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r1224n series pwm/vfm step-down dc/dc converter no.ea-0 96-0 6 1 1 02 outline the r1 224 n serie s are cmos-b ase d pwm step -d o w n dc /dc converte r co ntrolle rs with lo w su pply cu rrent. each of the s e ics con s ist s of an oscillato r , a pwm con t rol circuit, a referen c e volt age unit, an e rro r amplifie r , a pha se comp e n satio n ci rcuit, a sof t -st a rt circuit, a p r ote c tion circuit, a pwm/vfm a l ternative ci rcuit, a chip en able circuit, re sisto r s for o u tput volt age d e tect, and input vol t age dete c t ci rcuit. a low ri pple, high ef fi cien cy step -d own dc/ dc co nve r ter can be e a s ily com p o s e d of this ic wi th onl y seve ral external co mpone nt s, o r a po wer-tra n sistor , an ind u cto r , a diode an d ca p a citors. out put v o lt ag e i s fix ed or ca n be adj uste d with external re sisto r s (adj ust able types are without pwm/v f m alternativ e circuit). with a p w m/ vfm altern ative circuit, wh en the lo ad current is sm al l, the ope rati on is autom atically switchin g into the vfm oscillator from pwm oscill ator . therefore, the ef ficiency at sm all load current is i m proved. several types of the r1224nxxx, whi c h are wit hout a pwm/ vfm alternati v e circuit, are also available. if the term of maximum duty cycle ke ep s on a ce rt ai n time, the embed ded prote c tion circuit wo rks. t he prote c tion ci rcuit is re set-type protectio n circuit, and it works to re st a r t the operati on with sof t -st a rt and re peat this op eratio n until maximu m duty cycl e con d ition i s re leas ed. when the ca use of l a rge load current or som e th ing else i s rem o ved, the opera t ion is autom atica lly rele ased and return s to norm a l o peratio n. furthe r , built-in uvlo fun c tion wo rks when the inp u t volt age is e q ual or le ss than uvl o thresh old, it make s this ic be st a ndby and sup p re sses the consum ption current and av oid an un st a b l e operation. features ? supply current ................................................................ t y p. 20 a (r1224 nxx2e/f/m/l, r1224 n10 2 m) t y p. 30 a (r1224 nxx2g , r12 2 4 n 102 g ) t y p. 40 a (r1224 nxx2h, r12 2 4 n 102 h) ? s t andby current .............................................................. t y p. 0 a ? input v o lt age rang e ....................................................... 2.3v ~18.5v ? output v o lt age ra nge ..................................................... 1.2v to 6. 0v (r1224nxx2x) 1.0v to v in (r1224 n1 02x) ? output v o lt age ac curac y ................................................. 2.0% ? oscillator f r e quency ....................................................... t y p. 180khz (r1224nxx2 m, r1224n102m) t y p. 300khz (r1 224 nxx2 e/g , r1224 n102g ) t y p. 500khz (r1 224 nxx2 f/h, r12 24n102 h) ? ef fic i enc y ......................................................................... t y p. 90% ? low t e mperature-drif t coef fic i ent of output v o lt age...... t y p. 100 pp m/c ? pac k age .......................................................................... sot - 23-5 ? built-in sof t -st a rt func tion ............................................... t y p. 10ms ? built-in cu rr e n t limit circ ui t applications ? powe r sou r ce for hand-h e ld comm uni cation eq uip m ent, came ras, video instrum ent s su ch as vcrs, cam c o r de rs. ? powe r so urce for battery-p owe r ed e quip m ent. ? powe r so urce for hou sehol d electri c al a pplian c e s . 1
