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mic2007/2017 adjustable current limit pow e r dis t ribution s w itch kickstart i s a trademark of micrel, inc mlf and mi c r o l eadfram e are t r ademarks of am kor technolog y , i n c. micrel inc. ? 2180 fortu ne drive ? san jose, ca 95131 ? usa ? te l +1 (408) 9 44-08 00 ? fax + 1 (408) 474-1000 ? htt p :/ /www.micre l.com general description the mi c20 0 7 an d mi c20 17 a r e curre n t limiting, hi gh- side po wer swit che s , de sign ed for g eneral pu rp o s e power dist rib u tion a nd co ntro l i n pcs , pdas , pri n ters and othe r self -po w e r ed systems. the mic2 00 7 and mic2 017? s prima r y functions are curre n t limiting and po wer swit chin g. they are therm a lly protected and will shutdown shoul d their internal temperature reach un safe l e vels. this p r otect s both t he device an d the l oad unde r hi gh current or fault conditions. features in clude: user adju s table o u tput sle w rate limiting, automatic load d i scharge an d under volta ge detectio n . both devices off e r u s e r programmabl e cu rrent limiting the r eby p r ovidin g de sig ners a co ntinu ous spe c tru m of current limits from 200ma to 2 amps. the mi c20 1 7 offers a uni que ne w feat ure: ki cksta r t ? , whi c h all o ws momenta r y high cu rre nt surge s to p a s s unre s tri c ted without sacrific ing ove r all system safety. the mic200 7 and mic2 017 a r e excellent choi ce s fo r usb and ieee 1394 (firewire) appli c ations or for any system wh ere cu rrent lim it ing and po wer control are desi r ed. the mi c20 0 7 and mic201 7 a r e offere d in spa c e savi ng 6-pin so t-2 3 and 2mm x 2mm mlf tm p a ckag es. fe ature s ? 70m ? t y pical on- re sist a n c e ? 2.5v ? 5.5v operating ra ng e ? user a d ju sta b le cu rrent limit: 0.2a ? 2.0a ? kick st art ? ? user a d ju sta b le output sl e w rate control ? automatic load disc harge ? thermal protection ? und e r voltag e lock-out ? low q u ie scen t current applicati o ns ? usb / ieee 1394 po we r di strib u tion ? de skto p and l aptop pcs ? set top boxes ? game con s ol es ? pdas ? printers ? do cki ng stati ons ? c h ar ge rs ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ ___ _ ___ ___ __ _ ty pical a pplic ation vin d+/d- d+/d- 5v suppl y c slew vout gnd enable mic2007 MIC2017 usb controller i limit v bus usb port usb port f i g u re 1. t y p i cal a p p licatio n circu it oc tober 2005 m999 9-10 280 5
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 2 m999 9-10 280 5 mic2000 family mem b ers part nu mb er pin f unc tio n normal limiting kickstart i limit i adj. enable c sle w f a u l t / d l m * loa d dischar ge 2 0 0 3 2 0 1 3 - - - - - - - - - - - - 200 4 2 0 1 4 - - - - - - - - 200 5 2 0 1 5 - - - - - - 200 6 2 0 1 6 f i xed -- - - - - 200 7 2 0 1 7 - - - - 200 8 2 0 1 8 - - - - - - 200 9 2 0 1 9 a d j. - - - - - - * dynami c lo ad man agem ent adj = adjusta b le cu rrent limit fixed = fa cto r y prog ram m ed cu rrent lim it ordering inform ation part nu mb er markin g (1 ) c u rren t l i m i t kickst a r t pb -f r e e pack ag e mic200 7 y m 6 f h aa sot - 23-6 mic200 7yml (2 ) h a a no 2mm x 2mm ml f mic201 7 y m 6 f q aa sot - 23-6 mic201 7yml (2 ) q a a 0.2a ? 2.0a yes yes 2mm x 2mm ml f notes : 1. under-bar s y mbol ( _ ) ma y n o t be to scale. 2. consult factory for availability
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 3 m999 9-10 280 5 pin c onfi gur ation n o d a p e d i s k c a b d n u o r g s i v out 1 2 34 5 6 c slew i limit v in gnd enable 6-pin 2mm x 2mm mlf (ml) t op vie w enable gnd v out i limit vin 3 16 2 4 5 c slew so t 23-6 (m6) top view pin d e s c r i ption pin number sot-2 3 pin number mlf pin name ty pe d e s c r i p t i o n 1 6 v i n i n p u t supp l y inp ut. t h is pin provi d e s po w e r to bot h the outp u t s w itch and the mic200 7/201 7? s interna l contr o l circuitr y . 2 5 g n d - - g r o u n d . 3 4 e n a b l e i n p u t o u tput ena ble pin. a log ic hig h activate s the outp u t s w itc h , appl yi ng p o w e r to the load attached to v out . 4 3 i lim i t i n p u t sets the curren t limit threshol d via a resistor c onn ected b e t w een i lim i t and gnd. i lim i t = current limiting f a cto r (clf ) / r se t . 5 2 cslew i n p u t sle w rate co ntrol. addi ng a s m all val ue ca p a citor bet w e en this pin a nd vin slo w s turn-on of the po w e r f e t. 6 1 vo ut o u t p u t s w itc h outp u t. t he load bei ng driven b y mic 200 7/201 7 is c onn ected to thi s pin.
