may 2003 1 mic811/812 mic811/812 micrel mic811/812 microprocessor reset circuits final information general description the mic811 and mic812 are inexpensive microprocessor supervisory circuit that monitors 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 v cc has risen above the designed reset threshold level. the mic811/812 comes in a 4-pin sot-143 package. typical application v cc reset p reset v cc mic811 v cc mr features precision voltage monitor for 3v, 3.3v or 5v power supplies /reset remains valid with v cc as low as 1.4v <15 a supply current 140ms minimum reset pulse width available manual reset input available in 4-pin sot-143 package applications portable equipment intelligent instruments critical microprocessor power monitoring printers/computers embedded controllers 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 ordering information threshold operating part number marking voltage temp. range package mic811lu kl 4.63 ?0 c to +85 c 4-lead sot-143 mic811mu km 4.38 ?0 c to +85 c 4-lead sot-143 mic811ju kj 4.00 ?0 c to +85 c 4-lead sot-143 mic811tu kt 3.08 ?0 c to +85 c 4-lead sot-143 mic811su ks 2.93 ?0 c to +85 c 4-lead sot-143 mic811ru kr 2.63 ?0 c to +85 c 4-lead sot-143 mic812lu ll 4.63 ?0 c to +85 c 4-lead sot-143 mic812mu lm 4.38 ?0 c to +85 c 4-lead sot-143 mic812ju lj 4.00 ?0 c to +85 c 4-lead sot-143 mic812tu lt 3.08 ?0 c to +85 c 4-lead sot-143 mic812su ls 2.93 ?0 c to +85 c 4-lead sot-143 mic812ru lr 2.63 ?0 c to +85 c 4-lead sot-143
mic811/812 micrel mic811/812 2 may 2003 pin description pin number pin number mic811 mic812 pin name pin function 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 (140ms min.) after v cc exceeds the reset threshold 3 3 /mr manual reset input. a logic low on /mr forces 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. pin configuration 1 2 4 v cc gnd mic812 reset 3 mr 1 2 4 v cc gnd mic811 reset 3 mr mic811 4-lead sot-143 mic812 4-lead sot-143
may 2003 3 mic811/812 mic811/812 micrel absolute maximum ratings (note 1) terminal voltage (v cc ) ............................... ?.3v to +6.0v input current (v cc , /mr) ............................................ 20ma output current (/reset, reset) ............................. 20ma lead temperature (soldering, 10 sec.) ..................... 300 c storage temperature (t s ) ......................... ?5 c to 150 c rate of rise (v cc ) ................................................. 100v/ s esd rating, note 3 operating ratings (note 2) operating temperature range mic811 ..................................................... ?0 c to 85 c mic812 ..................................................... ?0 c to 85 c power dissipation (t a = +70 c) .............................. 320mw electrical characteristics 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 ?0 c t a +85 c; unless noted symbol parameter condition min typ max units v cc operating voltage range t a = 0 c to 70 c 1.4 5.5 v t a = ?0 c to 85 c 1.6 5.5 v i cc supply current mic811l/m/j, mic812l/m/j 9 15 a v cc < 3.6v, mic811r/s/t, mic812r/s/t 6 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 ?.5v v i source = 500 a, mic811r/s/t 0.8 v cc v v ol /reset output voltage v cc = v th min., i sink = 3.2ma, mic811l/m/j 0.4 v v cc = v th min., i sink = 1.2ma, mic811r/s/t 0.3 v v cc > 1.4v, i sink = 50 a, t a = 0 c to +70 c 0.3 v v cc > 1.6v, i sink = 50 a, t a = ?0 to +85 c 0.3 v v oh reset output voltage 1.8v < v cc < v th min., i source = 150 a 0.8 v cc v v ol reset output voltage i sink = 3.2ma, mic812l/m/j 0.4 v i sink = 1.2ma, mic812r/s/t 0.3 v /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 0.7 v cc v v il /mr input threshold v cc . v th max., mic81-l/m/_ 0.8 v mic81_r/s/t 0.25 v cc /mr pull-up resistance 10 20 30 k ? /mr glitch immunity 100 ns 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.
mic811/812 micrel mic811/812 4 may 2003 functional diagram + - reset threshold (v) v cc (4) reset (2) reset (mic812) gnd (1) reset generator mr (3) timing diagram /mr /reset v cc v th t rst t rst reset timing diagram
may 2003 5 mic811/812 mic811/812 micrel applications 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 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 1.4v. 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 50 s (25 s for mic8_r/s/t) or less will not cause a reset. interfacing to bidirectional reset pins the mic811/812 can interface with ps with bidirectional reset pins by connecting a 4.7k ? resistor in series with the mic811/812 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. v cc reset p reset v cc mic811 v cc 100k reset valid to v cc = 0v
mic811/812 micrel mic811/812 6 may 2003 package information 0.150 (0.0059) 0.089 (0.0035) 8 0 0.400 (0.016) typ 3 places 2.50 (0.098) 2.10 (0.083) 1.40 (0.055) 1.20 (0.047) 0.950 (0.0374) typ 3.05 (0.120) 2.67 (0.105) 0.800 (0.031) typ 1.12 (0.044) 0.81 (0.032) 0.10 (0.004) 0.013 (0.0005) dimensions: mm (inch) 0.41 (0.016) 0.13 (0.005) c l c l 4-lead sot-143 (m3) 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 the information furnished by micrel in this datasheet is believed to be accurate and reliable. however, no responsibility is as sumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intend ed 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 significant inj ury to the user. a purchaser s use or sale of micrel products for use in life support appliances, devices or systems is at purchaser s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2003 micrel, incorporated.
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