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AIC1622 high efficiency selectable current limit synchronous step-up dc/dc converter features high efficiency 9 3 % (v in =2. 4 v , v out =3. 3 v , i out =200ma). output current up to 500ma. (v in =2. 4 v , at v out = 3 .3v, clsel= o ut) 20 a quiescent supply current. power-saving shutdown mode (0.1 a typic a l). internal synchronous rectifier ( no external diode ) selectable current limit for reduced ripple low noise , anti-ringing feature on-chip low battery detector. low battery hysteresis space-saving package: msop-10 applications palmtop & notebook computers. pdas wireless phones pocket organizers. digital cameras. hand-held devices with 1 to 2-cell of nimh/nicd batteries . description the AIC1622 is a high efficiency step up dc- dc converter. the start-up voltage is as low as 0.8v and operate with an input voltage down to 0.7v. consuming only 20 a of quies- cent current. these devices offer a built-in synchronous rectifier that reduces size and cost by eliminating the need for an external schottky diode and improves overall effi- ciency by minimizing losses. the switching frequency can range up to 500khz depending on the load and input volt- age. the output voltage ranging from 1.8v to 4.0v can be easily set by two external re- sistors, connecting fb to out to get 3.3v. in terms of design flexibilit y, the peak current of internal switch is sele ctable (0.45a or 0.8a). AIC1622 also features a circuit that eliminates noise due to inductor ringing. typical application circuit out put 3. 3v or a d j . (1. 8 v t o 4. 0v ) up t o 300m a low -bat t e ry d e te ct o u t a i c1622 out fb gnd re f lb o sh d n l x lb i + on off + low b a t t ery det e c t i on 0. 1 f v in 22 h 47 f 47 f s e l e c t abl e current li m i t (0. 8 a or 0. 45a ) c l sel 200 ? batt a n alog integrations corporation si-soft research center ds-1622p-03 010405 3a1, no.1, li-hsin rd. i , science park , hsinchu 300, taiw an , r.o.c. te l: 886-3-5772500 fa x : 886-3-5772510 www. anal og.c o m .tw 1
AIC1622 ordering information a i c 16 22x xx x pi n co n f i g ura ti o n t o p vi ew 1 3 4 2 10 8 7 9 fb lb i lb o cl sel ref ou t lx gn d b a tt sh d n 5 6 e x am pl e : a i c 1 6 22c o t r i n m s o p - 1 0 p a c k ag e & t a pi n g & r e e l p a c k i ng t y pe a i c 1 6 22p o t r i n m s o p - 1 0 lea d f r ee p a c k ag e & t a p i ng & r eel p a c k i ng t y pe pac ki n g t y pe t r : t ape & r eel pac kag i n g t y pe o : m s o p -10 c : c o m m e r c ia l p : lea d f r ee c o m m er c i al absolute maximum ratings supply voltage (out to gnd) 8.0v switch voltage (lx to gnd) v out + 0.3v battery voltage (batt to gnd) 6.0v , lbo to gnd 6.0v shdn lbi, ref, fb, clsel to gnd v out +0. 3 v switch current (lx) -1.5a to + 1 .5a output current (out) -1.5a to + 1 .5a operating temperature range -40 c ~ +85 c maximum junction temperature 125 c storage temperature range -65 c ~150 c lead temperature (soldering 10 sec.) 260 c absolute m aximum ratings are those values beyond which the life of a device may be impaired. test circuit refer to typical application circuit. 2
