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1 of 8 122001 features halts and restarts an out-of-control microprocessor holds microprocessor in check during power transients automatically restarts microprocessor after power failure monitors pushbutton for external override accurate 5%, 10%, or 20% (3v only) microprocessor power monitoring eliminates the need for discrete components 20% tolerance for use with 3.0v systems pin- and function-co mpatible with the max823/24/25 products low cost sot-23-5 package industrial temperature range: -40 c to +85 c device rst rst pbrst wd ds181xa ds181xb ds181xc x x x x x x x x x x = "ds1814" for 5v devices x = "ds1819" for 3v devices pin assignment pin description ds181xa 1 rst active low reset output 2 gnd ground 3 pbrst pushbutton reset input 4 st strobe input 5 vcc power supply ds181xb 1 rst active low reset output 2 gnd ground 3 rst active high reset output 4 st strobe input 5 vcc power supply ds181xc 1 rst active low reset output 2 gnd ground 3 rst active high reset output 4 pbrst pushbutton reset input 5 vcc power supply description the ds1814 5-volt micromonitor and the ds1819 3.3v mi cromonitor monitor three vital conditions for a microprocessor: power supply, software execution, a nd external override. first, a precision temperature- compensated reference and comparator circuit monitor the status of v cc . when an out-of-tolerance condition occurs, an internal power-fail signal is generated which forces the reset(s) to an active state. when v cc returns to an in-tolerance condition, the reset si gnal is kept in the active state for a minimum of 140ms to allow the power supply and processor to stabilize. ds1814/ds1819 5v and 3.3v micromonito r www.maxim-ic.com 321 45 sot-23-5 package see mech. drawing
ds1814/ds1819 2 of 8 the ds1814/ds1819 ?a? and ?c? perf orm pushbutton reset control. they debounce the pushbutton input and generate an active reset pul se width of 140ms minimum. the ds 1814/9 ?a? and ?b? versions perform a watchdog function. the watchdog is an internal timer th at forces the reset signals to the active state if the strobe input does not change state every 1.12 seconds. the watchdog timer function can be disabled by leaving the watchdog strobe input disconnected. operation power monitor the ds1814 detects out-of-tolerance power supply c onditions and warns a processor-based system of impending power failure. when v cc falls below a preset level, a comparator outputs the signal rst (or rst). rst (or rst) are excellent control signals for a mic roprocessor, as processing is stopped at the last possible moment of valid v cc . on power-up, rst (or rst) are kept active for a minimum of 140ms to allow the power supply and processor to stabilize. pushbutton reset the ds1814 ?a? and ?c? provide an i nput pin for direct connection to a pushbutton reset (see figure 2). the pushbutton reset input requires an active low sign al. internally, this input is debounced and timed such that a rst (or rst) signal of at least 140ms minimum will be generated. the 140ms delay commences as the pushbutton reset input is re leased from the low level (see figure 3). watchdog timer the ds1814/ds1819 ?a? and ?b ? versions watchdog timer function forces rst (and rst) signal(s) active when the st input is not clocked within the 1.12 s econd watchdog time-out period. time-out of the watchdog starts when rst (and rst) become(s) inactive. if a transition occurs on the st input pin prior to time-out, the watchdog timer is reset and begins to time out again. if the watchdog timer is allowed to time out, then the reset output(s) will go active for 140ms. the watchdog can be disabled by floating (or tri-stating) the st input. the st input can be derived from many microprocessor outputs. the most typical signals used are the microprocessor data i/o signals and control signals. when the microprocessor functions normally, these signals would as a matter of routine cause the watchdog to be reset prior to time-out. to guarantee that the watchdog timer does not time out, a transition mu st occur at or less than 1.12 seconds. a typical circuit example is shown in figure 4. the ds1814/19 watchdog function can be disabled at any time by tri-starting the strobe input. a sample circuit to disable the watchdog is shown in figure 6.
ds1814/ds1819 3 of 8 ds1814/ds1819 block diagram figure 1 *notes: st available on'a' and 'b' versions pbrst available on 'a' and 'c' versions rst available on 'b' and 'c' versions pushbutton reset figure 2 timing diagram: pushbutton reset figure 3
ds1814/ds1819 4 of 8 watchdog timer figure 4 timing diagram: strobe input figure 5 watchdog disable circuit figure 6 timing diagram: power-down figure 7
ds1814/ds1819 5 of 8 timing diagram: power-up figure 8 rst valid to 0 volts v cc figure 9 output valid conditions the rst output uses a push-pull output which can maintain a valid output down to 1.0v v cc . to sink current below 1.0v a resistor can be connected form rst to ground (see figure 9.) this arrangement will maintain a valid value on rst during both power-up and -down but will draw current when rst is in the high state. a value of about 100k should be adequate in most situations. the output with a resistor pull-down can mainta in a valid reset down to v cc equal to 0v.
