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SGM708 low-cost, microprocessor supervisory circuit general description the SGM708 microprocessor supervisory circuit reduces the complexity and number of components required to monitor power-supply and monitor microprocessor activity. it significantly improves system reliability and accuracy compared to separate ics or discrete components. the SGM708 provides power-supply monitoring circuitry that generates a reset output during power-up, power-down and brownout conditions. the reset output remains operational with v cc as low as 1v. in addition, there is a 1.25v threshold detector for power-fail warning, low-battery detection, or monitoring an additional power supply. an active-low manual-reset input ( mr ) is also included. the SGM708 is available in green soic-8 package. it operates over an ambient temperature range of -40 to +85 . features ? precision supply-voltage monitor 4.65v for SGM708-l 4.40v for SGM708-m 4.0v for SGM708-j 3.08v for SGM708-t 2.93v for SGM708-s 2.63v for SGM708-r ? guaranteed reset valid at v cc = 1v ? 200ms reset pulse width ? debounced ttl/cmos-compatible manual-reset input ? voltage monitor for power-fail or low-battery warning ? dual reset outputs (active-low and active-high ) ? -40 to +85 operating temperature range ? green soic-8 package applications computers controllers intelligent instruments automotive systems critical p power monitoring rev. a. 3 sg micro corp www.sg-micro.com
low-cost, microprocessor SGM708 supervisory circuit 2 sg micro corp www.sg-micro.com package/ordering information model reset threshold (v) package description ordering number package marking package option 4.65 soic-8 SGM708-lys8g/tr SGM708-lys8 tape and reel, 2500 4.40 soic-8 SGM708-mys8g/tr SGM708-mys8 tape and reel, 2500 4.0 soic-8 SGM708-jys8g/tr SGM708-jys8 tape and reel, 2500 3.08 soic-8 SGM708-tys8g/tr SGM708-tys8 tape and reel, 2500 2.93 soic-8 SGM708-sys8g/tr SGM708-sys8 tape and reel, 2500 SGM708 2.63 soic-8 SGM708-rys8g/tr SGM708-rys8 tape and reel, 2500 note: order number is de fined as the follow: order number sgm 708- x y x g / tr package type tape and reel s8 soic-8 operating temperature range y -40 to +85 reset threshold l: 4.65v m: 4.40v j: 4.0v t: 3.08v s: 2.93v r: 2.63v green product caution this integrated circuit can be damaged by esd if you don?t pay attention to esd protection. sgmicro recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper handling and installation procedures can cause damage. esd damage can range from subtle performance degradation to complete device failure. precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. sgmicro reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. please contac t sgmicro sales office to get the latest datasheet. absolute maximum ratings (typical values are at t a = +25 , unless otherwise noted.) terminal voltage (with respect to gnd) v cc ........................................................................-0.3v to 6.0v all other inputs........................................ -0.3v to (v cc + 0.3v) input current, v cc ..............................................................20ma gnd.................... ...................... ................. ............... ....... 20ma output current, (all outputs)............................................. 20ma operating temperature range. .......................... -40 to +85 junction temperature................. ........................ .............. 150 storage temperature............ .............. .............. -65 to +150 lead temperature (soldering, 10sec).............................. 260 esd susceptibility hbm.............. ......................... ................ ................... ........4000v mm......................... ..................... ............... ................. ........300v note: stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability.