AIC1622 electrical characteristics (v in = 2 .0v, v out = 3 .3v (fb= out), r l = , t a =25 c, unless otherw ise specified.) (note1) parameter test conditions min. typ. max. unit minimum input voltage 0.7 v operating v o l t a g e 1 . 1 4 . 0 v start-up voltage r l =3k ? (note2) 0.8 1.1 v start-up voltage tempco -2 mv/ c output voltage r a n g e 1 . 8 4 . 0 output voltage fb = v out 3 . 1 7 3 . 3 3 . 4 3 v c l s e l = o u t 3 0 0 4 0 0 steady state output current (note 3) fb=out ( v out = 3 .3v) c l s e l = g n d 1 5 0 2 2 0 ma reference voltage i ref = 0 1.199 1.23 1.261 v reference voltage tempco 0.024 mv/ c reference load regulation i ref = 0 to 100 a 1 0 3 0 m v reference line regulation v out = 1.8v to 4v 5 10 mv/v fb , lbi input threshold 1.199 1.23 1.261 v internal switch on-resistance i lx = 100ma 0.3 ? c l s e l = o u t 0 . 6 0 . 8 1 . 0 lx switch current limit c l s e l = g n d 0 . 3 0 . 4 5 0 . 6 a lx leakage current v lx = 0 v, 4v; v out = 4 v 0 . 0 5 1 a operating current into out (note 4) v fb = 1.4v , v out = 3.3v 20 35 a shutdown current into out shdn = gnd 0.1 1 a v out = 3.3v ,i load = 200ma 90 effic i enc y v out = 2v ,i load = 1ma 85 % lx switch on-time v fb = 1 v , v out = 3.3v 2 4 7 s lx switc h off-time v fb = 1 v , v out = 3.3v 0.6 0.9 1.3 s fb input current v fb = 1.4v 0.03 50 na 3
AIC1622 electrical characteristics (continued) parameter test conditions min. typ. max. unit lbi input current v lbi = 1.4v 1 50 na clsel input current clsel = out 1.4 3 a shdn input current v shdn = 0 or v out 0 . 0 7 5 0 n a lbo low output voltage v lbi = 0, i sink = 1ma 0.2 0.4 a lbo off leakage current v lbo = 5.5v, v lbi = 5.5v 0.07 1 lbi h y s t e r e i s i s 5 0 m v damping switch resistance v in = 2v 50 100 ? v il 0.2v out shdn input voltage v ih 0 . 8 v out v v il 0.2v out clsel input voltage v ih 0 . 8 v out v note 1: specifications are production tested at t a =25 c. specifications over the -40 c to 85 c operating tem- perature range are assured by design, characterizati on and correlation with statistical quality controls (sqc). note 2: start-up voltage operation is guar anteed without the addition of an ex ternal schottky diode between the input and output. note 3: steady-state output current indicates that the dev ice maintains output voltage regulation under load. note 4: device is bootstrapped (power to the ic comes from out). this correlates directly with the actual battery supply. typical performance characteristics 0. 0 1 0.1 1 10 10 0 1 000 0 10 20 30 40 50 60 70 80 90 100 f i g. 1 v out =3.3v , clsel= o u t (0. 8 a) (r ef . to f i g.16) v in =2.4 v v in =1 .2v e f ficienc y (%) lo adi ng ( m a ) 0 . 0 0 .5 1. 0 1 .5 2. 0 2 .5 3.0 0 20 40 60 80 100 120 140 160 i_li mit= 0.45a , v ou t =3 . 3 v input ba tter y cur r en t ( a) inpu t ba tt er y v o lt a g e ( v ) f i g. 2 no-l oad ba tter y c u r r en t vs . inp u t b a tter y v o lt ag e i_li m i t= 0.8a , v ou t =3 .3 v 4
AIC1622 typical performance characteristics (continued) 0. 01 0.1 1 10 100 1 000 f i g. 3 v out = 3 .3v , clsel= g nd ( 0 .45a) (r ef . to f i g.16) ef ficienc y ( % ) loadi ng ( m a) 40 50 60 70 80 90 10 0 v in =2 .4 v v in =1 .2v 0.0 1 0. 1 1 10 10 0 0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 1. 6 1. 8 f i g. 4 s t art-up v o lt age vs . o u tput curr ent w i th out di ode w i th diode s t art- up v o lt age (v) o u tpu t cur r ent (m a) 1.0 1. 5 2.0 2. 5 3.0 3.5 4. 0 -0 .1 0 -0 .0 8 -0 .0 6 -0 .0 4 -0 .0 2 0.0 0 0.0 2 0.0 4 0.0 6 0.0 8 0.1 0 f i g. 5 shut dow n curr e n t vs . o u tput v o l t age shut down cur r ent ( a) o u t put v o lt a ge ( v ) 1. 0 1 .5 2.0 2 .5 3.0 3 .5 4.0 0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 1. 6 1. 8 2. 0 2. 2 f i g. 6 s hut d o w n t h r e shol d v s . o u tput v o l t age shutdown t h res hol d (v) ou t p u t v o l t ag e ( v ) f i g.7 max i m u m o u tpu t cur r ent vs. inpu t v o lt age max i mum o u tput c u rr ent (ma) o u tput v o lt age (v) 1. 0 1. 2 1. 4 1. 6 1.8 2.0 2. 2 2. 4 2. 6 2.8 3.0 100 200 300 400 500 600 700 800 vou t =3 . 3 v cl s e l = g nd cl s e l = o ut f i g. 8 heavy l oad w a v e f o r m lx p i n w a ve form v ou t a c c oup le ind u c to r cu rren t v in =2 .4v v out =3 .3v 5