micrel mic2007/MIC2017 october 2005 4 m9999-102805 absolute maximum ratings (1) all pins ...........................................................?0.3 to 6v power dissipation...............................in ternally limited continuous output current.................................. 2.25a maximum junction te mperature ........................ 150 c storage temper ature ........................... ?65 c to 150 c operating ratings (2) supply voltage ............................................. 2.5v to 5.5v continuous output current range .................... 0 to 2.1a ambient temperat ure range .................... ?40 c to 85 c package thermal resistance ( ja ) sot-23-6 .................................................... 230c/w mlf 2x2 mm ...................................................90c/w mlf 2x2 mm jc (5) .........................................45c/w electrical characteristics v in = 5v, t ambient = 25 c unless specified otherwise. bold indicates ?40c to +85c limits. symbol parameter conditions min typ max units v in switch input voltage 2.5 5.5 v i in internal supply current switch = off, enable = 0v 1 5 a i in internal supply current switch = on, i out = 0 enable = 1.5v 80 330 a i leak output leakage current v in = 5v, v out = 0 v, enable = 0 1.2 10 a 70 100 m r ds(on) power switch resistance v in = 5v, i out = 100 ma 125 m r dschg load discharge resistance v in = 5v, i sink = 5 ma 70 126 200 i out = 2.0a, v out = 0.8v in 210 250 286 v i out = 1.0a, v out = 0.8v in 190 243 293 v i out = 0.5a, v out = 0.8v in 168 235 298 v clf current limit: factor r set ( ) = clf (v) i out (a) i out = 0.2a, v out = 0.8v in 144 225 299 v i limit_2nd secondary current limit (kickstart) MIC2017, v in = 2.5v 2.2 4 6 a v in rising 2.0 2.25 2.5 v uvlo threshold under voltage lock out threshold v in falling 1.9 2.15 2.4 v v il (max.) 0.5 v en enable input voltage v ih (min.) 1.5 v i en enable input current v en = 0v to 5.0v 1 5 a t j increasing 145 ot threshold over-temperature threshold t j decreasing 135 c
micrel mic2007/MIC2017 october 2005 5 m9999-102805 ac characteristics symbol parameter condition min typ max units t rise output turn-on rise time r l = 10 ?, c load = 1 f, v out = 10% to 90% 500 1000 1500 s t d_limit delay before current limiting MIC2017 77 128 192 ms t reset delay before resetting kickstart current limit delay, t d_limit out of current limit following a current limit event. MIC2017 77 128 192 ms t on_dly output turn-on delay r l = 43 ?, c l = 120f, c slew ? 10pf, v en = 50% to v out = 10% 1000 1500 s t off_dly output turn-off delay r l = 43 ?, c l = 120f, c slew ? 10pf, v en = 50% to v out = 90% 700 s esd symbol parameter condition min typ max units v out and gnd 4 kv v esd_hb electrostatic discharge voltage: human body model all other pins 2 kv v esd_mchn electrostatic discharge voltage: machine model all pins machine model 200 v notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to f unction outside its operating rating. 3. devices are esd sensitive. handling precautions re commended. human body model: 1.5k in series with 100pf. 4. specification for packaged product only. 5. requires proper thermal mounting to achieve this performance.
