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power management 1 www .semt ech.com SC2603 simple pwm boost controller f eatures applications revision: nov 14, 2006 t ypical application cir cuit the SC2603 is a versatile, low-cost, voltage-mode pwm contr oller designed f or 1 6v in put dc/dc po w er supply applications. a simple, fixed-voltage boost regulator can be implemented using the SC2603 with a minimum of external components. the small device footprint allows for compact circuit design. SC2603 features include a temperature compensated v oltage ref erence, triangle w av e oscillat or , current limit com parat or , freq uency shif t o v er -current pr ot ection, and an int ernally com pensat ed err or am plif ier . pulse b y pulse current limiting is implemented by sensing the dif f erential v oltage acr oss an e xt ernal resist or , or an appropriately sized pc board trace. the SC2603 operates at a fixed frequency of 200khz, pr o viding an optimum com pr omise be tw een ef f iciency , external component size, and cost. u low cost / small size u switch mode efficiency up to 95% u 1% reference voltage accuracy u over-current protection u 800ma output drive u 5v t o 1 6v in put po w er sour ce u no need for external compensation network u sot23-6 is fully weee and rohs compliant u portable devices u flat p anel t v u t v se t t op bo x u auxiliary supplies u peripheral card supplies u industrial power supplies u high density dc/dc conversion description r2 r3 l1 q1 d1 c2 c1 r4 vin vout gnd d2 optional u2 SC2603 vin 5 en/ss 3 fb 1 gnd 2 cs 6 gate 4 r1 c4 enable c3 r5 c5 (open collector) open drain with < 100 pull down impedance
2 ? 2005 semtech corp. www .semt ech.com SC2603 power management electrical characteristics absolute maximum ratings rete m ara p slo b m y s s n oitid n o c ni m p y t x a m stin u e c n erefe r v f e r 5 2 2.1 0 5 2.1 5 7 2.1 v tn erru c s aib k c a b d e e f i b f v b f v = s s/n e v , ni v 2 1 = 0.2 0.8 a tn erru c tn e c s eiu q i q v otnitn erru c ni nip 0.5 0.8 a m n oitalu g e r d a o l v o i; v 5 2 = o a 1 ot a 1.0 = 5.0 0.1 % n oitalu g e r e nil v ni v ; v 5 1 ot v 5 = o i; v 5 2 = o a m 0 0 1 = 4.1 2 % dlo h s erh t ti m il tn erru c s c 8 6 3 7 8 7 v m y c n e u q erf rotallic s o t a 5 2 = o c 0 9 1 0 0 2 0 1 2 z h k tfih s y c n e u q erf rotallic s o v b f v < f e r 2/ 0 5 z h k elcy c ytu d x a m 0 9 5 9 % dlo h s erh t o l v u v o l v u v ni p u g nip m ar 2.4 5.4 v sis eretsy h o l v u 0 0 4 v m tn erru c e cru o s re vir d i e c r u o s v ni c ,v 2 1 = e t a g f n 0 1 = 5.0 8.0 1.1 a tn erru c k nis re vir d i k nis v ni c ,v 2 1 = e t a g f n 0 1 = 5.0 8.0 1.1 a tn erru c e gra h c trats tfo s i s s 0 6 a k a e p p m a r la nretni v k a e p _ r 4.1 v y ella v p m a r la nretni v y e l l a v _ r 4.0 v dlo h s erh t elb a n e v n e _ h t le v el siht w ole b n w o d llu p tu ptu o e ht elb a sid ot 9 0.0 2 1.0 v v in = 12v; v o = 25v; t a = t j = -40c to 125c unless otherwise specified. note: (1) mounting pad has to be larger than one square inch on two sided printed circuit board with minimum 1 ounce copper (2) human model. exceeding the specifications below may result in permanent damage to the device, or device malfunction. operation outside of the parameters specified in the electrical characteristics section is not implied. rete m ara p lo b m y s m u m ix a m stin u e g atlo v tu p ni v n i d n g ot 0 2 ot 3.0- v e g n a r erutare p m e t e g arots t g t s 0 5 1 + ot 5 4- c erutare p m e t n oitc n u j m u m ix a m t j 0 5 1 c .c e s 0 1 )g nire dlo s ( erutare p m e t d a e l t d a e l 0 0 3 c tn eib m a ot n oitc n u j ,e c n atsis e r la m re h t )1( a j 5 6 1 w /c e s a c ot n oitc n u j ,e c n atsis e r la m re h t c j 2 0 1 w /c e gra h c sid e gru s la cirtc ele )2( d s e 2 v k
