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consonance www .consonance-elec.com rev.1.1 1 5a, multi-chemistry battery charger ic w i th photovoltaic cell mppt function CN3722 general descriptions: the cn 37 22 ( n ote 1) is a pwm switc h-m ode bat t ery char ge r contr o ll er that ca n be powere d by ph ot ovolt a ic cel l w i t h m a xim u m p ow e r poi nt tra c ki n g fu nc tio n. the cn 37 22 is speci al ly desi gne d for ch ar gin g 1 or m u lti-cel l lit hi u m ion ba tteri es or life po4 batteries with cons tan t c u rrent a nd c o nsta n t vo lta ge m ode. in constan t v o l t a g e m ode, th e regul at io n v o l t ag e is set by th e ex tern al res i stor d i v i d e r . the cons tan t c h ar gin g c u rren t is pro g ram m a ble w ith a si ngl e c u rrent s e nse re sistor . deeply disc ha rged ba tteri es are autom a tic ally trickle char ge d at 15% of t h e program m e d cons tan t c h arg i ng curre nt un til th e c ell v o lt age exce eds 66 .7 % of t h e re gu l a ti on vo lta ge . in cons tan t vol ta ge m ode, t h e c h argi ng c u rrent decre a ses gra dua lly, t h e charge cyc l e wi l l be term inate d when t h e chargi ng c u rrent drops to 9.5% of the full-scal e c u rren t , a nd a new charge cyc l e a u tom a tical ly restarts if th e bat t ery vo lt ag e falls be low 95. 8% of t h e regul at io n v o l tag e i n c ons ta nt vo lta ge m ode. cn 372 2 w i ll aut o m a tically ent e r slee p m ode when in put v o lta ge is l o wer tha n b a t t ery vol ta ge. o t her feat ures i n cl u d e un derv olt a ge loc k o u t, ba tt ery te m p erature m onitori ng an d status i ndi cat i on, et c. CN3722 is availa bl e in a space-saving 16-pin tssop packa g e. applications: ? the c h ar ger p o w e red by ph oto v o t ai c c e ll ? elec tric t o ols ? bat t ery-backup syst e m s ? s t andal o ne ba ttery char gers note 1: pa ten t pend in g featur es: ? phot ov olt a ic cell ma xim u m pow e r point t r acking ? w i de i n p u t v o lta ge: 7. 5v t o 28v ? com p lete ch ar ger c ontr o ll er for 1 or m u lti-ce ll lith ium - ion b a ttery o r lifepo4 battery ? char ge c u rre nt u p to 5a ? h i gh pwm sw itchi ng fr equ e ncy : 30 0k h z ? c o n s t a nt c h ar g i ng v o lt ag e se t b y the ext e rna l r e sistor d i vi de r ? char gin g c u rrent is program m e d with a sense resistor ? autom a tic c o n d it io ni ng o f deeply disch a rged b a tter i es ? batt ery t e m p erature moni t o ring ? 2 s ta tus i ndi c a ti ons ? soft s t art ? batt ery overvolt age prote c ti on ? operati ng am bie n t t e m p erature 40 to 85 ? a v ail a bl e i n 16 pin tssop packa g e ? pb-free , rohs com p liant, and haloge n free pin assignment: pg nd vg gn d ba t vc c cn 3722 1 2 3 4 drv 5 temp 6 mp p t 7 com1 8 9 10 11 12 13 14 15 16 chr g done com2 com3 nc fb cs p http://
consonance www .consonance-elec.com rev.1.1 2 t y pical application cir c uit: CN3722 vcc dr v csp co m 2 com1 chrg done tem p gnd pgnd mppt l r cs c6 bat bat vg com3 1 16 15 2 3 4 5 6 7 8 9 11 14 13 nc 12 fb 10 d1 d2 m1 c1 d4 c2 c3 c4 c5 r2 nt c r3 r4 r5 input power supply r7 r6 c7 r8 d3 r1 figure 1 t ypical application circuit ordering information: part no. operati ng am bie n t t e m p erature cons tant c h ar ging v o l t a g e cn 372 2 40 t o 85 set by ex tern al r e sist or di vid e r
consonance www .consonance-elec.com rev.1.1 3 pin description: pin no . na me descriptio ns 1 vg interna l v o lta ge re gul at or . vg int ernal ly supp li es powe r to g ate driv e r , co nn ec t a 10 0nf c a pa ci t o r be tw een v g pin an d v c c pi n. 2 pgnd po wer ground. 3 gnd an alog ground. 4 chrg open-drain o u tp ut . whe n t h e b a t t ery is b e in g c h ar g e d, this pi n is pu ll ed l o w by an i n t e rna l switc h. ot herwis e th is pin is in hi gh im pedan ce st ate. 5 done open-drain outp ut . wh en t h e ch ar gi ng is term inated , th is p i n is p u ll e d l o w by a n int e rna l sw itc h. o t herw ise t h is pin is in hi gh im pedance state . 