3 , v cc18 = 1.8v (note 4) l 1 2 a i vcca v cca input current v cca = 1v l C15 0 15 na t rst reset pulse width rst low (note 5) l 140 200 280 ms t uv v cc undervoltage detect to rst v cc18 , v cc3 or v cca less than reset (note 5) threshold v rt by more than 1% 110 s v ol output voltage low, rst i sink = 2.5ma, v cc3 = 3v, v cc18 = 0v i sink = 100a, v cc3 = 1v, v cc18 = 0v i sink = 100a, v cc3 = 0v, v cc18 = 1v i sink = 100a, v cc3 = 1v, v cc18 = 1v l l l l 0.15 0.05 0.05 0.05 0.4 0.3 0.3 0.3 v v v v v oh output voltage high, rst i source = 1a (note 6) l v cc3 C 1 v ltc1728-1.8 the l denotes specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc3 = 3v, v cc18 = 1.8v, v cca = v cc3 unless otherwise noted.
ltc1727/ltc1728 4 17278fb e lec t rical ch arac t eris t ics ltc1728-3.3 the l denotes specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc3 = 3.3v, v cc18 = 1.8v, v cca = v cc3 unless otherwise noted. note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: all voltage values are with respect to gnd. note 3: the ltc1727e/ltc1728e are guaranteed to meet specifed performance from 0c to 70c and are designed, characterized and assured to meet the extended temperature limits of C40c to 85c but are not tested at these temperatures. symbol parameter conditions min typ max units v rt3 reset threshold v cc3 v cc3 input threshold l 3.036 3.086 3.135 v v rt18 reset threshold v cc18 v cc18 input threshold l 1.656 1.683 1.710 v v rta reset threshold v cca v cca input threshold l 0.985 1.000 1.015 v v ccop v cc3 , v cc18 operating voltage rst in correct logic state l 1 7 v i vcc3 v cc3 supply current v cc18 > v cc3 v cc18 < v cc3 , v cc3 = 3.3v (note 4) l l 1 10 2 20 a a i vcc18 v cc18 supply current v cc18 < v cc3 , v cc18 = 1.8v (note 4) l 1 2 a i vcca v cca input current v cca = 1v l C15 0 15 na t rst reset pulse width rst low (note 5) l 140 200 280 ms t uv v cc undervoltage detect to rst v cc18 , v cc3 or v cca less than reset (note 5) threshold v rt by more than 1% 110 s v ol output voltage low, rst i sink = 2.5ma, v cc3 = 3.3v, v cc18 = 0v i sink = 100a, v cc3 = 1v, v cc18 = 0v i sink = 100a, v cc3 = 0v, v cc18 = 1v i sink = 100a, v cc3 = 1v, v cc18 = 1v l l l l 0.15 0.05 0.05 0.05 0.4 0.3 0.3 0.3 v v v v v oh output voltage high, rst i source = 1a (note 6) l v cc3 C 1 v note 4: both v cc3 and v cc5 /v cc25 /v cc18 can act as the supply depending on which pin has the greatest potential. note 5: measured from when input passes through the input threshold (v rtx ) until rst or compx passes through 1.5v. note 6: the output pins rst and compx have internal pull-ups to v cc3 of typically 6a. however, external pull-up resistors may be used when faster rise times are required or for v oh voltages greater than v cc3 . note 7: the v cc5 reset override voltage is valid for an operating range less than approximately 4.15v. above this point the override is turned off and the v cc5 pin functions normally.