3 ? 2005 semtech corp. www .semt ech.com SC2603 power management pin configuration ordering information pin descriptions t op vie w sre b m u n tra p e g a k c a p t r t k s 3 0 6 2 c s 1( () )2 6-3 2 t o s b v e 3 0 6 2 c s note:(1) only available in tape and reel packaging. a reel contains 3000 devices. (2) lead free product. this product is fully weee and rohs compliant # nip e m a n nip n oitc n u f nip 1 b f .)-(tu p nireifilp m a rorr e 2 d n g .d n u org e civ e d 3 s s/n e .nip trats tfo s/elb a n e 4 eta g .tu ptu o re vird eta g 5 niv .e g atlo v tu p ni e civ e d 6 s c .tu p ni e s n e s tn erru c block diagram 2 1 3 fb gnd en/ss 4 6 cs 5 vin gate sot23-6 vin fb gate cs uvlo gnd pwm en/ss 70mv current limit vin uv s q r oscillator oscillator 1.25v ref 1.25v ref 25k
4 ? 2005 semtech corp. www .semt ech.com SC2603 power management application information soft-startsoft-start prevents a dc-dc converter from drawing excessive current from the power source during start up. if the soft-start time is made sufficiently long, then the output will enter regulation without overshoot. an external capacitor is connected from the en/ss pin to the ground. after the part?s input voltage surpasses the uvlo, the en/ss pin is allowed to charge its capacitor with 60a. when 100mv is reached at the en/ss pin, the internal com p node is at 0.4v . the SC2603 will star t switching, and the converter output comes into regulation. because the fb pin v oltage f ollo ws en/ss pin v oltage, f inally , the en/ss pin voltage will be clamped at 1.25v same as therefernece voltage. setting the output voltage an external resistive divider r 1 and r 2 with its center tap tied to the fb pin sets the output voltage. ?? ? ?? ? out v r r under voltage lockoutthe under voltage lockout circuit of the SC2603 assures that the gate driver output remains in the off state when- ever the supply voltage drops below set parameters. lock- out occur s if v in f alls belo w 3.8v . normal operation re- sumes once v in rises abo v e 4.2v . theor y of operation the SC2603 is a versatile, low-cost, voltage-mode pwmcontroller designed for dc/dc power supply applications. in normal condition, the SC2603 operats at a fixed 200khz. one exception is that when the fb pin voltage drops to one half, the frequency will be shifted to one fouth of 200khz. SC2603 features include a temperature compensated v oltage ref erence, triangle w av e oscillat or , current limit com parat or , freq uency shif t o v er -current pr ot ection, and an int ernally com pensat ed err or am plif ier . pulse b y pulse current limiting is implemented by sensing thedif f erential v oltage acr oss an e xt ernal resist or , or an appropriately sized pc board trace. vout r2 r1 fb 1 SC2603
5 ? 2005 semtech corp. www .semt ech.com SC2603 power management application information over current protectionthe over-current protection is implemented by a sensing resistor and an internal current-limit comparator with a threshold of 70mv . if the switching current thr ough the sensing resistor causing voltage to drop at the cs pinreachs 70mv , the SC2603 will immediat ely turn the gat e pulse off to limit the current through the power switch.the figure below shows over-current waveforms. at t1, the input current i in begins to increase as the load i out builds up until it hits the ocp threshold at t2. at t2, v out begins to drop as i out starts increasing toward t3 while v in and i in remain the same. at t3, there two events are happening. 1) v out is at half of its regulating voltage. at this point, the internal oscillator runs into frequency shift mode and shifts the frequency to one fourth of the oper-ating freq uency . 2) the diode star ts conducting current without limit causing v in to fall due to supply current limit. finally , v in and v out bo th dr ops t o zer o and i in becomes the input supply current limit.a rc filter at the cs pin is necessary to filter out noise to ensure accurate sensing. the value of the sensing resistor can be caculated by the following equation: peak s i mv r / 70 = where i peak is the input peak current through the power mosfet . v in v out i out i in t0 t1 t2 t3 t4 over current waveforms
