power&rf 20 0 5 spring white led driver ic ? led ? ic TK11851L-G description the TK11851L-G is a pulse skipping step-up dc-dc converter ic designed for whit e led driver applications, suitable for 2 to 4 leds, with the following built in : a high current switching transistor (400ma peak),an inductor current limit detector, a low voltage reference (vref=0.515v),a high speed oscillator, an error comparator, a zener diode for open- circuit protection (ovp) and an on/off control(en pin). the ic works with a wide operating supply range (2.3~10v). the white leds are connected in series and driven at a constant current resulti ng in uniform brightness. TK11851L-G 2~4 l?m?? led l??? ???NR dc-dc ` ic ? ?????? (400ma ?` ) ???R?k`?` `?o (ovp) ???`` on/off ?`C (en ? ) i???R 2.3~10.0v ???? ? led ??Al???x?b?? ???? features ? wide operating volt age: 2.3 to 10.0v ? ??R : v op =2.3 to 10.0v ? built-in switching transistor ? ??????i ? active high on/off control: en pin ? ??? on/off ?` : en ? ? available intensity control using en pin with pwm signal ? pwm ? (en ? ) ?{ (pulse w idth m odulation) ? operates with toko d31fb miniature coil ? ??? (current limited by input current sensor) ? few external components ? ???? ? ovp (open-circuit v oltage p rotection) ? `?oC ? small package: sot23l-8 ? ???` : sot23l-8 applications ? the white led driving systems: 2 to 4 ? ? led l?? : for back-lighting and front-lighting, flashlights etc. ? ? , ?? , ???? mobile communication systems: ??C : cellular phone, phs, dsc, pda, ? phs dsc pda computer peripheral equipment ?`xC battery & dry cell battery systems ??`l?C portable equipment C ? step-up dc-dc converter (voltage supply) ? NR dc-dc ` camera, radio, communications equipment etc ??C package outline part name package marking pin configuration ordering information TK11851L-G sot23l-8 1851 see next page 1 t k 5 8 1 t l storage direction tl: left type g - environment code g: lead free package code l: sot23l-8 l 1 absolute maximum ratings parameter ? symbol ? rating unit g remarks q operating voltage range ?R v op 2.3 to 10.0 v operating temperature range ?? t op -30 to +85 c power dissipation SM p d 400 mw operating frequency range ? f op 800 mhz
power&rf 20 0 5 spring electrical charcteristics v in =3.0v, t a =25 c value parameter ? symbol ? min typ max units g conditions switch maximum voltage ??R v sw, max 20 v switch maximum current ? i sw, peak 400 ma maximum duty ratio ?`? d max 68 % inductor current limit i limit 220 260 300 ma fb reference voltage fb ?R v ref 0.495 0.515 0.535 v open circuit voltage `??R v ovp 17 18.5 20 v quiescent current ? i in, on 11.52ma shutdown supply current ??? i in,off 0.01 1 ua block diagram 1 2 3 4 8 7 6 5 en c x v in gnd e xt i s bandgap reference 0.1v i s comp osc q r s clk error comp vref 0.525v clk clk c x 0.86v 0.3v 1k ? 200k ? 200k ? r sc 0.3 ? 300 k ? 2.3k ? v fb v ovp 3 w-led driver application ? designed performance input voltage v in =2.7 to 6.5v output current i led =15ma oscillation frequency 300khz inductor peak current 280ma coil (toko) type d31fb 984fb-220m c x r led 68pf 33 ? l 22 h 2.2 fc out 1 f c in d i led v led on/off en 4 81 2 3 tk11851l 5 6 7 v in i s e xt v ovp v fb c x gnd
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