low-cost, microprocessor SGM708 supervisory circuit 3 sg micro corp www.sg-micro.com typical operation circuit v cc mr pfi pfo v cc unregulated dc +5v dc linear regulator SGM708 microprocessor pushbutton switch interrupt reset/reset reset/reset
low-cost, microprocessor SGM708 supervisory circuit 4 sg micro corp www.sg-micro.com pin configuration (top view) SGM708 soic-8 v cc 1 2 3 4 5 6 7 8 mr gnd pfi n.c. pfo reset reset pin description pin name function 1 mr manual-reset input triggers a reset pulse when pulled below 0.8v. this active-low input has an internal 250 a (v cc = +5v) pull-up current. it can be driven from a ttl or cmos logic line as well as shorted to ground with a switch. 2 v cc power supply voltage that is monitored. 3 gnd 0v ground reference for all signals 4 pfi power-fail voltage monitor input. when pfi is less than 1.25v, pfo goes low. connect pfi to gnd or v cc when not used. 5 pfo power-fail output goes low and sinks current when pfi is less than 1.25v; otherwise pfo stays high. 6 n.c. no connect. 7 reset active-low reset output pulses low for 200ms when triggered, and stays low whenever v cc is below the reset threshold (4.65v for SGM708-l, 4.40v for SGM708-m, 4.0v for SGM708-j, 3.08v for SGM708-t, 2.93v for SGM708-s and 2.63v for SGM708-r). it remains low for 200ms after v cc rises above the reset threshold or mr goes from low to high. 8 reset active-high reset output is the inverse of reset . whenever reset is high, reset is low, and vice versa.
low-cost, microprocessor SGM708 supervisory circuit 5 sg micro corp www.sg-micro.com electrical characteristics (v cc = 4.75v to 5.5v for SGM708-l; v cc = 4.5v to 5.5v for SGM708-m; v cc = 4.07v to 5.5v for SGM708-j; v cc = 3.14v to 5.5v for SGM708-t; v cc = 2.95v to 5.5v for SGM708-s; v cc = 2.68v to 5.5v for SGM708-r; t a = -40c to +85c, unless otherwise noted.) parameter conditions min typ max units operating voltage range (v cc ) 1.0 5.5 v supply current (i supply ) 20 60 a SGM708-l 4.5 4.65 4.75 SGM708-m 4.25 4.4 4.5 SGM708-j 3.91 4.0 4.07 SGM708-t 3.02 3.08 3.14 SGM708-s 2.85 2.93 2.95 reset threshold (v rt ) SGM708-r 2.56 2.63 2.68 v SGM708-t, SGM708-s, SGM708-r 25 SGM708-j 35 reset threshold hysteresis SGM708-l, SGM708-m 40 mv reset pulse width (t rs ) 120 200 290 ms i source = 800 a v cc - 1.5 i sink = 3.2ma 0.4 reset output voltage v cc = 1v, i sink = 50 a 0.3 v i source = 800a v cc - 1.5 v reset output voltage i sink = 1.2ma 0.4 v mr pull-up current mr = 0v 100 250 600 a mr pulse width (t mr ) 250 ns low 0.8 mr input threshold high t a = +25 c 2 v mr to reset out delay (t md ) 100 350 ns pfi input threshold v cc = 5v 1.17 1.25 1.3 v pfi input current 0.2 na i source = 800 a v cc - 1.5 pfo output voltage i sink = 3.2ma 0.4 v
low-cost, microprocessor SGM708 supervisory circuit 6 sg micro corp www.sg-micro.com block diagram + _ + _ SGM708 v cc 250a 1.25v 7 5 1 2 4 3 gnd pfi v cc 4.65v for SGM708-l * mr pfo reset generator reset 8 reset * 4.65v for SGM708-l 4.40v for SGM708-m 4.0v for SGM708-j 3.08v for SGM708-t 2.93v for SGM708-s 2.63v for SGM708-r
low-cost, microprocessor SGM708 supervisory circuit 7 sg micro corp www.sg-micro.com typical performance characteristics v cc v cc 2k 330pf gnd reset reset + - pfi + 5 v pfo +1.25v 30pf 1k + - pfi + 5v +1.25v 30pf pfo 1k v cc v cc 10k 330pf gnd reset reset 330pf 10k v cc 10k 330pf gnd reset v cc v cc 10k 330pf gnd reset reset 330pf 10k
low-cost, microprocessor SGM708 supervisory circuit 8 sg micro corp www.sg-micro.com typical performance characteristics