6 ? 2005 semtech corp. www .semt ech.com SC2603 power management applications information layout guidelinescareful attention to layout requirements are necessary for successful implementation of the SC2603 pwm con- tr oller . high currents switching at 200khz are present in the application and their effect on ground plane voltagedifferentials must be understood and minimized. 1) the high power parts of the circuit should be laid out first. a ground plane should be used, the number and position of ground plane interruptions should be such as t o no t unnecessarily com pr omise gr ound plane int egrity . isolated or semi-isolated areas of the ground plane maybe deliberately introduced to constrain ground currents to particular areas, for example the input capacitor and bottom schottky ground. 2) the loop formed by the output capacitor(s) (cout), the fet (q1), the current sensing resist or , and the scho ttky (d1) must be kept as small as possible. this loop con-tains all the high current, fast transition switching. con- nections should be as wide and as short as possible to minimize loop inductance. minimizing this loop area will reduce emi, lower ground injection currents, resulting in electrically ?cleaner? grounds for the rest of the system and minimize source ringing, resulting in more reliable gate switching signals. 3) the connection between the junction of q1, d1 and the output capacitor should be a wide trace or copper region. it should be as short as practical. since this con- nection has fast voltage transitions, keeping this con- nection short will minimize emi. 4) the output capacitor(s) (cout) should be located as close to the load as possible, fast transient load cur- rents are supplied b y cout only , and connections be- tween cout and the load must be short, wide copperareas to minimize inductance and resistance. 5) the SC2603 is best placed over an isolated groundplane area. the sof t-star t capacit or , the v in decoupling capacit or , and the current sensing f ilt er capacit or should also connected to this ground pad area. this isolatedground area should be connected to the main ground by a trace that runs from the gnd pin to the ground side of the output capacit or . if this is no t possible, the gnd pin may be connected to the ground path between the out-put capacitor and the cin, q1, d1 loop. under no cir- cumstances should gnd be returned to a ground inside the cin, q1, d1 loop. 6) input voltage of the SC2603 should be supplied from the po w er rail thr ough a 2.2~1 0 w resist or , the v in pin should be decoupled directly t o gnd b y a 0. 1f~1f ceramic capacit or , trace lengths should be as shor t as possible.7) an r c lo w pass f ilt er is req uired t o f ilt er out leading edge current spik es on the current sensing resist or . the filter capacitor needs to be very close to the cs andgnd to reduce noise pickup.
7 ? 2005 semtech corp. www .semt ech.com SC2603 power management applications information (cont.) layout diagram for the SC2603 vout 12vin + cout 2.2 0.1uf q1 0.1uf d1 SC2603 gnd 1 vin 5 3 cs 6 gate 2 fb 4 rb ra rs en/ss 20uh cin heavy lines indicate the critical loop carrying hig h pulsating current. the inductance of this loop needs to be minimized.
8 ? 2005 semtech corp. www .semt ech.com SC2603 power management applications circuit 12v to 25v @ 1a boost converter r2 34k r4 1.78k l1 18uh q1 ao4442 d1 3a, 40v c2 330u/35v c1 470u r5 1k vin = 12v vout=25v u2 SC2603 vin 5 en/ss 3 fb 1 gnd 2 cs 6 gate 4 c11 1u r1 2.2 c4 0.1u enable c3 1u r6 20m c5 120p (open drain) r2 34k r4 1.78k l1 18uh q1 ao4442 d1 3a, 40v c2 330u/35v c1 470u r5 1k vin = 12v vout=25v u2 SC2603 vin 5 en/ss 3 fb 1 gnd 2 cs 6 gate 4 c11 1u r1 2.2 c4 0.1u enable c3 1u r6 20m c5 120p (open drain) bill of material open drain with < 100 pull down impedance semtech sot23-6 SC2603 u1 1 16 