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 6 m999 9-10 280 5 timing di agrams enable vout 50% 90% 10% t on_d l y t off_d l y 50% s w itch ing dela y t i mes 90% 10% 90% 10% t fa l l t rise ris e a nd fa ll time s 90% 10% t rise vout o u t pu t ri se ti me
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 7 m999 9-10 280 5 ty pical characteri stics 0 20 40 60 80 10 0 23456 sup p ly cur rent ( a) v in (v ) supply c u rrent output enabled -4 0c 85 c 25c 0 0. 1 0 0. 2 0 0. 3 0 0. 4 0 0. 5 0 0. 6 0 0. 7 0 0. 8 0 0. 9 0 1. 0 0 234 5 6 7 sup p l y curre n t ( a) v in (v ) s upp l y c u r r ent out p ut di sab l e d -4 0 c 85 c 25 c 0 0. 1 0 0. 2 0 0. 3 0 0. 4 0 0. 5 0 0. 6 0 0. 7 0 0. 8 0 0. 9 0 1. 0 0 - 5 0 - 3 0 - 1 0 1 03 05 07 09 0 ( a) te m p erat ure ( c ) s w itch leakage c u rrent - off 2. 0 5 2. 1 2. 1 5 2. 2 2. 2 5 2. 3 -5 0 0 50 1 0 0 1 50 th resh o l d ( v ) t e m p era t ure ( c) uvlo threshold vs. temperature v risi ng v fal l i n g 0 20 40 60 80 10 0 2 2 . 5 33 . 544 . 5 55 . 5 r on (mohm) v in (v ) r on vs. supply voltage 0 20 40 60 80 10 0 12 0 - 5 0 - 3 0 - 1 0 1 03 05 07 09 0 r on (mohm) te m p erat ure ( c ) r on vs. temper ature 2. 5 v 3. 3 v 5v 21 5 22 0 22 5 23 0 23 5 24 0 24 5 25 0 0 0 . 5 1.0 1 .5 2.0 current li mi t factor curre nt li mi t ( a ) cur r en t l i mit fa ct or vs . t e mp era t u r e @ 2. 5v 85 c 25 c -4 0 c 21 5 22 0 22 5 23 0 23 5 24 0 24 5 25 0 0 0 .5 1.0 1 .5 2.0 c urr en t li mi t fac t o r current lim i t (a) cu rrent l i mi t factor v s . t e mp e r at ur e @ 3v 25 c 85 c -40 c 215 220 225 230 235 240 245 250 0 0 .5 1.0 1 .5 2.0 c urr en t li mi t fa cto r current lim i t (a) cu rrent l i mi t factor v s . t e mp e r at ur e @ 5v 85 c 25 c -40 c 21 5 22 0 22 5 23 0 23 5 24 0 24 5 25 0 0 0 .5 1.0 1 .5 2.0 c urr en t li mi t fac t o r current lim i t (a) cu rrent l i mi t factor vs. inpu t vo ltage @ -40c 5v 2. 5 v 3v note: the 2.5v and 3v pl ots ov er lap. 21 5 22 0 22 5 23 0 23 5 24 0 24 5 25 0 0 0 .5 1.0 1 .5 2.0 c urr en t li mi t fac t o r current lim i t (a) cu rrent l i mi t factor vs. inp u t v o ltage @ 25 c 5v 3v 2. 5 v 215 220 225 230 235 240 245 250 0 0 .5 1. 0 1 . 5 2. 0 c urr en t li mi t fac t o r c urr ent li mi t ( a ) cu rr en t li mit f a cto r v s . in put voltag e @ 85 c 5v 3v 2. 5v
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 8 m999 9-10 280 5 functi onal characteristics enable (2.5v/div) v out (1v/div) i out (200ma/div) 0 t ime (ms) 24 6 81 0 12 14 v in = 5.0v r load c load = 100 f t urn-on/ t urn-of f enable (2.5v/div) v out (1v/div) i out (200ma/div) 0 t ime (ms) r l c slew = 0pf 48 1 2 16 20 24 28 32 36 40 inrush current response mic20xx-0.5 inrush curre nt r inrush curre nt r e s 0 f 10 f 22 f 47 f 100 f 220 f 470 f enable (2.5v/div) v out (1v/div) i out (250ma/div) 0 t ime (ms) 50 100 150 200 250 300 350 400 450 500 550 v in = 5.0v r load c load = 47 f current limit response thermal shutdown enable (2.5v/div) v out (1v/div) i out (150ma/div) 0 t ime ( s) 2000 6000 10000 14000 18000 22000 v in = 5.0v r load c load = 0 f 0pf 100pf 820pf 1800pf 2700pf 3500pf c slew response enable (2.5v/div) v out (1v/div) v in (1/div) 0 t ime ( s) 4 8 12 16 20 24 28 32 36 40 44 48 uvlo increasing enable tied to v in enable (2.5v/div) v out (1v/div) v in (1/div) 0 enable tied to v in 4 8 12 16 20 24 28 32 36 40 44 48 uvlo decreasing p o n se inrush curre nt respo n se inrush curre nt respo n se
