mic811/812 microprocessor reset circuits general description the mic811 and mic812 are inexpensive microprocessor supervisory circuits that monitor power supplies in micropro cessor based systems. the function of this device is to assert a reset if either the power supply drops below a designated reset threshold level or /mr is forced low. several different reset threshold levels are available to accommodate 3v, 3.3v or 5v powered systems. the mic811 has an active low /reset output, while the mic812 offers an active high reset output. the reset output is guaranteed to remain asserted for a minimum of 140ms after vcc has risen above the designed reset threshold level. having a push - pull output stage, the mic811/812 does not requ ire a pull - up resistor at the output. the mic811/812 comes in a 4 - pin sot - 143 package. if a microprocessor voltage supervisor with an open - drain output stage is needed, see mic6315. datasheets and support documentation are available on micrels web site at : www.micrel.com . features ? precision voltage monitor for 3v, 3.3v or 5v power sup plies ? /reset remains valid with vcc as low as 1v ? 5a typical supply current ? 140ms minimum reset pulse width available ? manual reset in put ? available in 4 - pin sot - 143 package applications ? portable equipment ? intelligent instruments ? critical microprocessor power monitoring ? printers/computers ? controllers typical application micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com sep t ember 9 , 2014 revision 2.0 downloaded from: http:///
micrel, inc. mic811/812 ordering information part number pb- free marking (1) threshold voltage operating temp. range package mic811luy kl 4.63 C 40 c to +85 c 4- pin sot - 143 mic811muy km 4.38 C 40 c to +85 c 4- pin sot - 143 mic811juy kj 4.00 C 40 c to +85 c 4- pin sot- 143 mic811tuy kt 3.08 C 40 c to +85 c 4- pin sot - 143 mic811suy ks 2.93 C 40 c to +85 c 4- pin sot - 143 mic811ruy kr 2.63 C 40 c to +85 c 4- pin sot - 143 mic812luy ll 4.63 C 40 c to +85 c 4- pin sot - 143 mic812muy lm 4.38 C 40 c to +85 c 4- pin sot - 143 mic812juy lj 4.00 C 40 c to +85 c 4- pin sot - 143 mic812tuy lt 3.08 C 40 c to +85 c 4- pin sot - 143 mic812suy ls 2.93 C 40 c to +85 c 4- pin sot - 143 mic812ruy lr 2.63 C 40 c to +85 c 4- pin sot - 143 note: 1. _ underbar symbol not to scale pin configuration mic811 4 - pin sot - 143 (u) mic812 4 - pin sot - 143 (u) pin description mic811 mic812 pin name pin name 1 1 gnd ic ground pin. 2 n/a /reset /reset goes low if v cc falls below the reset threshold and remains asserted for one reset timeout period (140ms min.) after v cc exceeds the reset threshold. n/a 2 reset reset goes high if v cc falls below the reset threshold and remains asserted for one reset timeout period (14 0ms min.) after v cc exceeds the reset threshold. 3 3 /mr manual reset input. a logic low on /mr will force a reset. the reset will remain asserted as long as /mr is held low and for one reset timeout period (140ms min.) after /mr goes high. this input can be shorted to ground via a switch or driven from cmos or ttl logic. float if unused. 4 4 vcc power supply input. september 9 , 2014 2 revision 2.0 downloaded from: http:///
micrel, inc. mic811/812 absolute maximum ratings ( 2 ) terminal voltage (v cc ) ................................ - 0.3v to + 6.0 v input current (v cc , /mr ). ........................................... 20ma output current (/reset, reset) .............................. 20ma lead temperature (soldering, 10s) ............................ 30 0c storage temperature (t s) ............................... 5c to 150 c rate of rise (v cc ) ................................................. 100v/ s esd rating ( 4 ) ................................................... ............... 3 kv operating ratings ( 3 ) operating temperature range mic811 ................................................. C 40 c to +85c mic8 12 ................................................. C 40c to +85c power dissipation (t a = +70c) ............................... 320 mw thermal resistance sot - 143 ( ja ) .................................................. 265 c/w electrical characteristics ( 5 ) for typical values, v cc = 5v for mic8_l/m/j, v cc = 3.3v for mic8_s/t, vcc = 3v for mic8_r; t a = 25 c, bold values indicate C 40 c to t a +85 c; unless noted . symbol parameter condition min typ max units v cc operating voltage range t a = C 40c to 85c 1 5.5 v i vcc supply current mic811l/m/j, mic812l/m/j: v cc = 5.0v, no load 5 15 a mic811s/t, mic812s/t: v cc = 3.3v, no load 5 10 a mic811r, mic812r: v cc = 3. 