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| standalone linear li-ion charger with thermal regulation general description the BP13504 is a comp let e linea r c h ar ger for s i n g le ce ll lit h i um-io n bat t e ries. w i t h small tdfn- 1 0 package and few ext ernal compo nent s, BP13504 is we ll su it ed for port abl e a p plicat ions. i n ad dit ion, t h e BP13504 is specific a lly designed t o work wit hin u s b power spe cifications. no ext ernal s e nse resist or and bl ock ing d i ode are required. charging cu rrent can be pro gr ammed exter n a l l y wi th a sin gl e r e si stor . t h e b u il t-in th er mal regu lat ion facilit at es charging wit h max imu m power w i th o u t r i s k o f ov e r h e a t i n g . the BP13504 al ways precondit ions t h e batt ery wit h 1/10 of t h e program med charge cu rre nt at t h e b e ginn ing of a c h arg e c y cle, af ter i t v e rifies th a t th e bat t e ry can be fast -charged. the BP13504 au to m ati c a l l y te r m i n at e s t h e c h ar g e c y cl e w h e n th e c h ar g e c u r r e n t d r o p s to 1 / 10 th th e p r o g r amm e d v a l u e af ter th e f i n a l fl oat v o l t ag e i s r e ach e d. the BP13504 feat ures 13. 5v maximum rat ing vo l t age fo r a c adapt er , and it pro v ides the charge curre nt up t o 1. 2a . ot her feat ures incl ude batt ery t e mperat ure monit oring, rev e rse cu rrent prot ect ion, shut down mode, charging curre nt monit or, under vo l t age locko ut, aut omat ic recha rge a n d st a t us ind icat or. features programm able charge current up t o 1. 2a no m o sfet, sense resist or or b l o c king d i od e required comp l e t e line ar charger in tdfn- 10 for single ce ll li-io n bat t e ries t h er m a l r e g u l a ti o n m ax i mi z e s c h ar g e r ate wi th ou t r i s k o f ov e r h e at i n g the rmist or inpu t for t e mperature qualified cha rging char ges single ce ll li- io n bat teries direct l y from usb port . preset 4 . 2v charge vol t age wit h d 1% accura cy a u to ma ti c re ch ar g e charge st at us ind icat or c/10 c h arge t e rminat ion bat t e ry rev erse l e akage cu rre nt l e ss t h an 1u a applications w i rel ess ha nds et s hand- he l d inst rument s port ab l e informat ion ap p lia nces b p 1350 4 1 b p semi http://
typical application circuit acin 1uf gnd acin = 4.5v~13.5v r set batt ts 1k 1k 1uf 4.2v li -ion battery pac k iseta chg_sb pgoodb enb 1uf 1 complete charger cycle v bat i bat v is et ? 3 ? ? ? ? ? ? ? ? ? ?????? ????? ? a ??3 ? ? ? ? ?? ? 3 ? ? ? 3 ? ? ? ? ? ? ? ? ? ? 3 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?????? ????? ? ? ? 3 ? ?? ? 3 ? ? b p 1 3 5 0 4 2 BP13504 connection diagrams t op v i ew order information BP13504-4 2ff 10nrr 42 out put v o l t age ff10 t d fn-10 packag e nrr rohs & ha logen free pa cka ge rat ing: -40 t o 85c packag e in t a pe & reel order, marking & packing information packag e p roduct id. t d fn-10 BP13504-42 ff1 0nrr tape & r eel 5kpcs b p 1 3 5 0 4 3 packing pin functions name tdfn-10 function ac i n 1 positive input supply voltage. provides power to the charger. acin can range from 4.5v to 13.5v and should be bypassed with at least a 1 p f capacitor. when acin drops to within 30mv above the batt pin voltage, the BP13504 enters shutdown mode, dropping i batt to less than 1 p a. nc 2 not connected. chg_sb 3 open-drain c h arge st a t us out pu t. a n int er nal n-chan nel mosfet co nn ec ts chg_sb pin to grou nd wh e n th e b a ttery i s chargi n g . a f ter th e cha rg e cy c l e is com pl eted , th e i n ter nal n-channel mosfet is replaced by a weak pull-down of approximately 25 p a, indicating an ac present condition. when the BP13504 detects an under voltage lockout condition, chg_sb is forced high impedance. pgoodb 4 open-drain battery power good output. an internal n-channel mosfet connects pgoodb pin to ground when acin is under 4.2v. pgoodb is forced low during normal operation. gnd 5 ground. iset a 6 charge cu rrent program , cha rge current monit o r and shut dow n pin. t h e charge current is prog rammed by connecting a 1% resi st or, r se t , t o g r ound. w h en charg ing in cons t a n t -curr ent mod e, this pin serv os t o 1 . 