20m r6 1 15 603 1k r5 1 14 603 1.78k r4 1 13 603 0 r3 1 12 603 34k r2 1 11 603 2.2 r1 1 10 alpha & omega ao4442 q1 1 9 cooper 18uh l1 1 8 1n5819 d1 1 7 805 1u c11 1 6 603 120p c5 1 5 603 0.1u c4 1 4 603 1uf c3 1 3 sanyo 330u/alum c2 1 2 sanyo 470u/alum c1 1 1 vendor footprint part reference quantity item semtech sot23-6 SC2603 u1 1 16 20m r6 1 15 603 1k r5 1 14 603 1.78k r4 1 13 603 0 r3 1 12 603 34k r2 1 11 603 2.2 r1 1 10 alpha & omega ao4442 q1 1 9 cooper 18uh l1 1 8 1n5819 d1 1 7 805 1u c11 1 6 603 120p c5 1 5 603 0.1u c4 1 4 603 1uf c3 1 3 sanyo 330u/alum c2 1 2 sanyo 470u/alum c1 1 1 vendor footprint part reference quantity item
9 ? 2005 semtech corp. www .semt ech.com SC2603 power management error amplifier: gain and phase t ypical charact eristics load regulation (v in = 12v , v o = 25v) line regulation (v o = 25v , i o = 1a) efficiency (v in = 12v , v o = 25v) ocp (v in = 12v , v o = 25v) -10 -5 0 5 10 15 20 25 30 35 40 100.0e+0 1.0e+3 10.0e+3 100.0e+3 1.0e+6 10.0e+6 frequency (hz) gain (db) -45 0 45 90 135 180 phase (deg) gain phase 23.000 23.500 24.000 24.500 25.000 25.500 26.000 4 6 8 10 12 14 16 input v oltage - (v ) output voltage - (v) 23 23.5 24 24.5 25 25.5 26 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 output current - (a) output voltage - (v) 80 82 84 86 88 90 92 94 96 98 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 output current - (a) efficiency - (%) 24.2 24.4 24.6 24.8 25 25.2 25.4 25.6 0 0.5 1 1.5 2 2.5 3 output current - (a) output voltage - (a) frequency shift (v fb vs. f sw )
10 ? 2005 semtech corp. www .semt ech.com SC2603 power management t ypical charact eristics reference v olt age vs t emperature oscillator frequency vs t emperature uvlo threshold vs t emperature 1.22 1.225 1.23 1.235 1.24 1.245 1.25 1.255 1.26 -50 -25 0 25 50 75 100 125 150 temperature ( o c ) reference voltage ( v ) 1 8 0 1 8 5 1 9 0 1 9 5 2 0 0 2 0 5 2 1 0 -5 0 -2 5 0 2 5 5 0 7 5 1 0 0 1 2 5 1 5 0 t e m p e r a t u r e ( o c ) oscillator frequency (khz) 4 . 0 5 4 . 0 8 4 . 1 0 4 . 1 3 4 . 1 5 4 . 1 8 4 . 2 0 4 . 2 3 4 . 2 5 4 . 2 8 4 . 3 0 -5 0 -2 5 0 2 5 5 0 7 5 1 0 0 1 2 5 1 5 0 t e m p e r a t u r e ( o c ) uvlo threshold (v) uvlo hysteresis vs t emperature 0 .1 5 0 .2 0 .2 5 0 .3 0 .3 5 0 .4 0 .4 5 0 .5 0 .5 5 -5 0 0 5 0 1 0 0 1 5 0 t e m p e r a t u r e ( o c ) uvlo hysteresis (v) current limit threshold vs t emperature 68 69 70 71 72 73 74 75 -50 -25 0 25 50 75 100 125 150 temperature ( o c) current limit threshold (mv) vin=12v vin=5v
11 ? 2005 semtech corp. www .semt ech.com SC2603 power management semt ech cor poration power management products division 200 flynn r oad, camarillo, ca 930 12 phone: (805)498-2 11 1 f ax (805)498-3804 outline drawing - sot23-6 contact information land pattern - sot23-6 .110 bsc .037 bsc detail aaa c seating ccc c 2x n/2 tips 2x e/2 6 see detail a1 a a2 bxn a .008 1 2 n e .060 .114 .063 .118 .010 - 6 a 0.20 1.60 3.00 2.80 bsc 0.95 bsc .069 1.50 2.90 .020 0.25 1.75 0.50 - ei l (l1) c 01 0.25 plane gage h 2.80 .110 bbb c a-b d 0 .008 - .004 .012 .003 (.024) .018 - .035 .000 .035 - - .045 0.10 0.20 10 0 - 10 1.15 (0.60) 0.45 .024 .009 0.30 0.08 .057 .051 .006 0.00 .90 0.90 0.22 0.60 - 0.15 1.45 1.30 - - 1.90 bsc .075 bsc a e1 d e b c h nom inches dimensions l1 aaa bbb ccc 01 n dim c e e1 l e1 e d a1 a2 b a min millimeters max min nom max plane d datums and to be determined at datum plane controlling dimensions are in millimeters (angles i n degrees). dimensions "e1" and "d" do not include mold flash, protrusions 3. or gate burrs. notes: 1. 2. -a- -b- -h- side view this land pattern is for reference purposes only. consult your manufacturing group to ensure your company's manufacturing guidelines are met. notes: 1. dimensions inches y z dim g p x c millimeters p (c) z y g .043 .141 .055 (.098) .037 .024 1.40 (2.50) 0.95 0.60 1.10 3.60 x dimensions inches y z dim g p x c millimeters

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