r1224n block diagram *fixed ou tp ut v o lt age t y pe os c am p vr e f vr e f v ou t ce v in ex t gnd pw m/ v f m cont rol s o ft s t a r t p r ot ect i on chi p e nabl e uv lo 5 4 2 1 3 *adjust a ble outpu t v o lt a g e t y pe os c am p vr e f vr e f v fb ce v in ex t gnd s o ft s t a r t p r ot ect i on chi p e nabl e uv lo 5 4 2 1 3 2 r1224 n selection guide in the r122 4 n seri es, th e output volt ag e, the o scill ator freque ncy , the option a l f unctio n , and the t api ng typ e for the ics can b e sele cted at the use r ' s req uest. the sel e ctio n can be ma de with desi gnat ing the p a rt numbe r as sho w n bel ow; r 1 2 2 4 n x x 2 x - x x - x part number a b c d e f c o d e c o n t en t s a de sign ation o f packa ge type; n: sot-2 3 -5 b setting outpu t voltage (v out ): stepwise sett ing with a ste p of 0.1v in the ran ge of 1 . 2v to 6.0v is possible. adjustabl e type; a = 10 m e a n s refere nce voltage = 1.0 v optional fu nction i s g/h/ m. c 2 : f i x e d d de sign ation o f optional fu nction e : 300khz, with a pwm/ vfm alternati v e circuit f : 500khz, with a pwm/vfm alternativ e circuit g : 300khz, without a pwm/vfm altern ative circuit h : 500khz, without a pwm/vfm altern ative circuit l : 180khz, with a pwm/vfm alternativ e circuit m :180khz, without a pwm / vfm alternat ive circuit e de sign ation o f taping type ; (refe r to tapi ng specifi c ati on)"t r" is prescrib ed a s a standa rd. f de sign ation o f compo s ition of pin plating -f: lead free plating 3 r1224n pin configuratio ? 12 3 4 5 ( m ar k s i de) pin description pin no sy mbol pin descrip tion 1 ce chip ena b le pin (?h ? activ e ) 2 g n d grou n d p i n 3 v out (v fb ) pin for monitoring o u tput v o lt age (fee dba ck v o lt ag e) 4 ext external t r an sisto r drive pin (cm o s ou tput) 5 v in powe r suppl y pin absolute maximum rating s sy m b o l i t e m ratin g u n i t v in v in supply voltage 20 v v ex t ext pin output v o lt age ? 0.3 to v in + 0. 3 v v ce ce pin input v o lt age ? 0.3 to v in + 0. 3 v v out v out /v fb pin input v o lt ag e ? 0.3 to v in + 0. 3 v i ex t ext pin inductor drive ou tput current 50 a p d powe r di ssi p a tion (sot -2 3-5 ) * 420 mw t o p t o p e r a t i n g t e m p e r a t u r e ra n g e ? 40 to + 85 c t s t g s t orage t e m peratu r e ran g e ? 55 to + 12 5 c * ) for po we r dissip ation, p l ease refe r to package informatio n to be describ ed. 4 r1224 n electrical characteristics ? topt=25 c sy m b o l i t e m conditio n s m i n . t y p . max. unit v in operating inp u t v o lt age 2 . 3 18.5 v v out s t ep-do wn o u tput v o lt age v in = v ce = v se t + 1.5v , i out =? 100ma whe n v se t < = 1.5v , v in = v ce = 3.0v v set 0.98 v set v set 1.02 v ? v out / ? t opt s t ep-do wn o u tput v o lt age t e mperature coef fici ent ? 40 c < = t opt < = 85 c 100 p p m / c f o s c o s c i l l a t o r f r e quen c y v in = v ce = v se t + 1.5v , i out =? 100ma whe n v se t < = 1.5, v in = v ce = 3.0 v l/m v e rsi o n e/g v e r s ion f/h v e rsion 144 240 400 180 300 500 216 360 600 kh z ? f o sc/ ? t opt oscillator f r e quen cy t e mperature coef fici ent ? 