1 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d fm1233b 3-pin c supervisor circuit connection diagram august 2002 ?2002 fairchild semiconductor corporation general description the fm1233b is a supervisor circuit that monitors a microproces- sor power supply or other system voltage and issues a reset pulse when a fault condition exists. several different threshold voltages are offered to accommodate 5v systems with different tolerances. the device features a precision temperature-compensated volt- age reference and comparator. when v cc falls to the threshold voltage, a reset pulse is issued, holding the output in the active state. when power rises above v th , the reset remains for approxi- mately 250 ms to allow the system clock and other circuits to stabilize. the reset output of fm1233b is of open-drain active low type. the fm1233b also can monitor a switch closure on its output, enabling it to recognize an external reset from a pushbutton switch or a p. in the case of a switch, the closure will be debounced by circuitry internal to the fm1233b. features precision monitoring of 5v and lower voltage microprocessor systems v th values of 4.62v, 4.38v and 4.12v automatic restart of microprocessor after power failure 140ms (min) power-on reset delay (typ.: 256ms) internal 5k ? pull-up resistor other reset choices available: 32 to 128ms operating temperature -40 c to +105 c monitors external pushbutton override internal switch debounce circuitry sot23-3 package gnd vcc /reset 1 fm1233b 2 3 sot23-3 package typical operating circuit 1 fm1233b controller 2 3 vcc gnd /reset
2 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d absolute maximum ratings voltage on any pin relative to gnd v cc -0.3v to +6.0v /reset -0.3v to (v cc + 0.3v) input current 20ma output current (/reset) 20ma electrical characteristics (v cc = 5v; t a = -40 c to +105 c unless otherwise noted) (note 1) parameter symbol conditions min typ max units operating voltage v cc 1.2 5.5 v supply current i cc v cc < 5v 3 6 a reset threshold v th fm1233bf 4.40 4.62 4.86 v reset threshold v th fm1233bd 4.16 4.38 4.55 v reset threshold v th FM1233BE 3.91 4.12 4.32 v reset output voltage v oh fm1233b i source = 150 a 0.8v cc v v cc = v th (max) reset output voltage v ol fm1233b i sink = 5ma 0.4 v v cc = v th (min) reset timeout period t rst fm1233b 140 256 560 ms pushbutton detect pbv det fm1233b v cc = 5v 0.8 2.0 v pushbutton release pbv rel fm1233b note 2 0.3 1.5 v note 1: testing at production is done at 25 c only. limits over temperature are guaranteed by design. note 2: c = 100pf. v cc = 5v. it is recommended to connect 100pf capacitor between the reset pin and ground pin if pushbutton reset is implemented. esd rating: human body model 2kv machine model 200v continuous power dissipation (t a = 70 c) sot23 (derate 4mw above 70 c) 300mw operating temperature range -40 c to +105 c storage temperature range -65 c to +150 c lead temperature (soldering, 10s) +300 c these are stress ratings only, and functional operation is not implied for these levels or beyond. exposure to absolute maximum rating conditions for extended periods may affect device reliability.
3 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d pin descriptions pin number name function 1 gnd ground 2 /reset /reset remains low while v cc is below v th , and for at least 140ms after v cc rises above v th . 3v cc circuit timing when operating properly with 5v v cc (for example), /reset will also be about 5v. when v cc starts to fall, /reset will follow it down as shown. when v cc drops below v th , /reset drops to ground ("issues a reset") and stays there unless v cc also falls below its minimum operating voltage, approx. 1v. at this point, the supervisor loses control, and its output may rise, only to again follow v cc down to the ground. when v cc begins to rise, /reset follows it until 1.0v or so is reached, whereupon the device regains control, /reset is pulled to ground, etc. when v cc rises above v th , /reset comes out of reset 140 ms later. if it is required that a lower value than gnd + 1.0v is needed on reset signal during v cc 1v, a 100k resistor may be used on the device output to gnd. 3.3v v th 1v gnd 3.3v v th 1v gnd v cc reset 140ms (min)
4 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d general description the fm1233b features a highly accurate voltage reference to which v cc is compared. once v cc is below the specified thresh- old, it will drive the /reset line and continue to hold it low until v cc returns above the threshold and the time for the reset pulse duration has expired. the fm1233b is immune to short negative going transients on the v cc line. the placement of a 0.1 f bypass capacitor as close as possible to the v cc pin provides additional transient immunity. for a v cc value below 1.0v, the fm1233b does not sink very much current on the /reset pin. this is not a problem in most systems since common devices are not functional in this range. if it is desired for the fm1233b reset to be functional below this range, use a 100k ? pull-down resistor between /reset and v ss . bi-directional reset the fm1233b permits an external pushbutton to initiate a reset. such a connection to pin 2 will be debounced, reset will go low and recover in typically 250ms. for proper operation, the external switch should be paralleled by an external capacitor of 100pf to 0.01 f. connecting an external reset to the fm1233b 1 fm1233 controller 2 3 v cc gnd 100pf push button /reset
5 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d ordering information part top reset output package packing number marking threshold (v) type type method fm1233bfs3x 3bf 4.62 open-drain, active low 3-pin, sot23 3000 units in t&r fm1233bds3x 3bd 4.38 open-drain, active low 3-pin, sot23 3000 units in t&r FM1233BEs3x 3be 4.12 open-drain, active low 3-pin, sot23 3000 units in t&r note 3: devices listed above feature 250ms typical reset pulse width. consult fairchild sales for other reset pulse width options.
6 www.fairchildsemi.com fm1233b 3-pin c supervisor circuit fm1233b rev. d fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and fai rchild reserves the right at any time without notice to change said circuitry and specifications. life support policy fairchild's products are not authorized for use as critical components in life support devices or systems without the express w ritten approval of the president of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. a critical component is any component of a life support device or system whose failure to perform can be reasonably ex- pected to cause the failure of the life support device or system, or to affect its safety or effectiveness. fairchild semiconductor fairchild semiconductor fairchild semiconductor fairchild semiconductor americas europe hong kong japan ltd. customer response center fax: +44 (0) 1793-856858 8/f, room 808, empire centre 4f, natsume bldg. tel. 1-888-522-5372 deutsch tel: +49 (0) 8141-6102-0 68 mody road, tsimshatsui east 2-18-6, yushima, bunkyo-ku english tel: +44 (0) 1793-856856 kowloon. hong kong tokyo, 113-0034 japan fran?ais tel: +33 (0) 1-6930-3696 tel; +852-2722-8338 tel: 81-3-3818-8840 italiano tel: +39 (0) 2-249111-1 fax: +852-2722-8383 fax: 81-3-3818-8841 0 .12 0 0 .1 05 0 . 0 7 9 0 . 0 7 1 0 . 004 0 . 001 0 . 0 4 0 0 . 031 0 . 0 2 1 0 . 0 1 5 0 . 055 0 . 0 4 7 0 . 098 0 . 083 0 . 0 1 0 0 . 005 0 . 0059 0 . 0035 0 - 8 ? pk g c l 0.76 0.76 0.95 2.29 land pattern recommendation physical dimensions inches (millimeters) unless otherwise noted sot-23 package dimensions fs pkg code au
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