mic705/706/707/708 p supervisory circuit general description the mic705, mic706, mic707, and mic708 are inexpensive microprocessor supervisory circuit s that monitor power sup plies in microprocessor - based systems. the circuit functions include a watchdog timer, microprocessor reset, power - failure warning , and a debounced manual reset input. the mic705 and mic706 offer a watchdog timer function while the mic707 and mic708 have an active - high reset o utput in addition to the activ e- low reset output. supply voltage monitor levels of 4.65v and 4.4v are available. the mic705 and mic707 have a nominal reset threshold level of 4.65v while the mic706 and mic708 have a 4.4v nominal reset threshold level. when the supply voltage drops below the respective reset threshold level, /reset is asserted. datasheets and support documentation are available on micrels web site at : www.micrel.com . features ? debounced manual reset input is ttl/cmos compatible ? res et pulse width: 200ms ? watchdog timer: 1.6s (mic705 /706) ? 4.65v or 4.40v precision voltage monitor ? early power - fail warning or low - battery detect applications ? automotive systems ? intelligent systems ? critical microprocessor power monitoring ? battery - powered com puters ? 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 september 1 5 , 2014 revision 2.1 downloaded from: http:///
micrel, inc. mic705/706/707/708 ordering information part number threshold (v) /reset reset wdi junction temperature range package mic705my 4.65 ? 40 c to +85 c 8- pin soic mic706my 4.40 ? 40 c to +85 c 8- pin soic mic707my 4.65 ? 40 c to +85 c 8- pin soic mic708my 4.40 ? 40 c to +85 c 8- pin soic pin configuration mic705/706 8- pin soic (m) (top view) mic707/ 7 08 8- pin soic (m) (top view) pin description pin number mic706 pin number mic708 pin name pin name 1 1 /mr manual reset input forces /reset to assert when pulled below 0.8v. an internal pull - up current of 250a on this input forces it high when left floating. this input can also be driven from ttl or cmos logic. 2 2 vcc primary supply input, +5v. 3 3 gnd ic ground pin, 0v reference. 4 4 pfi power - fail input: internally - connected to the power - fail comparator which is referenced to 1.25v. the power - fail output (/pfo) remains high if pfi is above 1.25v. pfi should be connected to gnd or v cc if the power - fail comparator is not used. 5 5 /pfo power - fail output : the power - fail comparator is independent of all other function on this device. 6 n/a wdi watchdog input. the wdi input monitors microprocessor activity; an internal watchdog timer resets itself with each transition on the watchdog input. if the wdi pin is held high or low for longer than the watchdog timeout period, /wdo is forced to active low. the watchdog function can be disabled by floating the wdi pin. n/a 6 n/c not internally connected. september 1 5 , 2014 2 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 pin description (continued) pin number mic706 pin number mic708 pin name pin name 7 7 /reset /reset is asserted if either vcc goes below the reset threshold voltage or by low signal on the manual reset input (/mr). /reset remains asserted for one reset timeout period (200ms) after v cc exceeds the reset threshold voltage or after the manual reset pin transition from low to high. the watchdog timer will not assert /reset unless /wdo is connected to /mr. 8 n/a /wdo output for the watchdog timer. the watchdog timer resets itself with each transition to the watchdog input. if the wdi pin is held high or low for longer than the watchdog timeout period, /wdo is forced low. /wdo will also be forced low if vcc is below the reset threshold voltage and will remain low until v cc returns to a valid level. n/a 8 reset reset is the compliment of /reset and is asserted if either vcc goes below the reset threshold voltage or by a low signal on the manual reset input (/mr). reset is suitable for microprocessor systems that use active high reset. september 1 5 , 2014 3 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 absolute maximum ratings ( 1 ) terminal voltage v cc ................................................... .... ? 0.3v to +6.0v all other inputs. ........................... ? 0.3v to (v cc + 0.3v) input curren t v cc , gnd ................................................... ......... 25ma output current (all) ................................................... .. 20ma lead temperature (soldering, 10s) ............................ 300c storage temperature (t s ) ......................... ? 65c to +150 c operating ratings ( 2 ) operating temperature range ................... C 40c to +85c power dissipation (sop) ......................................... 400mw thermal resistance 8- pin soic ................................................... .... 150c/w electrical characteristics ( 3 ) v cc = 4.75v to 5.5v for mic705/707; v cc = 4.5v to 5.5v for mic706/708; t a = operating temperature range, bold values indicate C 40c t a +85c, unless noted. parameter condition min. typ . max . units operating voltage range 1.4 5.5 v supply current 60 a reset voltage threshold mic705, mic707 4.50 4.65 4.75 v mic706, mic708 4.25 4.4 4.5 reset threshold hysteresis 40 mv reset pulse width (t rs ) 140 200 280 ms /reset output voltage i source = 800 a v cc ? 1.5v v i sink = 3.2ma 0.4 reset output voltage i source = 800 a v cc ? 