40 c < = t opt < = 85 c 0.2 % / c i dd1 supply cu rre nt 1 v in = v ce = v ou t = 18.5v e/f/l/m v e rsi on g versi on h versi on 20 30 40 50 60 80 a ist and b y s t andby cu r r e n t v in = 18.5v , v ce = 0v , v out = 0v 0 . 0 0 . 5 a i ex t h ext ?h? o u tp ut current v in = 8v , v ex t = 7.9v , v out = 8v , v ce = 8v ? 17 ? 10 ma i ex t l ext ?l? outp ut current v in = 8v , v ex t = 0.1v , v out = 0v , v ce = 8v 2 0 3 0 m a i ce h ce ?h? input curre n t v in = v ce = v ou t = 18.5v 0 . 0 0 . 5 a i ce l ce ?l? input current v in = v out = 18. 5v , v ce = 0v ? 0.5 0 . 0 a v ce h ce ?h? input v o lt age v in = 8v , v out = 0v 1 . 5 v v ce l ce ?l? in put v o lt age v in = 8v , v out = 0v 0 . 3 v maxd ty oscillator m a ximum duty cy cle 1 0 0 % vfmd ty vfm duty cyc l e e/f/l v e rs ion 35 % v uv l o 1 u v l o v o lt ag e v in = v ce = 2.5v to 1.5v , v out = 0v 1 . 8 2 . 0 2 . 2 v v uv l o 2 u v l o relea s e v o lt a g e v in = v ce = 1.5v to 2.5v , v out = 0v v uv l o 1 + 0.1 2 . 3 v ts ta r t d e l a y t i m e b y s o ft - s ta r t f u n c t i o n v in = v se t + 1.5 v , i out =? 10m a v ce = 0v v set + 1.5v 5 1 0 2 0 m s tprot delay t i me for protec tion c i rc uit v in = v ce = v se t + 1.5v v out = v set + 1.5v 0v 5 1 5 3 0 m s 5 r1224n ? topt=25 c sy m b o l i t e m conditio n s m i n . t y p . max. unit v in operating inp u t v o lt age 2 . 3 18.5 v v fb f e e d b ack v o l t a g e v in = v ce = 3.5v , i fb =? 10 0ma 0 . 9 8 1 . 0 0 1.02 v ? v fb / ? t opt feedb ack v o l t age t e mperature coef fici ent ? 40 c < = t opt < = 85 c 100 p p m / c f o s c o s c i l l a t o r f r e quen c y v in = v ce = 3.5v , i fb =? 10 0ma m v e rsi on g v e rsion h v e rsion 144 240 400 180 300 500 216 360 600 kh z ? f o sc/ ? t opt oscillator f r e quen cy t e mperature coef fici ent ? 40 c < = t opt < = 85 c 0.2 % / c i dd1 supply cu rre nt 1 v in = v ce = v fb = 18.5v m v e rsi on g v e rsion h v e rsion 20 30 40 50 60 80 a ist and b y s t andby cu r r e n t v in = 18.5v , v ce = 0v , v fb = 0v 0 . 0 0 . 5 a i ex t h ext ?h? o u tp ut current v in = 8v , v ex t = 7.9v , v fb = 8v , v ce = 8v ? 17 ? 10 ma i ex t l ext ?l? outp ut current v in = 8v , v ex t = 0.1v , v fb = 0v , v ce = 8v 2 0 3 0 m a i ce h ce ?h? input curre n t v in = v ce = v fb = 18.5v 0 . 0 0 . 5 a i ce l ce ?l? input current v in = v fb = 18.5v , v ce = 0v ? 0.5 0 . 0 a v ce h ce ?h? input v o lt age v in = 8v , v fb = 0v 1 . 5 v v ce l ce ?l? in put v o lt age v in = 8v , v fb = 0v 0 . 3 v maxd ty oscillator m a ximum duty cycle 100 % v uv l o 1 u v l o v o lt ag e v in = v ce = 2.5v to 1.5v , v fb = 0v 1 . 8 2 . 0 2 . 2 v v uv l o 2 u v l o relea s e v o lt a g e v in = v ce = 1.5v to 2.5v , v fb = 0v v u v lo1 + 0.1 2 . 3 v ts ta r t d e l a y t i m e b y s o ft - s ta r t f u n c t i o n v in = 2.5v , i fb =? 