1 of 5 122001 features automatically restarts microprocessor after power failure 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 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 temperature-compensated reference and comparator circuit are used 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 state fo r 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 ge nerate 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 powe r supply has reached the selected tolerance. this allows the power supply and microprocessor to stabilize before rst is released. ds1233 a 3.3v econoreset www.maxim-ic.com 1 2 3 1 2 3 bottom view to-92 package see mech. drawings section on website 2 3 4 top view sot-223 package see mech. drawings section on website 1 dallas ds1233a econo reset
ds1233a 2 of 5 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 debounce 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 looking for a rising edge. upon detecting 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 a dditional 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
ds1233a 3 of 5 pushbutton reset figure 3 power-up figure 4 power-down figure 5
ds1233a 4 of 5 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 -40c to +85c storage temperature range -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 1.2 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 0ns 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 connected from rst to ground.
ds1233a 5 of 5 econoreset selec tion 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
|
