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aug. 23. 2012 / rev0.0 1/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver adt6780 ? ? ?? ? led ?, ? ? led ? a (vin : 4.5v~28v) ? ( 2a). ??? ? (v fb =0.2v) ? . ? ? . adt6780 ? ??. . ? ? sop8-pp(with e-pad) ?. ? ? ? ? ? : 0.2v (?) ?? ? 925khz ? ? ? 4.5v 28v ? : 2a ? ? 93% ? mosfet : 80m? ? ?? : 10ua ? , (3a), uvlo ? ? sop8-pp(with e-pad) figure 1. typical application circuit ? ? led/ir-led ? ? ? ? ? thermally enhanced low v fb step-down led driver adt6780 en l1 c2 r1 d2 vout c5 d1 c6 option c4 u1 gnd fb vin en sw bst 1 7 2 3 5 ss comp 6 4 8 vin c1 c3 r2
aug. 23. 2012 / rev0.0 2/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? ? ? ? 1bst ? ? . ? ? ? ? . 10nf ? sw bst. 2vin ? . ? ?? ? . 3sw . ? sw gnd. 4 gnd ?? . 5fb ? . ? ? 0.2v ? . 6comp . 7en ??? . uvlo . 8ss ? . ss ?? ? ? . 1 2 3 45 6 7 8 bst vin sw gnd fb comp en ss exposed pad * connect to gnd ? u1 ic adt6780 adtech d1 schottky barrier diode b230a diodes l1 chip inductor 6.8uh / 3a tdk c1 mlcc 10 ? / 35v - c2 mlcc 10 ? / 10v - c3 mlcc 8.2 ? - c4 mlcc 100 ? - c5 mlcc 10 ? - r1 chip resistor 0.2 ? /1% - r2 chip resistor 2 ? - adt6780 ? adt6780 aug. 23. 2012 / rev0.0 3/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? ? ? ( ? 1) ( ? 1) ? ? ? ? . ( ? 2) 25 ? 17mw/ ?? . ( ? 3) jesd51-7, pcb ? ? ? ? ? v in -0.3 - 30 v sw ? v sw -0.5 - v in + 0.3 v bst ? v bst -0.3 - v sw + 6 v ? ? - -0.3 - +6 v ?? (ta=25 ) ( ? 2) p d - - 2.08 w , sop8-pp(with e-pad) ( ? 3) ja -60- /w t stg -65 - +150 t j.max --+150 ? ? ? ? ? v in 4.5 12.0 28.0 v ? v out 0.2 - 16 v t opr -40 - +85 t j --+125 figure 2. functional block diagram en fb voltage reference internal regulator error amplifier 7 5 comparator control logic + - + - driver gnd 4 shutdown sw 3 bst 1 vin 2 osc regulator + - r s current sense amplifier current limit comp 6 ss 8 driver aug. 23. 2012 / rev0.0 4/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver (ta=25 , vin=12v, ? ) ? ? ? ?? i off v en = 0v - 10 - ? ? i q v en = 3v, v fb = 1.4v - 0.7 - ? ? v fb 4.5v v in 28v, v comp < 2v 0.184 0.200 0.216 v ? ? a ea - - 750 - v/v ?? g ea i comp = 10 ? - 750 - ? /v ? ? ( ? 4) r on.h - - 80 - m? ? ? ( ? 4) r on.l - - 10 - ? ? ? v en = 0v , v sw = 0v - 0.1 10 ? ( ? 4) duty=50% - 3 - a current sense to comp g cs --11-a/v ? f sw - - 925 - ? fold-back ? v fb = 0v - 125 - ? ?? d max v fb = 0.15v, io=1a 76 86 99 % ? t on - - 100 - ? uvlo ?? v en rising 2.00 2.35 2.70 v uvlo ??? - - 250 - ? en ?? - 0.8 1.1 1.4 v en v en = 0v - 2.0 - ? ? c4 = 100 ? -3- ? ( ? 4) - - 145 - ( ? 4) guaranteed by design.( ? ) aug. 23. 