10ma v ce = 0v 2.5 v 5 1 0 2 0 m s tprot delay t i me for protec tion c i rc uit v in = v ce = 2.5v v fb = 2.5v 0v 5 1 5 3 0 m s 6 r1224 n typical appli cation and application hints (1) fixed outpu t v o lt age t y p e (r1 224 nx x 2 e/f/g/h/l/m excep t xx =10 ) ce con t rol r 1224n ext gnd v out v in ce c3 l lo ad c1 r1 c2 pm o s sd 5 1 2 3 4 pmos: ha t1 044m (hit a c h i ) l : cr10 5 -2 70 mc (sumi da, 27 h) sd1 : rb063l -30 (ro h m) c3 : 47 f (t ant alum t y pe) c1 : 10 f (cera m ic t y pe ) c2 : 0.1 f (cera m ic t y pe ) r1 : 10 ? (2) adjust a b le o u tpu t t y pe (r12 24 n102 g / h/m) examp l e: outp ut v o lt age = 3.2v ce con t rol c3 l lo ad c1 r1 c2 pm o s sd c4 r3 r4 r2 r 1224n ext gnd v fb v in ce 5 1 2 3 4 pmos: ha t1 044m (hit a c h i ) l : cr10 5 -2 70 mc (sumi da, 27 h) sd1 : rb063l -30 (ro h m) c3 : 47 f (t ant alum t y pe) c1 : 10 f (cera m ic t y pe ) c2 : 0.1 f (cera m ic t y pe ) c4: 1000 pf (ceramic t y p e ) r1 : 10 ? , r 2 = 22k ? , r3= 2 .7k ? , r4= 3 3k ? 7 r1224n whe n you use these ics, consi der the fo llowing i s sue s ; ? as sho w n in the blo ck dia g ram, a p a ra sitic di ode i s f o rme d in e a ch termin al, ea ch of the s e di ode s is not fo rmed for load cu rre n t, therefore do not u s e it i n su ch a way . whe n you co ntrol t he ce p i n by anoth e r power sup p ly , do not make it s ?h? level mo re than the volt age level of v in pin. ? set external comp one nt s as clo s e as p o ssible to th e ic an d mini mize th e con nectio n bet ween the comp onent s and the ic. i n p a rticul ar , a ca p a citor should b e con necte d to v ou t pin with th e minimum conne ction. m a ke suf f icie nt gro und and reinf o rce su pplyin g . a large swi t chi ng current could flow th roug h the co nne ction of powe r sup p ly , an in ducto r and th e con n e c tion of v out . if the impedan ce o f the conne cti on of power supply is hig h , the volt age level of powe r su p p ly of the ic fluctuate s with the switching current. this may cause u n st a b le op era t ion of the ic. ? prote c tion ci rcuit may work if the maximum duty cycl e co ntinue for the time defined in the electrica l cha r a c teri stics. on ce af te r stop ping th e output volt age, output will re st a r t with sof t -st a rt operation. if the dif f eren ce bet wee n input volt age a nd ou tput volt age is sm all, the protectio n ci rcuit may work. ? u s e ca p a cit o rs wit h a c a p a cit y of 22 p f or mo re f o r v out pi n, an d with go od hig h freq uen cy chara c te risti c s su ch as t ant alum cap a citors. w e reco mmen d you to use ou tput cap a cito rs with an all o wabl e volt age at least twice as much a s sett ing output volt age. this is becau se the r e may be a ca se wh ere a spike-sha p ed high volt a ge is gene rated by an indu ctor when an extern al transi s to r is on an d of f. ? ch oo se an i ndu ctor that has suf f icie nt ly small d.c. resi st an ce a n d large all o wable current and is h a rd t o rea c h magneti c sat u ration. an d if the value of induct a n c e of an inducto r is extremel y small, the i lx may ex cee d t he absolute max i mum rating a t the maximum loading. use an ind u ct or with ap pro p riate ind u ct a n ce. ? use a dio de of a schottky type with high switching sp eed, and al so p a y attention to it s current ca p a city . ? do n o t use t h is ic un der t he co ndition with v in volt age at equal o r less tha n minimum op erat ing volt age. ? wh en the th resh old level of an external power m o s f et is rathe r low a nd the d r ive-a b ility of volt age sup p li er i s small, if the output pin is short ci rc uit, input volt age m a y be equal o r less than uvlo detecto r