mic706p/r/s/t, mic708r/s/t p supervisory circuit general description the mic706 and mic708 are inexpensive microprocessor supervisory circuits that monitor power supplies in 3.0 v and 3.3v mic roprocessor - based systems. the circuit functions include a watchdog timer, microprocessor res et, power - failure warning , and a debounced manual reset input. the mic706 offers a watchdog timer function, while the mic708 has an active - high reset o utput in addition to the active - low reset output . t he r, s, and t versions are similar in all respects except for supply voltage reset threshold levels. the threshold levels are 2.63, 2.93, and 3.08v , respectively. when the supply voltage drops below the reset threshold level, /reset (and reset for the mic 708) is asserted. the mic706p is identical to the mic706r, except that the reset output is asserted high. datasheets and support documentation are available on micrel?s web site at : www.micrel.com . features ? maximum s upply current: 30 a ? debounced manual reset input is ttl/cmos compatible ? reset pulse width: 200ms ? watchdog timer: 1.6s (mic706) ? precision supply voltage monitor ? easy power - fail warning or low - battery detect applications ? laptop and desktop computers ? intellig ent systems ? critical microprocessor power monitoring ? printers ? 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 may 28, 2014 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t ordering information part number threshold (v) /reset reset wdi junction temperature range package mic706pmy 2.63 ? 40c to +85c 8 - pin soic m ic706r my 2.63 ? 40c to +85c 8 - pin soic m ic706s my 2.93 ? 40c to +85c 8 - pin soic m ic706t my 3.08 ? 40c to +85c 8 - pin soic m ic708r my 2.63 ? 40c to +85c 8 - pin soic m ic708s my 2.93 ? 40c to +85c 8 - pin soic mic708tmy 3.08 ? 40c to +85c 8 - pin soic pin configuration mic706 8 - pin soic (m) (top view) mic708 8 - pin soic (m) (top view) pin description pin number mic706 pin number mic708 pin name pin name 1 1 /mr manual reset i nput forces reset outputs 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 out 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 disable d by floating the wdi pin. n/a 6 n/c not internally connected. may 28, 2014 2 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t pin description (continued) pin number mic706 pin number mic708 pin name pin name 7 7 /reset /reset is asserted if either v cc 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 watchd og 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. 7 (mic706p) 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. may 28, 2014 3 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t absolute maximum ratings ( 1 ) terminal voltage v cc ......................................................... ? 0.3 v to +6.0v all other inputs . ........................... ? 0.3v to (v cc + 0.3v) input current 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 ................... ? 40c to +85c power d issipation (sop) ......................................... 400mw thermal resistance 8 - pin soic ....................................................... 150 c/w electrical characteristics ( 3 ) v cc = 2.70v to 5.5v for mic70_p/r; v cc = 3.00v to 5.5v for mic70_s; v cc = 3.15v to 5.5v for mic70_t. t a = operating temperature range , bold values indicate ? 40c ? t a ? +85c, unless noted. parameter condition min . typ . max . units operating voltage range 1.4 5.5 v supply current 30 a reset voltage threshold mic70_p/r 2.55 2.63 2.70 v mic70_s 2.85 2.93 3.00 mic70_t 3.00 3.08 3.15 reset threshold hysteresis 20 mv reset pulse width (t rs ) 140 200 280 ms /reset output voltage (mic70_r/s/t) i source = 200 a 0.8 v cc v i sink = 1.2ma 0.3 i sink = 50 a, v cc = 1.4v 0.3 reset output voltage (mic706p) i source = 200 a 0.8 v cc v i sink = 1.2ma 0.3 reset output voltage (mic708r/s/t) i source = 200 a 0.8 v cc v i sink = 500 a 0.3 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 100 ns v il = 0.4v, v ih = 80% of v cc > 4.5v 50 wdi threshold voltage v ih 0.7 v cc v v il 0.6 wdi input current wdi = 0v or v cc ? 1 1 a wdo output voltage i source = 200 a 0.8 v cc v i sink = 500 a 0.3 /mr pull - up current /mr = 0v 20 250 600 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. may 28, 2014 4 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t electrical characteristics ( 3 ) (continued) v cc = 2.70v to 5.5v for mic70_p/r; v cc = 3.00v to 5.5v for mic70_s; v cc = 3.15v t o 5.5v for mic70_t. t a = operating temperature range, bold values indicate ? 40c t a +85c, unless noted. parameter condition min . typ . max . units /mr pulse width (t mr ) v cc ! 4.5v 500 ns 150 /mr input threshold v il 0.6 v v ih 0.7 v cc /mr -to - reset output delay (t md ) 750 ns pfi input threshold 1.2 1.25 1.3 v pfi input current 25 0.01 +25 na /pfo output voltage i sink = 1.2ma 0.3 v i source = 200 a 0.8 v cc may 28, 2014 5 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t timing diagram figure 1 . timing diagram for reset may 28, 2014 6 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t block diagram mic706 block diagram mic708 block diagram may 28, 2014 7 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t application information an additional comparator which is independent of the other functions on the mic706p and mic708 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 power - fail comparator (/pfo) can be used to int errupt the microprocessor when used in this mode and exec ute shutdown procedures prior to power loss. hysteresis c an be added to this comparator with external resistors, as is comm only done with any comparator. figure 2 . power - fail comparator watchdog time r 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 th e wdi pin within in the watchdog timeout period, then /wdo will go low. a minimum pulse of 100ns or any transi t 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 sees a valid transition within the watchdog period . i f v cc falls below the reset threshold voltage, then /wdo goes low immediately regardless of wdi. /wdo can be connected to /mr to generate a reset pulse upon watchdog timeout. 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 period of 200ms after v cc has risen above the reset threshold voltage and /mr goes high . the reset function ensures the microprocessor is properly re set and powers up into a known condition after a power failure. /reset will remain valid wi th vcc as low as 1.4v . may 28, 2014 8 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t 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 . may 28, 2014 9 revision 2.0
micrel, inc. mic706p/r/s/, mic708r/s/t 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 makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. this information is not intended as a warranty and micrel does not assume responsibility 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. except as provided in micrel?s terms and conditions of sale for such products, micrel assumes no liab ility whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyri ght or other intellectual property right . micrel products are not designed or authorized for use as components in life support appliances, devices or systems where mal function of a product can reasonably be expected to result in personal injury. life supp ort 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 signific ant 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 agr ees to fully indemnify micrel for any damages resulting from such use or sale. ? 20 00 micrel, incorporated. may 28, 2014 10 revision 2.0
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