5 v . i n a l l modes, the v o l t age on this pin can be used t o m e asur e t h e char ge c u rren t usin g t h e foll o w ing for m ul a: i ba t t = ( v se t / r se t ) * 500 th e i s et a pin can al so be used t o shu tdo w n the charger. disconnect ing t h e program resist or from gr ound all o w s a 1 p a curren t t o pull t h e i s e t a p i n high . w h en it reach es th e 2. 15 v shu tdo wn threshol d v o l t a g e, the char ger en ters shu tdow n mode. t h is pin is a l so cl amped t o ap proximatel y 2. 5v. r e c o nn ec t i n g r se t t o grou n d w ill ret urn th e char ger t o normal opera t ion . the is eta pin m u st not be dire c tly shorted to ground at any co ndition. nc 7 not connected. enb 8 charge enable input (active low). this pin is weakly pulled low internally. ts 9 t s pin is t h e input for an ex ternal nt c ther mist or. w h en t h e t s pin v o l t age is out of the wi ndow, determined by the v tmin and v tmax , the BP13504 stops charging and indicates a fault condition. batt 10 char ge curr en t ou t p u t and b a ttery v o l t age f e edback . this pin pro v ides charge curr en t t o t h e ba ttery and regul ates the final f l oat v o l t age t o 4 . 2 v . a n int ernal precision resis t o r di v i der from t h is pin set s the fl oat v o l t age w h i c h is disconnected in shu t d o w n mode. bp 1 3 5 0 4 4 functional block diagram body switch acin bat bs bs bs acin batt + - 1.2v regulation controller + - + - temperature controller 1.5 v 0.15v + - 2.9 v bat + - + - 0.15v 2.15v logic controller iseta uvlo/ovp ts + - + - 2. 5 v 0.5 v + - bat 4.05v hot col d gnd disable pgoodb ch g_sb en b fi g. 1 . fu ncti onal bl ock di a g ram of BP13504 b p 1 3 5 0 4 5 state diagram tri ck le c harg e mo de 1/10th full current chg_bs: strong pull-down c harg e mod e f u ll cu rr en t chg_sb: strong pull-down s t andb y mod e no charge current chg_sb: wea k pull-down batt < 2.9v batt > 2.9v batt > 2.9v iseta < 0.15v 2.9v < batt < 4.05v shutdown mode chg_sb: hi-z in uvlo weak pull-down otherwise iseta floated, iseta > 2.15v or uvlo/ovp condition batt < 2.9v is eta recon nected or uvlo/ovp condition stops power on battery thermal fault n o ch ar ge cu rr ent chg_sb: weak pull-down no fault therma l fault f i g. 2. BP13504 flow c h ar t b p 1 3 5 0 4 6 absolute maximum ratings ( n o t e s 1, 2) v ac i n , v ba t t , v ch g s b , v pr oo d b - 0 . 3 v t o 1 3 . 5 v v is e t a , v ts , v en - 0 . 3 v t o 3 . 6 v pow er dissipat i o n ( n ote 5 ) st ora g e t e mperat u re range -65c t o 150c juncti on te mp era t u r e (t j ) 1 5 0 c l e a d t e m p e ra t u re ( s o l d e ri n g , 1 0 s e c . ) 2 6 0 c operating ratings ( n o t e 1, 2) s u p p l y v o l t a g e 4 . 5 v t o 1 3 . 5 v opera t i n g tem pera t u r e ran g e -40c to 85 c t h e rmal re sist a n ce ( t ja , no te 3)) 110c/ w t h e rmal re sist a n ce ( t jc , n o t e 4 ) ) 8 . 5 c / w electrical characteristics t a = 25c, v ac i n = 5. 0 v ; unl ess other w ise specified. symbol parameter conditions min typ max units v ac i n input operating voltage range 4.5 5 13 .5 v v ov vin over-volta ge lock out threshold from v ac i n low to h i gh 7 v charge mode, r set = 30k (note 6) 300 ua standby mod e (charge terminated) 20 0 ua i cc input supply cu rrent shutdown mod e (r pr og not connected , v aci n typical performance characteristics u n l e ss ot he r w is e spe cifie d, v ac i n = 5. 0v, t a = 25 c v set vs. t e mper ature (v batt > 2. 9v) v set vs. t e mper ature (v batt < 2. 9v) vse t v . s . t e m p e r a t u r e 1. 48 5 1. 48 7 1. 48 9 1. 49 1 1. 49 3 1. 49 5 1. 49 7 1. 49 9 1. 50 1 1. 50 3 1. 50 5 1. 50 7 1. 50 9 1. 51 1 1. 51 3 1. 