RT9284A/b pin configurations applications z camera flash white led z mobile phone, smart phone led backlight z pda led backlight z digital still camera z camcorder ordering information top view features z z z z z v in operating range : 2.7v to 5.5v z z z z z maximum output voltage up to 20v z z z z z dimming with zero-inrush and wide frequency range of 100 to 100khz z z z z z over voltage protection z z z z z output current up to 100ma at v out = 12v. z z z z z zero shutdown supply current z z z z z minimize the external component z z z z z small lc filter z z z z z internal soft start z z z z z rohs compliant and 100% lead (pb)-free general description the RT9284A/b is a compact, high efficient and high integration led driver. internal 22v mosfet can support 2 to 5 white leds for backlighting and camera flashing. highly integration and internal compensation network minimizes as 5 external component counts. optimized operation frequency can meet the requirement of small lc filters value and low operation current with high efficiency. internal soft start function can reduce the inrush current. tiny package type of tsot-23-5 and tsot-23-6 packages provide the best solution for pcb space saving and total bom cost. marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area, otherwise visit our website for detail. note : there is no pin1 indicator on top mark for tsot-23-6 type, and pin 1 will be lower left pin when reading top mark from left to right. tsot-23-6 lx gnd fb en ovp vdd 4 23 5 6 1 lx 23 54 1 gnd fb en vdd tsot-23-5 rt9284 package type j5 : tsot-23-5 j6 : tsot-23-6 operating temperature range p : pb free with commercial standard g : green (halogen free with commercial standard) ovp voltage 15 : 15v 20 : 20v ( ) fb voltage a : 1.235v b : 0.25v - product specification 1 of 5 4008-318-123 sales@twtysemi.com http://www.twtysemi.com
typical application circuit figure 1. application for driving 3 series wleds figure 2. application for driving 4 series wleds figure 4. application for constant output voltage vdd gnd lx fb ovp rt9284 v in en 6 4 2 3 5 1 i led + dimming control 2.7v to 5.5v c1 1uf c2 1uf/16v r1 d1 ss0520 l1 4.7uh to 22uh 100hz-100khz ovp 15v figure 3. application for driving 5 series wleds vdd gnd lx fb ovp RT9284A v in en 6 4 2 3 5 1 + 2.7v to 5.5v c1 1uf c2 r2 d1 ss0520 l1 4.7uh to 22uh r1 130k 15k v out 12v ovp 15v 1uf/16v v fb = 1.235v vdd gnd lx fb ovp rt9284 v in en 6 4 2 3 5 1 i led + dimming control 2.7v to 5.5v c1 1uf c2 r1 d1 ss0520 l1 4.7uh to 22uh 100hz-100khz 1uf/25v ovp 18v ovp 15v r2 600k vdd gnd lx fb ovp rt9284b v in en 6 4 2 3 5 1 i led + dimming control 2.7v to 5.5v c1 1uf c2 1uf/25v r1 d1 ss0520 l1 4.7uh to 22uh 100hz-100khz ovp 20v v fb = 0.25v RT9284A/b product specification 2 of 5 4008-318-123 sales@twtysemi.com http://www.twtysemi.com
pin description pin no. tsot-23-5 tsot-23-6 pin name pin function 1 1 lx switch pin. connect this pin to inductor and catch diode. minimize the track area to reduce emi. 2 2 gnd ground pin 3 3 fb feedback reference voltage pin. series connect a resistor between wled and ground as a current sense. sense the current feedback voltage to set the current rating. 4 4 en chip enable (active high). voltage sens ing input to trigger the function of over voltage protection. note that this pin is high impedance. there should be a pull low 100k resistor connected to gnd when the control signal is floating. -- 5 ovp over voltage protection pin. voltage sensing input to trigger the function of over voltage protection. leave it un connected to disable this function. 5 6 vdd supply input voltage pin. bypass 1uf capacitor to gnd to reduce the input noise. function block diagram current bias soft start ocp 750ma bandgap ovp uvlo timer 5ms en ovp vdd + - + - v ref pwm logic 1.2mhz osc gnd fb lx v ref ibias protection circuit buffer RT9284A/b product specification 3 of 5 4008-318-123 sales@twtysemi.com http://www.twtysemi.com
absolute maximum ratings (note 1) z supply input voltage ------------------------------------------------------------------------------------------------------ ? 0.3v to 7v z lx input voltage ----------------------------------------------------------------------------------------------------------- ? 0.3v to 22v z ovp v oltage ---------------------------------------------------------------------------------------------------------------- ? 0.3v to 22v z the other pins ------------------------------------------------------------------------------------------------------------- ? 0.3v to 6v z power dissipation, p d @ t a = 25 c tsot-23-5 ------------------------------------------------------------------------------------------------------------------- 0.455w tsot-23-6 ------------------------------------------------------------------------------------------------------------------- 0.455w z package thermal resistance (note 4) tsot-23-5, ja ------------------------------------------------------------------------------------------------------------- 220 c/w tsot-23-6, ja ------------------------------------------------------------------------------------------------------------- 220 c/w z lead temperature (soldering, 10 se c.) ------------------------------------------------------------------------------- 260 c z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c z esd susceptibility (note 2) hbm (human body mode) ---------------------------------------------------------------------------------------------- 2kv mm (ma chine mode) ------------------------------------------------------------------------------------------------------ 200v recommended operating conditions (note 3) z supply input v oltage ------------------------------------------------------------------------------------------------------ 2.7v to 5.5v z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c electrical characteristics to be continued (v in = 3.7v, t a = 25 c unless otherwise specified) parameter symbol test condition min typ max units system supply input operation voltage range v dd 2.7 -- 5.5 v under voltage lock out v dd 1.8 2.2 2.5 v quiescent current i dd fb = 1.5v, no switch 50 300 1000 ua supply current i dd fb = 0v, switch 0.1 2 3 ma shut down current i dd v en < 0.4v -- -- 1 ua line regulation v in : 3.0~4.3v -- 3 -- % oscillator operation frequency f osc 0.9 1.2 1.5 mhz maximum duty cycle 85 -- -- % dimming frequency 100 -- 100k hz reference voltage RT9284A 1.173 1.235 1.296 v feedback voltage (note 5) rt9284b 0.237 0.25 0.263 v RT9284A/b product specification 4 of 5 4008-318-123 sales@twtysemi.com http://www.twtysemi.com
note 1. stresses listed as the above ? absolute maximum ratings ? may cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. note 2. devices are esd sensitive. handling precaution recommended. note 3. the device is not guaranteed to function outside its operating conditions. note 4. ja is measured in the natural convection at t a = 25 c on a low effective thermal conductivity test board of jedec 51-3 thermal measurement standard. note 5. floating the ovp pin to disable ovp function. parameter symbol test condition min typ max units mosfet on resistance of mosfet r ds(on) -- 0.75 -- protection for 2,3,4 wleds application 14 15 16 v ovp threshold v ovp for 5 wled application 19 20 21 v ovp sink current -- 5 -- a ocp -- 750 -- ma shut down voltage v en -- -- 0.4 v enable voltage v en 1.5 -- -- v RT9284A/b product specification 5 of 5 4008-318-123 sales@twtysemi.com http://www.twtysemi.com
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