AIC1620/aic1621 high efficiency 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. (AIC1620 at v in =2.4v and v out =3. 3 v ) 20 a quiescent supply current. power-saving shutdown mode (0.1 a typic a l). internal synchronous rectifier ( no external diode ) on-chip low battery detector. low battery hysteresis. space-saving package: msop-8 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 AIC1620/aic1621 are high efficiency step up dc-dc converter. the start-up volt- age is as low as 0.8v and operate with an in- put voltage down to 0.7v. consuming only 20 a of quiescent current. these devices of- fer a built-in synchronous rectifier that re- duces size and cost by eliminating the need for an external schottky diode and improves overall efficiency by minimizing losses. the switching frequency depends on the load and the input voltage can range up to 500khz. the output voltage can be easily set by two external resistors from 1.8v to 4.0v, connect- ing fb to out to get 3.3v.the peak current of the internal switch is fixed at 0.8a (AIC1620), at 0.45a (aic1621) for design flexibility. typical application circuit + + outpu t 3.3v, o r a d j . ( 1 .8 v to 4 . 0 v ) up t o 300 m a lo w - batt er y d e te ct ou t fb gnd on off l o w - ba tte r y d e te ct in 0. 1 f v in 22 h 47 f 47 f a i c162 0 a i c162 1 ou t re f lb o sh d n l x lb i lb o fb a n alog integrations corporation si-soft research center ds-1620p-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
AIC1620/aic1621 ordering information a i c 16 20x x xx a i c 16 21x x xx p i n c o nf i g ura ti o n t o p vi ew gnd 1 3 4 2 8 6 5 7 out lb i lb o re f lx sh dn fb exam p l e: ai c 1 62 0 c o t r i n m s o p - 8 p a c k age & t a pi n g & r e el p a c k i n g t y p e a i c1 6 2 0 p o t r i n m s o p - 8 le ad f r ee p a c k a ge & t api ng & r eel p a c k i n g 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: ms op - 8 c: co m m e r c i a l p : le ad f r ee c o m m e r c i a l absolute maximum ratings supply voltage (out to gnd) 8.0v switch voltage (lx to gnd) v out + 0.3v , lbo to gnd 6.0v shdn lbi, ref, fb, 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
AIC1620/aic1621 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 a i c 1 6 2 0 3 0 0 4 0 0 steady state output current (note 3) fb=out ( v out = 3 .3v) a i c 1 6 2 1 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 ? a i c 1 6 2 0 0 . 6 0 . 8 1 . 0 lx switch current limit a i c 1 6 2 1 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
AIC1620/aic1621 electrical characteristics (continued) parameter test conditions min. typ. max. unit lbi input current v lbi = 1.4v 1 50 na 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 v il 0.2v out shdn 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 bat- tery 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 ou t = 3 .3 v , aic162 0 (0.8 a) ( r ef . to f i g.14) 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 a ic 16 21 , v out =3.3 v input batter y cur r ent ( a) i npu t ba tter y v o l t age ( v ) f i g. 2 no-load battery cu rr ent vs . input battery a ic1620, v ou t =3 .3 v 4
AIC1620/aic1621 typical performance characteristics (continued) 0. 01 0.1 1 10 100 1 000 fi g . 3 v ou t = 3 .3v , aic162 1 (0.4 5a) ( r ef . to f i g.14 ) 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 t pu t c u r 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 ai c1 621 (i _lim i t = 0. 45 a) ai c 162 0 (i _l im it = 0 . 8 a) f i g. 8 he av y l o ad w a vef o r m lx p i n w a ve form v out ac cou p l e in du ct or c u r r ent v in =2 .4v v ou t =3 .3 v 5
AIC1620/aic1621 typical performance characteristics (continued) f i g. 9 lx s w i t chin g w a v e fo r m ? i ou t = 200 ma v ou t a c co upl e f i g. 10 l oad t r ans i ent res p o n s e v in =2 .4v v out =3 .3v block diagram + - + - + - + - + 47 f 47 f c2 0. 1 f c1 vin c3 out l 47 h lx fb re f gnd out c4 0. 1 f q2 q1 lb o lb i s hdn f/ f q r s ref e renc e v o l t age m i rror m a x i mu m o n - t i m e one s hot mi n i m u m of f - t i m e one s hot 6
