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asm1232lp/lps 5v p power supply monitor and reset circuit ?2010 scillc. all rights reserved. publication order number: january 2010 C rev. 2 asm1232 /d general description the asm1232lp/lps is a fully integrated microprocessor supervisor. it can halt and restart a hung - up microprocessor, restart a microprocessor after a power failure. it has a watchdog timer and external reset override. a precision te mperature - compensated reference and comparator circuits monitor the 5v, v cc input voltage status. during power - up or when the v cc power supply falls outside selectable tolerance limits, both reset and reset become active. when v cc rises above the threshold voltage, the reset signals remain active for an additional 250ms minimum, allowing the power supply and system microprocessor to stabilize. the trip point tolerance signal, tol, selects the trip level tolerance to be either 5% or 10%. each device has bot h a push - pull, active high reset output and an open drain active low reset output. a debounced manual reset input, pbrst, activates the reset outputs for a minimum period of 250ms. there is a watchdog timer to stop and restart a microprocessor that is hu ng - up. the watchdog timeouts periods are selectable: 150ms, 610ms and 1200ms. if the st input is not strobed low before the time - out period expires, a reset is generated. devices are available in 8 - pin dip, 16 - pin so and compact 8 - pin microso packages. key features 5v supply monitor selectable watchdog period debounce manual push - button reset input precision temperature - compensated voltage reference and comparator. power - up, power - down and brown out detection 250ms minimum reset time active low open drai n reset output and active high push - pull output selectable trip point tolerance: 5% or 10% low - cost surface mount packages: 8 - pin/16 - pin so, 8 - pin dip and 8 - pin micro so packages wide operating temperature - 40c to +85c (n suffixed devices) applications microprocessor systems computers controllers portable equipment intelligent instruments automotive systems
asm1232lp/lps rev. 2 | page 2 of 13 | www.onsemi.com typical operating circuit block diagram
asm1232lp/lps rev. 2 | page 3 of 13 | www.onsemi.com pin configuration pin description pin # 8 - pin package pin # 16 - pin package pin name funct ion 1 2 pbrst debounced manual pushbutton reset input. 2 4 t d watchdog time delay selection. (t td = 150ms for t d = gnd, t td = 610ms for t d =open, and t td = 1200ms for t d = v cc ). 3 6 t ol selects 5% (t ol connected to gnd) or 10% (t ol connected to v cc ) tr ip point tolerance. 4 8 gnd ground. 5 9 reset active high reset output. reset is active: 1. if v cc falls below the reset voltage trip point. 2. if pbrst is low. 3. if st is not strobed low before the timeout period set by t d expires. 4. during power - u p. 6 11 reset active low reset output. (see reset). 7 13 st strobe input. 8 15 v cc 5v power. 1,3,5,7, 10,12,14,16 nc no internal connection.
asm1232lp/lps rev. 2 | page 4 of 13 | www.onsemi.com detailed description the asm1232lp/lps monitors the microprocessor or micro controller power supply and generates reset signal, both active high and active low, that halt processor operation whenever the power supply voltage levels are outside a predetermined tolerance. reset and reset outputs reset is an active high signal developed by a cmos push - pull ou tput stage and is the logical opposite to reset. reset is an active low signal. it is developed with an open drain driver. a pull up resistor of typical value 10k to 50k is required to connect with the output. trip point tolerance selection the tol input is used to determine the level v cc can vary below 5v without asserting a reset. with tol co n nected to v cc , reset and reset become active whenever v cc falls below 4.5v. reset and reset become active when the v cc falls below 4.75v if tol is connected t o ground. after v cc has risen above the trip point set by tol, reset and reset remain active for a minimum time period of 250ms. on power - down, once v cc falls below the reset threshold reset stays low and is guaranteed to be 0.4v or less until v cc drops below 1.2v. the active high reset signal is valid down to a v cc level of 1.2v also. tolerance select tolerance trip point voltage (v) min nom max tol = v cc 10% 4.25 4.37 4.49 tol = gnd 5% 4.5 4.62 4.74
asm1232lp/lps rev. 2 | page 5 of 13 | www.onsemi.com application information manual reset o peration push - button switch input, pbrst, allows the user to override the internal trip point detection circuits and issue reset signals. the pushbutton input is debounced and is pulled high through an internal 40k resistor. when pbrst is held low for the minimum time t pb , both resets become active and remain active for a minimum time period of 250ms after pbrst returns high. the debounced input is guaranteed to recognize pulses greater than 20ms. no external pu ll - up resistor is required, since pbrst is pulled high by an internal 40k resistor. the pbrst can be driven from a ttl or cmos logic line or shorted to ground with a mechanical switch.