0v , no load 5 10 a v th reset voltage threshold mic811l, mic812l 4.50 4.63 4.75 v mic811m, mic812m 4.25 4.38 4.50 v mic811j, mic812j 3.89 4.00 4.10 v mic811t, mic812t 3.00 3.08 3.15 v mic811s, mic812s 2.85 2.93 3.00 v mic811r, mic812r 2.55 2.63 2.70 v t rst reset timeout period 140 240 560 ms v oh /reset output voltage i source = 800 a, mic811l/m/j v cc C 1.5v v i source = 5 00 a, mic81 1 r/s/t 0.8xv cc v v ol /reset output voltage v cc = v th min., i sink = 3 .2 ma, mic811l/m/j 0.4 v v cc = v th min., i sink = 1 .2 ma, mic811r/s/t 0.3 v v cc >1v, i sink = 50 a, t a = C 40c to +85c 0.3 v v oh reset output voltage 1.8v micrel, inc. mic811/812 electrical characteristics (continued) ( 5 ) for typical values, v cc = 5v for mic8_l/m/j, v cc = 3.3v for mic8_s/t, v cc = 3v for mic8_r; t a = 25 c, bold values indicate C 40 c to t a +85 c; unless noted . symbol parameter condition min typ max units /mr minimum pulse width 10 s /mr to reset delay 0.5 s v ih /mr input threshold v cc > v th max., mic81_l/m/j 2.3 v mic81_r/s/t 0.7xv cc v v il /mr input threshold v cc > v th max., mic81 - l/m/j 0.8 v mic81_r/s/t 0.25xv cc v /mr pull - up resistance 10 20 30 k ? /mr glitch immunity 100 ns timing diagram reset timing diagram functional diagram september 9 , 2014 4 revision 2.0 downloaded from: http:///
micrel, inc. mic811/812 application information microprocessor reset the /reset (or reset) pin is asserted whenever v cc falls below the reset threshold voltage. the /reset pin remains asserted for a period of 140ms after v cc has risen above the reset threshold voltage. the reset function ensures that the microprocessor is properly reset and powers up in a known condition after a power failure. /reset will remain valid with v cc as low as 1v. v cc transients the mic811/812 are relatively immune to negative - going v cc glitches below the reset threshold. typically, a negative - going transient 125mv below the reset threshold with a duration of 20s or less will not cause a reset. interfacing to bidirectional reset pins the mic8 11 /81 2 can interface with ps with bidirectio nal reset pins by connecting a 4.7k ? resistor in series with the mic8 11 /81 2 output and the p reset pin. /reset valid at low voltage a resistor can be added from the /reset pin to ground to ensure the /reset output remains low with v cc down to 0v. a 100k ? resistor connected from the /reset to ground is recommended. the size of the resistor should be large enough not to load the output excessively and small enough to pull - down any stray leakage currents. reset valid to vcc = 0v september 9 , 2014 5 revision 2.0 downloaded from: http:///
micrel, inc. mic811/812 package information 4-pin sot- 143 (u) september 9 , 2014 6 revision 2.0 downloaded from: http:///
micrel, inc. mic811/812 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944 - 0800 fax +1 (408) 474 - 1000 web http://www.micrel.com micrel , inc. is a leading global manufacturer of ic solutions for the worldwide high performance linear and power, lan, and timing & communications markets. the companys products include advanced mixed - signal, analog & power semiconductors; high - performance communication, clock management, mems- based clock oscillators & crystal - less clock generators, ethernet switches, and physical layer transceiver ics. company customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunicati ons, automotive, and computer products. corporation headquarters and state - of - the - art wafer fabrication facilities are located in san jose, ca, with regional sales and support offices and advanced technology design centers situated throughout t he americas, europe, and asia. additionally, the company maintains an extensive network of distributors and reps wor ldwide. micrel makes no representations or warranties with respect to the accuracy or completene ss of the information furnished in th is datasheet. this information is not intended as a warranty and micrel does not assume responsibilit y for its use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. ex cept as provided in micrels terms and conditions of sale for such products, micrel assumes no liability whatsoever, and micre l disclaims any express or implied war r anty relating to the sale and/or use of micrel products including liability or warranties relatin g to fitness for a particular pur pose, merchantability, or infringement of any patent, copyright, or other intellectual property right. micrel products are no t 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 s ystems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain li fe, and whose failure to perform can be reasonably expected to result in a significant injury to the user. a purchasers use or sale of m icrel products for use in life support appliances, devices or systems is a purchasers own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2014 micrel, incorporated. september 9 , 2014 7 revision 2.0 downloaded from: http:///
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