6 temp batt ery t e m p erature monit o ring input. c o n n ec t an nt c resistor fro m this pin t o gnd. 7 mppt phot ov olt a ic cell ma xim u m pow e r point t r a c k i n g pin. co nne ct t h is p i n to th e ext e rnal res i st or di vid e r for m a xim u m pow er poin t tra c k in g. in m a xim u m pow er poi nt trac kin g stat us, t h e m ppt pin? s vo lt age is reg u la t e d t o 1 . 0 4 v ( 25 ) with a tem p erature c o ef fic i ent of 0.4% . 8 com1 lo op compensation input 1. connect a 470pf capacitor from this pin to gnd. 9 co m2 loop c o m p ensation i n put 2. connect a 220nf ca pac i t o r in s e ries wi t h a n 120 ? resisto r fro m th is p i n to gnd. 10 fb batt ery voltage feedback input. need to connect to the external resistor divider. 1 1 com3 lo op compensation input 3. connect an 100nf capacitor from this pin to gnd. 12 n c n o connection 13 csp positive input for char gi ng curre nt sen s ing . csp and bat pin m easure t h e vol ta ge drop a c ross th e se ns e resist or r cs to prov id e t h e current si gna l s requ ired. 14 ba t n e gat i ve i n p u t for c h arg i ng c u rren t sensi ng. ba t and csp pin m easure the vol ta ge drop a c ross th e se ns e resist or r cs to prov id e t h e current si gna l s requ ired. 15 v cc exter n al dc power supp ly inp u t. vcc is als o the p o w er sup p ly f o r i n tern al circu it. by pas s this pi n wi th a ca pa cit o r . 16 d r v d rive the gate of external p-channel mosfet. absolute maximum ratings v o ltag e fro m vcc, vg , d r v , chrg , done to gnd??.? 0. 3 v to 30v v o ltage from csp , ba t to gnd??? ????????? 0. 3v to 2 8 v v o ltage from com3 to gn d?????????????.6.5v v o ltage from other pins to gnd??? ????????... 0.3 v t o v com3 +0 . 3 v s t orage t e m p erature?? ?????????????...? 65 ---150 operating am bient t e m p erature??? ???????.?? 40 ---85 lead t e m p erature(solder ing, 10 seconds) ??????..??300 s t r e sses beyond those listed un der ?absol ut e maximum rat i n gs ? may caus e p e r m anent dama ge to the de vic e . t hes e ar e s t r e ss ratings only an d functional op eration o f the d evi ce at these o r any o t her con ditions abo ve th ose indi cat e d in the operat i onal sections of th e specifications is not im plied . exposur e to abso lute ma ximum rating conditions for extended periods may af fect devi ce r e liabil i t y .
consonance www .consonance-elec.com rev.1.1 4 electrical characteristics: vcc=15v , t a = 40 to 85 , un l e ss o t herwi s e no ted parameters symbol conditions min t y p max unit i n p u t v o l t a g e r a n g e v c c 7 . 5 2 8 v u nderv olt ag e lo ck out thresh old u v l o 4.2 6 7. 3 v operati n g cur r ent i vcc n o sw itc hin g 1 1.5 5 2. 1 m a feedbac k v o lt age v fb fb pi n,c onst a nt vo lta ge m ode 2.3 9 2 2 . 4 1 6 2. 44 v fb pin bias current i fb v fb 2.4v 5 0 3 00 na v ba t 66.7% v reg 1 90 200 21 0 current sense v o lta ge (v csp v ba t ) v cs v ba t 66.7% v reg 1 8 3 0 4 2 mv current i n to b a t pin i ba t v ba t 12v 5 10 15 ua precharge thr e shold v pre v bat rising 66.7 % recharge thr e shold v re v bat fallin g 95.8 % o v ervo lta ge t r ip le ve l v ov v ba t rising 1.0 6 1 . 0 8 1. 1 overvo lta ge clear l e v e l vclr v ba t fallin g 0.9 8 1 1.0 2 v reg (n ote 2 ) mppt pin mppt regul at ion v o lt age v mppt ma xi mum pow er po in t tra c ki ng 1 . 0 1.04 1 . 0 8 v v mppt tc tc mppt ma xi mum pow er po in t tra c ki ng 0. 4 % mppt pin bias current i mppt 10 0 0 1 00 na temp pin pull up curre nt i up 41 5 0 65 ua h i gh thresh ol d v t hh temp v o l t ag e ris i n g 1.5 7 1. 6 1 1. 65 v low thres h o l d v t hl temp v o l t ag e fall in g 0.1 4 5 0 . 1 7 5 0.2 05 v chrg pin chrg pin sink current i chrg v chrg =1v , ch arge m ode 7 1 2 18 m a chrg leaka g e c u rrent i lk1 v chrg =25v ,te r m i natio n m o de 1 ua done pin done sink c u rrent i don e v done =1v , term inatio n m o de 7 1 2 18 m a done leaka g e c u rrent i lk2 v done =25v , charge m ode 1 ua oscillator sw itchi ng freque ncy f osc 24 0 30 0 3 60 kh z maxim u m du ty cycle dm ax 94 % sleep mode v bat =8v 0.0 6 0. 1 0. 14 v bat =12v 0.1 0.1 4 0. 18 sleep mode t h resho l d (m easure vcc v bat ) v slp v cc f a lling v bat =18v 0.1 8 0. 2 3 0. 28 v v bat =8v 0.2 6 0. 3 2 0. 39 v bat =12v 0.3 2 0. 4 2 0. 52 sleep mode rele ase thresh old (m easure vcc v bat ) v slpr vcc rising, v bat =18v 0.3 8 0. 4 7 0. 58 v
