june 2009 1 mic2775 mic2775 micrel, inc. mic2775 micro-power voltage supervisor general description the mic2775 is a power supply supervisor that provides under-voltage monitoring, manual reset capability, and power-on reset generation in a compact 5-pin sot package. features include an under-voltage detector, a delay genera - tor, a manual reset input, and both active-high and active-low reset outputs. the under-voltage detector compares v dd against a fxed threshold. ten factory-programmed thresholds are available. the reset outputs are asserted for no less than 140ms at power-on and any time the input voltage drops below the reference voltage. it remains asserted for the timeout period after the input voltage subsequently rises back above the threshold boundary. a reset can be generated at any time by asserting the manual reset input, /mr. this reset output will remain active at least 140ms after the release of /mr. the /mr input can also be used to daisy-chain the mic2775 onto existing power monitoring circuitry or other supervisors. hysteresis is included to prevent chattering due to noise. typical supply current is a low 3.5a. typical application rst /rst vdd /mr gnd mic2775-17 vdd other logic /reset gnd microprocessor manual reset 1.8v features ? monitors power supply for under-voltage conditions ? choice of factory-programmed thresholds ? generates 140ms (minimum) power-on reset pulse ? manual reset capability ? both active-high and active-low reset outputs ? /rst output valid down to 1.2v ? ultra-low supply current, 3.5a typical ? rejects brief input transients ? no external components ? pin compatible upgrade for max825 ? ittybitty? 5-pin sot-23 package applications ? monitoring processor core and input/output voltages ? computer systems ? pdas, hand-held pcs ? embedded controllers ? telecommunications systems ? power supplies micrel, inc. ? 2180fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com ittybitty? is a trademark of micrel, inc. ordering information part number junction temp. range package standard marking pb-free marking mic2775-xxbm5 ujxx mic2775-xxym5 ujxx C40oc to +85oc sot-23-5
mic2775 micrel, inc. mic2775 2 june 2009 pin confguration /rst vdd /mr rst 1 3 4 5 2 gnd sot-23-5 (m5) standard voltage options* voltage typical nominal threshold code application (v dd ) voltage (v th ) 46 5.0v 5% 4.68 44 5.0v 10% 4.43 31 3.3v 5% 3.09 29 3.3v 10% 2.93 28 3.0v 5% 2.81 26 2.85v 5% 2.67 25 2.70v 5% 2.53 23 2.5v 5% 2.34 22 2.4v 5% 2.25 17 1.8v 5% 1.69 *there are ten s tandard versions available with an order increment of 3000 pieces. samples of standard versions are normally available from stock. contact factory for information on non-standard versions. available in tape-and-reel only. pin description pin number pin name pin function 1 /rst digital (output): asserted low whenever v dd falls below the reference volt - age. it will remain asserted for no less than 140ms after v dd returns above the threshold limit. 2 gnd ground 3 rst digital (output): asserted high whenever v dd falls below the reference volt - age. it will remain asserted for no less than 140ms after v dd returns above the threshold limit. 4 /mr digital (input): driving this pin low initiates an immediate and unconditional reset. assuming v dd is above the threshold when /mr is released (returns high), the reset output will be de-asserted no less than 140ms later . /mr may be driven by a logic signal or a mechanical switch. /mr has an internal pull-up to v dd and may be left open if unused. 5 vdd analog (input): power supply input and the voltage being monitored.
june 2009 3 mic2775 mic2775 micrel, inc. absolute maximum ratings (note 1) supply voltage (v dd ) ....................................... C0.3v to +7v input voltage (v /mr ) ........................................ C0.3v to +7v rst, (/rst) current ................................................... 20ma storage temperature (t s ) ........................ C65c to +150c esd rating, note 3 .................................................... 1.5kv operating ratings (note 2) supply voltage (v dd ) .................................. +1.5v to +5.5v input voltage (v /mr ) ..................................... C0.3v to +6.0v ambient temperature range (t a ) .............. C40c to +85c package thermal resistance ( ja ) ....................... 256c/w electrical characteristics note 5 ; t a = +25c, bold values indicate C40c t a +85c; unless noted symbol parameter condition min typ max units i dd supply current v dd = v th +1.6%, /mr, rst, /rst 3.5 a open, note 5 vdd voltage threshold under-voltage threshold on v dd v th C1.5% v th v th +1.5% v v v hyst hysteresis voltage 1 % rst, /rst outputs t prop propagation delay v dd = v th + 1.5% + 100mv to 20 s v dd = v th C 1.5% - 100 mv t rst reset pulse width 140 280 ms v ol rst or /rst output voltage low i sink = 1.6ma; 0.3 v v dd 1.6v i sink = 100a; 0.3 v v dd 1.2v; note 4 v oh rst or /rst output voltage high i source = 500a; 0.8v dd v v dd 1.5v i source = 10a; 0.8v dd v v dd 1.2v; note 4 /mr input v ih input high voltage 0.7v dd v v il input low voltage 0.3v dd v t prop propagation delay from v /mr < (v il C100mv) 5 s t min minimum input pulse width reset occurs, v /mr < v il 33 ns i pu internal pull-up current 100 na i in input current, /mr v /mr < v il 100 na 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 dd operating range is 1.5v to 5.5v. output is guaranteed to be asserted down to v dd = 1.2v. note 5. v dd equals nominal typical application (v dd ) as shown in standard voltage options table.