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 9 m999 9-10 280 5 enable (2.5v/div) v out (1v/div) i out (0.5a/div) 0 t ime (ms) 50 100 150 200 250 300 350 400 450 500 550 kickstart response normal load with t emporary high loa d enable (1v/div) v out (1v/div) i out (0.5a/div) 0 t ime (ms ) 50 100 150 200 250 300 350 400 450 500 550 kickstart response no load to short circuit enable (2.5v/div) v out (1v/div) i out (0.5a/div) 0 t ime (ms) 50 100 150 200 250 300 350 400 450 500 550 kickstart response normal load with t emporary short circuit enable (2.5v/div) v out (1v/div) i out (0.5a/div) 0 t ime (ms) 50 100 150 200 250 300 350 400 450 500 550 kickstart response device enabled into a short circuit
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 10 m999 9-10 280 5 functi onal dia g ra m en a b le vin vo u t gn d v re f po w e r fe t sl e w r a t e c ont r o l current mi rror fe t c u rrent li mi t co n t r o l l o o p gate c o ntr o l un d e r voltag e de t e ct o r th e r m a l se ns or c o n t r o l l o gic a n d d el ay t i m e r i li m i t c sl e w f i g u re 2. mic 200 7/20 17 blo ck diag ra m
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 11 m999 9-10 280 5 functi onal de scri p tion input and outpu t v in is both the power sup p ly conn ectio n for the inte rna l circuitry drivi ng the swit ch and the input (sou rce con n e c tion) o f the power mosfet swi t ch. v out is the drai n con n e c tion of the p o we r m o sf et and supp lies power to the load. in a typi ca l circuit, cu rre nt flows f r om v in to v out toward the l oad. since the switch i s bi- dire ctional when e nabl ed, if v out is g r eate r than v in , current will flow from v out to v in . when the switch is di sabl ed, current will not flow to the load, ex cept for a sm all u navoida ble le aka ge cu rren t of a few mi cro a m ps. however, sh ould v ou t exce ed v in by more tha n a diode drop (~0.6v ), whil e the swit ch is disabled, current will flow fr om output to input via the power mosf et?s body di ode. while th is effect can be use d to a d vantage wh en larg e bypa ss capa cito rs are placed on mi c20 07/20 17? s?s output, it can n o t be re lied upon to fully or reli ably discha rge the lo ad ca pa citan c e, becau se di schargi ng d epe nds upon th e cha r a c teri sti c s of the circuitry at vin. to en su re p r oper disch a rge of any o u tput ca pa citan c e, mic200 7/201 7 is eq uippe d with a di sch a rge fet whi c h is on a n y time the device i s not enable d . curre nt sen s ing and limiting the mi c20 0 7 /2017 p r ote c ts th e syste m po we r su pply and lo ad f r om da mage by co ntinu ously m onito ring curre n t thro u gh the on -chip p o we r mosfet. l oad curre n t is monitore d, by mean s of a curre n t mirro r, in parall e l with t he po wer m o sfet swit ch. current limiti n g is invo ke d when th e l oad exce ed s an extern ally set over-cu r rent t h re shol d. wh en current limiting is ac tivated the output cu rre nt is con s t r aine d to the limit value, and remai n s at this level u n til either t he lo ad/fault is remove d, the load?s curre n t requi reme nt drop s bel o w the limiting value, o r th e mic200 7/2017 go es i n to thermal shutd o wn. kicks tar t (mi c 20 17 only ) the mic201 7 is d e si gne d to allo w m o menta r y cu rrent s u rg es ( k icks ta r t ) b e f or e th e on set of cu rrent limiti ng, whi c h pe rmit s dynami c lo ads, such as small di sk d r i v es or p o rtabl e printe rs to d r aw the e n e r gy ne eded to overcome in ertial load s wi thout sa crifici ng sy stem safety. in this respe c t, t he mic2 017 differs m a rke d ly from mi c20 0 7 an d its p e e rs, which i mmediately li mit load cu rrent, potentially starving th e m o tor a nd ca u s ing the applia nce to stall or stu tter. duri ng thi s d e lay pe riod, t y pically 12 8 ms, a