ltc1727/ltc1728 5 17278fb typical p er f or m ance ch arac t eris t ics reset pulse width vs temperature rst, compx i sink vs supply voltage i vcc25 vs temperature (ltc1727-2.5/lt1728-2.5) i vcc3 vs temperature (ltc1727- 2.5/ltc1728-2.5/ltc1728-3.3) i vcc3 vs temperature (ltc1727-5/ltc1728-5) i vcc5 vs temperature (ltc1727-5/ltc1728-5) v cca input current vs input voltage v cca threshold voltage vs temperature typical transient duration vs comparator overdrive input voltage (v) 0.80 0.85 0.95 1.05 1.15 input current (na) 0 1.0 1.20 1727/28 g01 ?1.0 ?2.0 ?0.5 ?1.5 0.90 1 1.10 2.0 0.5 1.5 t a = 25c temperature (c) ?60 0.985 v cca threshold voltage, v rta (v) 0.990 0.995 1.000 1.005 ?20 20 60 100 1727/28 g02 1.010 1.015 ?40 0 40 80 reset comparator overdrive voltage (% of v cc ) 0.1 250 typical transient diration (s) 300 350 400 450 1 10 100 1727/28 g03 200 150 50 0 100 reset occurs above curve t a = 25c temperature (c) ?60 ?40 reset pulse width, t rst (ms) 220 240 260 60 1727/28 g04 200 180 ?20 20 40 80 0 100 160 140 280 v cc3 or v cc5 (v) 0 0 i sink (ma) 2 4 6 1 2 3 4 1727/28 g05 5 8 10 1 3 5 7 9 6 v ol = 0.4v t a = 25c v ol = 0.2v temperature (c) ?60 0.5 i vcc25 (a) 0.6 0.8 0.9 1.0 1.5 1.2 ?20 20 40 1727/28 g06 0.7 1.3 1.4 1.1 ?40 0 60 80 100 v cc3 = 3.3v v cc25 = 2.5v v cca = 3.3v temperature (c) ?60 5 i vcc3 (a) 6 8 9 10 15 12 ?20 20 40 1727/28 g07 7 13 14 11 ?40 0 60 80 100 v cc3 = 3.3v v cc25 = 2.5v v cca = 3.3v temperature (c) ?60 0.5 i vcc3 (a) 0.6 0.8 0.9 1.0 1.5 1.2 ?20 20 40 1727/28 g08 0.7 1.3 1.4 1.1 ?40 0 60 80 100 v cc5 = 5v v cc3 = 3.3v v cca = 3.3v temperature (c) ?60 5 i vcc5 (a) 6 8 9 10 15 12 ?20 20 40 1727/28 g09 7 13 14 11 ?40 0 60 80 100 v cc5 = 5v v cc3 = 3.3v v cca = 3.3v
ltc1727/ltc1728 6 17278fb typical p er f or m ance ch arac t eris t ics i vcc18 vs temperature (ltc1728-1.8/ltc1728-3.3) i vcc3 vs temperature (ltc1728-1.8) v cc18 threshold voltage vs temperature (ltc1728-1.8/ltc1728-3.3) v cc3 threshold voltage vs temperature (ltc1728-1.8) v cc25 threshold voltage vs temperature (ltc1727-2.5/ltc1728-2.5) v cc3 threshold voltage vs temperature (all but ltc1728-1.8) v cc5 threshold voltage vs temperature (ltc1727-5/ltc1728-5) temperature (c) ?60 v cc25 threshold voltage, v rt25 (v) 2.3750 2.3675 2.3600 2.3525 2.3450 2.3375 2.3300 2.3225 2.3150 2.3075 2.3000 ?20 20 40 1727/28 g10 ?40 0 60 80 100 temperature (c) ?60 v cc3 threshold voltage, v rt3 (v) 3.135 3.125 3.115 3.105 3.095 3.085 3.075 3.065 3.055 3.045 3.035 ?20 20 40 1727/28 g11 ?40 0 60 80 100 temperature (c) ?60 0.5 i vcc18 (a) 0.6 0.8 0.9 1.0 1.5 1.2 ?20 20 40 1727/28 g13 0.7 1.3 1.4 1.1 ?40 0 60 80 100 v cc3 = 3v v cc18 = 1.8v v cca = 3v temperature (c) ?60 v cc5 theshold voltage, v rt5 (v) 4.675 4.700 4.750 4.725 0 40 100 1727/28 g12 4.650 4.625 4.600 ?40 ?20 20 60 80 temperature (c) ?60 5 i vcc3 (a) 6 8 9 10 15 12 ?20 20 40 1727/28 g14 7 13 14 11 ?40 0 60 80 100 v cc3 = 3v v cc18 = 1.8v v cca = 3v temperature (c) ?60 1.650 v cc18 threshold voltage, v rt18 (v) 1.660 1.670 1.680 1.690 ?20 20 60 100 1727/28 g15 1.700 1.710 ?40 0 40 80 temperature (c) ?60 v cc3 threshold voltage, v rt3 (v) 2.845 2.835 2.825 2.815 2.805 2.795 2.785 2.775 2.765 ?20 20 40 1727/28 g16 ?40 0 60 80 100