51 5 - 40 - 15 10 35 60 8 5 te m p e r a t u r e ( : ) vs et ( v ) vse t v s . t e m p er a t u r e 0. 1 4 5 0. 1 46 0. 1 47 0. 1 48 0. 1 49 0. 1 50 0. 1 51 0. 1 52 0. 1 53 0. 1 54 0. 1 55 - 4 0 - 15 1 0 35 6 0 85 te m p e r a t u r e ( : ) vs e t ( v ) charge current vs. battery volt age regulated output voltage vs. temperature c h a r g e c u rren t v s . b a t t e r y v o l t a g e 0 20 0 40 0 60 0 80 0 100 0 120 0 140 0 160 0 2 .1 2 .4 2 . 7 3 . 0 3 . 3 3 .6 3 .9 4 .2 4 .5 v b a tt (v ) i ba t (m a) rp r o g=3k rp r og=1 . 5 k rp r o g=1k rp r o g = 0.5 k r e g u l ated output v o l t a g e vs . t e m p e r a t u r e 4. 15 4 . 155 4. 16 4 . 165 4. 17 4 . 175 4. 18 4 . 185 4. 19 4 . 195 4. 2 - 4 0 - 3 0 - 2 0 - 1 0 0 1 0 2 03 0 4 05 0 6 07 0 8 09 0 1 0 0 1 1 0 te m p e r a t u r e ( : ) v fl o a t (v ) regulated outp ut voltage vs. s u pply voltage trickle charge current vs. supply voltag e re gula t e d o u t p ut v o lt a g e v s . sup p l y v o lt a g e 4. 1 5 4. 1 55 4. 1 6 4. 1 65 4. 1 7 4. 1 75 4. 1 8 4. 3 4 . 5 4 . 7 4 . 9 5. 1 5 . 3 5 . 5 v ac i n (v ) v fl o a t ( v ) ? ? t? ? 3 ? ???3? ? 3 3 ? ? 3 ? ? ? ? ?? ?? ?? ?? ? ? ? ?? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 3 ? ? ? ? ?t ? ? 3 ? ? ? ???ae?t ?? ?ae?t ??? a e ? t ?? ?ae?t bp 1 3504 9 operation the BP13504 is a single ce ll lit hium-io n bat tery char ger us ing a co nst ant -curre nt /const ant -v o l t a ge a l gorit hm. i t can de liver up t o 1. 2 a of cha rge cur rent ( u si ng a good t h e r ma l pc b layo ut) wit h a fina l f l o at vo l t a g e a ccura cy of 1%. the BP13504 inclu des an int erna l p-c ha nne l power mosfe t and t h erma l regu lat ion c i r c uit ry. n o bl ocking di od e or external curre nt sense resi stor i s requ ired; thus, the basic charg er circui t requ i r es onl y two ext ernal com p onent s. furt her more, t h e BP13504 is c apa b l e of operat ing from a u s b p ower source. normal ch arg e cycl e a charge cycle begins whe n t h e v o l t age at t h e a c i n pin rises above t h e uvlo t h reshold l e v e l and a 1% pro gram res ist or is co nne ct ed from t h e i s e t a p i n t o grou nd or whe n a batt ery is connect ed t o t h e charger ou tp u t . i f th e ba tt pi n i s l e s s th an 2 . 9 v , th e c h ar g e r e n te r s tr i c kl e c h ar g e m od e . i n th i s m od e , th e BP13504 suppl i e s approxi matel y 1 / 1 0 th e progr ammed ch ar g e curr en t to br i n g the batter y v o l t age up to a safe l e v e l f o r fu ll current charging. w h en t h e ba tt pin vol t a ge rises ab ov e 2. 9v, t h e charge r ent ers const ant -current mode , where t h e program med charge cu rre nt is supplied t o t h e bat t e ry . w h en t h e b a tt pin approaches t h e fina l fl o at v o l t a g e ( 4 . 2v), t h e BP13504 ent ers co nst ant - v o l t age mode and the charge cu rr ent begins t o decrease. w h en t h e charge curre nt drops t o 1/10 of t he programme d v a lue, t h e charge cycle e n ds. programmin g charge curren t the charge current is programmed using a singl e res ist or from t h e i s e t a pin t o grou nd. the batt er y charge curre nt is 50 0 t i mes t h e curre nt out of t h e i s et a p i n. vset is 1. 5v whe n c h arging in co nst ant -current m ode. the pro gram resist or and t h e charge cu rre nt ar e cal cu l a t ed using t h e follo wing equat ions: set set chg chg set set r 500v i , i 500v r the charge current out of the b a tt pin can be det ermined at any t i me by monit oring t h e i s e t a pin vo l t age usin g t h e fo llo wing equat io n : 500 r v i set set batt u charge termination a charge cycle is t e rminat ed when t h e charge curre nt falls t o 1/10t h t h e program m ed v a lue aft er t h e final fl oat v o l t age is reached. this condit io n is det ec t ed by using an i n t e rna l , fil t ered co mparat or t o mon it or t h e i s e t a pin. w h en t h e i s e t a pin v o l t age falls be low 150mv for l o nger t h an t term ( t ypic a lly 1ms) , cha rg ing is t e rminat