AIC1620/aic1621 pin descriptions AIC1620/ aic1621 pin 1: fb- connect to out f o r +3.3v output. use a resistor network to set the output voltage 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 v lbi is <1.23v. lbo is high impedance during shutdown. pin 4: ref- 1.23v re ference voltage. bypass with a 0.1 f capacitor. pin 5: shdn- shutdown input. high=operating, low=shutdown. pin 6: gnd- ground pin 7: lx- n-channel and p-channel power mosfet drain. pin 8: out- power output. out provides boot- strap power to the ic. application information overview AIC1620/aic1621 series are high efficiency, step- up dc-dc converters, designed to feature a built-in synchronous rectifier, whic h reduces size and cost by eliminating the need for an external schottky di- ode. the start-up voltage of AIC1620/aic1621 is as low as 0.8v and it operates with an input voltage down to 0.7v. quiescent supply current is only 20 a. the internal p-mosfet on-resistance is typically 0.3 ? to improve overall efficiency by minimizing ac losses. the output voltage can be easily set by two external resistors from 1. 8v to 4.0v, connecting fb to out to get 3.3v. the peak current of the internal switch is fixed at 0.8a (AIC1620) or 0.45a (aic1621) for design flexibility. the current limit of AIC1620 and aic1621 are 0.8a and 0.45a respectively. the lower current limit allows the use of a physically smaller inductor in spac e-sensitive applications. pfm control scheme the key feature of the AIC1620 series is a unique minimum-off-time, constant -on-time, current-limited, pulse-frequency-modulation (pfm) control scheme (see block diagram) with the ultra-low quies- cent current. the peak current of the internal n- mosfet power switch can be fixed at 0.8a (AIC1620) or 0.45a (aic1621). the switch frequency depends on either loading condition or input voltage, and can range up to 500khz. it is 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, the p-mosfet turns on and shunts the 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 body diode of the p-mosfet. v out falls to approximately vin-0.6v and lx remains high 7
AIC1620/aic1621 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. selecting the output voltage v out can be simply set to 3.3v by connecting fb pin to out due to the use of internal resistor divider in the ic (fig. 14). in order to adjust output voltage, a resistor divider is connected to v out , fb, gnd (fig. 15). vout can be calculated by the following equa- tion: 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 AIC1620 series contains an on-chip comparator with 50mv internal hysteresis (ref, ref+50mv) for low battery detection. if the voltage at lbi falls below the internal reference voltage. lbo ( an open-drain out- put ) sinks current t o gnd. 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) 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 AIC1620 series. therefore nippon tantalum capacitor mcm series with 100 f/6v is recommended. a smaller capacitor (down to 47 f with higher esr) is acceptable for light loads or in applications that can tolerate higher output ripple. 3. pcb lay out and grounding since AIC1620?s switching frequency can range up to 500khz, it makes AIC1620 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. 8
AIC1620/aic1621 fig.11 top layer fig.12 bottom layer fig.13 placement application examples vo ut vi n r4 100k ? a i c 1620/21 c5 c1 l 22 h 47 f 47 f 0.1 f c4 0.1 f c3 l o w ba tter y out p ut r2 r1 lx out fb gnd ref lb i lb o sh dn l: t d k s l f7045t -22om r 90 c1 , c5 : ni ppon t a n t a l u m ca p a c i t or 6m c m 476m b 2 t e r 0.1 f c2 vout vi n 100k ? r4 47 f 47 f 0. 1 f 0. 1 f lo w ba tt er y out p ut c4 c3 c5 c1 a i c 1620 / 21 r6 r5 r2 r1 shdn lx fb lb o gnd ref lb i out l 22 h l: t d k s l f7045t - 22o m r 90 c 1 , c 5 : n i p p o n t ant al u m c a p a ci t o r 6m c m 476m b 2 t e r v ou t =v ref * ( 1+ r 5 / r 6) 0. 1 f c2 fig.14 v out = 3.3v application circuit. fig.15 an adjustable output application circuit 9
AIC1620/aic1621 physical dimension (unit: mm) msop-8 a a1 a2 0.2 5 se ct io n a - a bas e me tal with p l atin g b c e d a e a e1 see v i ew b e l c e e1 d a2 b a1 0. 65 b s c 0. 40 0 0. 70 6 4. 90 b s c 0. 13 2.9 0 2.9 0 0. 75 0. 25 0. 05 0. 23 3. 10 3. 10 0. 95 0. 40 0. 15 s y m b o l a ms op - 8 milli mete rs mi n . 1.1 0 ma x . 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. 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. vi ew b 10
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