consonance www .consonance-elec.com r e v . 1 . 1 5 electrical characteristics: (cont in ue d from last pa ge) parameters symbol conditions min t y p max unit drv pin v drv high (vcc v drv ) vh i drv 10ma 60 m v v dr v low (vc c v dr v ) vl i dr v 0 m a 5 6 . 5 8 v rise time t r cload 2nf, 10% to 90% 30 4 0 65 ns fall time t f cload 2nf, 90% to 10% 30 4 0 65 ns no te 2 : v reg i s the reg u la ti o n v o l t ag e a t b a t pi n in co ns tan t v o l t ag e m ode detailed description: the cn 37 22 i s a c onst a n t c u rrent, c onst a nt vo lta ge ba tt ery charg e r co ntrol l er tha t c a n b e p o w e red by the ph oto v o lta ic c ell w i th m axi m u m pow er poin t tra ck i n g f unc ti on, th e d evi ce is spe cia lly des i g n ed for 1 or m u lti-cel l li-i on bat t ery or lifepo4 ba tt eries. t h e ch a r ge c u rrent is set by a n ext e rnal s e nse resis t or (r cs ) across t h e csp and ba t p i ns. t h e fi nal b a ttery reg u l a ti on vo lta ge v reg in c onst a n t vol ta ge m ode is set by t h e ext e rnal resist or di vi der. a charge cycle begins when the fol l owi n g 3 c o ndi tions are m e t: (1) the vo lta ge at vcc p i n ris e s abo v e th e u v lo leve l (2) the volta ge at vcc pin is gr eater th an th e bat t ery vo lt ag e by sle e p m ode re lease t h re shol d v slpr (3) the vo lta ge at v cc p i n is n o less th an th e m axim u m pow er poi nt vo lt age s et by th e external resist ors a t the b e gi nn i ng of t h e char ge cy c l e, if t h e ba tt ery vol ta ge is less th an 66. 7% v reg , the c h arger goes i n t o trickle char ge m ode. the tri c kl e c h arge c u rrent is intern a lly set to 15% ( typical) of t h e ful l -scal e c u rrent. w h en the ba ttery vol t age e x ce eds 66.7% v reg , the charger goes into the full -scale consta nt curre nt charge m ode. i n cons tan t c u rre nt m ode, t h e c h arge curre nt i s set by the e x terna l se nse re sistor r cs an d a n in te rn al 200 m v reference, so the charge c u rrent eq ua ls t o 2 00m v / r cs . when th e bat t er y vol tag e a ppr oac h es the reg u la tio n vol ta ge, th e c h arger go es i n to c ons ta nt vo lta ge m ode, a nd the c h arge current w i l l st art t o d ecreas e . in c ons tan t vol ta ge m ode, the c h arge cy cle wi ll be ter m inated once th e charge cur r ent decre a ses to 9. 5% of the ful l -scal e current . duri ng th e char ge t e rm ination st a t us, the drv pin is pu lle d u p t o vcc, an d an in terna l c o m p arator t u rn s off the i n tern a l p u ll- down n-chan ne l mo sfet at t h e p i n, an ot h e r i n t e rn al pu ll -d own n-ch ann e l mosfet at t h e pi n i s tu rn e d on to in dic a t e th e te r m i n a t i o n st at u s . to rest art t h e charge cyc l e, j u st rem ove and rea p ply the i n put volta ge. also, a new c h arge cycl e wi ll aut o m a tically beg i n if t h e ba ttery v o lt ag e d r ops b e l o w th e rech arge thr e sho l d vo lta ge of 9 5 .8 % v reg . when th e i n p u t vo lta ge is n o t presen t, th e char ger g o es int o sl eep m o de. a 10k ? ntc (nega t i v e tem p erat ure c o eff i cie n t) therm i stor c a n be co n n ec ted fro m th e temp pi n t o gro u n d for bat t ery tem p erature qual ifica tion. t h e charge cyc l e is sus p ende d if the bat t ery ? s tem p erature is outs i de of t h e acce pt abl e ra nge. an overvolt age com p arat or guar d s a g ai nst vo lta ge trans i ent ov ersho o ts (>8% of regulati o n vol t age). in t h is case , p-channel m o sfet are turned off unti l t h e over v o ltag e co nd it io n is cleare d . this feat ure is useful for batt ery loa d d u m p or sudd en r e m oval of ba ttery . the char gi ng profil e is s h o w n in fig u re 2.