se con dary curre n t limit is in effect. if the load dem and s a curre n t in exce ss of the se con d a r y limit, the MIC2017 acts immediately to rest rict out put cu rre nt t o t he se con d a ry limit for the duratio n of the kic k s t art period. after this time, the MIC2017 reve rts to its no rmal curre n t limit. an example of kicksta r t operation is sho w n belo w . t u o t u o figure 3. kickstart o p er ation picture ke y : a) mic201 7 is enabl ed into an exce ssiv e load (sle w rate limiting not visible at t h is time scal e) the initial curre n t surg e is limite d by either the o v erall circuit resi stan ce a nd p o wer supply compli ance, o r the se con dary cu rre nt limi t, w h ic hever is less . b) r on of the power fet i n crea se s du e to internal heating (effect exaggerate d for empha si s). c) kickstart pe ri od. d) current limiting initiated. fault/ g o e s low. (note: mic200 7/201 7 doe s not prov ide a faul t/ output.) e) v out is non -zero (l oad i s h eavy, but not a dead sho r t whe r e v out = 0. limiting response will be the same for dead sho r ts). f) therm a l sh utdown followe d by thermal cyclin g. g) excessive lo ad rel e a s ed, norm a l loa d rem a ins. mic201 7 dro p s out of current limiting. h) fault/ d e la y perio d foll owe d by fa ult/ g o ing high. (note: mic2 007/2 0 17 d o e s n o t provide a fault/ outp u t.) under volta g e lock ou t und e r voltag e lock-o ut insure s no an o m alou s ope ration occurs b e fore the device ? s minimu m input voltage of 2.5v had bee n achieve d . prior to rea c hing this voltage, the output switch (po w er mosfet) is off an d no circuit fun c tio n s, such as e n able, are consi dered to be valid or operative.
micrel mic2007/MIC2017 october 2005 12 m9999-102805 enable enable is a high true control signal, which activates the main mosfet switch. enable will operate with logic running from supply voltages as low as 1.8v, once v in has exceeded the uvlo threshold. enable can be wire-or?d with other mic2007/ 2017s or similar devices without damage to the device. enable may be driven higher than v in , but no higher than 5.5v. slew rate control large capacitive loads can create significant current surges when charged through a high-side switch such as the mic2007/2017. for this reason, the mic2007/2017 provides built-in slew rate control to limit the initial inrush currents upon enabling the power mosfet switch. slew rate control is active upon powering up, and upon re-enabling the load. at shutdown, the discharge slew rate is controlled by the external load and output capacitor. on mic2007/2017 slew rate is adjustable and can be further reduced by adding an external capacitance between vin and the cslew pins. thermal shutdown thermal shutdown is employed to protect the mic2007/2017 from damage should the die temperature exceed safe operating levels. thermal shutdown shuts off the output mosfet if the die temperature reaches 145c. the mic2007/2017 will automati cally resume operation when the die temperature cools down to 135c. if resumed operation results in reheating of the die, then another shutdown cycl e will occur and the mic2007/2017 will continue cycling between on and off states until the offending load has been removed. depending upon pcb layout, package type, ambient temperature, etc., hundreds of milliseconds may elapse from the incidence of a fault to the output mosfet being shut off. this delay is due to thermal time constants within the system itself. in no event will the device be damaged due to thermal overload because die temperature is monitored continuously by on-chip circuitry.
