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a m c d o c . #: a m c 7580_e (l f ) f e b 2005 amc7580 ? a dd microtech corp. 7a l ow d ropout r eg ulator description features the a m c7580 i s a hi gh perform ance l o w dropout regul at or rat e d for 7a out put current w i t h fi xed 2.5v / 3.3v / 5.0v and adj u st abl e out put . i t i s desi gned for use i n appl i cat i ons requi ri ng l o w dropout charact eri s t i c s ov er t h e rat e d current range. when t h e second l o w - current i nput v o l t a ge i s appl i e d, t h e drop out v o l t a ge can be as l o w as 100m v at l i ght l o ads and up t o 500m v at m a xi m u m out put current . o n chi p t r i m m i ng adj u st s the reference v o ltage to 1%. these features are ideal for low v o l t a ge m i croprocessor appl i cat i ons requi ri ng a regul at ed 2.5v t o 3.6v pow er suppl y . i n addi t i on, t h e a m c7580 prov i d es t h e dev i ce prot ect i ons i n cl udi ng ov er current and t h erm a l shut dow n. the a m c7580 seri es are i d eal t o t h e next generat i on m i croprocessor on m o t h erboards w h ere bot h 5v and 3.3v are av ai l a bl e. input-output di f f erential of typical 500mv at 7a and low quiescent current output current is ex cess of 7a rem o te sense pin av ailable rev e rse battery protection short circuit protection i n ternal therm a l ov erload protection av ailable in 5l plastic t o - 220 and surface m ount 5l t o - 263 pack ag es pin assig n m e nt identical to ez 1585 series. applications packag e pin out 5- pi n pl as t i c t o - 220 (t op v i ew ) pe ntium ? processor supplies pow e r p c tm supplies computer add-on cards other applications requiring l o w dropout voltag e over rated current. amc7580-2.5 ? 2.5v f i x e d amc7580-3.3 ? 3.3v f i x e d amc7580-5.0 ? 5.0v f i x e d amc7580-adj ? adjustable 5- pi n pl as t i c t o - 263 su rf ace mou n t (t op view ) v po w e r v co nt ro l gnd/a d j v ou t sen se v po w e r v co nt ro l gnd/a d j v ou t sen se order inform ation pl as t i c t o - 220 pl as t i c t o - 263 t a ( o c) p 5- pi n dd 5- pi n 0 to 70 am c7580-x.xp am c7580-x.xdd 0 to 70 am c7580-x.xpf (l ead free) am c7580-x.xddf (l ead free) 0 to 70 a m c 7580-a d j p a m c 7580-a d j d d 0 to 70 am c7580-adjpf (l ead free) am c7580-adjddf (l ead free) note: 1.a ll s u rf ace- m o u n t pack ag es are av ailable in t a pe & r eel. a ppen d th e letter ? t ? to part n u m ber (i.e., a m c 7580- x.xddt ). 2.t h e letter ? f ? is m a rk ed f o r l ead free proces s . co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 1 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or typical application sen s e c3 68 f 1 g n d v ou t v po w e r v co nt ro l c1 33 f c2 10 f 2 3 4 5 po w e r in cont rol i n x. xv o u t p u t ground amc7580-x.x a pp lic a tion sc he ma tic sen se c3 68 f r1 1% r2 1% ad j v ou t v po w e r v co nt ro l c1 33 f c2 10 f po w e r in out put cont rol i n ground v out = v ref (1 + ( r2 /r1 )) + i ad j r2 amc7580-adj a pp lic a tion sc he ma tic co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 2 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or ab solute m axim u m rating s (n ot e 1) in pu t voltag e (vpow er) 7v in p u t vo ltag e (vco n t ro l) 1 3 v o p e r a t i ng j unc t i o n t e m p e r a t ur e 1 5 0 o c storag e t e m p eratu r e r a n g e - 6 5 o c t o 150 o c l ead tem p eratu r e (solderin g , 10 s econ d s ) 300 o c note 1: ex ceedin g th es e ratin g s cou l d cau s e dam a g e to th e dev i ce. a ll v o ltag e s are w ith res p ect to grou n d . cu rren t s are p o s itiv e in to , n e g a tiv e o u t o f th e sp ecif i ed term in al. p o wer dissip a tio n tab le p ack ag e ja ( o c/w ) deratin g f actor ( m w / o c ) t a 25 o c t a 25 o c p o w e r ratin g ( m w ) t a =70 o c p o w e r ratin g ( m w ) t a = 85 o c p o w e r ratin g (m w) p 4 5 2 2 . 