ltc1727/ltc1728 7 17278fb p in func t ions v cc3 (pin 1/pin 5): 3.3v sense input and power supply pin. (3v sense input and power supply pin for ltc1728- 1.8.) this pin provides power to the part when the voltage on v cc3 is greater than the voltage on v cc5 /v cc25 /v cc18 . bypass to ground with a 0.1f ceramic capacito r . v cc5 (pin 2/pin 4): 5v sense input and power supply pin. this pin is used on the ltc1727-5/ltc1728-5 to provide power to the part when the voltage on v cc5 is greater than the voltage on v cc3 . bypass to ground with a 0.1f ceramic capacito r . v cc25 (pin 2/pin 4): 2.5v sense input and power supply pin. this pin is used on the ltc1727-2.5/ltc1728-2.5 to provide power to the part when the voltage on v cc25 is greater than the voltage on v cc3 . bypass to ground with a 0.1f ceramic capacito r . v cc18 (pin 2/pin 4): 1.8v sense input and power supply pin. this pin is used on the ltc1728-1.8/ltc1728 - 3.3 to provide power to the part when the voltage on v cc18 is greater than the voltage on v cc3 . bypass to ground with a 0.1f ceramic capacito r . v cca (pin 3/pin 3): 1v sense, high impedance input. if un- used, it can be tied to either v cc3 or v cc5 /v cc25 /v cc18 . gnd (pin 4/pin 2): ground. compa (pin 5): v cca comparator output for the ltc1727. active high, open-drain logic output with weak pull-up to v cc3 . asserted when v cca is above v rta . deasserted when v cca is below v rta or if both the v cc3 and v cc5 supply pins are too low to power the internal bandgap reference (typically < 2.0v). can be pulled greater than v cc3 using an external pull-up. rst (pin 6/pin 1): reset logic output. active low, open- drain logic output with weak pull-up to v cc3 . can be pulled up greater than v cc3 when interfacing to 5v logic. asserted when one or all of the supplies are below trip thresholds and held for 200ms after all supplies become valid. comp5 (pin 7): v cc5 comparator output for the ltc1727-5. active high, open-drain logic output with weak pull-up to v cc3 . asserted when v cc5 is above v rt5 . can be pulled greater than v cc3 using an external pull-up. comp25 (pin 7): v cc25 comparator output for the ltc1727-2.5. active high, open-drain logic output with weak pull-up to v cc3 . asserted when v cc25 is above v rt25 . can be pulled greater than v cc3 using an external pull-up. comp3 (pin 8): v cc3 comparator output for the ltc1727. active high, open-drain logic output with weak pull-up to v cc3 . asserted when v cc3 is above v rt3 . can be pulled greater than v cc3 using an external pull-up. (ltc1727/ltc1728)
ltc1727/ltc1728 8 17278fb b lock diagra ms ltc1727-5/ltc1727-2.5 200ms delay v cc internal bandgap reference power detect 200ms pulse generator ? + ? + ? + 1v cc3 2 v cc5 / v cc25 3v cca 4gnd 5 compa 1727 bd1 6 rst 7 comp25/ comp5 8 comp3 6a v cc3 6a v cc3 6a v cc3 6a v cc3
ltc1727/ltc1728 9 17278fb b lock diagra ms t i m ing diagra m ltc1728-5/ltc1728-2.5/ltc1728-1.8/ltc1728-3.3 200ms delay v cc internal bandgap reference power detect 200ms pulse generator ? + ? + ? + 5v cc3 4 v cc5 / v cc25 / v cc18 3v cca 2gnd 1727 bd2 1 rst 6a v cc3 v cc monitor timing t rst t uv 1.5v 1727 td01 v rtx v ccx rst compx
ltc1727/ltc1728 10 17278fb applica t ions in f or m a t ion supply monitoring the ltc1727 is a low power, high accuracy triple sup - ply monitoring circuit with three monitor outputs and a 200ms microprocessor reset output. the ltc1728 is a low power, high accuracy triple supply monitoring circuit with a single 200ms microprocessor reset output. all three v cc inputs must be above predetermined thresh- olds for reset not to be invoked. the ltc1727/ltc1728 will assert reset during power-up, power-down and brownout conditions on any one or all of the v cc inputs. power detect the ltc1727/ltc1728 are powered from the 3.3v/3v input pin (v cc3 ), the 1.8v input pin (v cc18 ), the 2.5v input pin (v cc25 ) or the 5v input pin (v cc5 ), whichever pin has the highest potential. this ensures the part pulls the rst pin low as soon as either input pin is 1 v . power-up upon power-up, either the v cc5 /v cc25 / v cc18 or v cc3 pin, can power the part. this ensures that rst will be