AIC1622 typical performance characteristics (continued) fig. 9 w i th o u t da m p i n g ri ng i n g f u nc t i on fi g . 1 0 w i th da m p i n g ri ng i n g fu nc t i on ? i ou t =2 00 m a v ou t a c co upl e f i g. 1 1 l oad t r ans i ent r e s p o n se v in =2 .4v v ou t =3 .3 v 6
AIC1622 block diagram + - + - + - + - + 47 f 47 f 47 h r1 l 20 0 ? fb re f gn d lx ba t t ou t q3 sw i t ch da m p i n g c4 0. 1 f c1 0. 1 f c3 ou t vin lb o lb i clse l sh d n f/ f q r s q2 q1 r e f e ren c e v o l t ag e m i rror ma xi m u m o n - t i m e one s h ot m i n i mu m o f f - ti me o ne s h ot pin descriptions pin 1: fb- connecting to out to get +3.3v output, or using a resistor network to set output voltage ranging from + 1 .8v to + 4 .0v. pin 2: lbi- low-battery comparator input. in- ternally s e t to trip at + 1 .23v. pin 3: lbo- open-drain low battery comparator output. output is low when vlbi is <1.23v. lbo is high impedance during shutdown. pin 4: clsel- current-limit selects input. clsel= out sets the current limit to 0.8a. clsel=gnd sets the current limit to 0.45a. pin 5: ref- 1.23v re ference voltage. bypass with a 0.1 f capacitor. pin 6: shdn- shutdown input. high=operating, low=shutdown. pin 7: batt- battery input and damping switch connection. if damping switch is unused, leave batt unconnected. pin 8: gnd- ground. pin 9: lx- n-channel and p-channel power mosfet drain. pin 10: out- power output. out provides bootstrap power to the ic. 7
AIC1622 8 application information overview AIC1622 is a high efficiency, step-up dc-dc con- verter, designed to feature a built-in synchronous rectifier, which reduces si ze and cost by eliminating the need for an external schottky diode. the start- up voltage of AIC1622 is as low as 0.8v and it op- erates with an input voltage down to 0.7v. quies- cent supply current is only 20 a. in addition, AIC1622 features a circuit that eliminates inductor ringing to reduce noise. the internal p-mosfet on- resistance is typically 0.3 ? to improve overall effi- ciency by minimizing ac losses. the output voltage ranging from 1.8v to 4.0v can be easily set by two external resistors, connecting fb to out to get 3.3v. clsel pin of AIC1622 offers a selectable current limit (0.8a or 0.45a). the lower current limit allows the use of a physically smaller inductor in space- sensitive applications. pfm control scheme the key feature of AIC1622 is a unique minimum- off-time, constant-on-time , current-limited, pulse- frequency-modulation (pfm) control scheme (see block diagram) with ultra-low quiescent current. the peak current of the internal n-mosfet power switch is selectable. the switch frequency depends on either loading condition or input voltage, and can range up to 500khz. it is governed by a pair of one- shots that set a minimum off-time (1 s) and a maximum on-time (4 s). sy nchronous rectification using the internal synchronous rectifier eliminates the need for an external schottky diode. therefore, the cost and board space is reduced. during the cy- cle of off-time, p-mosfet turns on and shunts n- mosfet. due to the low turn-on resistance of mosfet, the synchronous rectifier significantly improves efficiency without the addition of an external component. thus, the conversion ef- ficiency can be as high as 93%. reference voltage the reference voltage (ref) is nominally 1.23v