2 2 7 7 5 1 7 7 6 1 4 4 3 pf 4 5 2 2 . 2 2 7 7 5 1 7 7 6 1 4 4 3 d d 4 5 2 2 . 2 2 7 7 5 1 7 7 6 1 4 4 3 d d f 4 5 2 2 . 2 2 7 7 5 1 7 7 6 1 4 4 3 no te : 1. ja : t h erm a l r e s i s t an ce- j u n c tion to a m bien t, d f : deratin g f acto r , p o : p o w e r co n s u m p tio n . j unc t i o n t e m p e r a t ur e ca l c ul a t i o n: t j = t a + (p d ja ), p o = d f ( t j - t a ) th e ja n u m bers are g u i delin es f o r th e th erm a l perf orm a n ce of th e dev i ce/p c - board s y s t em . a ll of th e abov e as s u m e n o am bien t airf low . 2. jt: t h erm a l r e s i s t an ce- j u n c tion to t a b, t c : cas e(t a b) tem p eratu r e, t j = t c + (p d jt ) for p an d dd pack ag es , jt = 3.0 o c / w . 3. if pow er con s u m ption is ov er abov e ratin g , adeq u a te h eat sin k is req u ired to d i ssip a te h eat. recom m e nded operat ing conditions reco m m e n d ed op eratin g co n d itio n s p a ram e ter s y m bol min . ty p . max . un its v power 2 7 in p u t vo ltag e (v in ) v control 2 . 7 5 1 2 v lo a d cur r e nt ( w i t h a d e q ua t e he a t si nki ng) i o 0 . 0 1 0 7 a in pu t c a pacitor (v in to gnd) 1 0 f ou tp u t cap acito r w ith esr o f 1 0 ? m a x ., (v out to gnd) 3 3 f co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 3 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or b l ock diag ram v po w e r v ou t v co nt ro l sen s e th er m a l li m i t gnd 1. 25v v re f amc7580-x.x circuit schematic v co nt ro l v po w e r sen se th er m a l li m i t 1. 25 v v re f v ou t ad j amc7580-adj circuit schematic co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 4 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or electrical ch aracteristics un les s oth e rw is e s p ecif i ed, th es e s p ecif i cation s apply t j = 25 c f o r a m c 7580; i o = 10m a , v out = v se n s e , an d are f o r dc ch aracteris tics on ly . (l ow du ty cy cle pu ls e tes tin g tech n i qu es are u s ed w h ich m a in tain s j u n c tion an d cas e tem p eratu r es equ a l to th e am bien t tem p eratu r e.) a m c 7580 p a ram e ter s y m bol t e st co n d itio n s min . ty p . max . un its a m c 7580- 2 . 5 v control = 5.0v , v power = 3.3v 2 . 4 7 4 2 . 5 0 0 2 . 5 2 5 a m c 7580- 3 . 3 v control = 5.8v , v power = 3.8v 3 . 2 6 7 3 . 3 0 0 3 . 3 3 3 ou tp u t vo ltag e a m c 7580- 5.0 v out v control = 7.5v , v power = 5.5v 4 . 9 5 0 5 . 0 0 0 5 . 0 5 0 v a m c 7580- 2.5 v control = 5.0v , v power = 3.3v 2 . 4 6 0 2 . 5 0 0 2 . 5 4 0 a m c 7580- 3.3 v control = 5.0v , v power = 4.1v 3 . 2 4 7 3 . 3 0 0 3 . 3 5 3 ou tp u t vo ltag e a m c 7580- 5.0 v out v control = 6.5v , v power = 5.8v i o = 7a 4 . 9 2 0 5 . 0 0 0 5 . 0 8 0 v v c o n t r o l (n ot e 1) = 5.0v , v power = 3.3v , 1 . 2 3 8 1 . 2 5 0 1 . 2 6 2 r e f e ren ce vo ltag e a m c 7580- a d j v ref v control = (v out + 1.5v ) t o 12v , v power = (v out + 0.8v ) t o 7v , i o = 10m a t o 7a 1 . 2 3 0 1 . 2 5 0 1 . 