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december 2000 1 mic841/2 mic841/2 micrel mic841/2 comparator with reference advance information typical application hth out vdd lt h gnd mic841 v in r1 r2 r3 v out v dd v lt h > v hth v ref = 1.24v 1.5v v dd 5.5v 5 3 1 4 2 threshold detection with hysteresis set by a third external resistor features optimized for pdas, cellular telephones, pagers, and other battery-powered devices input and output can be pulled up to 6v regardless of supply voltage high 1.25% voltage threshold accuracy built in hysteresis for noise suppression extremely low 1.5 a typical supply current immune to brief input transients 5-lead sc-70 package applications pdas pagers cordless phones consumer electronics embedded controllers personal electronics micrel, inc. ?1849 fortune drive ?san jose, ca 95131 ?usa ?tel + 1 (408) 944-0800 ?fax + 1 (408) 944-0970 ?http://www.mic rel.com general description the mic841 and mic842 are micropower, precision voltage comparator with an on-chip voltage reference. both devices are intended for voltage monitoring applica- tions, external resistors are used to set the voltage monitor threshold and when the threshold is crossed the outputs switch polarity. the mic842 incorporates a voltage reference and compara- tor with fixed internal hysteresis; two external resistors are used to set the switching threshold voltage. the mic841 provides a similar function with user adjustable hysteresis, this part requires three external resistors to set the upper and lower thresholds (the difference between the threshold volt- ages being the hysteresis voltage). both the mic841 and mic842 are available with push-pull outputs and active-high or active-low inputs. the active-low part is also available with an open-drain output. supply current is extremely low (1.5 a, typical), making it ideal for portable applications. the mic841/2 is supplied in micrel? teeny 5-lead sc-70 package. teeny is a trademark of micrel, inc. ordering information hysteresis output output part number marking adjustment stage function temperature range package mic841hbc5 b13 external push pull active high ?0 c to +85 c sc70-5 mic841lbc5 b14 external push pull active low ?0 c to +85 c sc70-5 mic841nbc5 b15 external open drain active low ?0 c to +85 c sc70-5 mic842hbc5 b16 internal push pull active high ?0 c to +85 c sc70-5 mic842lbc5 b17 internal push pull active low ?0 c to +85 c sc70-5 mic842nbc5 b18 internal open drain active low ?0 c to +85 c sc70-5 inp out vdd gnd mic842 v in r1 r2 v out v dd v ref = 1.24v 1.5v v dd 5.5v 4 2 1 5 threshold detector with internal fixed hysteresis
mic841/2 micrel mic841/2 2 december 2000 pin configuration hth vdd out lth 1 3 45 2 gnd bxx mic841 sc-70-5 (c5) pin description mic841 pin number pin name pin function 1 hth high-voltage threshold (input): analog input to a comparator. this is the voltage input assigned to detect a high-voltage condition when the level on this pin exceeds v ref , out is asserted and the condition is latched until v lth < v ref . 2 gnd ground 3 lth low-voltage threshold (input): analog input to a comparator. this is the voltage input assigned to detect a low voltage condition. when the level on this pin falls below v ref , out is de-asserted and the condition is latched until v hth > v ref . 4 out output: active-high, open-drain output. this output is deasserted and latched when v lth v ref . 5 vdd power supply (input): independent supply input for internal circuitry. inp vdd out nc 1 3 45 2 gnd bxx mic842 sc-70-5 (c5) pin description mic842 pin number pin name pin function 1 inp input: analog input to the comparator. when v inp >v ref +v hyst , v out is asserted to a logic-high level output. 2 gnd ground 3 nc no connect 4 out output: active-high, open-drain output. this output is de-asserted when v inp v ref +v hyst. 5 vdd power supply (input): independent supply input for internal circuitry.
december 2000 3 mic841/2 mic841/2 micrel absolute maximum ratings (note 1) supply voltage (v dd ) ..................................... 0.3v to +7v input voltage (v inp ) ...................................................... +7v output current (i out ) ................................................. 20ma storage temperature (t s ) ....................... 65 c to +150 c esd rating, note 3 ...................................................... 1kv operating ratings (note 2) supply voltage (v dd ) .................................. +1.5v to +5.5v input voltage (v inp ) ......................................... 0.3v to 6v ambient temperature range (t a ) ............. 40 c to +85 c junction temperature (t j ) ....................... internally limited package thermal resistance ( ja ) ...................... 450 c/w electrical characteristics 1.5v v dd 5.5v; t a = +25 c, bold values indicate 40 c t a +85 c; unless noted symbol parameter condition min typ max units i dd supply current output not asserted 1.5 3 a i inp input leakage current 0.005 10 na v ref reference voltage 0 c to 85 c 1.225 1.240 1.256 v 40 c to 85 c 1.221 1.240 1.259 v v hyst hysteresis voltage, note 4 842 only 8 20 35 mv t d propagation delay v inp = 1.352v to 1.128v 12 s v inp = 1.143v to 1.367v 8 s v out output voltage-low, note 5 out de-asserted, i sink = 1.6ma, v dd 1.6v 0.05 0.3 v out de-asserted, i sink = 100 a, v dd 1.2v, 0.005 0.4 v note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. human body model, 1.5k in series with 100pf. note 4. v hth = v ref + v hyst . note 5. v dd operating range is 1.5v to 5.5v. output is guaranteed to be held low down to v dd = 1.2v.
