1 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a fm1233 precision reset generator circuit block diagram august 2000 ?2000 fairchild semiconductor international general description the fm1233 features comprehensive reset generation for microcontroller/microprocessor based systems. if the system v cc voltage level is determined to be in an out-of-tolerance state, the device automatically generates a low-going reset signal. the reset signal is held in the active state (low) for a specified duration (minimum 140 ms) after the v cc returns to an in-tolerance state. the fm1233 also allows an external reset to be connected to the reset pin without adding aditional debounce logic or extra pins. this device is fabricated using cmos technology. this device is available in the sot-23 package. features automatic reset generation on power-up minimum 140 ms reset pulse ?compatible with other similar 1233 class devices other reset pulse choices available: 32 - 256 ms choice of commercial and extended temperature ranges choice of reset thresholds: 4.63v, 4.38v, 4.00v, 3.08v, 2.93v, 2.63v package available: sot-23 connection diagram 1 2 3 fm1233 1 = gnd 2 = reset' 3 = v cc v cc tolerance detect & reset monitor v cc temp. compensated reference output stage reset_out (active low) external reset detection
2 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a each fm1233 device has the following identifier (fm1233yz) (top mark on devices will be 10yz) reset characteristics reset threshold (v) identifier(y) fairchild part number 4.63 l fm1233lz 4.38 m fm1233mz 4.00 j fm1233jz 3.08 t fm1233tz 2.93 s fm1233sz 2.63 r fm1233rz reset pulse duration (ms) identifier(z) fairchild part number 32 e fm1233ye* 64 f fm1233yf* 128 h fm1233yh* 256 blank fm1233y note*: these choices are available upon special request only. please work with fairchild marketing to determine availability.
3 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a product specifications absolute maximum ratings ambient storage temperature 65 c to +150 c all input or output voltages with respect to ground -0.3v to 6.5v lead temperature (soldering, 10 seconds) +300 c esd rating 2000v min. electrical characteristics parameter symbol temp conditions min typ max units v cc range com 1.0 5.5v v ind 1.2 5.5 v supply current i cc com 50 a 100 a reset threshold v th com l identifier 4.50 4.63 4.75 v ind 4.40 4.63 4.85 v com m identifier 4.25 4.38 4.50 v ind 4.16 4.38 4.56 v com j identifier 3.89 4.00 4.10 v ind 3.80 4.00 4.20 v com t identifier 3.00 3.08 3.15 v ind 2.92 3.08 3.23 v com s identifier 2.85 2.93 3.00 v ind 2.78 2.93 3.08 v com r identifier 2.55 2.63 2.70 v ind 2.50 2.63 2.75 v nreset output voltage high v oh all isource = 150 ma 0.8v cc v nreset output voltage low v ol all isink = 1.2ma 0.4 v reset timeout period t rst all 175 240 375 ms note: production testing done at ta = +25 c, over temperature limits guaranteed by design only. operating conditions ambient operating temperature commercial 0 c to +70 c industrial -40 c to +85 c
4 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a general description the fm1233 features a highly accurate voltage reference against which the vcc is compared. once the vcc is below the specified threshold, it will drive the reset line and continue to hold it low until the v cc returns above the threshold and the time for the reset pulse duration has expired. the fm1233 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-1.3v, the fm1233 does not sink current on the reset pin. this is not a problem in most systems since most common devices are not functional in this range. if it is desired for the fm1233 reset to be functional below the range above, it is suggested to use a 100k ? pull-down resistor between reset and v ss . bi-directional reset the fm1233 allows for the connection of an external reset switch to be wired to the reset pin. the fm1233 has the feature of allowing an external reset pin to be connected without having to add debounce logic or an extra pin to the package. the fm1233 detects when an external source is pulling the reset line low. once this occurs the fm1233 will pull the reset line low as well. when the external source stops driving the reset line the fm1233 will continue to hold the reset line low so as to prevent debounce. after a certain length of time the fm1233 will stop driving the reset line and it will return to its non-active (high) state. interfacing to bidirectional reset pins fm1233 can be used with microprocessors with bidirectional reset pins. the microprocessors can still drive the reset line but when the microprocessor has released the reset line the fm1233 will continue to hold it for a duration no longer that 300 ms. connecting an external reset to the fm1233 reset fm1233
5 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a typical operating characteristics supply current vs. temperature (fm1233r/s/t) power up reset timeout vs. temperature fm1233(r/s/t) normalized reset threshold vs. temperature fm1233(r/s/t) 0 -60 -40 -20 0 20 40 60 80 100 1 2 3 4 5 6 7 8 temperature (c) i cc ( a) v cc = 5v v cc = 3.3v 200 220 240 260 280 300 -60 -40 -20 0 20 40 60 80 100 temperature (c) power up reset timeout (ms) 0.950 0.975 1.000 1.025 1.050 -60 -40 -20 0 -20 -40 60 80 100 temperature (c) normalized threshold
6 www.fairchildsemi.com fm1233 precision reset generator circuit fm1233 rev. a 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 0.96~1.14 0.12 0.03~0.10 0.38 ref 0.40 0.03 2.90 0.10 0.95 0.03 0.95 0.03 1.90 0.03 0.508ref 0.97ref 1.30 0.10 0.45~0.60 2.40 0.10 +0.05 0.023 0.20 min 0.40 0.03 physical dimensions inches (millimeters) unless otherwise noted dimensions in millimeters sot-23 package dimensions fs pkg code au
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