2 7 0 v li ne re gul a t i o n ( n o t e 2 ) v oi (1.5v + v out ) v control 12v , 0.8v (v power - v out ) 5.5v 0.04 0.2 % lo a d r e gul a t i o n ( n o t e 2 ) v ol v control = v out + 2.5v , v power = v out + 0.8v , i o = 10m a t o 7a 0.08 0.3 % i o = 10m a 1.00 1.15 d r opou t v o l t a g e v control - v out (n ot e 3) v v power = v out + 0.8v i o = 7a 1.15 1.30 v i o = 10m a 0.10 0.17 d r opou t v o l t a g e v power - v out (n ot e 3) v v control = v out + 2.5v i o = 7a 0.45 0.50 v a d j u st p i n cur r e nt i ad j v control = 2.75v , v power = 2.05v , i o = 10m a 50 120 a co nt r o l p i n cur r e nt i ctnl v control = v out + 2.5v , v power = v out + 0.8v , i o = 10m a t o 7a 80 135 ma c u rren t l i m it i cl (v in - v out )=1.5v 7 8 a min i m u m l o ad c u rren t (note 4) im in v control = 5.0v , v power = 3.3v 5 10 ma r i ppl e r e j ect i o n (n ot e 5) r r v control = v power = v out + 2.5v , v ri ppl e = 1v pp , i o = 2.5a 60 80 db t h erm a l reg u l atio n t a = 25 c 0.003 % / w no te 1 ou tp u t v o ltag e is set to b e 2 . 5 v . no te 2 : l i n e an d lo ad reg u l atio n s are g u a ran t eed u p to m a x i m u m p o w er d i ssip a tio n d e term in ed b y in p u t/o u t p u t d i f f e ren tial an d th e o u tp u t cu rren t . ho w e v e r, th e m a x i m u m p o w er w ill n o t b e av ailab l e o v er th e f u ll in p u t/o u t p u t v o ltag e ran g e . no te 3 : t h e dropou t v o l t a g e i s m eas u r ed by ei t h er m i n i m u m con t rol v o l t a g e or pow er v o l t a g e . t h e s p eci f i cat i o n s rep r esen t th e m i n i m u m in p u t/o u t p u t v o ltag e req u ired to m a in tain 1 % reg u l atio n . no te 4 : t h e m i n i m u m lo ad cu rren t is th e m i n i m u m cu rren t req u ired to m a in tain reg u l atio n . no rm ally th e cu rren t in th e resisto r d i v i d e r u s ed to set th e o u tp u t v o ltag e is selected to m eet th e m i n i m u m lo ad cu rren t req u irem en t. no te 5 : t h e s e p a r a m e t e r s , a l t h o ugh gua r a nt e e d , a r e no t t e st e d i n p r o d u c t i o n p r i o r t o shi p m e nt co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 5 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or ap p l icat ion inf o rmat ion gen eral t h e a m c 7580 s e ri es i s des i g n e d t o pow er t h e n e w g e n e rat i o n of m i croproces s o rs . it i s des i g n e d t o m a k e u s e of m u ltiple pow er s u pplies , pres en t in m o s t s y s t em s , to redu ce th e dropou t v o ltag e . on e of th e adv a n t ag es of th e tw o- s u pply approach is m a x i m i zin g th e ef f i cien cy . t h e s econ d s u pply is at leas t 1v g r eater th an ou tpu t v o lta g e an d is p r o v id in g th e p o w er f o r th e co n t ro l circu itry an d su p p lies th e d r iv e cu rren t to th e np n o u tp u t tran sisto r . t h is allo w s th e np n o u tp u t tran sisto r to b e d r iv en in to satu ratio n . fo r th e co n t ro l v o ltag e th e cu rren t req u irem en t is sm all, ab o u t 1 % o f th e o u tp u t cu rren t o r ap p r o x im ately 50 m a f o r a 7a load. t h is driv e cu rren t becom e s part of th e ou tpu t cu rren t . t h e m a x i m u m v o ltag e on th e c o n t rol p i n is 1 3 v. t h e m a x i m u m v o ltag e at th e p o w e r p i n is 7 v. b y try i n g th e co n t ro l an d p o w er in p u ts to g e th er th e a m c 7580 can als o be operated as a s i n g l e s u pply dev i ce. in s i n g l e s u pply operation , th e dropou t v o ltag e w ill be d e term in ed b y th e m i n i m u m th e co n t ro l v o ltag e . t h e ne w ge ne r a tio n o f m i c r o p r o c e sso r s c y c l e lo a d c u r r e nt fr o m se ve r a l hund r e d m illia m p e r e s to se ve r a l a m p e r e s in t e ns o f na no se c o nd s. o u t p ut vo l t a ge t o l e r a nc e s a r e t i ght e r an d in clu d e tran s i en t res pon s e as part of th e s p ecif i cation . d e s i g n e d t o m eet t h e