consonance www .consonance-elec.com rev.1.1 6 p r ech ar g e ph a s e c ons t a nt c ur r e nt ph a s e c o n s ta n t v o lta g e ph a s e c h ar g e c u r r en t b a tt e r y v o lta g e 66 . 7% *v re g v reg c h a r g e t e r m in a tio n figure 2 the char ging profile application information u ndervolta ge lock out (u vlo) a n un derv ol ta ge l o c k o u t cir c ui t m onitors t h e i n p u t v o lt a g e a n d k eeps t h e c h arg e r off if v cc fal l s bel o w 6v(typical). set the regulation voltage in constant voltage mod e a s show n i n f i gure 1, b a tt ery vol tag e is f e edb ack t o fb pin v i a t h e res i stor di vid e r c o m posed of r 6 a nd r7. cn 372 2 dec i d ed t h e ch ar gi n g sta t us base d on fb? s v o l t a g e. w h e n fb? s vo lta ge ap proac h es 2.4 16v , th e c h ar ger goes in to co ns tan t v o l t ag e m ode. in co nsta nt vo ltage m ode, th e c h ar g e current d ecrea se gra dually , a nd the b att ery vol ta ge rem ains u n ch an ge d. in li gh t of fb pin?s bias curr ent, t h e re gu la tio n vol ta ge in co nsta nt vo ltage m ode is det erm ined by th e fol l ow i ng equ a ti on : v ba t 2.4 1 6 ( 1 r7 r6 ) i b r7 where, i b is f b pi n?s b i as c u rrent, w h i c h is 5 0na typ i ca l. fro m the above equa ti on, we can see that a n error is introduc ed due t o t h e e x is tence of bias current i b , the error is i b r7. if r7 5 00k ? , the n t h e error is ab ou t 25m v . so t h e error shou ld be ta ke n i n t o ac co un t w h ile desi gn in g t h e resistor div i d e r . th e reg u l a ti on vo lt age range t h at can be set i s fro m 3 v t o 25 v. the maximu m power point tracking cn 372 2 ad op ts th e c ons tan t vo lta ge m e th od to trac k th e ph ot ov olt a ic cell?s m a xim u m pow er poi nt . fro m i-v curve of ph ot o vol taic c ell , u nder a g i v en t e m p erature, th e p hot ov ol taic cel l?s v o lt age s at t h e m axim u m pow er poi nt are nearl y const a n t reg a rdless of t h e differen t irra d i an ces. so t h e m a xim u m pow er poi nt ca n be tr ack ed if the ph ot ov ol ta ic c e ll?s ou tp u t v o lt ag e is re gul ate d to a c onst a n t v o l t ag e. b u t the m a x i m u m pow er poin t vol ta ge has a tem p erature c o effic i ent of a b out 0. 4% . at 2 5 , cn37 22 ?s m ppt pin ? s vo lt age i s reg u l a ted to 1.04v wi th a t e m p erature c o e fficient of 0.4% to track the m a ximu m power point work ing with the off-chip resistor divider(r3 and r8 in figure 1). at 2 5 , th e m a xim u m pow er poi nt vo lt age is d eci de d by th e fo llow ing eq ua ti on: v mppt 1. 0 4 ( 1 r8 r3 )
consonance www .consonance-elec.com rev.1.1 7 CN3722 pow ered b y b o th ac adaptor and photov ol taic ce ll bot h a c a d a p tor a nd ph ot ov olt a ic ce ll can be used to p o w er cn 372 2. the char ge c u rrent c a n be s e t bas e d on ac ada p t o r?s capa b i l i t y whi c h is ge nera lly larg er th an th at of ph ot ov ol taic ce ll. whe n p h o t o v o lta ic cel l is use d , cn 372 2 can a u tom a tical ly a d jus t t h e ch arge c u rren t t o t h e ph oto v o l t a i c ce ll?s m a xim u m pow er poin t c u rren t . it shou ld be n o te d t h at a c a d a p tor?s o u t p u t vol ta ge s h o u l d b e n o l e ss t h an t h e p hot ov olt a ic ce ll?s m ppt volt a g e . trickl e c h ar ge mode at the begi nni ng of a char ge cycle, if t h e battery vol t a g e is be low 66. 