ed. the charge current is lat ched off and t h e BP13504 ent ers st andby mode, where t h e input supply curre nt drops to 150u a . ( n o t e: c/10 t e rminat ion is disab le d in t r ick l e cha rging and t h erma l limit ing m odes). the BP13504 dra ws no curre nt from t h e batt er y in st andby mode. this fe at ure reduces t h e charge and discharge cycl es on t h e bat t e ry , fur t her prol ongi ng t h e batt ery l i f e. a n y e x te r n al so u r c e ( v se t ) t h at ho l d s t h e i s et a p i n abo ve 15 0mv w i ll pr ev e n t t h e BP13504 f r om t e rmin at in g a charge cycle. howe v e r, if t h e i s e t a pin is cont rolled by ex t e rna l source, current sourcing from t h e b a t t p i n ca n be in fin i t y ( u n t i l th e i n ter n a l power m o sfet is bur n ed out or th e ba tt pi n v o l t ag e i s cl ose to i t s f i n a l fl oat v o l t ag e), and t h e formu la for c h a r ge c u rrent is not v a lid a n ymo re. w h e n c h ar ging , tr an s i en t l oad s o n th e ba tt p i n c a n c aus e th e i s eta pin to f a l l b e l ow 150 m v f or sh or t p e r i od s o f t i me before t h e dc charge curre nt has dropped t o 1/ 10t h t h e programmed v a lue. the 1ms fil t er t i me ( t term ) o n th e ter min ation comp ar ator en sur es th at tr an sien t l oads of th i s n atur e do n ot r e sul t in p r ematur e char g e cycl e t e rminat ion. once t h e av erage charge current drop s be l ow 1/10t h the programm ed v a l u e, t h e BP13504 t e rminat es t h e charge cy cl e and ceases t o provide any current t h rough t h e ba tt pin. this is t h e st andby mode , and a ll loads on t h e b a tt p i n must be supp lied by t h e batt ery . i n t h e st andby mode, any signal below t h e manua l shut down t h resho l d vo l t age ( t ypica lly 2. 15v) on the i s et a pin is trans pare nt t o BP13504. b p 1 3 5 0 4 10 the BP13504 const ant l y mo nit ors t h e ba tt pin v o l t age in st andby mode. i f t h is vo l t age drops be l o w t h e 4. 05v recharge t h resho l d ( v re chrg ), anot her c h arge cyc l e be gins and curre nt is once again s u pplied t o t h e batt ery . to ma nua lly re st art a charge cyc l e whe n in st andby mo de , t h e input v o l t age must be remov ed and reapplied, or t h e charger must be shu t down and rest art ed using t h e i s e t a pin. charge s t atus indic ator (chg_sb) the charge st at us out put has t h ree different s t at es : s t rong pu ll-dow n ( ~ 10m a ) , weak pu ll -d own ( ~ 25u a ) and high impedance. the st rong pu ll -d ow n st a t e indicat es t h at t h e BP13504 is in a charge cyc l e . once t h e charge cyc l e has t e rmin at ed, t h e pin st at e is det ermined by under- vo l t age lockout condit ions. a weak pu ll -d ow n ind icat es t h at a c i n meet s t h e u v lo co ndit io ns and t h e BP13504 is ready t o charge. high im pedance i n di cates that the BP13504 is i n un der-vol t ag e l o ckout m ode: ei t h er vi n i s l e ss t h an 60mv abov e t h e ba tt pin vol t age or insu ffi ci ent v o l t age i s appl i ed t o t h e a c i n pi n. a microproces sor can be used t o di st i n gui s h bet ween t h ese t h ree st a t es . this met hod is discussed in t h e a pplic at ions i n form at io n sect ion. thermal limitin g a n int ernal t h e r mal feedback l o op reduce s t h e program med charge current if t h e die temperat ure att emp t s t o rise abov e a preset v a lue of approx imat el y 120c. this feat ure prot ect s t h e BP13504 from excessiv e t e mperat ure a n d allo ws t h e user t o push the lim it s of t h e power ha nd ling capa bilit y of a given c i rc uit board wi th out r i sk of damagi ng th e bp1350 4. t h e ch arg e curr en t can be set accor din g to typi cal ( n ot wor st-case) am b i en t te m p e r at u r e w i th th e a s s u r an c e tha t th e c h ar g e r w i l l a u to m ati c a l l y r e d u c e th e c u r r e n t i n wo r s t- c as e cond it ions. tdf n-10 p ower c o nside