f a s t cu rren t l o ad s t ep requ i r em en t s of t h es e m i croproces s o rs , t h e a m c 7580- x . x al s o s a v e s to tal co st b y n eed in g less o u tp u t cap acitan ce to m a in tain reg u l atio n . t h e s e n s e pin perm its v e ry accu rate reg u l ation of ou tpu t v o ltag e . a s a res u lt, ov er an ou tpu t cu rren t ran g e of 100m a to 7 a , th e ty p i cal lo ad reg u l atio n is less th an 1 m v. in ad d itio n to th e en h a n cem en ts m e n tio n e d , th e ref e ren ce accu racy h a s b een im p r o v ed a f acto r o f tw o w ith a g u a ran t eed in itial to leran ce o f 1% at 25 c an d 1.6% accu racy ov er th e f u ll tem p eratu r e an d load cu rren t ran g e . t y pi cal appl i cat i o n s f o r t h e a m c 7580 i n cl u d e 3.3v t o 2.5 v con v e rs i o n w i t h a 5v con t rol s u ppl y , 5v t o 4.2v con v e rs i o n w i t h a 12v con t rol s u ppl y or 5v t o 3.6v con v e rs i o n w i t h a 12v con t rol s u ppl y . it i s eas y t o obt ai n dropou t v o l t a g e s of l e s s t h an 0.5v at 2.5a al on g w i t h ex cel l e n t s t at i c an d dy n a m i c s p eci f i cat i o n s . t h e dev i ce i s f u l l y p r o t ected ag ain s t o v er cu rren t an d o v er tem p eratu r e co n d itio n s . g r ounding and out put se nsing t h e a m c 7580- a d j al l o w s t r u e k e l v i n s e n s i n g f o r bot h t h e h i g h an d l o w s i de of t h e l o ad. a s a res u l t t h e v o l t a g e reg u l atio n at th e lo ad can b e easily o p tim ized . vo ltag e d r o p s d u e to p a rasitic resistan ces b e tw een th e reg u l ato r an d th e load can be placed in s i de th e reg u l ation loop. t h e ad v a n t ag es of rem o te s e n s in g are illu s t rated in f i g u r es 1 t h r o ugh 3 . fig u r e 1 s h ow s th e dev i ce con n ected as a con v e n tion a l 3 term in al reg u l ator w ith th e sen s e lead con n ected directly to th e o u tp u t o f th e d e v i ce. rp is th e p a rasitic resistan ce o f th e co n n ectio n s b e tw een th e d e v i ce an d th e lo ad . t r ace a o f f i g u r e 3 illu strates th e ef f ect o f rp . fig u r e 2 s h ow s th e dev i ce con n ected to tak e adv a n t ag e of th e rem o te s e n s e f eatu r e. t h e sen s e pin an d th e top of th e res i s t or div i der are con n ected to th e top of th e load; th e bo tto m o f th e resisto r d i v i d e r is co n n ected to th e b o tto m o f th e load. t h e ef f ect on ou tpu t reg u l ation can be s een in trace b of f i g u r e 3. it is im portan t to n o te th at th e v o ltag e drops du e to r p are n o t elim in ated; th ey w ill add to th e dropou t v o ltag e of th e reg u l at or reg a rdl e s s . t h ea mc 7580- a d j can con t rol t h e v o l t a g e at t h e l o ad as l o n g as t h e i n pu t - ou t p u t v o l t a g e i s g r eat er t h an t h e t o t a l of t h e dropou t v o l t a g e of t h e dev i ce pl u s t h e v o l t a g e drop acros s r p . co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 6 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or fi gur e 1 . co nve nt i o na l lo a d se nsi ng fi gur e 2 . re m o t e lo a d se nsi ng r 2 r 1 r p r p loa d adj po w e r v ou t s e n s e c ontrol c ontrol s e n s e v ou t po w e r adj r 2 r 1 r p r p loa d ( ? i ou t )(r p ) b a v ou t fi gure 2 v ou t fi gure 1 i ou t fi gur e 3 . re m o t e se nsi ng i m p r o v e s lo a d re gul a t i o n ti m e st abilit y t h e c i rcu i t des i g n u s ed i n t h e a m c 7580 s e ri es requ i r es t h e u s e of an ou t p u t capaci t o r as part of t h e dev i ce f r eq u e n c y co m p