b w 7 3 8 6 accuracy const a nt current led driver rev 2.0 aug. 201 3 ! 1 fea t ures z a c c u r a c y c o n s t a n t c u r r e n t z l o w b o m c o s t z c u r r e n t m o d e / f i x e d f r e q u e n c y c o n t r o l z g a t e o u t p u t v o l t a g e c l a m p z l e d o p e n p r o t e c t i o n ( o v p ) z o v e r c u r r e n t p r o t e c t i o n ( o c p ) z 3 0 0 m a d r i v i n g c a p a b i l i t y f o r o u t p i n applica t ions z e 2 6 / 2 7 , t 5 / t 8 l e d l a m p z o t h e r s l e d l i g h t i ng appli c ations description the bw 73 86 is a hig hly-integ rated, l ow startup curre n t, current mode, and fixed switchi ng freque ncy p w m cont rolle r. the s e fu nctions e nabl e the led drive r to ea sily me et the accu ra cy avera ge led cu rre nt requireme nts. the integrate d function s also in clud e the led ope n protectio n, and intern al over temp erature p r ote c tion. the comp pi n controls th e duty by conne cted an rc comp en satio n network to grou nd a n d forming th e clo s ed l oop feedba ck control. to prote c t the external po wer mosfet from being d a mage d by sup p ly over voltage, the bw 7386 o u t p i n voltage is clamp ed to about 17v. the bw 7386 im prove s the perfo rman ce and redu ce s the co st of the led drive r . it is a 6-pin sot-2 6 pa cka ge. order informa t ion pin configura tions (t op view) bw 7386 - k f r circuit t y pe kf:sot-26 shipping r : r e e l t : tube bruckewell http://
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 2 pin descriptions pin name pin description vcc power supply pin gnd ground pin out the output driver for driving the external mosfet dim dimming control pin by input a dc voltage comp feedback compensation network cs current sense pin, connect to sense the mosfet current typical applica t ion circuits led+ led- va c (90v~264v) gn d 2 ou t 3 dim 4 comp 5 cs 6 vc c 1 bw 7 386
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 3 absolute maximum ra tings (note 1 ) parameter sy mbol range unit powe r su pply pin v dd 3 0 v di m volt age to g n d v di m - 0 . 3 t o 7 v cs volt ag e to g n d v cs - 0 . 3 t o 7 v out volt a ge to gnd v out 1 5 v maximum junction temperature tj 150 c st o r a g e t e m p e r a t u r e r a n g t st g - 6 5 t o + 1 5 0 c lead temp erature (sol de ri ng 5 se c) t lead 260 c powe r dissi p ation @t a =2 5 c p d 3 00 m w therm a l re si st ance jun c tio n to ambient (note 2) , ja 333 c/w therm a l re si st an ce , jc 1 0 6 .6 c / w esd rating, human bo dy mode (note 3 ) v esd 2 k v esd rating, machi ne mo d e (note 3 ) v esd 2 0 0 v recommended opera t ing conditions (note 4) parameter sy mbol operation conditions unit supply volt ag e v dd 2 6 v operating jun c tion tempe r a t ure ra nge t j 150 c operating am bient tempe r a t ure ra nge t op a -20 to +85 c note 1: stresse s listed as the a bove absolute maximum r a ting s ma y cause pe rmanent damage to the device. t hese are for stre ss ratings. function al operation of th e device at t h e s e o r a n y o t h e r c o n d i t i o n s b e y o n d th ose indicated in t he ope rational se ctions o f the specification s is not imp lied. exposure to a b solute ma ximum r ating conditions f or exte nded pe riods ma y remain possibili t y to affect device r e liability . note 2 : the r mal resistance is specified w i th the component mou nted on a lo w eff e ctive thermal conductivity test b oard in free air a t t a =25 c. note 3 : d e v i c e s a r e e s d s e n s i t i v e . h a n d i n g p r e c a u t i o n r e c o m m e n d e d . note 4 : the device is not guaranteed to func tion outside its operating conditions.
