ds1233a 3.3v econoreset www.maxim-ic.com features ? automatically restarts microprocessor after power failure 1 of 5 122001 ? monitors pushbutton for external override ? internal circuitry debounces pushbutton switch ? maintains reset for 350ms after v cc returns to an in-tolerance condition or pushbutton released ? accurate 10% or 15% microprocessor 3.3v power supply monitoring ? reduces need for discrete components ? precision temperature- compensated voltage reference and voltage sensor ? low-cost to-92 package or surface mount sot-223 package ? internal 5k ?? pull-up resistor ? operating temperature of -40 ?c to +85 ?c pin assignment dallas ds1233a econo reset 1 pin description pin 1 ground pin 2 reset pin 3 v cc pin 4 ground (sot-223 only) description the ds1233a econoreset monitors two vital conditions for a microprocessor: power supply and external override. a precision temperat ure-compensated reference and comparat or circuit are used to monitor the status of the power supply (v cc ). when an out-of-toler ance 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 state for approximately 350ms to allow the power supply and processor to stabilize. the second function of the ds1233a is pushbutton reset control. the ds1233a debounces a pushbutton closure and will gene rate a 350ms reset pulse upon release. operation ? power monitor the ds1233a provides the functions of detecting out -of-tolerance power supply conditions and warning a processor-based system of impending power failure. when v cc is detected as out-of-tolerance as defined by the tolerance of the part selected, the rst signal is asserted. on power-up, rst is kept active for approximately 350ms after the power supply has reached the selected tolerance. this allows the power supply and microprocessor to stabilize before rst is released. 1 2 3 1 2 3 2 3 4 top view sot-223 package bottom view t o-92 package
ds1233a operation ? pushbutton reset the ds1233a provides for a pushbutton switch to be connected to the rst output pin. when the ds1233a is not in a reset cycle, it continuously monitors the rst signal for a low-going edge. if an edge is detected, the ds1233a will de bounce the switch by pulling the rst line low. after the internal timer has expired, the ds1233a will continue to monitor the rst line. if the line is still low, the ds1233a will continue to monitor the line look ing for a rising edge. upon detecti ng a release, the ds1233a will force the rst line low and hold it low for 350ms. note: for proper operation with an external pushbutton, a capacitor between 100pf and 0.01 ? f must be connected between rst and ground. in applications where add itional reset current is required, a minimum capacitance of 500 pf should be used, along with a parallel external pull-up resistor of 1k? minimum. block diagram figure 1 application example figure 2 2 of 5
ds1233a pushbutton reset figure 3 power-up figure 4 power-down figure 5 3 of 5
ds1233a absolute maxi mum 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 -40c to +85c storage temperature range -55c to +125c soldering temperature 260c for 10 seconds * this is a stress rating only and functional operati on of the device at these or any other conditions above those indicated in the opera tion sections of this specifica tion is not implied. exposure to absolute maximum rating conditions for extende d periods of time may affect reliability. recommended dc operating co nditions (-40? c to +85 ? c) parameter symbol min typ max units notes supply voltage v cc 1.2 3.3 5.5 v 1 dc electrical characteristics (-40 ? c to +85 ? c; v dd = 3.3v ? 10%) parameter symbol min typ max units notes low level @ rst v ol 0.4 v 1 output current @ 0.4v i ol +8 ma operating current i cc 50 ? a v cc trip point 10% v cctp1 2.80 2.88 2.97 v 1 v cc trip point 15% v cctp2 2.64 2.72 2.80 v 1 output capacitance c out 10 pf pushbutton detect pb dv 0.8 2.0 v 1 pushbutton release pb rd 0.3 0.8 v 1, 2 internal pull-up resistor r p 3.75 5 6.25 k? ac electrical characteristics (-40 ? c to +85 ? c; v cc = 3.3v ? 10%) parameter symbol min typ max units notes reset active time t rst 250 350 450 ms v cc detect to rst t rpd 100 ns v cc slew rate (2.85v - 2.3v) t f 300 ? s v cc slew rate (2.3v - 2.85v) t r 0 ns pushbutton debounce pb db 250 350 450 ms v cc detect to rst t rpu 250 350 450 ms notes: 1) all voltages are referenced to ground. 2) with a 100pf to 0.01 ? f capacitor co nnected from rst to ground. 4 of 5
ds1233a econoreset selection guide v cc trip point pushbutton detect min typ max min typ max ds1233-15 4.0 4.125 4.24 1.8 - 3.3 ds1233-10 4.25 4.375 4.49 1.8 - 3.3 ds1233-5 4.5 4.625 4.75 1.8 - 3.3 ds1233d-15 4.0 4.125 4.24 n/a n/a ds1233d-10 4.25 4.375 4.49 n/a n/a ds1233d-5 4.5 4.625 4.75 n/a n/a ds1833-15 4.0 4.125 4.24 n/a n/a ds1833-10 4.25 4.375 4.49 n/a n/a 5v ds1833-5 4.5 4.625 4.75 n/a n/a DS1233A-15 2.64 2.72 2.80 0.8 - 2.0 3.3v ds1233a-10 2.8 2.88 2.97 0.8 - 2.0 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. to 92 q3+1 21-0248 to 92 q3+4 21-0250 sot 223 k3+1 21-0264 5 of 5
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