ds1814/ds1819 6 of 8 absolute maximum ratings* voltage on v cc pin relative to ground -0.5v to +7.0v voltage on i/o relative to ground -0.5v to v cc + 0.5v operating temperature range -40 c to +85 c storage temperature range -55 c to +125 c soldering temperature 260 c for 10 seconds * this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. recommended dc operating conditions (-40 c to +85 c) parameter symbol min typ max units notes supply voltage v cc 1.0 5.5 v 1 st and pbrst input high level v ih 0.8 v cc v1 st and pbrst input low level v il 0.3 v cc v1 dc electrical characteristics (-40 c to +85 c; v cc = 1.2v to 5.5v) parameter symbol min typ max units notes v cc trip point ds1814-5 v cctp 4.50 4.75 v 1 v cc trip point ds1814-10 v cctp 4.25 4.50 v 1 v cc trip point ds1819-5 v cctp 3.00 3.15 v 1 v cc trip point ds1819-10 v cctp 2.85 3.00 v 1 v cc trip point ds1819-20 v cctp 2.55 2.70 v 1 reset trip point hysteresis (ds1814) v rh 10 mv reset trip point hysteresis (ds1819) v rh 5mv output current @ 2.4v i oh 350 a 3 output current @ 0.4v i ol 3.2 6 ma 3 output voltage @ -30 a v oh v cc *.8 v cc *.9 v 3 operating current ds1814 i cc 10 15 a 4 operating current ds1819 i cc 812 a 5 st input current st = v cc , time averaged 120 160 a 6 st input current st = gnd, time averaged -20 -15 a 6
ds1814/ds1819 7 of 8 ac electrical characteristics (-40 c to +85 c; v cc = 1.2v to 5.5v) parameter symbol min typ max units notes pbrst = v il t pb 1 s 7 reset active time t rst 140 200 280 ms st pulse width t st 50 ns 8 watchdog time-out t td 1.12 1.60 2.40 s v cc detect to rst and rst t rpd 30 40 s 9 v cc slew rate (rising edge) 12.5 v/ s v cc detect to rst and rst t rpu 140 200 280 ms pbrst stable low to rst and rst t pdly 500 ns capacitance (t a = 25 c) parameter symbol min typ max units notes input capacitance c in 5pf output capacitance c out 7pf notes: 1) all voltages are referenced to ground. 2) pbrst is internally pulled up to v cc with an internal impedance of 50k typical. 3) measured with v cc 2.7v. 4) measured with outputs open, v cc 5.5v, and all inputs at v cc or ground, except the st input at <10khz duty cycle-square wave or st input open. 5) measured with outputs open, v cc 3.6v, and all inputs at v cc or ground, except the st input at <10khz duty cycle-square wave or st input open. 6) the st input current is defined as the average input current when st is driven high or low. this input must be driven high or low by an out put that can source or sink at least 200 a when active. 7) noise immunity: pulses <100ns at pushbutton input will not cause a reset. 8) must not exceed t td minimum. 9) noise immunity: pulses <2 s at v cctp minimum will not cause a reset and v cctp - v cc = 100mv.
ds1814/ds1819 8 of 8 part marking codes ?a?, ?b? and ?c? represents the device type. 14a - ds1814a 14b - ds1814b 14c - ds1814c 19a - ds1819a 19b - ds1819b 19c - ds1819c ?d? represents the device tolerance. a - 5% b - 10% c - 20% sot-23-5 package
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs m axim > p roduc ts > supervis ors , v oltage m onitors , sequenc ers ds1814, ds1819 5 volt and 3.3 volt micromonitor quickview technical documents ordering info more information all ordering information notes: other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 1. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 2. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 3. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 4. devices: 1-59 of 59 ds1814a fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1814ar-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1814ar-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814ar-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814ar-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1814ar-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1814ar-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1814ar-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1814b fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1814br-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1814br-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814br-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814br-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1814br-10+t&r -40c to +85c rohs/lead-free: see data sheet
ds1814br-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1814br-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1814br-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1814c fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1814c r-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1814c r-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1814c r-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1814c r-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814c r-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1814c r-10+t&r -40c to +85c rohs/lead-free: see data sheet ds1814c r-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1814c r-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819a fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1819ar-10+t&r -40c to +85c rohs/lead-free: see data sheet ds1819ar-20+t&r -40c to +85c rohs/lead-free: see data sheet ds1819ar-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819ar-20-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819ar-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819ar-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1819ar-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819ar-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819ar-20-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819ar-20/t&r -40c to +85c rohs/lead-free: see data sheet
ds1819ar-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1819ar-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1819b fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1819br-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1819br-20/t&r sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819br-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1819br-20+t&r -40c to +85c rohs/lead-free: see data sheet ds1819br-10+t&r -40c to +85c rohs/lead-free: see data sheet ds1819br-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819br-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819br-20-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819br-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819br-20-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819br-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819br-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1819c fre e sam ple buy pack age : type pins footprint drawing code/var * te m p rohs/le ad-fre e ? m ate rials analys is ds1819c r-20+t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-20/t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-10-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis ds1819c r-5-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819c r-20-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819c r-10-u+ sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5+1 * -40c to +85c rohs/lead-free: lead free materials analysis ds1819c r-5-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis
ds1819c r-10/t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-5/t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-10+t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-5+t&r -40c to +85c rohs/lead-free: see data sheet ds1819c r-20-u sot-23;5 pin;9 mm dwg: 21-0057f (pdf) use pkgcode/variation: u5-1 * -40c to +85c rohs/lead-free: no materials analysis didn't find what you need? next day product selection assistance from applications engineers parametric search applications help quickview technical documents ordering info more information des c ription key features a pplic ations /u s es key spec ific ations diagram data sheet a pplic ation n otes des ign guides e ngineering journals reliability reports software/m odels e valuation kits p ric e and a vailability samples buy o nline p ac kage i nformation lead-free i nformation related p roduc ts n otes and c omments e valuation kits 1 9 9 9 -1 1 -1 9 t his page las t modified: 2 0 0 7 -1 0 -0 9 c ontac t us: send us an email c opyright 2 0 0 7 by m axim i ntegrated p roduc ts , dallas semic onduc tor ? legal n otic es ? p rivac y p olic y

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