7% v reg , the char ger g o es int o tr ick l e charge m ode with the charge curre nt re duced to 15% of the f u ll-sc ale current . charge current setting the fu ll-sca l e charg e c u rrent , nam e ly the c h arge curre nt i n c onst a n t c u rrent m ode, is dec i de d by th e foll ow in g for m ula: where: i ch is the full sc ale char ge cur r ent r cs is t h e resist or be tw een t h e csp pi n a n d ba t pi n c h arge term ination in co nsta nt v o lta ge m ode, t h e ch arge cy cle will be term i n at ed on ce the char ge curren t de creases to 9.5% of the full-sca l e curr ent. automatic b a ttery recharge after the charge cy c l e is c o m p leted and b o th t h e bat t ery an d t h e in pu t pow er su pp ly (wall a d ap ter) are sti ll con n ec te d, a new c h arge cy cle w i ll be gi n if th e b a tt ery vol ta ge drops bel o w 9 5 .8 % v reg due to self-disc h arg e or ex tern al loa d in g. this wil l ke ep th e bat t e ry capa c ity a t m o re tha n 9 0 % at al l t i m e s witho u t m a nu ally rest arti ng the charge cyc l e. battery tem p erature monitoring a neg a ti ve te m p erature c o e fficien t (n tc) therm i stor loc a te d c l ose to t h e bat t ery pa c k ca n be used to m onitor bat t ery tem p erature an d w i l l not al low c h ar gin g un less t h e batt ery tem p erature is wit h in an acc ept a ble ra nge . co nn ect a 10 k ? therm i stor fro m the tem p pin to gro u n d . in tern ally , f o r ho t tem p erature, th e l o w v o lt age thresh ol d is se t at 1 75m v whic h is eq ua l t o 5 0 (r ntc 3.5 k ? ). for col d tem p erature, t h e hi gh volt age thresh ol d is se t at 1. 61v w h i ch is eq ua l t o 0 (r ntc 32k ? ) w i t h 50 ua of p u l l -up current . once t h e tem p erature is outs i de the wind ow, the charge cycle wi ll be s u spe n ded, and the c h arge cy cle resu m e s if the tem p eratur e is bac k t o the ac cepta ble range. the te mp p i n?s pu ll up cur r ent is a b o u t 5 0ua, s o t h e n t c t h erm i stor?s resistance s h ould be 10k ? at 25 , abo u t 3. 5k ? a t hot tem p erature t h reshol d, and about 32k ? at c o l d tem p erat ure t h res hol d. the ntc therm i stor su ch as th11 -3 h1 03 f, m f 52 (1 0 k ? ), q w x - 103 a n d n c p18x h 1 0 3 f03r b ca n w o r k w ell w i t h c n 372 2. t h e above m e ntioned par t num b ers are for ref e renc e only, t h e users ca n s e lec t t h e r i ght ntc therm i stor part num b e r base d o n t h e i r requ irem ents. if batt ery tem p erature m onitorin g fu nc ti on is not nee d e d , j u st connect a 10k ? resisto r fro m temp p i n to gnd. status indication the cn 37 22 has 2 o p e n -dr ain s t at us ou tp uts: and . is p u ll ed low when the c h ar ger is in charging st at us, ot herwise bec o m e s high im pedan ce. is pull ed low i f the charger i s in char ge term inati o n st atus, o t herwis e bec o m e s high impedance. when the batt ery is not pr esent, t h e char ger char ges th e out pu t c a p aci t o r to t h e re gu l a ti on vo lta ge qui ck ly , th en the ba t p i n?s vo lta ge de cay s slow ly t o rec h arge t h resho l d b eca use of l o w lea k a g e cu rrent a t ba t pin , w h i c h results in a ri p p le wa veform at bat pi n, in the m eanti m e , p i n ou tp ut s a pu l s e to in di c a t e th at th e
