product brief CP2126 dc/dc series step-up white-led driver CP2126_pb_ eng _rev1.0 march,2004 copyright ?2004 chiphomer technology limited page 1 of 1 overview the CP2126 is a step-up dc/dc converter specifically designed to drive white leds with a constant current. the device can drive two, three or four white leds in series from a li-ion cell. series connection of leds provides identical led currents resulting in uniform brightness. the CP2126 switches at 900khz allowing the use of tiny components. the external capacitor can be as small as 0.22uf, saving space and cost versus alte rnative solutions. a low 95mv feedback voltage minimizes power loss in the current setting resistor for better efficiency. features inherently matched led current high efficiency: 85% typical drives up to four leds from a 3.2v supply 20v stable bipolar switch fast 900khz switching frequency uses tiny 1mm tall inductors requires only 0.22uf output capacitor operating industrial temperature range: -40 ~ 85 sot23-5l package sot23-5l -40 85 vref 1.25v + 1 cs - + 95mv r c c c lx 3 2 gnd - + ramp generator 900khz oscillator + - r s q q1 0.2 ohm 4 power down shdn a1 a2 a3 5 vin
product brief CP2126 dc/dc series step-up white-led driver CP2126_pb_ eng _rev1.0 march,2004 copyright ?2004 chiphomer technology limited page 2 of 2 applications cellular phones digital cameras mp3 players pdas handheld computers gps receivers typical application CP2126 l1 22uh vin lx led3 led1 r1 c1 1uf shdn gnd c2 0.22uf vout cs led2 d1 vin off on related products cp2127: step up white led driver, switches at 1200khz, can drive two to four leds in series. cp2128: regulated charge pump dc/dc converter with low noise, constant frequency. chiphomer technology limited add: 4f, building d, 1618 yishan road, shanghai, p.r.c. tel: +86-(0)21-64058488, 64014543 fax: +86-(0)21-64050030 email: sales@chiphomer.com web: www.chiphomer.com
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