micrel mic2007/MIC2017 october 2005 13 m9999-102805 application information setting i limit the mic2007/2017?s current limit is user programmable and controlled by a resistor connected between the i limit pin and ground. the value of this resistor is determined by the following equation: i limit = current limit factor (clf) r set or r set ( ? ) = current limit factor (v) i limit (a) example: set i limit = 1.25a looking in the electrical spec ifications we will find clf at i limit = 1a. for the sake of th is example, we will say the typical value of clf at an i out of 1a is 235v. applying the equation above: r set ( ? ) = 235 v 1.25 a r set = 188 ? designers should be aware t hat variations in the measured i limit for a given r set resistor, will occur because of small differences between individual ics (inherent in silicon processing) re sulting in a spread of i limit values. in the example above we used the typical value of clf to calculate r set . we can determine i limit ?s spread by using the minimum and maximum values of clf and the calculated value of r set . r set = 187 ? (the closest standard 1% value) i limit_min = 210v = 1.12a 187 ? i limit_min = 260v = 1.39a 187 ? giving us a maximum i limit variation over temperature of: i limit_min i limit_typ i limit_max 1.12a 1.25a 1.39a or 1.25a 11% i limit vs. i out measured the mic2007/2017?s current limiting circuitry is designed to act as a constant current source to the load. as the load tries to pull more than the allotted current, v out drops and the input to output voltage differential increases. when v in -v out exceeds 1v, i out drops below i limit to reduce the drain of f ault current on the system?s power supply and to limit internal heating of the mic2007/2017. when measuring i out it is important to bear this voltage dependence in mind. otherwise, the measurement data may appear to indicate a problem when none really exists. this voltage dependence is illustrated in figures 4 and 5. in figure 4, output current is measured as v out is pulled below v in , with the test terminating when v out is 1v below v in . observe that once i limit is reached i out remains constant throughout the remainder of the test. in figure 5, this test is repeated but with v in - v out exceeding 1v. when v in - v out > 1v, the mic2007/2017?s current limiting circuitry responds by decreasing i out , as can be seen in figure 5. in this demonstration, v out is being controlled and i out is the measured quantity. in real life applications, v out is determined in accordance with ohm?s law by the load and the limiting current.
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 14 m999 9-10 280 5 figure 4. i out in c u rrent limiting for v in - v out 1v figure 5. i ou t in current limiting for v in - v out >1v this folding back of i li m i t can be ge neral ized by plottin g i li m i t as a fun c tion of v out , as sho w n bel ow. the slop e of v out betwe en i out = 0 an d i out = i li m i t (wh e r e i li m i t = 1) is dete r min ed by r on of mic200 7/201 7 and i lim it . 0 0.2 0.4 0.6 0.8 1.0 1.2 01 23 456 normalized outpu t c urren t (a) out p ut voltage ( v ) n o rmal ize d o u tp ut cu rre nt v s . o u t put vo ltag e ( 5 v) figure 6. 0 0.2 0.4 0.6 0.8 1.0 1.2 0 0 .5 1.0 1 .5 2.0 2 .5 3.0 normalized ou tput cur rent (a) out p ut v o lt age ( v ) n o rma lize d o u t put cu rrent vs. o u tpu t v o lta g e (2.5 v) figure 7. c slew the cslew input is provided to i n crea se cont rol of the output volta ge ramp at turn -on. t h is in put all o ws desi gne rs the option of decrea s ing the o u tput?s sl ew rate (slo win g the voltage rise) by addin g an external cap a cita nce betwe en the pin, csle w, and vin. this cap a cita nce slo w s th e rate at which th e pa ss fet gate voltage incre a se s an d thu s , slo w s b o th the respon se to an enable co mmand a s well as v out ? s ascent to its fina l value. figure 8 illust rates effect of c sle w on turn-o n delay a nd output rise time.