mic841/2 micrel mic841/2 4 december 2000 block diagrams gnd v dd out 1.24v bandgap reference low-voltage detect high-voltage detect r s q q lt h hth v lt h v hth mic841h vdd v in 3 1 2 4 5 gnd v dd out 1.24v bandgap reference low-voltage detect high-voltage detect r s q q lth hth v lth v hth mic841l vdd v in 3 1 2 4 5 gnd v dd out 1.24v bandgap reference low-voltage detect high-voltage detect r s q q lt h hth v lt h v hth mic841n vdd v in 3 1 2 4 5 gnd v in 1.24v bandgap reference high-voltage detect inp v th mic842h 2 1 5 vdd v dd out 4 gnd v in 1.24v bandgap reference high-voltage detect inp v th mic842l 2 1 5 vdd v dd out 4 gnd v in out 1.24v bandgap reference high-voltage detect inp v th mic842n 4 2 1 5 vdd v dd
december 2000 5 mic841/2 mic841/2 micrel v 3.6v 1.24 1m r3 in(hi) == ? ? ? ? ? ? ? r3 344k =? once r3 is determined, the equation for v in(lo) can be used to determine r2. a single lithium-ion cell, for example, should not be discharged below 2.5v. many applications limit the drain to 3.1v. using 3.1v for the v in(lo) threshold allows calculation of the two remaining resistor values. v 3.1v 1.24 1m r2 344k in(lo) == ? + ? ? ? ? ? ? r2 56k =? 1m r2 r3 r1 ?? ? () = r1 600k =? the accuracy of the resistors can be chosen based upon the accuracy required by the system. the inputs may be subjected to voltages as high as 6v steady state without adverse effects of any kind, regardless of the ic supply voltage. this applys even if the supply voltage is zero. this permits the situation in which the ic supply is turned off, but voltage is still present on the inputs. see electrical characteritics. programming the mic842 thresholds the voltage threshold is calculated using: vv r1 r2 r2 in(lo) ref = + ? ? ? ? ? ? where: v 1.240v ref = inp out vdd gnd mic842 470k v in r1 r2 v out 4 2 1 5 figure 2. example circuit in order to provide the additional criteria needed to solve for the resistor values, the resistors can be selected such that they have a given total value, that is, r1 + r2 = r total . a value such as 1m ? for r total is a reasonable value because it draws minimum current but has no significant effect on accuracy. input transients the mic841/2 is inherently immune to very short negative- going glitches. very brief transients may exceed the v in(lo) threshold without tripping the output. applications information output the the mic841n and mic842n outputs are an open-drain mosfet so most applications will require a pull-up resistor. the value of the resistor should not be too large or leakage effects may dominate. 470k ? is the maximum recommended value. note that the output may be pulled up as high as 6v regardless of the ic s supply voltage. see electrical charac- teristics. when working with large resistors on the input to the devices a small amount of leakage current can cause voltage offsets that degrade system accuracy. the maximum recommended total resistance from v in to ground is 3m ? . the accuracy of the resistors can be chosen based upon the accuracy re- quired by the system. the inputs may be subjected to voltages as high as 6v steady-state without adverse effects of any kind regardless of the ic s supply voltage. this applies even if the supply voltage is zero. this permits the situation in which the ic s supply is turned off, but voltage is still present on the inputs. see electrical characteristics. programming the mic841 thresholds the low-voltage threshold is calculated using: vv r1 r2 r3 r2 r3 in(lo) ref = ++ + ? ? ? ? ? ? the high-voltage threshold is calculated using: vv r1 r2 r3 r3 in(hi) ref = ++ ? ? ? ? ? ? where, for both equations: v 1.240v ref = in order to provide the additional criteria needed to solve for the resistor values, the resistors can be selected such that they have a given total value, that is, r1 + r2 + r3 = r total . a value such as 1m ? for r total is a reasonable value because it draws minimum current but has no significant effect on accuracy. hth out vdd lt h gnd mic841 604k 1% 56k 1% 340k 1% 470k v in r1 r2 r3 v out v dd 5 3 1 4 2 figure 1. example circuit once the desired trip points are determined, set the v in(hi) threshold first. for example, use a total of 1m ? = r1 + r2 + r3. for a typical single-cell lithium ion battery, 3.6v is a good high threshold because at 3.6v the battery is moderately charged. solving for r3:
mic841/2 micrel mic841/2 6 december 2000 as shown in figure 3, the narrower the transient, the deeper the threshold overdrive that will be ignored by the mic841/2. the graph represents the typical allowable transient duration for a given amount of threshold overdrive that will not gener- ate an output. 0 20 40 60 80 100 120 140 1 10 100 1000 max. transient duration ( s) reset comp. overdrive, v ref v lth (mv) input transient response figure 3. input transient response
december 2000 7 mic841/2 mic841/2 micrel package information 0.30 (0.012) 0.10 (0.004) 2.20 (0.087) 1.80 (0.071) 2.40 (0.094) 1.80 (0.071) 1.35 (0.053) 1.15 (0.045) 0.65 (0.0256) bsc 1.00 (0.039) 0.80 (0.032) 0.10 (0.004) 0.00 (0.000) dimensions: mm (inch) 0.30 (0.012) 0.15 (0.006) 0.18 (0.007) 0.10 (0.004) 1.10 (0.043) 0.80 (0.032) sc-70 (c5)
mic841/2 micrel mic841/2 8 december 2000
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mic841/2 micrel mic841/2 10 december 2000
december 2000 11 mic841/2 mic841/2 micrel
mic841/2 micrel mic841/2 12 december 2000 micrel inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 2000 micrel incorporated

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