en satio n . t h e ad d itio n o f 1 5 0 f a l u m in u m electroly tic or a 22 f so lid tan t alu m o n th e o u tp u t w ill en su re stab ility f o r all o p e ratin g co n d itio n s . in o r d e r to m eet th e tran sien t p e rf o r m a n ce o f th e p r o cesso r larg er v a lu e cap acito rs are n eed ed . t o lim it th e h i g h f r eq u e n c y n o ise g e n e rated b y th e p r o cesso r, h i g h q u ality b y p a ss cap acito rs m u st b e u s ed . in o r d e r to lim it p a rasitic in d u ctan ce (e sl ) an d resistan ce (esr) in cap acito rs to accep tab l e lim its, m u ltip le sm all ceram ic cap acito r in ad d itio n to h i g h q u ality so lid tan t alu m cap acito rs are req u ired . w h en th e ad j u stm e n t term in al is b y p a ssed to im p r o v e th e ripple rej ection , th e requ irem en t f o r an ou tpu t capacitor in creases. t o f u rth e r im p r o v e stab ility an d tran sien t resp o n se o f th ese d e v i ces larg er v a lu es o f o u tp u t cap acito r can b e use d . t h e m o d e r n p r o c e sso r s ge ne r a t e l a r g e hi gh fr e q ue nc y c u r r e nt t r a n si e n t s . t h e l o a d c u r r e nt st e p c o nt a i ns hi ghe r o r d e r fr e q ue nc y c o m p o n e n t s t h a n t h e o u t p ut c o up l i ng ne t w o r k m u st ha nd l e u n til th e reg u l ato r th ro ttles to th e lo ad cu rren t lev e l. b ecau se th ey co n t ain p a rasitic resistan ce an d in d u ctan ce, cap acito rs are n o t id eal elem en ts. t h es e p a rasitic elem en ts d o m in ate th e ch an g e in o u tp u t v o ltag e at th e b e g i n n i n g of a tran s i en t load s t ep ch an g e . t h e esr of th e ou tpu t capacitors produ ces an d in s t an tan e ou s s t ep in ou tpu t v o ltag e at th e beg i n n i n g of a tran s i en t load s t ep ch an g e . t h e esr of th e ou tpu t capacitors produ ces an in s t an tan e ou s s t ep in o u t v o ltag e ? v = ? i(es r ). t h e es l of t h e ou t p u t capaci t o rs produ ces a droop proport i o n a l t o t h e rat e of ch an g e of th e o u tp u t cu rren t ? v = l ( ? i/ ? t ) . t h e ou t p u t capaci t a n ce produ ces a ch an g e i n ou t p u t v o l t a g e proport i o n a l t o t h e tim e u n til th e reg u l ato r can resp o n d ? v = ? t( ? i/c). fig u r e 4 illu strates th ese tran sien t ef f ects. co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 7 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or fi gur e 4 . capaci n c e t a e ffects esl e f fects esr e f fects slope , v/t = ? i/c point at w h ich regulat or takes control output voltage t h e a m c 7580- a d j dev e l ops a 1.25v ref e ren ce v o l t a g e bet w een t h e s e n s e pi n an d t h e a d j u s t pi n (f i g u r e 5). p l a c i ng a r e si st o r b e t w e e n t h e s e t w o t e r m i n a l s c a u se s a c o nst a nt c u r r e nt t o fl o w t h o ught r1 a n d d o w n t h o ugh r2 t o set th e o u tp u t v o ltag e . in g e n e ral r1 is ch o s en so th at th is cu rren t is th e sp ecif i ed m i n i m u m lo ad cu rren t o f 1 0 m a . t h e cu rren t o u t o f th e a d j u st p i n is sm all, ty p i cally 5 0 a an d it ad d s to th e cu rren t f o r r1 . fo r b e st reg u l atio n th e t op of t h e res i s t or di v i der s h ou l d be con n ect ed di rect l y t o t h e s e n s e pi n . f i g u r e 5 se tting output volta g e f i g u r e 6. optiona l cla m p diode s pr ote c t ag ainst i nput crowbar circuit d2 d1 r2 r1 ad j a m c7580 - ad j sen se v po w e r v co nt ro l r2 r1 i ad j = 50 a ad j v re f a m c7580 - ad j sen se v ou t v po w e r v co nt ro l