consonance www .consonance-elec.com rev.1.1 8 bat t ery?s abse nce. the op en drai n sta t us ou tp ut tha t is n o t use d sh ou ld be ti ed t o grou nd . the tab l e 1 lis ts th e tw o i n d i cat or sta t us a n d i t s c o rrespo ndi ng char g i n g sta t us. it is sup pose d t h a t r e d led is connec te d t o pi n a n d gre e n led is co nn ecte d to pin. pin pin state description low(the red led on) high impedance(the green led off ) charging high impedance(the red led off) low(th e green led on) charge termination pulse signal pulse signal battery not connected high im pedance(the red led off) h i gh im pedan ce(th e gre e n le d o f f ) there are t h re e possible s t at e: ? the volt age at the v cc pi n b e lo w the uvlo level o r ? the volt age at the v cc pi n bel o w v bat ,or ? abnorm al ba tt ery?s te m p table 1 indication status gate drive the cn 37 22? s gat e dr iver c an prov id e h i g h tra n sie n t cur r en ts t o drive t h e e x t e rna l pa ss transis t or. the ris e a nd fall tim es are t y pical ly 40ns when dr iv in g a 20 00 p f lo ad, wh ich i s t ypical fo r a p-chan n e l m o sfet wi th rd s(on ) in the ran g e of 50m ? . a vol tage c l a m p is ad ded t o l i m it th e g at e dri v e to 8v m ax. bel o w v cc. for exam ple, if v c c is 20v , the n t h e d r v pin ou tp ut w i ll be pu ll ed dow n to 1 2 v m i n. this al low s l o w vo lt age p-c h an ne l mo sfets w ith s uperi or rds(on) to be used as t h e pa ss tran sis t or t h us i n creas ing efficie n cy. loop c o mpe n sation in ord er to m a ke sur e t h at t h e curre nt lo op and th e vol ta g e lo op are s t ab le, the fol l ow i ng com p ensati on com ponents a r e nec e ssary : (1 )a 4 7 0 p f cap a cito r fro m th e com1 p i n to gnd (2)a series 220nf c e ram i c capac it or a nd 120 ? res i stor f r o m the com2 pin to gnd (3 )an 1 0 0 n f ceram ic cap acito r fro m th e com3 p i n to gnd (4)the c ap acit ance c 7 i n fi gure 1 c an be roug hly c alc ul ate d by ? c7 8 h (r6 ? r7) (pf) battery dete ction cn 372 2 do es not pro v i d e ba ttery de tec t i o n func ti on, w h e n t h e bat t ery i s no t pres ent , t h e c h arg e r c h a r ges t h e out pu t c ap aci t o r to t h e re gu l ati on vo lta ge qui ck ly , th en t h e ba t pi n?s vol ta ge dec ay s slow ly t o rec h arge thresh ol d b eca use of low lea k ag e c u rrent a t ba t p i n , w h ich r e sul t s i n a ripp le w a vefo rm at ba t pi n, i n the m eantim e, p i n ou tp uts a p u lse to in di cat e that the batt ery?s absenc e. it is g e n e rally not a go od pra c tic e t o c o n n e c t a ba ttery w h il e t h e char g e r is ru nni ng . the char ger m a y prov id e a large surge current in to th e b a tt e r y fo r a bri e f t i m e . input and ou tput capacitors since th e i n p u t ca pac i t o r is a ssu m e d to abs o rb a ll in pu t s w itch i n g rip p l e curre nt, it m u st hav e a n a d equ a te rip p le current rat i ng. worst-case r m s ripple cur r ent is a ppro x i m ately one- h a l f of o u t p u t c h arge c u rren t . the se lec t i on of ou tp ut ca pa cit o r is prim arily de term ined by th e esr re quire d to m i nim i ze ripp le vo lta ge an d loa d st ep trans i ents. general l y speaking, a 10 uf ceram ic capa c i t or c a n be used . inductor selection d u ring p-c h a nne l mo sfet?s on tim e, the i n d u c t or c u rrent i n cre a ses , an d decre a se s duri n g p-cha nne l mosfet?s off tim e, the inductor?s ri pp le current i n crea ses w ith low er in duc ta nce an d h i g h er i n p u t vo lta ge.