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 4 block diagram cmpdl!ejbhsbn com ptd pof ! tipu esjwfs pro (vcc_ovp, otp) out cs vref rst se t cl k vwmp0ch vcc gnd ts mbu d i s r q vref ovp_vcc g m dim pdq ejnnjoh cu r r en t t o v o l t ag e
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 5 electrical characteristics v cc =15v , t a = 2 5 c, unless othe r w ise specified. parameter sy mbol conditio n min t y p max u nit supply voltage st a r t u p c u r r e n t v dd(st ) v cc =uvlo o n -1v 8 ua operating cu rre nt v co m p w i t h 1 n f l o a d o n o u t p i n 1 . 5 2 . 5 m a operating cu rre nt i opa with 1nf loa d on out pin protectio n t r i pped (ocp , ovp , scp , otp) 1 .2 1 . 8 ma uvlo(of f ) 7 8 8 v uvlo (on ) 17 18 19 v ovp level on vcc pin ovp 26 28 30 v vol t age feedback feedb ack re feren c e v o lt a g e v fb 0 . 1 9 4 0 . 2 0 . 2 06v tr a n - c o n d u c t a n c e 120 u s output sink curre n t i o-sink 12 u a output source curre n t i o-source 1 2 u a cu r re nt s e ns i ng input over v o lt age prote c ti on f osc 0 . 8 v open l oop v o lt age, cs pi n open 5 v leadi ng-ed g e blankin g t i me 4 1 0 n s delay to output 1 0 0 n s sw itch in g fr equ ency switchin g fre quen cy 42 45 48 khz maximum duty 90 % freq uen cy jit t er ran ge +/-6 % te m p . s t a b i l i t y -40 w! ~12 5 w 6 % vo l t a g e s t a b i l i t y v cc =1 1v ~25 v 1 % gate drive r ou tput risi ng t i me load ca p a cit ance = 10 00p f 160 ns falling t i m e load ca p a cit ance = 10 00p f 80 ns vga t e-clamp v cc =25v 17 19 v
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 6 dim input section saturation th reshold v o lt a g e 3.0 v linea r dimmi ng ra nge 0.6 3.0 v curre n t source 270 300 330 ua thermal section therm a l shut down t sd 1 5 0 w
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 7 applica t ion informa t ion s t art-up current the typical start-up current is a r oun d 8ua. very low sta r t-up cu rrent al l o w s t h e p w m c o n t r o l l e r to incre a se the value of start-up resi stor and the n redu ce the p o w er di ssipatio n on it. uvlo(und er v o lt age lockout) a hystere s is uvlo comp arato r is impl emented i n bw 7386 the n the turn-on a n turn-off threshol ds leve l are fixed at 1 8 v and 8v re spe c tively. this hyste r e s i s sho w n in fi g . 1 ensu r e s th at the start-u p cap acito r will be adequ ate to supply the chip duri ng start-up. for qui ckly startup the le d driver, the start-u p resi sto r sh o uld be mat c he d with the startu p cap acito r. du e to the low uvlo on level, so the turn-on d e lay time will also neve r g r ea ter than th e gene ral pwm ic. oscillator the maximum duty-cycl e of in ternal oscillator i s up to 90% for driving hig h led voltage string. th e freque ncy of the oscillat or is fixed to 45khz by internal s e tting. leb(leadi ng-edge blanking) each time the powe r mosfet is switche d on, a turn-on spike will inevitably occur at the sense resi sto r . to a v oid fault trig ger, a 4 10n s l eadin g-e dge blan king time is built in. conve n tional rc filtering can the r efore be omitted. durin g this blan kin g perio d, the current-limit compa r ator is disa bled and can n o t swit ch off the gate driver. ocp(over current protection) the bw 7386 has an over current prote c tion functio n on cs pin. an intern al circuit dete c ts the cu rrent level, when the cu rrent is large r than a threshol d level, the gate output will keep on low level. then vcc d e crea ses b e low uv lo off level, the controll er resets ag ain. ovp (over v o lt age protection) on vcc the prevent the led d r iver from b e in g dama ged, the bw 7386 is i mplement ed an ovp function o n vcc. wh en the vcc volta ge is highe r than the ovp threshold volt age 28v, the output gate driver circuit will be shut down im medi ately to stop the switchi ng of power mo sfet. the vcc pin ovp functio n is an auto re cove ry type pro t ection (lat ch off type optional ). if the ovp cond ition happe ns, the pulse s will be stopp ed and never recove ry unless the vcc pin voltage i s do wn to t he uvl o off level. the bw 7386 i s worki ng in an auto-recovery mode a s sho w n in fig. 2. fig. 1 uvlo ( on ) 18v uvl o (o f f ) 8v
bw 7 3 8 6 accuracy const a nt current led driver r e v 2 . 0 a u g . 2 0 1 3 ! 8 gate clam p/sof t driving drive r is cla m ped to 17v by an intern al clam pin g circuit. tho s e dama g e s usu a lly come from unde sired o v er-voltag e gate si gnal s. und er the conditions listed below, th e gate output will turn off immediately to prote c t the power circuit. th e bw 7386 al so has soft dri v ing function to minimize emi. fig. 2
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