rat ions a r e discuss ed fur t her in t h e a p p licat io ns i n f or m at ion sect ion . under-vol tage lockout (uvl o) a n int ernal u n der- v o l t a g e l o ckout circuit monit ors t h e input v o l t age and keeps t h e charger in shut down mode unt i l a c i n rises abo v e t h e under- v o l t a g e l o ckout t h resho ld. the uvlo circuit has a built -in hyst eresis of 150mv. furt hermore, to prot ect aga inst re v e rse cu rrent in t h e po wer m o sfe t, the u v lo c i rcu it keeps t h e charger in shut down mo de if a c i n fa lls t o wit hin 3 0 m v of t h e bat t e ry v o l t age. i f t h e uvlo comparat or is t r ipped, t h e ch ar g e r will n o t come ou t of sh utdown mode un ti l a c i n r i ses 6 0 m v abov e th e batter y v o l t age. manual shu tdown a t any po int in t h e charge c y c l e, t h e BP13504 can be put int o shut do wn mode by remov ing r se t th us fl oating th e i s eta pi n . th i s r e d u c e s th e b at t e r y d r ai n c u r r e n t to a b ou t to 0 u a an d th e s u p p l y c u r r e n t to l e s s th an 1 5 0 u a . a new ch arg e cycl e can be in i t i ated by r e con n e cti ng th e pr ogr am r e si stor . i n manual s h utdown, t h e ch g_sb pin is in a weak pull- down st at e as long as a c i n is high enou gh to exceed t h e u v lo condit ions. the ch g_s b p i n is in a high impe d ance st at e if t h e BP13504 is in under- vo l t a ge lockout mode: ei t h er a c i n i s wi t h i n 60m v of t h e ba tt pin v o l t age or i n su ffi ci ent v o l t age i s appl i ed t o t h e a c i n pi n. automa tic rec harge once t h e charge cycle is t e rminat ed , t h e BP13504 cont inuous l y mo n i t ors t h e v o l t a g e on t h e b a t t pin usi ng a compa rat or wit h a 2ms fil t er t i me ( t recha rge ). a charge cy cl e rest arts when th e batt ery vol t a ge fall s be l ow 4. 05v (w h i c h co r r e spo n d s to a p p r ox i m at el y 80 % t o 90 % ba tte r y c ap a c i ty ). t h i s e n s u r e s th at t h e b atte r y i s k e p t a t o r near a fu lly charged cond it ion and e l iminat es t h e need for pe riodic charge cy cl e init iat ions. chg_sb out put ent ers a st rong pu ll -do wn st ate during rec ha rge cy c l es. b p 1 3 5 0 4 11 application information stability considerations the const ant - vol t age mod e feedback loop is st abl e wi t h out an out pu t capacit or provided a bat t e ry is connect ed t o t h e charger out pu t. w i t h no batt ery present, an out pu t capacit or is recommended t o reduce rippl e vol t a ge. w h en using high val ue, l ow esr ceram ic capacit ors, i t is recommended t o add a 1 o resist or in series w i t h t h e capacit or. no series res istor is needed if t ant a l um ca pacit ors are used. i n const ant -current mode, t h e i s e t a pin is in t h e feedback l oop, not the bat t e ry . the const ant -current mode st abilit y is affect ed by t h e impedance at t h e i s e t a pin. w i t h no addit i ona l ca pac it ance o n t h e i s e t a p i n , t h e c h a r g e r i s s t ab l e w i t h p r o g r a m r e s i s t or v a l u e s a s h i g h a s 1 0 0 k . h owe v e r , ad d i t i on a l c a p ac i t an c e o n t h i s n od e reduces t h e maximum allo wed program resist or. the pol e frequency at t h e i s et a pin shou ld be kept abov e 100k hz. therefore, if t h e i s eta p i n is loade d wit h a capa cit ance, c se t , the fol l o wing equat i on can be used t o cal cu l at e t h e maxi mum res i s t ance val ue for r se t : set 5 set c 10 2 ? 