1 of 5 041002 features automatically restarts a microprocessor after power failure monitors pushbutton for external override maintains reset for 150 ms after v cc returns to an in-tolerance condition reduces need for discrete components precision temperature-compensated voltage reference and voltage sensor accurate 5%, 10% or 20% power monitoring low-cost to-92 or space saving surface mount sot-23 packages available efficient open-drain output with internal 5.5 k pull-up resistor operating temperature -40 c to +85 c pin assignment pin description to-92 1 rst active low reset output 2 v cc power supply 3 gnd ground sot-23 1 rst active low reset output 2 v cc power supply 3 gnd ground description the DS1818 econoreset uses a precis ion temperature-compensated refe rence and comparator circuit to monitor the status of the power supply (v cc ). when an out-of-tolerance condition is detected, an internal power-fail signal is generated which forces reset to the active state. when v cc returns to an in-tolerance condition, the reset signal is kept in the active stat e for approximately 150 ms to allow the power supply and processor to stabilize. the DS1818 also monitors a pushbutton on the reset out put. if the reset line is pulled low, a reset is generated upon release and the DS1818 output will be held in reset output low for typically 150 ms. DS1818 3.3v econoreset with pushbutton www.maxim-ic.com 12 3 top view sot-23 package see mech. drawings section on website 1 2 3 1 2 3 bottom view to-92 package see mech. drawings section on website dallas DS1818 econo reset
DS1818 2 of 5 operation - power monitor the DS1818 provides the functions of detecting out-o f-tolerance power supply conditions and warning a processor-based system of impe nding power failures. when v cc is detected as out-of-tolerance, the rst signal is asserted. on power-up, rst is kept active for approximately 150 ms after the power supply has reached the selected tolerance. this allows the power supply and microprocessor to stabilize before rst is released. block diagram (open-drain output) figure 1 application example figure 2 operation - pushbutton reset the DS1818 provides a pushbutton switch for manual rese t control. when the DS1818 is not in a reset cycle, a pushbutton reset can be generated by pulling the rst pin low for at least 1 s. when the pushbutton is held low, the rst is forced active low and will rema in active low for about 150 ms after the pushbutton is released. see figure 2 for an application example and figure 3 for the timing diagram. timing diagram: pushbutton reset figure 3
DS1818 3 of 5 timing diagram: power-up figure 4 timing diagram: power-down figure 5
DS1818 4 of 5 absolute maximum ratings* voltage on v cc pin relative to ground -0.5v to +7.0v voltage on rst relative to ground -0.5v to +5v cc +0.5v operating temperature -40c to +85c storage temperature -55c to +125c soldering temperature 260c 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 dc electrical characteristics (-40 c to +85 c; v cc =1.2v to 5.5v) parameter symbol min typ max units notes output current @ 0.4 v i ol +10 ma 2, 3 voltage input low v il 0.4 v 1 voltage input high v ih 0.7 *v cc v1 operating current v cc < 5.5v i cc 28 35 a 4 v cc trip point (DS1818-5) v cctp 2.98 3.06 3.15 v 1 v cc trip point (DS1818-10) v cctp 2.80 2.88 2.97 v 1 v cc trip point (DS1818-20) v cctp 2.47 2.55 2.64 v 1 internal pull-up resistor r p 3.50 5.5 7.5 k 7 output capacitance c out 10 pf ac electrical characteristics (-40 c to +85 c; v cc =1.2v to 5.5v) parameter symbol min typ max units notes reset active time t rst 100 150 250 ms 5 v cc detect to rst t rpd 25 s v cc slew rate (v cctp (max) to v cctp (min)) t f 300 s 8 v cc slew rate (v cctp (min) to v cctp (max)) t r 0ns v cc detect to rst t rpu 100 150 250 ms 5, 6 pushbutton detect to rst t pb 1 s pushbutton reset t pbrst 100 150 250 ms 5
DS1818 5 of 5 notes: 1. all voltages are referenced to ground. 2. measured with v cc 2.7v. 3. a 1 k external pull-up resistor may be required in some applications for proper operation of the microprocessor reset control circuit. 4. measured with rst output open. 5. measured with 2.7v v cc 3.3v. 6. t r = 5 s. 7. v oh and i oh are a function of the value of r p and the associated output load conditions. 8. the t f value is for reference in defining values for t rpd and should not be considered a requirement for proper operation or use of the device. part marking codes ?a?, ?b?, &?c? represent the device type. 810 - ds1810 811 - ds1811 812 - ds1812 813 - ds1813 815 - ds1815 816 - ds1816 817 - ds1817 818 - DS1818 ?d? represents the device tolerance. a- 5% b - 10% c - 15% d - 20%
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