co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 8 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or p r otecti o n di od es in n o rm al operat i o n , a m c 7580 f a m i l y does n o t n eed an y prot ect i o n di odes bet w een t h e adj u s t m e n t pi n an d t h e o u tp u t an d f r o m th e o u tp u t to th e in p u t to p r ev en t d i e o v erstress. in tern al resisto r s are lim itin g th e in tern al cu rren t path s on th e a d j pin . t h eref ore ev en w ith by pas s capacitors on t h e adj u s t pi n n o prot ect i o n di ode i s n eeded t o en su re d e v i ce saf e ty u n d er sh o r t- circu it co n d itio n s . t h e a d j u st p i n can b e d r iv er o n a tran sien t b a sis 7 v w ith resp ect to th e o u tp u t w ith o u t an y d e v i ce d e g r ad atio n . a prot ect i o n di ode bet w een t h e o u t p u t pi n an d v power pin is n o t u s u a lly n eeded. micros econ d s u rg e cu rren t s of 50a t o 100a can be h a n d l e d by t h e i n t e rn al di ode bet w een t h e o u t p u t pi n an d v power pin of th e dev i ce. in n o rm al o p e ratio n s it is d i f f i cu lt to g e t th o s e v a lu es o f su rg e cu rren t s ev en w ith th e u s e o f larg e o u tp u t cap acitan ces. on ly w i t h h i g h v a l u e ou t p u t capaci t o rs , s u ch as 1000 f t o 5000 f an d th e v power p i n is in stan tan e o u sly sh o r ted to g r ou n d , dam a g e an occu r. a di ode f r om ou t p u t t o i n pu t i s recom m e n d ed (f i g u r e 6). if a m c 7851 i s con n ect ed as sin g l e su p p l y d e v i ce w ith th e co n t ro l an d p o w er in p u t p i n s sh o r ted to g e th er th e in tern al d i o d e b e tw een th e o u tp u t an d p o w er in p u t p i n w ill p r o t ect th e co n t ro l in p u t p i n . t h erm al con s i d erati on t h e a m c 7580- a d j s e ries h a s in tern al pow er an d th erm a l lim itin g circu itry des i g n e d to protect th e dev i ce u n d er o v erlo ad co n d itio n s . ho w e v e r m a x i m u m j u n c tio n tem p eratu r e ratin g s sh o u ld n o t b e ex ceed ed u n d er co n tin u o u s n o rm al lo ad co n d itio n s . caref u l co n s id eratio n m u st b e g i v e n to all so u r ces o f th erm a l resistan ce f r o m j u n c tio n to am bien t, in clu d in g j u n c tion - to- cas e, cas e- to- h eat s i n k in terf ace an d h eat s i n k res i s t an ce its elf . j unc t i o n t e m p e r a t ur e o f t h e co nt r o l se c t i o n c a n r un up t o 1 2 5 o c . j u n c tion tem p eratu r e of th e p o w e r s ection can ru n u p t o 150 o c . du e to th e th erm a l g r adien t s betw een th e pow er tran s i s t or an d th e con t rol circu itry th ere is a s i g n i f i can t dif f e ren ce in th erm a l res i s t an ce betw een th e c o n t rol an d p o w e r s ection s . v i rt u a l l y al l t h e pow er di s s i pat e d by t h e dev i ce i s di s s i pat e d in th e pow er tran s i s t or. t h e tem p eratu r e ris e in th e p o w er tran sisto r w ill b e g r eater th an th e tem p eratu r e rise in th e co n t ro l sectio n m a k i n g th e th erm a l resistan ce lo w e r in th e co n t ro l sectio n . a t p o w er lev e ls b e lo w 1 2 w , th e tem p eratu r e g r ad ien t w ill b e less th an 2 5 o c an d th e m a x i m u m am b i en t tem p eratu r e w ill b e d e term in ed b y th e j u n c tio n tem p eratu r e o f th e co n t ro l sectio n . t h is is d u e to th e lo w e r m a x i m u m j u n c tio n tem p eratu r e in th e co n t ro l sectio n . a t p o w er lev e ls ab o v e 1 2 w , th e tem p eratu r e g r ad ien t w ill b e g r