for excellent t.c. performanc e. in addition, ref pin can source up to 100 a to external circuit with good load regulation (<10mv). a bypass capacitor of 0.1 f is required for proper operation and good per- formance shutdow n the whole circuit is shutdown when shdn v is low. at shutdown mode, the current can flow from battery to output due to the body diode of p-mosfet. v out falls to approximately vin-0.6v and lx remains high impedance. the capacitance and load at out de- termine the rate at which v out decays. shutdown can be pulled as high as 6v, regardless of the volt- age at out. current limit select pin AIC1622 allows a selectable inductor current limit of either 0.45a or 0.8a. the flexibility contributes to designs for higher current or smaller applications. clsel draws 1.4 a when connecting to out. batt/damping sw itch AIC1622 is designed with an internal damping switch (fig. 15) to reduce ringing at lx. the damp- ing switch supplies a path to quickly dissipate the energy stored in inductor and reduces the ringing at lx. damping lx ringing does not reduce v out rip- ple, but does reduce emi. r1=200 ? works well for most applications while reducing efficiency by only
AIC1622 9 1%. larger r1 value provides less damping, but less impact on efficiency. in principle, lower value of r1 is needed to fully damp lx when v out /v in ratio is high. t off = l x s w itc h ? off-time in s i lim =0.45a or 0.8a 2. capacitor selection the output voltage ripple relates with the peak inductor current and the output capacitor esr. besides output ripple vo ltage, the output ripple current also needs to be concerned. the smaller the capacitor esr is, the higher the ripple cur- rent will be. a filter c apacitor with low esr is helpful to the efficienc y and steady state output current of AIC1622. ther efore nippon tantalum capacitor mcm series with 100 f/6v is recom- mended. a smaller capacitor (down to 47 f with higher esr) is acceptable for light loads or in applications that can tolerate higher output ripple. selecting the output voltage v out can be simply set to 3.3v by connecting the fb pin to out due to internal resistor divider (fig. 16). in order to adjust the output voltage, a resistor di- vider is connected to v out , fb, gnd (fig. 17). us e the following equation to calculate: r5=r6 [(v out / v ref )-1] where v ref =1.23v and v out may range from 1.8v to 4v. the recommended r6 is 240k ? . low -battery detection AIC1622 contains an on-chip comparator with 50mv internal hysteresis (ref, ref+50mv) for low bat- tery detection. if the voltage at lbi falls below the in- ternal reference voltage. lbo ( an open-drain output) sinks current t o gnd. 3. pcb lay out and grounding since AIC1622 switching frequency can range up to 500khz, it makes AIC1622 become very sensitive. so careful printed circuit layout is im- portant for minimizing ground bounce and noise. ic?s out pin should be as clear as possible. and the gnd pin should be placed close to the ground plane. keep the ic?s gnd pin and the ground leads of the input and output filter ca- pacitors less than 0.2in (5mm) apart. in addition, keep all connection to the fb and lx pins as short as possible. in particular, when using ex- ternal feedback resistors, locate them as close to the fb as possible. to maximize output pow- er and efficiency and minimize output ripple voltage, use a ground plane and solder the ic?s gnd directly to the ground plane. following are the recommended layout diagrams. component selection 1. inductor selection an inductor value of 22 h performs