low-cost, microprocessor SGM708 supervisory circuit 9 sg micro corp www.sg-micro.com application notes ensuring a valid reset output down to v cc = 0v when v cc falls below 1v, the SGM708 reset output no longer sinks current?it becomes an open circuit. high-impedance cmos logic inputs can drift to undetermined voltages if left undriven. if a pull-down resistor is added to the reset pin as shown in figure 1, any stray charge or leakage currents will be drained to ground, holding reset low. resistor value (r1) is not cr itical. it should be about 100k ? , large enough not to load reset and small enough to pull reset to ground. r1 SGM708 reset figure 1. reset valid to ground circuit monitoring voltages other than the unregulated dc input monitor voltages other than the unregulated dc by connecting a voltage divider to pfi and adjusting the ratio appropriately. if required, add hysteresis by connecting a resistor (with a value approximately 10 times the sum of the two resistors in the potential divider network) between pfi and pfo . a capacitor between pfi and gnd will reduce the power-fail circuit?s sensitivity to high-frequency noise on the line being monitored. reset can be asserted on other voltages in addition to the +5v v cc line. connect pfo to mr to initiate a reset pulse when pfi drops below 1.25v. figure 2 shows the SGM708 configured to assert reset when the +5v supply falls below the reset threshold, or when the +12v supply falls below approximately 11v. v cc mr pfo pfi reset +12v +5v 1m 1% 130k 1% to p gnd SGM708 figure 2. monitoring both +5v and +12v monitoring a negative voltage the power-fail comparator can al so monitor a negative supply rail (figure 3). when the negative rail is good (a negative voltage of large magnitude), pfo is low, and when the negative rail is degraded (a negative voltage of lesser magnitude), pfo is high. by adding the resistors and transistor as shown, a high pfo triggers reset. as long as pfo remains high, the SGM708 will keep reset asserted ( reset = low, reset = high). note that this circuit?s accuracy depends on the pfi threshold tolerance, the v cc line, and the resistors. v cc mr pfo pfi +5v gnd SGM708 r1 r2 v- 100k 100k to p +5v 0v +5v 0v v- v trip 0v mr pfo 5 C 1.25 r1 1.25 - v trip r2 v trip < 0 = 2n3904 reset figure 3. monitoring a negative voltage interfacing to ps with bidirectional reset pins ps with bidirectional reset pins, such as the motorola 68hc11 series, can contend with the SGM708 reset output. if, for example, the reset output is driven high and the microprocessor wants to pull it low, indeterminate logic levels may result. to correct this, connect a 4.7k ? resistor between the reset output and the p reset i/o, as in figure 4. buffer the reset output to other system components. v cc reset microprocessor gnd SGM708 v cc reset gnd 4.7k buffred reset to other system components figure 4. interfacing to microprocessors with bidirectional reset i/o
low-cost, microprocessor SGM708 supervisory circuit 10 sg micro corp www.sg-micro.com package outline dimensions soic-8 d e e1 e b a a2 a1 c l 1.27 0.6 2.2 5.2 recommended land pattern (unit: mm) dimensions in millimeters dimensions in inches symbol min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.100 0.185 0.200 e 3.800 4.000 0.150 0.157 e1 5.800 6.200 0.228 0.244 e 1.27 bsc 0.050 bsc l 0.400 1.270 0.016 0.050 0 8 0 8
low-cost, microprocessor SGM708 supervisory circuit 11 sg micro corp www.sg-micro.com tape and reel information note: the picture is only for reference. please make the object as the standard. key parameter list of tape and reel package type reel diameter reel width w1 (mm) a0 (mm) b0 (mm) k0 (mm) p0 (mm) p1 (mm) p2 (mm) w (mm) pin1 quadrant soic-8 13 12.4 6.4 5.4 2.1 4.0 8.0 2.0 12.0 q1 reel width (w1) reel diameter reel dimensions tape dimensions direction of feed p2 p0 w p1 a0 k0 b0 q1 q2 q4 q3 q3 q4 q2 q1 q3 q4 q2 q1
low-cost, microprocessor SGM708 supervisory circuit 12 sg micro corp www.sg-micro.com carton box dimensions note: the picture is only for reference. please make the object as the standard. key parameter list of carton box reel type length (mm) width (mm) height (mm) pizza/carton 13 386 280 370 5

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