1 r u u d avera g e, rat her t h an inst ant aneous, charg e current may be of int erest to t h e user . for exampl e, if a s wit ching power sup p l y operat ing in low curre nt mode is co nne c t ed in paralle l wit h t h e battery, t h e av erage curre nt b e in g p u l l e d o u t o f th e ba tt p i n i s ty p i c a l l y o f m or e i n te r e s t th an th e i n s t an ta n e ou s c u r r e n t p u l s e s . i n s u c h a case, a simpl e rc fil t er can be used on t h e i s et a pin t o me asure t h e av erage bat t e ry c u rrent as shown in figu re 3. a 10k o resist or has bee n added bet wee n t h e i s e t a pin an d t h e fil t er capacit or t o ensure st abilit y. f i g. 3. i s o l a t i n g capaci t i ve load on iseta pin and filtering po wer dissipa ti on the cond it io ns t h at cause t h e BP13504 t o reduce charge cu rrent t h rough t h erma l feedback can be appr oxim at ed by co ns ider in g t h e powe r d i ssipat ed in t h e i c . nea r l y a ll o f t h is p ower d i s s ipat io n is ge n e rat ed by th e i n te r n al mos f e t , th i s i s cal c u l ate d to b e a p p r ox i m ate l y : p d = ( a c i n C v ba tt ) ? i ba tt wh e r e p d i s t h e power di ssipat ed , a c i n i s the i n put suppl y v o l t age, v ba tt i s t h e ba tt ery v o l t age and i ba tt is t h e charge cu rrent. the approx imat e ambient t e mperat ure at which t h e therma l feedback begins t o prot ect t h e ic i s : t a = 120 : C p d ? e ja t a = 120 : C ( a c i n C v ba tt ) ? i bat t ? e ja exampl e: an BP13504 o p erat ing fr om a 5v u s b supp ly is pro gra mm ed t o s u ppl y 500m a fu ll-scale current t o a discharged l i - i on batter y wi th a v o l t age of 3 . 7 v . a s sumi ng e ja is 110 : / w , th e a m b i en t te m p e r at u r e a t w h ic h th e BP13504 will begin t o reduce t h e charge c u rrent is app ro ximat e l y: t a = 120 : C ( 5v C 3. 7v) ? ( 500m a ) ? 110 : /w t a = 120 : C 0. 6 5 w ? 100 : /w = 120 : C 71. 5 : b p 1 3 5 0 4 12 BP13504 t a = 48 . 5 : t h e BP13504 can be used abov e 55 : a m bie nt, but t h e char ge curr ent will be reduced from 500m a . the approxim at e current at a given amb ient t e mperat ure can be approx im at ed by : ja batt a o batt ) v (acin t c 120 i u u s ing t h e p r e vious ex amp le wit h an am bient t e mperature of 70 : , the charge cu rrent will be reduced to approxim at el y : 349ma i c/a 143 c 50 c/w 110 3.7) (5 c 70 c 120 i batt o o o o o batt x more ov er, when t h ermal fe edback reduces t h e charge current , t h e vol t a ge at t h e i s et a pin is al s o reduced prop ort iona lly as discussed in t h e operat ion sect ion. i t is im port ant t o remember t h at BP13504 a p p l ica t ions do not need t o be designed for worst -case t h ermal cond it ions since t h e i c will aut omat ically reduce powe r dissipat ion w h e n t h e junct io n t e mperat ure reaches a pproximat e l y 120 : . thermal consi derations because of t h e small size of t h e tdfn-10 package, it is v e ry import ant t o use a good t h erma l pc boa r d l ay out t o maxim ize t h e av ail a b l e charge curre nt. the t h ermal pat h for t h e heat gene rat ed by t h e i c is from t h e die t o t h e copper le ad frame, t h rough t h e pack age l e ads, ( e sp ecia lly t h e ground l e ad) t o t h e pc board copper. the pc board co p p er is t h e heat sink. the foot print coppe r pa ds ( t herma l la nd) shou l d be as wide as p os s ib le a n d expand out t o larger copper areas t o spread and diss ipat e t h e heat t o the surrou nd ing ambie nt . feed-t hrough vias t o inner or backs ide copper layers are al s o usefu l in impro ving t h e ov e r a ll t h ermal performance of t h e cha rge r. ot her heat source s on t h e boa rd, not rel at ed t o t h e charger, must al s o be cons idere d when designing a p c board layout because t h ey will affe ct ov erall t e mperat ure rise a n d t h e maximu m cha rge curre nt. increasing th e rmal regul atio n current reducing t h e vol t a ge d r op across t h e int ernal mosfe t c an sig ni f i ca nt l y decrease t h e power d i ssipat i on i n t h e i c . this has t h e effect of increasing t h e cu rre nt deliv e r ed t o t h e batt ery during t h erma l re gu l at i on. one met hod is by diss ipat ing some of t h e power t h rou gh an ext e rnal component , su ch as a res ist or or diode. examp l e : a n BP13504 ope r a t ing from a 5v wa ll adapt e r is p r o g ram m ed t o suppl y 1 a fu ll-sca le cu rrent t o a di scharged li - i on bat t e ry wi t h a v o l t age of 3. 