eater th an 2 5 o c an d th e m a x i m u m am b i en t tem p eratu r e w ill b e d e term in ed b y th e p o w e r sectio n . in b o t h cases th e j u n c tio n tem p eratu r e is d e term in ed b y th e to tal p o w er d i ssip a ted in th e d e v i ce. fo r m o st lo w dropou t application s th e pow er dis s i pation w ill be les s th an 12w . t h e pow er in th e dev i ce is m a de u p of tw o com pon en ts : th e pow er in th e ou tpu t tran s i s t or an d th e pow er in th e co n t ro l circu it. t h e p o w er in th e co n t ro l circu it is n e g lig ib le, w h ich is eq u a l to : p control = (v control ? v out ) / i control , w h ere i control is eq u a l i out / 100(t y p) t h e p o w er in th e o u tp u t tran sisto r is eq u a l to : p output = (v power ?v out ) / i out t h e to tal p o w er is eq u a l to : p control + p output j u n c tion- to - cas e t h er m a l res i s t an ce is s p ecif i ed f r o m t h e ic j u n c tion to t h e botto m of t h e c a s e directl y belo w th e die. t h is is th e lo w e s t res i s t a n ce path f o r th e h eat f l o w . in order to en s u re th e bes t pos s i ble th er m a l f l o w th i s area of th e pack ag e to t h e h eat sink pr oper m oun ti ng is requ ired. t h erm a l co m poun d at t h e c a s e - t o - h e a t s i nk i n terf ace is recom m e n d ed. a th er m a ll y co n d u c ti v e s p acer can be u s ed, i f t h e cas e of t h e de v i ce m u s t be electricall y is olated, bu t its ad d e d co n t rib u tio n to th erm a l resistan ce h a s to b e co n s id ered . co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 9 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or m a x i mu m p o w e r c a l c u l a t i o n : t j(ma x) ? t a( m a x ) p d(ma x) = ja t j ( o c) : m a xi m u m r e c o m m e nd e d j unc t i o n t e m p e r a t ur e t a ( o c ) : a m bien t tem p eratu r e of th e application ja ( o c/w ) : j u n c tio n - to - j u n c tio n tem p eratu r e th erm a l resistan ce of th e pack ag e, an d oth e r h eat dis s i patin g ma t e r i a l s . the m a xim u m po w er dissipa t i o n o f a sing le- o ut put reg ula t o r : p d(ma x) = [ (v in ( m ax ) - v out(nom) ) ] i out(nom) + v i n (ma x ) i q w h e r e : v out(nom) = t h e no m i na l o u t p ut vo l t a ge i out(nom) = t h e no m i na l o u t p ut c u r r e nt , a n d i q = th e qu ies cen t cu rren t th e reg u l ator con s u m es at i out(ma x ) v in ( m ax ) = th e m a x i m u m in p u t v o ltag e th e n ja = (150 o c ? t a ) / p d t h erm al cons ideration: w h e n pow e r c ons um ption is ov e r a bout 1.2w ( a t 70 o c a m bie n t te m p e r a t ur e ) , a dditiona l he a t s i nk is r e quir e d to c ontr o l the junc tion te m p e r a t ur e be low 125 o c. t h e j u n c tio n tem p eratu r e is: t j = p d ( jt + cs + sa ) + t a p d : ?d i s s i pat e d pow er. jt : ?t h erm a l res i s t an ce f r om th e j u n c tion to th e m o u n tin g tab of th e pack ag e. cs : ? t h e r m a l res i s t a n ce th ro ug h t h e in ter f ace bet w ee n th e i c an d th e s u rf ace on w h ic h it is m oun ted. (t y p icall y , cs < 1.0 c / w) sa: ?t h erm a l res i s t an ce f r om th e m o u n tin g s u rf ace to am bien t (th e rm al res i s t an ce of th e h eat s i n k ) . if pc board c oppe r i s g o i n g t o be u s ed as a h eat s i nk , bel o w t a bl e can be us ed t o det e rm i n e t h e appropri a t e s i ze of copper f o i l requ i r ed. f o r m u l t i - l a y ered pc b, t h es e l a y e rs can al s o be u s ed as a h eat s i n k . th e y can be con n ect ed w i t h se ve r a l t h r o ugh ho l e vi a s . pc b sa ( c / w ) 5 9 4 5 3 8 3 3 2 7 2 4 2 1 p c b h eat s i n k s i ze (m m 2 ) 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 r ecom m e n d ed f i g u r e of p c b area u s ed as a h eat s i n k . thr o ug h ho l e v i as (b ot t o m vi e w ) (t op vi e w ) co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 1 0 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or 5-p i n p l astic to-220 i n c h e s mi l l i me t e r s m i n t y p ma x mi n t y p ma x a 0. 