1.5v v i sink = 1.2ma 0.4 watchdog timeout period (t wd ) 1.0 1.6 2.25 s wdi minimum input pulse (t wp ) v il = 0.4v, v ih = 80% of v cc 50 ns wdi threshold voltage v ih , v cc = 5v 3.5 v v il , v cc = 5v 0.8 wdi input current wdi = 0v ? 150 ? 50 a wdi = v cc 50 150 wdo output voltage i source = 8 00 a v cc ? 1.5v v i sink = 1.2m a 0.4 /mr pull - up current /mr = 0v 10 0 250 600 a notes: 1. exceeding the absolute maximum ratings may damage the device. 2. the device is not guaranteed to function outside its operating ratings. 3. specification for packaged product only september 1 5 , 2014 4 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 electrical characteristics ( 3 ) (continued) v cc = 4.75v to 5.5v for mic705/707; v cc = 4.5v to 5.5v for mic706/708; t a = operating temperature range, bold values indicate C 40c t a +85c, unless noted. parameter condition min. typ . max . units /mr pulse width (t mr ) 150 ns /mr input threshold v il 0.8 v v ih 2.0 /mr- to - reset output delay (t md ) 250 ns pfi input threshold v cc = 5v 1.2 1.25 1.3 v pfi input current ? 25 0.01 +25 na /pfo output voltage i sink = 3.2ma 0.4 v v cc = 5v, i source = 800 a v cc ? 1.5v september 1 5 , 2014 5 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 t iming diagram figure 1 . timing diagram for reset september 1 5 , 2014 6 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 block diagram s mic705/mic706 block diagram mic707/mic708 block diagram september 1 5 , 2014 7 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 application information microprocessor reset the /reset pin is asserted whenever v cc falls below the reset threshold voltage or when /mr goes low . the re set pin remains asserted for a p eriod of 200ms after v cc has risen above the reset threshold voltage and /mr goes high . the reset function ensures the microprocessor is properly reset and powers up into a known condition after a power failure. /reset will remain valid wi th v cc as low as 1.4v . power - fail warning an additional comparator which is independent of the other functions on the mic706/706/707/708 is provided for early warning of power failure. an external voltage divider can be used to compare unregulated dc to an internal 1.25v reference. the voltage divider ratio on the inpu t of the power - fail comparator (pfi) can be chosen so as to tr ip the power - fail comparator a few milliseconds before v cc falls below the maximum reset threshold voltage. the outpu t of the powe r- fail comparator (/pfo) can be used to interrupt the microprocessor when used in this mode and execute shutdown procedures prior to power loss. hysteresis c an be added to this comparator with external resistors, as is commonly done with any comparator. figure 2 . power - fail comparator watchdog timer the microprocessor can be monitored by connecting the wdi pin (watchdog input) to a bus line or an i/o line. if a transition doesn't occur on the wdi pin within the watchdog timeout period, then /wdo will go low. a minimum pulse of 50 ns or any transit ion low - to - high or high - to - low on the wdi pin will reset the watchdog timer. the output of the watchdog timer ( / wdo) w ill remain high if wdi left floating. i f v cc falls below the reset threshold voltage, then /wdo goes low immediately regardless of wdi. september 1 5 , 2014 8 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 package information and recommended landing pattern ( 4 ) 8- pin soic (m) note: 4. package information is correct as of the publication date. for updates and most current information, go to www.micrel.com . september 1 5 , 2014 9 revision 2. 1 downloaded from: http:///
micrel, inc. mic705/706/707/708 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 & communi cations markets. the companys products include advanced mixed-signal, analog & power semiconductors; high-performance comm unication, clock management, mems-based clock oscillators & crystal-less clock generators, ethernet switches, and physi cal layer transceiver ics. company customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and computer pr oducts. corporation headquarters and state-of-the-art wafer fabrication facilities are located in san jose, ca, with regional sales and support offi ces and advanced technology design centers situated throughout the americas, europe, and asia. additionally, the company maintains an extensive network of distributors and reps worldwide. micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this datasheet. t his information is not intended as a warranty and micrel does not assume responsibility for its use. micrel reserves the right to change circ uitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel o r otherwise, to any intellectual property rights is granted by this document. except as provided in micrels terms and conditions of sale for such products, mi crel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel produc ts including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual propert y right. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a pr oduct 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 significant injury to the us er. a purchasers use or sale of micrel products for us e 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. ? 2000 micrel, incorporated. september 1 5 , 2014 10 revision 2. 1 downloaded from: http:///
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