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 15 m999 9-10 280 5 0 0.00 2 0.00 4 0.00 6 0.00 8 0. 0 1 0 . 0 1 2 0 . 0 1 4 0 0 0 0 0 0 0 0 0 0 time (ms) c sl e w (n f ) ty pical turn - o n t i mes vs. extern al c slew capacitan c e 2 4 6 8 10 12 14 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 t ri se t delay t on figure 8. c slew ?s effect on i lim i t an unavoida b l e con s e que n c e of addi ng c sle w cap a cita nce is a red u ctio n in the mic20 08/201 8?s a b i lity to quickly limit current tran sient s or surg es. a sufficie n tly large ca pa citan c e can preve n t both the prima r y and seco nda ry cu rrent limits fro m acting in time to prevent da mage to the mi c200 8/201 8 or the sy ste m from a sh ort circuit fault. fo r this re ason, the uppe r limi t on the value of c sle w is 4 n f . kicks tar t (mi c 20 17) kickstart all o ws bri e f cu rrent su rg es to pass to th e l oad before th e on set of no rmal curre n t limiting. this, in tu rn, permit s dyna mic loa d s to dra w bu rst s of energy without sa crif ici ng sy st em s a f e t y . functio nally, kickstart i s a force d overri de of th e n o rmal curre n t limiting function p r ov ided by the mic201 7. the kickstart pe ri od is govern ed by an internal timer wh ich allows cu rren t to pa ss uni mpede d to th e loa d for 12 8m s and then no rmal (p rima ry) current li miting goe s into action. duri ng ki ckst art a second ary current limiting ci rcuit is monitori ng o u tput cu rrent to prevent damag e to the mic201 7. t h is i s b e cau s e a h a rd sho r t, combin ed with a robu st po wer supply, ca n re sult in currents of m any tens of am pere s . thi s second ary current lim it is nominally set at 4 amp s and rea c ts i mmediately and indep ende ntly of the kickstart peri od. o n ce th e kickstart timer ha s fini she d its cou n t, the prima r y cu rre nt limiting circuit takes over an d hol ds i out to its prog ram m ed limit for as lon g as the excessiv e load pe rsi s t s . once the mi c20 17 d r op s out of current limiting t he kickstart time r initiates a lo ck-out p e rio d of 128m s su ch that no furth e r bu rsts of curre n t abo ve the prim ary current limit, will be allowed until the lock-out period has expired. kickstart ma y be over-ri d den by the therm a l prote c tion circuit a nd if sufficie n t inte rnal heatin g occurs, ki ckstart will be termi nated and i out ? 0. upo n cooli ng, if the load is still present i out ? i li m i t , not i ki ck st art . fa u l t / enable v out i out 0 t ime (ms) 100 200 300 400 500 600 kickstart current limiting load removed figure 9. kicks tar t oper ation w i th v a r y ing load supply filtering a 0.1f to 1 f bypa ss ca pacito r p o siti oned clo s e to the v in and g n d pins of mic2 007/20 17 i s b o th goo d d e si gn pra c tice a n d required fo r pro per o p e ration of the mic2007/2017. thi s will cont rol supply transients and ringin g . witho u t a bypass capa citor, larg e current surge s or an output sh ort may cause sufficie n t rin g ing on v in (from supply l ead indu ctan ce) to cau s e erratic ope rat i on of the mic2 007/20 17? s contro l circuitry. good qua lity, low es r ca pacit o r s, s u c h a s pa na so nic? s te or ecj seri es, a r e su gge sted. whe n bypa ssing with ca pacito r s of 1 0 f and up, it is good p r a c tice to place a smalle r value cap a cito r in parall e l with the larg er t o han dle the high fre que ncy comp one nts of any line transi ents. val ues in th e ra nge of 0.01f to 0.1f are recomme nde d. again, good quality, low esr cap a cito rs sh ould b e chosen. po w e r d i ssipation powe r dissip ation dep end s on several f a ctors su ch a s the load, pcb layout, ambi ent temperature, and sup p l y voltage. cal c ulation of po wer di ssipatio n can b e accompli sh ed by the following equ ation: 2 out ds(on) d i r p u to relate this to junc tion te mper ature, th e followin g