5 6 0 - 0. 6 5 0 14. 2 3 - 1 6 . 5 1 b 0 . 3 8 0 - 0. 4 2 0 9. 6 6 - 10. 6 6 c 0 . 1 4 0 - 0. 1 9 0 3. 5 6 - 4. 8 2 d 0 . 0 1 8 - 0. 0 3 5 0. 4 6 - 0. 8 9 f 0 . 1 4 0 - 0. 1 6 0 3. 5 6 - 4. 0 6 g 0 . 1 3 4 - - 3. 4 0 - - j 0 . 0 1 2 - 0. 0 4 5 0. 3 1 - 1. 1 4 k 0. 5 0 0 - 0. 5 8 0 12. 7 0 - 1 4 . 7 3 n 0 . 2 6 8 ty p 6. 8 0 ty p r 0 . 0 8 0 - 0. 1 1 5 2. 0 4 - 2. 9 2 s 0 . 0 4 5 - 0. 0 5 5 1. 1 4 - 1. 3 9 t 0 . 2 3 0 - 0. 2 7 0 5. 8 5 - 6. 8 5 k d g n r j b t f c s a 5-p i n p l astic to-263 i n c h e s mi l l i me t e r s m i n t y p ma x mi n t y p ma x a 0. 4 0 0 - 0. 4 2 0 10. 1 6 - 1 0 . 6 7 b 0 . 3 5 1 - 0. 3 6 1 8. 9 2 - 9. 1 7 c 0 . 1 7 1 - 0. 1 8 1 4. 3 4 - 4. 5 9 d 0 . 0 4 5 - 0. 0 5 5 1. 1 4 - 1. 4 0 e 0. 0 1 3 - 0. 0 1 7 0. 3 3 0 - 0 . 4 3 2 f 0. 0 2 9 - 0. 0 3 5 0. 7 3 7 - 0 . 8 8 9 g 0 . 0 6 2 - 0. 0 7 2 1. 5 7 - 1. 8 3 i - - 0. 0 6 5 - - 1. 6 5 k 0. 5 7 5 0. 6 2 5 14. 6 0 1 5 . 8 7 l 0 . 0 9 0 0. 1 1 0 2. 2 9 2. 7 9 m 7 7 n 3 3 f e g b i a m k d c n l co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 1 1 www. a d d m t e k . c o m
a m c d o c . #: a m c 7580_e ( l f ) amc7580 f e b 2005 7a l ow d ropout r eg u l a t or imp o rt ant not i ce a d d microtech ( a ddm) res e rv es t h e righ t to m a k e c h a n ges to i t s produ ct s or t o di s c ont i n u e any i n t e g r at ed ci rcu i t p r o d u ct o r serv ice w ith o u t n o tice, an d ad v i ses it s cu sto m er s to o b t ain th e latest v e rsio n o f relev a n t in f o r m atio n to v e rif y , b e f o re p l acin g o r d e rs, th at th e in f o rm atio n b e in g relied o n is cu rren t . a f e w appl i cat i o n s us i n g i n t e g r at ed ci rcu i t produ ct s m a y i n v o l v e pot e n t i a l ri s k s of deat h , pers on al i n j u r y , or s e v e re propert y or en v i ronm e n t a l da m a g e . a d d m i n t e g r at ed ci rcu i t produ ct s are n o t des i gn e d , i n t e n d ed, au t h ori zed, or w a rrant ed t o be s u i t a bl e f o r u s e i n l i f e - s u pport appl i cat i o n s , dev i ces or sy s t e m s or ot h e r cri t i cal appl i cat i o n s . u s e o f a d d m produ ct s i n su c h appl i cat i o n s i s un ders t ood t o be f u l l y at t h e ri s k o f t h e c u s t o m er. in or der t o m i n i m i ze ris k s as s o ciated w i th th e c u s t o m er ? s applications , t h e cus t o m er sh oul d prov i d e adeq u a t e des i gn an d operat i ng sa fe gua r d s. a d d m ass u m e s t o n o l i a bi l i t y t o cus t o m er produ ct des i gn or appl i cat i o n s u pport . a d d m w a rra n t s t h e perf or m a n ce o f its p r o d u cts to th e sp ecif i catio n s ap p licab le at th e tim e o f sale. u . s. a s ia pacif i c region a dd m i cro t ech in c. 492 altam ont dr ive milpitas , ca 95035 add m i cro tech co rp 13f , n o . 287, s ec. 3, n a n ji n g e. r d ., ta i p e i , ta i w a n 1 0 5 t e l : ( 408) 9410420 t e l : 2- 27132800 f a x : ( 408) 9410864 f a x : 2- 27132805 co py r i g h t ? 2 0 0 2 , ad d m i c r o t e c h c o r p . 1 2 www. a d d m t e k . c o m

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