consonance www .consonance-elec.com rev.1.1 9 h i gher in du ct or rip p le curre nt res u lts in h i gher char ge c u rrent r i p p le a nd grea ter c o re loss es. so th e in du ct or?s rippl e c u rren t shou ld be lim ited w i th in a re ason abl e ra ng e. the in duc tor? s ripp le curren t is gi ven by t h e fo ll ow in g f o rm ula: where, f i s the switc hi ng frequency 300khz l i s t h e i n d u c t o r v a l u e v bat is th e ba t t e ry vol tage v c c i s t h e i n p u t v o l t a g e a reasona bl e starti ng po in t for sett in g i n d u ct or rip p l e c u rrent is i l 0.4 i ch , i ch is the c h arge current. r e me mb e r t h a t t h e ma x i mu m i l occur s at t h e m a xi m u m input vo lta ge an d th e l o w e st i n d u c t o r val u e. so lower charge current generally ca lls for la rger in du ct or val u e. use tabl e 2 a s a gui d e for s e lec t i ng the c o rr ect i n duct or val u e f o r your appli cat ion. charge current input voltage inductor value >20v 40uh 1a <20v 30uh >20v 30uh 2a <20v 20uh >20v 20uh 3a <20v 15uh >20v 15uh 4a <20v 10uh >20v 10uh 5a <20v 8uh table 2 guide to select inductor value mosfet selection the cn 37 22 uses a p-c h a n nel pow er mo sfet sw itch. the mosfet m u st be se le c t ed to m eet t h e effici ency or pow er dissi pat i o n req u ire m ents of t h e c h argi ng circ ui t as wel l as the m a xim u m tem p erature of t h e mosfet. the pea k -to- p eak ga te driv e vo lta ge is se t int erna lly , t h is vo lta ge is ty p i cal ly 6. 5v. c onse q u ent ly , l ogi c-le vel thresh ol d mo sfets m u st be use d . pay c l ose a tte nt io n t o t h e bv dss spec ifica t i on f o r the mosfet as wel l; m a ny of the lo gic le vel mo sfets are lim ited t o 30v or l e ss. select ion cr ite ria for t h e power mosfet incl udes the ? on? resistance rds(on ), total gate charge q g , reverse t r a n sfe r ca p aci t a n c e c rss , i n put v o lt ag e a n d m a xim u m charge curre nt. the mo sfet pow er dissi pa tio n a t m a xim u m out put c u rrent is a pproxi m ated by t h e equati on : where: pd is the pow er dissi pat i o n of th e p o w e r mo sfet v b a t is t h e m a xim u m batt ery vol tag e v cc i s the m i nim u m input v o lt ag e r d s(o n ) is t h e pow e r mo sfet?s on res i sta n ce at ro om tem p erature ic h i s t h e ch a r g e curre n t dt is t h e t e m p erature differe nce between ac tual a m bient tem p eratur e and roo m te m p erature(25 ) in ad di tio n to the i 2 r d s(on) loss, the p o we r mosfet still has tra n si tio n l o ss, whi c h are h i g h est at the hi gh est
consonance www .consonance-elec.com rev.1.1 10 inp u t v o lt age . g e neral l y spe a ki ng, for v i n 20v , t h e i 2 rds( on) l o ss m a y be dom inant, so th e m o sfet with lower rds(on) should be selected for better efficiency; f o r vin 20v , the tra n sit i o n loss m a y be do m i nant , so the mosfet with lower c rs s ca n pr ovide bet t er effi cie n cy. c rss is us ual l y spec ifie d i n t h e mosfet chara c teris tics ; if n o t , t h e n c rss ca n be cal cul a te d usin g c rss = q gd / v ds . the mo sfets such as a o 4 45 9, stm 9 4 3 5 (or wt9 4 3 5 ), a o 3407a ca n be us ed. the part num bers liste d a b o v e are for refere nce only, the us ers can sel ect the r i g h t mosfet base d o n the i r req u irem ents. diode sele cti o n the di odes d 1 a nd d 2 i n fi gure 1 are sch o tt ky di od e, th e curre nt ra ti n g of the d i o d e s sho u ld b e at least th e charge c u rrent lim it, the volt age ra ti ng of t h e diode shoul d e x ce ed the m a xi m u m expecte d input volta ge. the di ode t h at is m u ch larg e r tha n t h a t is s u fficie n t ca n r e sult i n l a rger transi tion loss es du e t o the i r larg er jun c ti on ca pa c ita nce . disa ble cha r g i ng with temp pin the char gin g can be dis a bl e d w i t h te mp pin , as s how n in fi gure 3 ntc CN3722 m1 no te m 1 is n-channel mo sfet control signal te m p gn d figure 3 disable charging with temp pin when co ntro l sign