low when either v cc5 /v cc25 /v cc18 or v cc3 reaches 1 v . as long as any one of the v cc inputs is below its predetermined threshold, rst will stay a logic low. once all of the v cc inputs rise above their thresholds, an internal timer is started and rst is released after 200ms. rst is reasserted whenever any one of the v cc inputs drops below its predetermined threshold and remains asserted until 200ms after all of the v cc inputs are above their thresholds. on the ltc1727, each of the comparator outputs will be low until the v cc input that is monitored by that compara- tor rises above the appropriate predetermined threshold. the comp3, and comp5/comp25 outputs are guaran- teed to be in the correct logic state for either v cc3 or v cc5 /v cc25 greater than 1v. the compa output requires the internal bandgap reference to be valid before the correct logic state can be output. therefore, the compa output will be held low until v cca is above 1v and v cc3 or v cc5 /v cc25 is greater than 2v (typ). figure 1. transient duration vs comparator overdrive power-down on power-down, once any of the v cc inputs drop below its threshold, rst is held at a logic low. a logic low of 0.3v is guaranteed until both v cc3 and v cc5 /v cc25 /v cc18 drop below 1v. glitch immunity the rst output of the ltc1727/ltc1728 have two forms of glitch immunity built in. first, the input monitors require the input voltage to transition at least 10% of the input threshold (0.1 ? v rth ) below the input threshold for ap- proximately 50s in order to force the monitor output low. the duration of the transition must be longer for voltage transitions of lesser magnitude (see figure 1). secondly, the reset pulse width of approximately 200ms acts to debounce the rst output ensuring that the rst output will always be in the correct state. the individual monitor outputs of the ltc1727 do not have hysteresis and will track the monitor inputs relative to the monitors input threshold (v rta , v rt25 , v rt3 and v rt5 ). a very slow moving input voltage with ripple riding on it may cause the individual monitor outputs (compa, comp25, comp3 and comp5) to toggle on the ripple as the input voltage passes the input threshold. the slow response time of the ltc1727s input monitors has a tendency to integrate signals on the inputs improving their immunity to noise and ripple. reset monitor overdrive voltage (% of v cc ) 0.1 250 transient duration (s) 300 350 400 450 1 10 100 1727/28 f01 200 150 50 0 100
ltc1727/ltc1728 11 17278fb a pplica t ions i n f or m a t ion override functions (5v versions only) the v cca pin, if unused, can be tied to either v cc3 or v cc5 . this is an obvious solution since the trip points for v cc3 and v cc5 will always be greater than the trip point for v cca . the v cc5 input trip point is disabled if its voltage is equal to the voltage on v cc3 25mv and the voltage on v cc5 is less than 4.15v. in this manner, the ltc1727-5/ ltc1728-5 will behave as a 3.3v monitor and v cc5 reset capability will be disabled. the v cc5 trip point is reenabled when the voltage on v cc5 is equal to the voltage on v cc3 25mv and the two inputs are greater than approximately 4.15v. in this manner, the part can function as a 5v monitor with the 3.3v monitor disabled. when monitoring either 3.3v or 5v with v cc3 strapped to v cc5 (see figure 2), the part determines which is the appropriate range. the part handles this situation as shown in figure 3. above 1v and below v rt3 , rst is held low. from v rt3 to approximately 4.15v the part assumes 3.3v supply monitoring and rst is deasserted. above approximately 4.15v the part operates as a 5v monitor. in most systems the 5v