7v. a ssum i ng e ja is 100 o c/w , t h e approximat e charge curre nt at an amb ie nt t e mperat ure of 25 : is: 730ma c/w 100 3.7v) (5v c 25 c 120 i o o o batt x by dro pp ing vo l t age a c ross a resist or in ser ies w i t h a 5 v wa ll ada pt er ( s how n in figur e 4), t h e on-c hip po we r dissipat ion can be decrease d, t h us increas ing t h e t h ermally regu lat ed charge current b p 1 3 5 0 4 13 fi g. 4. a circ ui t t o maximi ze charg e current ja batt cc batt s o o batt ) v r i (v c 25 c 120 i x so lvin g fo r i ba tt using t h e quadrat ic formu l a . ] ) t c (120 4r ) v (v ) v [(v 2r 1 i ja a o cc 2 batt s batt s cc batt ( n o t e : large val ues of r cc w i ll resu l t in no s o l u t i on fo r i ba tt . t h i s in di ca tes th at th e BP13504 wil l n ot g e n e r ate enough he at to require t h ermal re gu lat ion.) us i n g r cc = 0. 25 o , v s = 5v, v ba t t = 3. 7v , t a = 25 : and e ja = 100 : / w we can calcu lat e t h e t h erma lly regu l a t ed cha rge cu rre n t t o be: i ba tt = 87 9. 5m a w h il e t h is a p p l icat io n de liv e r s more ene rgy t o t h e bat t e ry and reduces cha rge t i me in t h erma l mod e, i t may actual l y l e n g th en ch arg e ti me i n v o l t ag e mode i f a c i n becomes l ow en ough to put th e BP13504e in to dropout . this t e chnique works best when r cc v a lue s are minim ize d t o keep co mpone nt size sma ll and avoid dropout . remember to choose a resistor wi th adequate power ha nd l i n g capabili ty . acin bypass cap aci tor ma ny t y pes of capac it ors c an be used fo r input bypassi ng, howe v e r, caut ion must be exercised when us ing mul til ayer c e rami c c apaci tor s . b e c ause of th e sel f - r eson a n t an d hig h q ch arac ter i s tic s of some typ es of ceram ic ca p acit ors, high vo l t age t r ans ient s can be gene rat ed under some st art -up condit ions, such as c onn ec ti ng th e c h ar g e r in put to a l i v e po we r so ur c e . a ddi ng a 1 . 5 o resist or in series w i t h an x5r ceram ic c ap a c i to r w ill mi ni mi ze s t ar t- up v o l t ag e tr an s i en ts . charge curren t s oft-s tar t t h e BP13504 in cl udes a sof t-star t ci r c ui t to mi ni mi ze th e i n r u sh curr en t at th e s t ar t of a char ge cycl e. w h en a cha rge cyc le is init iat ed, the c h ar ge cu rrent ram ps fr om zero t o t h e fu ll-sca le cu rrent o v er a period of appr oxim at el y 100us. this ha s t h e effect of minimiz ing t h e t r ansie nt current l oad o n the power sup p l y during st art - up. b p 1 3 5 0 4 14 BP13504 chg_ sb s t a t us outpu t pin t h e chg _sb pi n can p r ov i d e an in dic ati on th at th e i n put v o l t ag e i s gr eater th an th e un der -v ol tag e l o c k out t h resho l d l e ve l. a weak pu ll- down current of app roxi mat e l y 25u a i n dic at es t h a t sufficient v o l t a g e is applied t o a c i n t o begin cha rging. w h en a disc har ge d batt ery is connect ed t o t h e char ger, t h e const ant curre nt port ion of t h e cha rge cyc l e begins a n d t h e chg_s b p i n pu lls t o ground. the ch g_s b p i n can s i nk up t o 10 m a t o d r ive an le d t h at indicat es t h at a cha rge cy c l e is in p r o g ress. wh e n th e b a t t e r y i s n e a r i n g ful l c h ar g e , th e c h ar g e r e n te r s th e c o n s ta n t - v ol ta g e p o r t io n of th e c h arg e c y cl e and t h e charge curre nt begins t o drop. w h en t h e charge cur rent drops be low 1/10 of t h e programmed curre nt, t h e charge cycl e e n ds and t h e st rong pu ll-dow n is replaced by t h e 25u a pu ll -down, ind icat ing t h at t h e charge cycl e has end ed. i f t h e i n put v o l t a g e i s remov ed or drops be l o w t h e under- v ol t a g e l o ckout t h reshol d, t h e chg_sb pin becomes high impedance. figure 5 s h ows t h at by using t w o