micrel mic20 07/mic20 1 7 o c to be r 20 0 5 16 m999 9-10 280 5 equatio n ca n be used: a a) - (j d j t r p t + = whe r e: t j = j unctio n temp eratu r e, t a = ambient temper ature r (j-a) is the therm a l re sist ance of the packag e in normal o peratio n, the mic2007/2 0 17?s r on is low enou gh that no sig n ifica n t i 2 r heating occur s . device heating i s mo st often ca used by a short cir c uit ? o r very heavy loa d ? when a significa nt por tion of the input sup p ly voltage appe ar s acro ss the mic2007/2 017? s power m o s f et. und e r thes e cond itions, the h eat generated wil l exceed the pac kage and pcb?s ability to cool the device and therma l limiting will be invoked. in figu re 10 , die tem per ature is plott ed a gain s t i out assumin g a con s tant case temper atur e of 85 c. the plots also a s sume a wo r s t ca se r on of 140 m at a die temper ature of 135 c. un der th ese con d itions, it i s cl ear that an sot-23 packaged devic e will be on the verge of thermal shut down (typica lly 145c di e temper atur e) whe n op erati ng at a l o a d cu rr ent of 1.25a. for this rea s on, it i s r e com m en d that mlf pa ckag e be u s e d for any mic20 07/201 7 de sign s inten d ing to su pply contin uou s curr ents of 1a or mor e . d i e t e m p er at u r e vs. i o u t f o r t case = 85 c 0 20 40 60 80 10 0 12 0 14 0 16 0 0 . 2 0 0.40 0.60 0.80 1.00 1.20 1.40 1 . 6 0 1.80 2.00 i out - a m ps d i e t e m p er at u r e - c so t - 2 3 ml f f i g u re 10. die t e mp eratu re v s . pack ag e figur e 10 assume s no b a c ksid e conta c t is m ade to the thermal p ad provide d on the mlf pa ckage. for o p timal perfo rman ce at hi ghe r cur r e n t level s , o r in hig h e r temper ature environ ment s, thermal co ntact with t h e pcb and th e exposed p o wer p addle on the ba ck sid e of the mlf pa ckag e sh ould be mad e . this signifi ca ntly redu ce s th e pa ckage? s therm a l r e sista n ce the r eby extending th e mic200 7/2017? s op er ating ran ge. it sho u ld be n o t ed that this backside p a d d le is ele c tri c ally active and is conne cted t o the mic20 07/201 7?s g n d pin. 2 v ias 0.3 mm diam. to ground plane 0.8 mm 1.4 mm figure 11. pad for the rmal mounting to pcb
micrel mic20 07/mic20 1 7 package inform ation 6-pin so t - 23 (m6) 6-pin 2mm x 2mm mlf (ml) o c to be r 20 0 5 17 m999 9-10 280 5 micrel, inc. 2180 fortune drive san jose, ca 9513 1 usa t e l + 1 (408) 9 44-0 800 f a x + 1 (408) 47 4-1 000 w eb http:/ www . m i crel.co m the information f u rnished b y micrel in this data sh eet is belie ved to be accurate and reliable. ho w e ver, no responsibility is as sumed b y micrel for its use. micrel re serves the right t o change circuitry and specificati ons at an y time w i thout notification to the customer. micrel products are not designed or autho ri zed for use as components in life support app liances, devi c es or sy stems where malfu nction of a product can reas onabl y be e x pect ed to result in pe rsonal injury . li fe support devices or s y stems ar e d e vices or sy stem s that (a ) a r e inte nded for surgical implant i n to the bod y or (b) support o r sustain life, and w h o s e failure to perf o rm can be re asonabl y e x pected to resul t in a significant injury to the use r . a purchaser?s use or sale of micrel products for u s e in life s upport appliances, devices or s y stems is a pu rchaser?s own risk and purchaser a g rees to full y ind e mnif y micrel fo r an y dama ges res u lting from such use or sale. ? 2005 micrel, in corporated.

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