2012 / rev0.0 5/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver vin=12v, load : 1a / one 4w white led and ta=25 , ? v sw 10v/div v out (ac) 20mv/div i inductor 0.5a/div 1 ? /div led current (a) efficiency (%) 60% 65% 70% 75% 80% 85% 90% 95% 100% 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 vin=24v vin=12v vin=6v 0.184 0.188 0.192 0.196 0.200 0.204 0.208 0.212 0.216 -40 -20 0 20 40 60 80 100 120 750 800 850 900 950 1000 1050 -40 -20 0 20 40 60 80 100 120 v out 2v/div v sw 10v/div i inductor 2a/div 4 ? /div ( ) ( ) feedback voltage (v) switching frequency (khz) inductor peak current (a) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 20406080100 ?? (%) ? ? ? aug. 23. 2012 / rev0.0 6/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver v en 5v/div v out 2v/div v sw 10v/div i led 1a/div 1 ? /div 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 20406080100 led current (a) pwm ?? (%) en ? pwm (c4 open, pwm frequency=500hz, duty=50%) led current vs pwm ?? (c4 open, pwm frequency=500hz) ? (c4=100nf) v sw 10v/div v en 5v/div v out 2v/div i led 0.5a/div 1 ? /div v sw 10v/div v en 5v/div v out 2v/div i led 0.5a/div 40 ? /div enable turn-off (c4=100nf) ? (c4 open) v sw 10v/div v en 5v/div v out 2v/div i led 0.5a/div 40 ? /div enable turn-off (c4 open) v sw 10v/div v en 5v/div v out 2v/div i led 0.5a/div 40 ? /div vin=12v, load : 1a / one 4w white led and ta=25 , ? aug. 23. 2012 / rev0.0 7/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? adt6780 ? nmos ? ? ? ? ? ? 4.5v 28v ? 2a ??? ? ?? ?? adt6780 ? ??? led fb ?? ? led ? ? ??? nmos led adt6780??? ? ???uvlo???? en ? 800mv ? ? ? en ? 1.1v ? 2.7v, ? ? en ?en ? pull-up? ? ? en? ? ? ? ua ? ss ?gnd ? ? ? ? ?? c4 ? ? c4 ? 100nf ? ? ? 3m? ? adt6780 ? ?? ? ? ? ? ??? ? 777khz1050khz fb ? 80mv ? ? ? ? 125khz adt6780? nmos ? ? nmos ? ?? ? ?? swbst? sw? ? ? ?? ? ? (ocp) ? ?? nmos ?? ? ? 2.2a 4a ? ?? ???? pwm ?? ? ?? ? ? ?? ? ? ? ? ? ? ?? comp ? ? ? adt6780 ? ? 0.2v ? ? ?? ? ? ? ? pwm ? ? aug. 23. 2012 / rev0.0 8/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? ? ? 1 adt6780 ? ? ? 2 adt6780 ? ? ? ? ? 1 ? 2 ?? led ? led fb gnd ? ? r1 1% ?? led ? 1a led ? r1 =0.2 ? ??? ? ?? ? ? ? 1? ? ? ? ?? ? ?? ? ?? ? rms ? ? ? ? ? ? 20% 30% ? ? ? ?? ? ?? ? toko tdk murata ? emi ? ? ? emi ? , ??? r1 0.2v i led = ? ? ? ? ? ? ? ? ? = in out sw out l v v 1 l f v i 2 i i i l out l.peak + = ?? ? ? ? ? ? ? ? ? ? ? ? ?? ?? ? , ? ? led pwm ? ? pwm en ?? led ? pwm ? ? led / ? ? pwm ? c4 ? pwm ? ? 100hz 1khz ? pwm ? ???? ? aug. 23. 2012 / rev0.0 9/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? ? ? ? ?? ? ? ? ?? ? ? 1? cin ? ? ? ? ? ? ?? ? rms ? ??? ? v in =2 v out (50% ), rms ? ?? ??? ? ? i cin_rms . ? ? esr ? ? ? ? ? ? x5r x7r ? ? ? ? ? ? ? 