supply will pass through the 3.1v to 4.15v region in <200ms during power-up, and the rst output will behave as desired. table 1 summa - rizes the state of rst at various operating voltages with v cc3 = v cc5 . table 1. override truth table (v cc3 = v cc5 ) inputs (v cc3 = v cc5 = v cc ) rst 0v v cc 1v 1v v cc v rt3 0 v rt3 v cc 4.15v 1 4.15v v cc v rt5 0 v rt5 v cc 1 figure 2. single supply monitor with others disabled figure 3. rst voltage vs supply voltage v cc3 v cc5 v cca gnd 1 5 4 3 2 rst ltc1728-5 1727/28 f02 to system reset r1 10k v cc 3.3v or 5v supply voltage (v) 0 rst output voltage (v) 3 4 5 4 1727/28 f03 2 1 0 1 2 3 5 v cc3 = v cc5 = v cca = 0v to 5v 10k pull-up from rst to v cc3
ltc1727/ltc1728 12 17278fb applica t ions in f or m a t ion figure 4 contains a simple circuit for 5v systems that cant risk the rst output going high in the 3.1v to 4.15v range (possibly due to very slow rise time on the 5v supply). diode d1 powers the ltc1728-5 while dropping 0.6v from the v cc5 pin to the v cc3 pin. this prevents the parts internal override circuit from being activated. without the override circuit active, the rst pin stays low until v cc5 reaches v rt5 ? 4.675v. (see figure 5.) ltc1727-2.5/ltc1728-2.5/ltc1728-1.8/ltc1728-3.3 override functions the v cca pin, if unused, can be tied to either v cc3 or v cc25 / v cc18 . this is an obvious solution since the trip points for v cc3 and v cc25 /v cc18 will always be greater than the trip point for v cca . likewise, the v cc25 /v cc18 , if unused, can be tied to v cc3 . v cc3 must always be used. tying v cc3 to v cc25 /v cc18 and operating off of a 2.5v/1.8v supply will result in the continuous assertion of rst. figure 4. ltc1728-5 monitoring a single 5v supply. d1 used to avoid rst high near 3.1v to 4v (see figure 3). figure 5. rst output voltage characteristics of the circuit in figure 4 v cc3 v cc5 v cca gnd 1 5 4 3 2 rst ltc1728-5 1727/28 f04 to system reset r1 10k 5v 0.1f d1 d1: mmbd914 or equivalent v cc5 (v) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 rst output voltage (v) 1727/28 f05 5 4 3 2 1 0 v cc5 = v cca = 0v to 5v 10k pull-up from rst to v cc5 t a = 25c t ypical applica t ions triple supply monitor (3.3v, 5v and adjustable) 5 4 3 2 1 v cc3 v cc5 v cca gnd rst ltc1728-5 3.3v system reset *to preserve threshold accuracy, set parallel combination of r1 and r2 66.5k 5v r2* r1* 1727/28 ta03 adjustable supply or dc/dc feedback divider
ltc1727/ltc1728 13 17278fb t ypical a pplica t ions dual supply monitor (3.3v and 5v, defeat v cca input) dual supply monitor (3.3v or 5v plus adjustable) dual supply monitor (3.3v plus adjustable) using v cca tied to dc/dc feedback divider 5 4 3 2 1 v cc3 v cc5 v cca gnd rst ltc1728-5 3.3v system reset 5v 1727/28 ta04 5 4 3 2 1 v cc3 v cc5 v cca gnd rst ltc1728-5 r2* 1727/28 ta05 r1* adjustable supply 3.3v or 5v 10k system reset *to preserve threshold accuracy, set parallel combination of r1 and r2 66.5k refer to ltc1728-5 override functions in the applications information section 5 4 3 2 1 v cc3 v cc25 v cca gnd rst ltc1728-2.5 system reset r2* 1727/28 ta06 r1* adjustable supply 3.3v 10k *to preserve threshold accuracy, set parallel combination of r1 and r2 66.5k 5 4 3 2 1 v cc3 v cc5 v cca gnd rst ltc1728-5 3.3v system reset 5v 22.1k 1% 1727/28 ta07 35.7k 1% ltc1435 adjustable reset trip threshold 2.74v 2.9v 2.8k 1% 6 v osense