well in most applications. the aic1620 series also work with inductors in the 10 h to 47 h range. an induc- tor with higher peak inductor current tends a higher output voltage ripple (i peak output filter capacitor esr). the inductor?s dc resistance significantly affects efficiency. we can calculate the maximum output current as follows: ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = l 2 v v t i v v i in out off lim out in ) max ( out where i o u t(max) =maximum output current in amps v in =input voltage l=inductor value in h =efficiency (typically 0.9)
AIC1622 10 fig.12 top layer fig.13 bottom layer fig.14 placement application examples da m p i n g sw i t c h vi n vo ut a i c 16 22 out ba tt l x gnd q3 q2 q 1 l1 r1 200 ? 22 h vo ut vi n r2 100k ? a i c 1622 c3 c1 l 22 h 47 f 47 f 0.1 f c2 0.1 f c4 r1 200 ? l o w ba tter y out p ut r4 r3 cl sel l x out fb gnd ref lb i ba tt lb o shdn l: t d k s l f7045t -22om r 90 c 1 , c 3 : n i p p o n t ant al um c a p a ci tor 6m c m 476m b 2 t e r fig.15 simplified damping switch diagram fig.16 v out = 3.3v application circuit. vo ut vi n 1 00k ? r1 200 ? r2 22 h 47 f 47 f 0. 1 f 0. 1 f lo w ba tt er y ou tpu t c2 c4 c3 c1 l a i c 1 622 r6 r5 r4 r3 sh dn c l sel lx fb lb o gn d ref lb i ba tt ou t l: t d k s l f 7 0 45t - 22o m r 90 c 1, c 3 : n i p p o n t a n t alu m c a p a c i tor 6mc m 4 7 6 m b 2t e r v ou t =v re f * ( 1+r 5 / r 6) fig.17 an adjustable output application circuit
AIC1622 11 e l c e e1 d a2 b a1 0 . 50 b s c 0.40 0 0.70 6 4.9 0 bs c 0.13 2. 9 0 2. 9 0 0.75 0.15 0.05 0.23 3.10 3.10 0.95 0.30 0.15 s y m b o l a ms o p - 1 0 mi ll im et er s min . 1.10 ma x. a2 a 0. 2 5 s e cti on a- a bas e met a l ga ug e p l a n e wi th plati n g a1 b c d e a e1 e se e vi e w b a physical dimension (unit: mm) (unit: mm) msop-10 msop-10 note: note: information provided by aic is believed to be accurate and reli able. how e ver, w e cannot assume responsibility for use of any ci r- cuitry other than circuitry entirely embodi ed in an aic product; nor for any infringement of patents or other rights of third p arties that may result from its use. we reserve the right to change the circuitry and specific ations w i thout notice. information provided by aic is believed to be accurate and reli able. how e ver, w e cannot assume responsibility for use of any ci r- cuitry other than circuitry entirely embodi ed in an aic product; nor for any infringement of patents or other rights of third p arties that may result from its use. we reserve the right to change the circuitry and specific ations w i thout notice. life support policy : aic does not authorize any aic product for us e in life support devices and/or sy stems. life support device s or sy stems are devices or sy stems w h ich, (i) are intended for surgic al implant into the body or (ii) support or sustain life, and wh o s e failure to perform, w hen properly used in accordance w i th instruct ions for use provided in the l abeling, can be reasonably expe cted to result in a significant injury to the user. life support policy : aic does not authorize any aic product for us e in life support devices and/or sy stems. life support device s or sy stems are devices or sy stems w h ich, (i) are intended for surgic al implant into the body or (ii) support or sustain life, and wh o s e failure to perform, w hen properly used in accordance w i th instruct ions for use provided in the l abeling, can be reasonably expe cted to result in a significant injury to the user.

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