al is h i g h , n - chan nel m o sfet m1 is turn ed on , t h e vo lta ge at te mp pi n is p u ll ed dow n to gnd, which will disable the charging; when co ntro l sign al is l o w, n-chan nel m o sfet is turn ed off, th e vol tag e a t temp pin is det e rm ined by ntc therm i stor, w h ich perform s norm a l bat t ery tem p erature m oni tori ng fun c tio n. about battery current in sleep mode in th e ty p i ca l app lic at io n cir c ui t sh own in figure 1, w h e n i n p u t vo lta g e is powere d o ff or lower t h a n b a tt ery vol ta ge, cn 37 22 w i ll en te r sleep m ode. in slee p m ode, th e b a t t ery c u rrent in cl ude s: (1) the curren t i n to ba t pi n a n d csp p i n, w h ich is a b o u t 1 0ua (v bat 12v ). (2) the curren t fro m batt ery to v cc pi n via d i od e d 1 , w h ic h is de term ine d by d 1 ?s l e a k ag e c u rrent . the curren t w ill ch arge ca pa cita nc e c 1 a t vcc pi n, wh i c h wil l m a ke vcc vo lt age a bi t hig h er. t o a voi d erratic operati on, a resist or i n parall el with c1 can be ne ede d t o disc ha rge t h e capaci t a nce , t h e r e sis t or val u e is de term ined by di ode d 1 ?s lea k a g e, ge ne rally spe a k i n g , a 20k ? resis t or c a n achie ve the t a sk. (3) th e cu rrent fro m b a ttery to gnd v i a d i o d e d2 , which is also d e term in ed b y d2 ?s leak age cu rren t . pcb layout considerati ons when lay i ng out t h e prin ted circ uit b o ard, the f o ll ow in g cons ider ati ons sho u l d b e t a k e n t o ensur e p r oper opera ti on of t h e ic. (1) to m i nim i ze radi ati o n , t h e 2 di odes , p a ss t r ansist or, i n d u c tor an d t h e in put by pass ca pac itor trac es shou ld be kep t as s hort a s possi bl e. t h e p o sit i ve si de of t h e in put c a pac i t o r sh ou l d b e c l ose to t h e so urce of t h e p-channel m o sfet; it pr ovides t h e ac current t o t h e pass tra n sist or . the c o n n ec ti on betwe e n the ca tch
consonance www .consonance-elec.com rev.1.1 11 dio d e an d t h e pass tra n sist or should also be kept as short as possible. (2) the com p ensation c a paci tor connec te d a t t h e com 1 , c o m2 a nd co m3 pi ns sh oul d ret u rn to th e ana l o g grou nd pi n of the ic . t h is w ill prev en t gr o u n d n o ise fro m disrupti n g t h e l o o p s t ab ili ty . (3) since mppt pin?s vol t age is a funct i on of a m bient tem p erature , w h i l e desi gn in g t h e pcb, cn 3 7 2 2 sho u l d be kep t aw ay fro m the he at source suc h as di odes , mo s f et, etc . (4) o u tp ut c a p aci tor gr ou nd co nne cti ons ne e d t o fee d i n t o sa m e copper t h at connects t o t h e input ca pac itor grou nd bef o re ty in g b ack i n t o sy stem ground. (5) a n alo g grou n d a nd pow er g r ound(or sw it chi ng grou n d ) sho u l d ret u rn to sy stem groun d sep a rat e ly . (6) the grou nd p i ns als o w o rks as a hea t si nk, ther efore use a ge nero us amou nt of co pp er arou nd the grou nd pins . th is is e s peci al ly im p o rtan t for hi gh v cc a nd/ or hig h gat e c apa cita nc e a p p lic ati ons. (7) place the c h ar ge c u rrent se nse resist or r cs righ t nex t t o t h e i n d u c t or ou tpu t but ori e nt ed su ch th at th e ic?s csp and bat traces going t o r cs are not l o ng. t h e 2 tra ces need t o b e rout ed to ge th er as a s i n g le pair on th e sa m e layer at any gi ve n t i m e with sm allest trac e spaci ng possi bl e. (8) the csp a n d ba t pins sh o u ld be c o n n ec t e d direc tly t o t h e c u rren t se n s e resist or (k elvi n se nsi ng) f o r bes t charge c u rrent accuracy. see figure 4 as an e x am ple. figure 4 kelvin sensing of char ge current
consonance www .consonance-elec.com rev.1.1 12 package information cons on an ce d o es n o t assu m e any resp o n sib ili ty for u s e of a n y c i rc uitry d e scri be d. c ons on anc e reserv es t h e righ t t o c h a n g e th e c i rcu itry an d sp eci fi cat i ons wi th out n o ti ce at an y t i m e.

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