thresh old. in this ca se, the d e v ise is re set with uvl o function th at is di f f ere n t from the reset-protectio n fu nction ca use d b y maximum dut y cycle. ? with the pwm/vfm altern ative circuit, whe n the o n duty cy cle of swit chin g is 3 5 % or le ss, the r122 4n a l ters from pwm m ode to vfm mode (pul se ski p mode ). the purpo se of this circuit is raisi ng the ef ficien cy with a light load by ski pp ing the frequ ency and sup p re ssi ng the con s um pt ion curre n t. however , the rati o of output volt age again s t inp u t volt age i s 35 % or le ss, (e x. v in >8.6v a nd v out =3.0v ) even if the l a rge cu rrent may be lo ade d, the ic ke ep s it s v f m mod e . as a re sult, freq uen cy might be de crea sed , and o scill ation waveform might be u n st able. these phe no mena a r e the typical cha r a c teri stics of the ic with pwm/vfm altern ative circuit. the p e rfo r mance of po wer sou r ce ci rcui t s u s ing t hes e ics extremely depe n d s up on the p e riph eral circuit s . pay attention in the selecti on of the peri pheral ci rcui t s . in p a rticula r , desi gn the perip he ral ci rcuit s in a way tha t the values su ch as volt a ge, current, and power of eac h comp onent, pcb p a ttern s and the ic do not excee d their respe c ted rated value s . 8 r1224 n how to adjust output voltage and about phase compensation as for adju st able outp ut type, feedba ck pin (v fb ) volt age is cont ro lled to maint a in 1.0v . output v o lt ag e, v out is as f o llowin g equ a t ion: v out : r2 + r4 = v fb : r2 v out = v fb (r 2 + r4 )/r 2 thus, with ch angin g the value of r2 an d r4, out put volt age can b e set in the sp ecified rang e. in the dc/ dc conve r ter , wi th the load cu rre nt and exter nal com pon ent s su ch a s l and c, pha se mig h t be b ehind 180 de gree. in this case, the pha se m a rgin of the syst em will be le ss and st abilit y will be wo rse. t o prevent this, pha se m a rgi n sho u ld b e se cured with p r oce edin g the pha se. a pol e is fo rmed with external compon ent s l and c3. c3 l 1/2 ~ fpole a zero (si gnal back to ze ro) is formed with r4 an d c4. ? fzero~1/(2 r4 c4) for exampl e, if l = 27 h, c3 = 47f , the cu t of f frequency of the pole is app roximat e ly 4.5khz. t o make the cut of f freque ncy of the pol e as mu ch a s 4.5khz, set r4 = 33 k ? an d c4 = 100 0pf . if v out is s e t at 2.5v , r2 = 22 k ? is a ppro p riate. r3 prevent s feedb ack of the noise to v fb pin, about 2.7k ? is a ppro p riate value. ce con t rol c3 l lo ad c1 r1 c2 pm o s sd c4 r3 r4 r2 r 1224n ext gnd v fb v in ce 5 1 2 3 4 9 r1224n operation of step-down dc/dc conv erter and output current the step -do w n dc/dc con v erter ch arg e s energy in th e inducto r wh en lx transist o r is on, and discha r g e s the energy from t he ind u cto r when lx tran si stor i s o ff a nd control s with less en erg y loss, so tha t a lowe r o u tput volt age tha n the input volt age i s obt ain ed. the ope ration will be explaine d with referen c e to the follo wing diagram s: r1224 n in the continu ous mo de, when equatio n 1 is solv ed fo r ton and a s sumed that the solution i s tonc, tonc t u v ou t /v in ..................................................................................... equat ion 2 whe n ton |