lr 246 white led step-up converter ? overvoltage function ? fast 1.2mhz switching frequency ? requires only 0.22uf output capacitor ? inherently matched led current ? high efficiency: 85% typical ? 2.5v to 10v v in ranges ? drives up to four series leds with a li-lon cell ? uses very tiny inductors ? sot-26 package lr 246 is a step-up dc/dc co n v ert e r specifically designed to drive white led with a constant current. it can drive two,three,or four leds. it switches at 1.2mhz and use tiny external components. the output capacitor can be as small as 0.22uf,which can save space and cost versus alternative solutions. feedback voltage is as low as 95mv. built-in overvoltage function. absolute maximum ratings parameter symbol value unit supply voltage v in 10 v feedback voltage fb 10 v switch voltage sw 20 v ce voltage v ce 10 v operating temperature range t opr -25 to +70 storage temperature range r stg -55 to +150 junction temperature t j 125 pin name description symbol description symbol 1 switch sw 6 supply voltage vin 2 gnd gnd 5 over voltage ovp 1 2 3 4 5 6 3 feedback fb 4 start-up ce leshan radio company, ltd. 1/8
block diagram pwm + control pin6(vin) - pin4 - shutdown + + sense current 0 - fosc pin3(fb) comp pin1(sw) pin5(ovp) pin2(gnd) slope vref + gm 0 0 d246 leshan radio company, ltd. lr 246 2/8
electrical characteristics t amb = 25 , v in =3v v ce =3v,unless otherwise specified. parameter test conditions / pins min type max unit minimum operating voltage 2.5 v maximum operating voltage 10 v feedback voltage i sw =100ma, duty cycle=66% 86 95 104 mv fb pin bias current 50 100 200 na supply current v ce =0v 1.9 0.1 2.5 1 ma ua switching frequency 0.8 1.2 1.6 mhz maximum duty cycle 85 90 % ovp protection 27 v switch current limit 320 ma switch v cesat i sw =250ma 350 mv switch leakage current v sw =5v 0.01 5 ua ce voltage high 1.5 v ce voltage low 0.4 v ce pin bias current 65 ua typical application d4 1 2 pin3(fb) pin1(sw) + 0 l1 22uh 1 2 vcc pin4 1k + gm d1 control sense 0 fosc pwm - d1 r1 vref - + + slope pin2(gnd) c2 0.22u c1 1u pin5(ovp) d1 shutdown current pin6(vin) - hi comp 0 leshan radio company, ltd. lr 246 3/8
analog voltage light control shutdown d4 1 2 d1 + pin3(fb) 0 l1 22uh 1 2 sense pin6(vin) slope 0 - pwm - c1 1u vdc vref d1 comp pin4 pin5(ovp) + c2 0.22u + + current vcc 5k pin1(sw) hi 90k gm r1 pin2(gnd) d1 hi control 0 fosc - logic voltage light control pwm pin5(ovp) r1 - + hi 0 d4 1 2 fosc hi 1k l1 22uh 1 2 vcc vref c1 1u pwm - pin6(vin) + sense pin3(fb) pin2(gnd) + 0 pin1(sw) - slope + d1 shutdown d1 control 0 c2 0.22u gm comp current d1 pin4 leshan radio company, ltd. lr 246 4/8
figure 6 z l f k ) u h t x h q f \ 9 v 7 t ? e c ? 6 z l f k ) u h t x h q f \? 0 + ]? , t 9 v 7 9 l q 9 , t p $ leshan radio company, ltd. lr 246 5/8
9 6 7 t ? e c ? ? ? , / ( ' p $ , / ( ' p $ , / ( ' p $ ' u l y h / ( ' , / ( ' p $ ? ? 9 l q 9 9 l q 9 leshan radio company, ltd. lr 246 6/8
' u l y h / ( ' , / ( '? p $? ? ? 9 l q 9 9 l q 9 leshan radio company, ltd. lr 246 7/8
sot-26 diagram dimension(in mm) dimension(in inch) symbol min max min max a 0.787 1.450 0.031 0.057 a1 0.152 0.006 b 1.397 1.803 0.055 0.071 b 0.250 0.559 0.010 0.022 c 2.591 2.997 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024 leshan radio company, ltd. lr 246 8/8
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