asm1232lp/lps rev. 2 | page 6 of 13 | www.onsemi.com watchdog timer and st input a watchdog timer stops and re starts a microprocessor that is hung - up. the p must toggle the st input within a set period (as selectable through td input) to verify proper software execution. if the st is not toggled low within the minimum timeout period, reset signals become active . in power - up after the supply voltage returns to an in - tolerance condition, the reset signal remains active for 250ms minimum, allowing the power supply and system microprocessor to stabilize. st pulses as short as 20ns can be detected. timeouts period s of approximately 150ms, 610ms or 1,200ms are selected through the td pin. td voltage level watchdog time - out period (ms) min nom max gnd 62.5 150 250 floating 250 610 1000 v cc 500 1200 2000 the watchdog timer can not be disabled. it must be strobed with a high - to - low transition to avoid watchdog timeout and reset.
asm1232lp/lps rev. 2 | page 7 of 13 | www.onsemi.com absolute maximum ratings 1 parameter min max unit voltage on v cc 2 - 0.5 7 v voltage on st, td 2 - 0.5 v cc + 0.5 v voltage on pbrst, reset, reset 2 - 0.5 v cc + 0.5 v operating temperatu re range (n suffixed devices) - 40 +85 c operating temperature range (others) 0 70 c soldering temperature (for 10 sec) +260 c storage temperature - 55 +125 c esd rating hbm 2 kv mm 200 v note s : 1 . these are stress ratings only and functional implication is not implied. exposure to absolute maximum ratings for extended periods may affect device reliability. 2. voltages are measured with respect to ground
asm1232lp/lps rev. 2 | page 8 of 13 | www.onsemi.com dc electrical characteristics unless otherwise stated, 4.5v v cc 5.5v and over the operating temperature range of 0c to 70c ( - 40c to +85c. for n devices). all voltages are referenced to ground. parameter symbol conditions min typ max unit supply voltage v cc 4.5 5.5 v st and pbrst input high level v ih 2 v cc + 0.3 v st and pbrst input low level v il - 0.3 0.8 v v cc trip point (t ol = gnd) v cctp 4.50 4.62 4.74 v v cc trip point (t ol = v cc ) v cctp 4.25 4.37 4.49 v watchdog timeout period t td t d = gnd 62.5 150 250 ms watchdog timeout period t td t d = v cc 500 1200 2000 ms watchdog timeout period t td t d floating 250 610 1000 ms output voltage v oh i= - 500 a 3 v cc - 0.5 v cc - 0.1 v output current i oh output = 2.4v 2 - 8 - 10 ma output current i ol output = 0.4v 10 ma input leakage i il 1 - 1.0 1.0 a reset low level v ol 3 0.4 v internal pull - up resistor 1 40 k operating current (cmos) i cc1 30 a input capacitance c in 5 pf output capacitance c out 10 pf pbrst manual reset minimum low time t pb pbrst = v il 20 ms reset active time t rst 250 610 1000 ms st pulse width t st 4 20 ns v cc fail detect to reset or reset t rpd 5 8 s v c c slew rate t f 4.75v to 4.25v 300 s pbrst stable low to reset and reset active t pdly 20 ms v cc detect to reset or reset inactive t rpu t rise = 5s 250 610 1000 ms v cc slew rate t r 4.25v to 4.75v 0 ns notes: 1. pbrst is internally pulled hig h to v cc through a nominal 40k resistor. cc on power - down until v cc falls below 2v. reset remains within 0.5v of ground on power - down until v c c falls below 2.0v. 4. must not exceed the minimum watchdog time - out period (t td ). the watchdog circuit cannot be disabled. to avoid a reset, st must be strobed.
asm1232lp/lps rev. 2 | page 9 of 13 | www.onsemi.com package information
asm1232lp/lps rev. 2 | page 10 of 13 | www.onsemi.com
asm1232lp/lps rev. 2 | page 11 of 13 | www.onsemi.com so (16 - pin) jedec drawing m s - 013aa
asm1232lp/lps rev. 2 | page 12 of 13 | www.onsemi.com ordering information note: for parts to be packed in tape and reel, add - t at the end of the part number.
asm1232lp/lps on semiconductor and are registered trademarks of semiconductor components industries, llc (sc illc). scillc reserves the right to make changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitabili ty of its products for any particular purpose, nor does scillc assume any liabilit y arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. typical parameters which may be provided in scil lc data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including typicals must be validated for each customer application by customer's technical experts. scillc does not con vey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a situation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indemnify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses , and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury o r death associated with such unintended or unauthorized use, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. u .s patent pending; timing - safe and active bead are trademarks of pulsecore semiconductor, a wholly owned subsidiary of on semiconductor. this literature is subject to all applicable copyright laws and is not for resale in any manner. publication ordering information literature fulfi llment: literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone: 303 - 675 - 2175 or 800 - 344 - 3860 toll free usa/canada fax: 303 - 675 - 2176 or 800 - 344 - 3867 toll free usa/canada email: orderlit@onsemi.com n. american tec hnical support : 800 - 282 - 9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81 - 3 - 5773 - 3850 on semiconductor website: www.onsemi.com order literature: http://www.onsemi.com/ orderlit for additional information, please contact your local sales representative

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