10uf ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? esr 1? co ? esr ?? ? esr ? ? ? esr ? ? esr ? ? ? ? ? ? ? 1? ? ? esr ? ?? ? ? ? ?? ? ? ??? ? ? ? ? ?? ? 10uf ? ? ? ? ? ? ? ? ? ? ? = in out in out in sw out in v v 1 v v c f i v ? ? ? ? ? ? ? ? ? = in out in out out cin_rms v v 1 v v i i ? ? ? ? ? ? ? ? + = o sw l out c f 8 1 esr i v ? ? ? ? ? ? ? ? = o sw l out c f 8 1 i v ( ) esr i v l out = ? ? ( ) aug. 23. 2012 / rev0.0 10/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ? adt6780 ? ? ? ????? ?? ? ?? lc ? ? ? ?? ?? ? ? ? ? ? ? ? ? ? ???? ? ? ? ?? comp gnd ? ? ? ? ? ? ?? ? ?1? a ea ? ? g cs ?? r1 ? ? ? ? ? ?? ? (c3) ? led (r led = v out / i led ) ? 1? gea ? ? ? ? ? ? ? ? ?? ? ? ? ? (r2-c3 ? f p2 1? ? ? ? esr ? ? 1? ? f z2 ? f p3 ? r2 ? ? (c6 comp gnd ? f p3 1? ? ? ? ? ?? ? ??? ? ? ? ?? ? fc ? ?? ? ? ? ? ? ?? ? ? ? ???? ? ? cs ea 1 vdc g a r a = 1 f a c3 2 g f = = r2 c3 2 1 f z1 = esr c 2 1 f o z2 = r2 c6 2 1 f p3 = ? ? ( ) aug. 23. 2012 / rev0.0 11/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ??? ? ? 1. ? ? ? ? ? ? ?? ? ???? 2. ? r2( h ?? ? r2 ? ?? 3. c3 ? ? ?? ? c3 ??? ? f z1 f z1 fc ???? ? c3 ? ?? 4. esr ? ? ????? (c6 ? f p3 =f z2 1? ? ?? n ? led vf led ? vfb ? ? r1 g g r c2 f 2 r2 cs ea led c = r2 f 2 4 c3 c r2 esr c2 c6 = vin (v) # of series irleds vout max (v) r2 ( ? )c3 ( ? )c6 ( ? )l1 (uh)c2 ( ? ) 12 1 ~ 5 10 2 8.2 none 6.8 ~ 10 10 24 1 ~ 8 16 2 8.2 none 15 ~ 22 10 vin (v) # of series wleds vout max (v) r2 ( ? )c3 ( ? )c6 ( ? )l1 (uh)c2 ( ? ) 12 1 ~ 2 8 2 8.2 none 6.8 ~ 10 10 24 1 ~ 4 16 2 8.2 none 15 ~ 22 10 fb f out v v v + = n 1. ? ? ? 2. ? led ? ? ? ? 1 ? 2 ?? ? ?? ? ? ? ( ) aug. 23. 2012 / rev0.0 12/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver adt6780 ? ? ?? ? ? 145 c ? ? ? ? dc/dc ? ? ? 10 ??? adt6780 ?? sop ? 50 c ? ? 1.25w ??? ? ? gnd ?? ? 25 c ? ? ? ? 17 mw ? pcb layout consideration ? ? ? pcb layout ???? pcb layout ?? 1. (c1) ? ? ? 2. 3. ? ? sw ? ?? 4. ? ? sw bst ? ? fb comp 5. ? ??? ? ? ? ? 6. ? gnd ? ?? ? ? ? ( ) aug. 23. 2012 / rev0.0 13/13 * ???? http://www.ad-tech.co.kr adt6780 thermally enhanced low v fb step-down led driver ?? ; sop8-pp(e-pad) , 4.9mm x 3.94mm body (units : mm) symbol dimensions in millimeters dimensions in inches min max min max a 1.350 1.750 0.053 0.069 a1 0.050 0.150 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.100 0.185 0.200 d1 3.202 3.402 0.126 0.134 e 3.800 4.000 0.150 0.157 e1 5.800 6.200 0.228 0.244 e2 2.313 2.513 0.091 0.099 e 1.270 (bsc) 0.050 (bsc) l 0.400 1.270 0.016 0.050 0 o 8 o 0 o 8 o |
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