ltc1727/ltc1728 14 17278fb p ackage descrip t ion ms8 package 8-lead plastic msop (reference ltc dwg # 05-08-1660) s8 package 8-lead plastic small outline (narrow 0.150) (reference ltc dwg # 05-08-1610) msop (ms8) 0204 0.53 0.152 (.021 .006) seating plane note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.18 (.007) 0.254 (.010) 1.10 (.043) max 0.22 ? 0.38 (.009 ? .015) typ 0.127 0.076 (.005 .003) 0.86 (.034) ref 0.65 (.0256) bsc 0 ? 6 typ detail ?a? detail ?a? gauge plane 12 3 4 4.90 0.152 (.193 .006) 8 7 6 5 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) 0.52 (.0205) ref 5.23 (.206) min 3.20 ? 3.45 (.126 ? .136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.42 0.038 (.0165 .0015) typ 0.65 (.0256) bsc .016 ? .050 (0.406 ? 1.270) .010 ? .020 (0.254 ? 0.508) 45 0? 8 typ .008 ? .010 (0.203 ? 0.254) so8 0303 .053 ? .069 (1.346 ? 1.752) .014 ? .019 (0.355 ? 0.483) typ .004 ? .010 (0.101 ? 0.254) .050 (1.270) bsc 1 2 3 4 .150 ? .157 (3.810 ? 3.988) note 3 8 7 6 5 .189 ? .197 (4.801 ? 5.004) note 3 .228 ? .244 (5.791 ? 6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm)
ltc1727/ltc1728 15 17278fb information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa - tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. p ackage descrip t ion s5 package 5-lead plastic sot-23 (reference ltc dwg # 05-08-1633) (reference ltc dwg # 05-08-1635) 1.50 ? 1.75 (.059 ? .069) (note 3) 2.60 ? 3.00 (.102 ? .118) .25 ? .50 (.010 ? .020) (5plcs, note 2) l datum ?a? .09 ? .20 (.004 ? .008) (note 2) a1 s5 sot-23 0401 pin one 2.80 ? 3.10 (.110 ? .118) (note 3) .95 (.037) ref a a2 1.90 (.074) ref .20 (.008) .90 ? 1.45 (.035 ? .057) sot-23 (original) .00 ? .15 (.00 ? .006) .90 ? 1.30 (.035 ? .051) .35 ? .55 (.014 ? .021) 1.00 max (.039 max) sot-23 (thinsot) a a1 a2 l .01 ? .10 (.0004 ? .004) .80 ? .90 (.031 ? .035) .30 ? .50 ref (.012 ? .019 ref) millimeters (inches) note: 1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale 4. dimensions are inclusive of plating 5. dimensions are exclusive of mold flash and metal burr 6. mold flash shall not exceed .254mm 7. package eiaj reference is: sc-74a (eiaj) for original jedec mo-193 for thin
ltc1727/ltc1728 16 17278fb linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com linear technology corporation 1999 lt 0207 rev b ? printed in usa triple supply monitor with manual reset button r ela t e d p ar t s typical a pplica t ion part number description comments ltc690 5v supply monitor, watchdog timer and battery backup 4.65v threshold ltc694-3.3 3.3v supply monitor, watchdog timer and battery backup 2.9v threshold ltc699 5v supply monitor and watchdog timer 4.65v threshold ltc1232 5v supply monitor, watchdog timer and push-button reset 4.37v/4.62v threshold ltc1326 micropower precision triple supply monitor for 5v, 3.3v and adj 4.725v, 3.118v, 1v thresholds ( 0.75%) ltc1326-2.5 micropower precision triple supply monitor for 2.5v, 3.3v and adj 2.363v, 3.118v, 1v thresholds (0.75%) ltc1443/ltc1444 ltc1445 micropower quad comparators with 1% reference ltc1443 has 1.182v reference, ltc1444/ltc1445 have 1.221v reference and adjustable hysteresis ltc1536 precision triple supply monitor for pci applications meets pci t fail timing specifcations ltc1540 nanopower comparator with 2% reference 1.182v reference, 300na supply current, 8-pin msop ltc1726-2.5 micropower triple supply monitor for 2.5v, 3.3v and adj adjustable reset and watchdog time outs ltc1726-5 micropower triple supply monitor for 5v, 3.3v and adj adjustable reset and watchdog time outs ltc1985-1.8 micropower triple supply monitor for 3.3v, 1.8v and adj push-pull reset output, sot-23 v cc3 v cc5 v cca rst gnd ltc1728-5 1727/28 ta02 100nf 5 5v 3.3v 12v (5%) v trip = 11.2v (0.17v) 1 2 r2 105k 0.1% *optional resistor recommended to extend esd tolerance r3* 10k 5% manual reset button (normally open) 4 3 r1 1.07m 0.1% 100nf v trip = (r1 + r2) r1 = r2 ? 1 v cca r2 ( ) v trip v cca

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