differe nt val ue pu ll-up resist ors, a micropro cessor c a n det ect all t h ree st a t es from t h is pin. fig.5. u s ing a microprocessor t o d e termine ch g_sb sta te to det ect when t h e BP13504 is in charge mode, force t h e digit a l out put pin ( o ut) high and measure t h e vol t a ge at t h e chg_sb pin. the int ernal n-channe l m o sfe t will pu ll t h e pin v o l t age l o w ev e n w i t h t h e 2k pu ll-up resist or. once t h e charge c y c l e t e rminat es, t h e n-channel mosfe t is t u rned off and a 25u a curre nt source is connect ed t o t h e chg_sb pin. the i n pin w i ll t h en be pu lle d high by t h e 2k pu ll -u p res ist or. to det ermine if t h ere is a weak pu ll- down current , t h e ou t pin s h ou l d be forc e d t o a high im pedance st ate. the weak current source will pu ll t h e i n pin l ow t h rou gh t h e 800k resist or ; if ch g_s b is high imped ance, t h e i n pin will be pu lled high, i n di c atin g th at th e p ar t i s i n a uv l o s t a t e . reverse pol arity inpu t v ol ta g e pro te ction i n some ap p l icat ions, prot ect ion from re verse po larit y vo l t age on v i n is desired. i f t h e supply vol t a ge is high enough, a series bl ock ing d i ode can be u s ed. i n ot he r cases, where t h e v o l t age drop must be k e pt l ow a p-cha nne l mo sfet can be used ( as shown in figure 6). f i g. 6. low loss input reve rse po lari t y protection b p 1 3 5 0 4 15 BP13504 BP13504 usb an d wall ada pter power the BP13504 a llows c h a r ging from bot h a wa ll adapt er and a u s b p o rt. figure 7 sho ws an exam p l e of ho w t o c o mbi n e w a l l a d a p ter a n d us b p o w e r in puts . a p - c h annel m o s f et , m p 1 , i s used to p r ev en t b a c k co n d uc ti ng int o t h e usb port when a wall adapt er is present and a schot t k y diode, d1, is used t o pre v e nt u s b power l o ss t h rough t h e 1k pull-dow n resist or . typica lly a wa ll adapt er can supp l y m o re current t h an t h e 500m a - lim it ed u s b port . therefore , an n-channe l m o sfe t, mn1, and an ext r a 10k program resist or are used t o increase t h e charge c u r r e n t to 5 8 0 ma wh en th e w a l l a d a p te r i s p r e s e n t. fig.7. combining wall adapter and usb power battery tem perature monitori ng the BP13504 cont inu ous l y monit ors batt ery t e mperat ur e by measuring t h e v o l t age bet ween t h e ts and gn d pins. the BP13504 has a n int erna l cur rent source t o provide t h e bias for t h e most common 10k o negat i v e-t emperat ure coeff ic ient t h erma l resistor ( ntc) (see figure 8). t h e BP13504 compares t h e vol t a ge on the t s pin ag ainst the i n ternal vt s_h i gh and vt s_lo w t h reshol ds t o det er mi ne i f charging i s al l o wed. w h en t h e t e m p erat ure out side t h e vts_h i gh and vts_lo w t h reshol ds is det ect e d , t h e device w i ll immediat e l y st op t h e charge. the BP13504 st ops charge and keep monit oring t h e ba tt ery t e mperature when t h e t e mperat ure s e nse input vol t age is back t o t h e t h resh old bet ween vts_hi gh and vt s_ low , t h e charger w i ll b e resumed. charge is resumed when t h e t e m p erat ure ret urns t o t h e norm al range. how ev e r t h e user may mod ify t h e t h resho lds by t h e negat i v e-t emperat ure coeff ic ie nt t h ermal res ist or. the capacit or shou l d be pl aced cl ose t o ts pin and conne ct ed t o the ground plane. the capacit ance v a lue ( 0 . 1 uf t o 10uf) shou l d be se le ct ed acco rding t o the qua lit y of p c b l ayout . f i g. 8. the b a ttery t hermal detecting circui t b p 1 3 5 0 4 16 BP13504 package outline drawing tdfn-10 (3x3 mm) sy mbpls mi n. nom. max. a 0. 70 0. 75 0.8 a1 0. 00 0. 02 0. 05 a3 0.20 ref. b 0. 18 0. 25 0. 30 d 3.00 bsc. e 3.00 bsc. d2 2. 20 - 2.70 e2 1. 40 - 1.75 e 0.50 bsc. l 0. 30 0. 40 0. 50 k 0. 20 - - u n i t : m m b p 1 3 5 0 4 17 |
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