mic2775 micrel, inc. mic2775 4 june 2009 timing diagram v /mr v ih v il v th v dd 0v v /rst (active low) v oh v ol v rst (active high) v oh v ol t rst t rst > t min t rst v hyst a a propagation delays not shown for clarity. note a. the mic2775 ignores very brief transients. see applications information for details.
june 2009 5 mic2775 mic2775 micrel, inc. functional diagram gnd v dd /mr mic2775 v ref rst r s q /q /rst delay line one shot v dd i pu functional description v dd input the v dd pin is both the power supply terminal and a monitored input voltage. the voltage at this pin is continually compared against the internal reference. the trip-point at which a reset occurs is factory programmed. a reset is triggered if and when v dd falls below the trip-point. hysteresis is employed to prevent chattering due to noise. the comparator on the v dd input is relatively immune to very brief negative-going transients. rst, /rst reset outputs typically, the mic2775 is used to monitor the power supply of intelligent circuits such as microcontrollers and micropro - cessors. by connecting the appropriate reset output of a mic2775 to the reset input of a c or p, the processor will be properly reset at power-on and during power-down and brown-out conditions. in addition, asserting /mr, the manual reset input, will activate the reset function. the reset outputs are asserted any time /mr is asserted or if v dd drops below the threshold voltage. the reset outputs remain asserted for t rst (min) after v dd subsequently returns above the threshold boundary and/or /mr is released. a reset pulse is also generated at power-on. hysteresis is included in the comparator to prevent chattering of the outputs due to noise. /mr, manual reset input the ability to initiate a reset via external logic or a manual switch is provided in addition to the mic2775s automatic su - pervisory functions. driving the /mr input to a logic low causes an immediate and unconditional reset to occur. assuming v dd is within tolerance when /mr is released (returns high), the reset outputs will be de-asserted no less than t rst later. /mr may be driven by a logic signal or mechanical switch. typically, a momentary push-button switch is connected such that /mr is shorted to ground when the switch contacts close. the switch may be connected directly between /mr and gnd. /mr has an internal 100na pull-up current to v dd and may be left open if unused.
mic2775 micrel, inc. mic2775 6 june 2009 application information ensuring proper operation at low supply at levels of v dd below 1.2v, the mic2775s /rst output can - not turn on suffciently to produce a valid logic-low on /rst. in this situation, circuits driven by /rst could be allowed to foat, causing undesired operation. (in most cases, however, it is expected that the circuits driven by the mic2775 will be similarly inoperative at v dd 1.2v.) if a given application requires that /rst be valid below v dd = 1.2v, this can be accomplished by adding a pull-down re - sistor to the /rst output. a value of 100k is recommended as this is usually an acceptable compromise of quiescent current and pull-down current. the resistors value is not critical, however. see figure 1. /rst rst vdd /mr manual reset gnd mic2775-xx /reset vcc gnd v cc microprocessor 100k figure 1. mic2775 valid /reset below 1.2v the statements above also apply to the mic2775s rst output. that is, to ensure valid rst signal levels at v dd < 1.2v, a pull-up resistor (as opposed to a pull-down) should be added to the rst output. a value of 100k is typical for this application as well. see figure 2. /rst rst vdd /mr gnd mic2775-xx /reset vcc gnd v cc manual reset microprocessor 100k figure 2. mic2775 valid reset below 1.2v transient response the mic2775 is inherently immune to very short negative- going glitches. very brief transients may exceed the voltage threshold without tripping the output. as shown in figure 3, in general the narrower the transient, the deeper the threshold overdrive that will be ignored by the mic2775. the graph represents the typical allowable transient duration for a given amount of threshold overdrive that will not generate a reset. 0 20 40 60 80 100 0 500 1000 1500 2000 reset comp. overdrive, v ref Cv dd (mv) ty pi ca l v dd tr an si en t re sp on se figure 3. typical v dd transient response
june 2009 7 mic2775 mic2775 micrel, inc. package information sot-23-5 (m5) micrel inc. 2180 fortune drive san jose, ca 95131 usa t e l + 1 (408) 944-0800 f a x + 1 (408) 474-1000 w e b http://www.micrel.com this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and specifcations at any time without notifcation to the customer . micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a signifcant injury to the user . a purchaser's use or sale of micrel products for use in life support appliances, devices or systems is a purchaser's own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2000 micrel, inc.
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