preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 1 of 7 no schttoy, high performance, constant current switching regulator for 9pcs white led general description the LP3303 is a 1.0mhz pwm boost switching regulator designed for constant- current white led driver applications. the LP3303 can drive a string of up to 8 white leds from a 3.6v in series, ensuring uniform brightness and eliminating several ballast resistors. the LP3303 implements a constant frequency 1.0mhz pwm control scheme. the high frequency pwm operation also saves board space by reducing external component sizes. to improve efficiency, the feedback voltage is set to 200mv, which reduces the power dissipation in the current setting resistor. highly integration and internal compensation network minimizes as 3 external component counts. optimized operation frequency can meet the requirement of small lc filters value and low operation current with high efficiency. ordering information LP3303 f: pb-free b6:sot23-6 pin configurations features high efficiency: 86% ? 1.2mhzfixed-frequency pwm operation maximum output voltage up to 28v operating range : 2.7v to 16v shutdown supply current:<1ua ? available in sot23-6 package ? built-in over voltage protection ? minimize the external component rohs compliant and 100% lead (pb)-free applications wled blacklight driver oled blacklight driver pda dsc camera flash wled driver typical application circuit 22uh LP3303 2 4 3 6 1 5 gnd ctrl fb vin sw out rset 1uf vin 1uf 10r marking information please view website .
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 2 of 7 functional pin description sot-23-6 pin name pin function 1 sw switch pin. connect this pin to inductor and catch diode. minimize the track area to reduce emi. 2 gnd ground pin 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 ctrl chip enable (active high) and dimming control pin. 5 out output pin.connect to output capacitor and leds.minimize trace between this pin and output capacitor to reduce emi. 6 vin supply input voltage pin. bypass 1uf x5r or x7r capacitor to gnd to reduce the input noise. function block diagram absolute maximum ratings supply input voltage(vin)------------------------------------------------------------------------------------------- ? 0.3v to 16v lx input voltage -------------------------------------------------------------------------------------------------------- ? 0.3v to 36v out pin voltage--------------------------------------------------------------------------------------------------------- ? 0.3v to 29v ctrl pin voltage------------------------------------------------------------------------------------------------------- ? 0.3v to 10v fb pins ------------------------------------------------------------------------------------------------------------------- ? 0.3v to 2.0v power dissipation, p d @ t a = 25c sot-23-5 ------------------------------------------------------------------------0.455w lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------------ 260 c operation temperature range --------------------------------------------------------------------------------- ? 40c to 80c storage temperature range ---------------------------------------------------------------------------------------- ? 65c to 150c
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 3 of 7 electrical characteristics parameter s y mbol test condition min typ max units system supply input operation voltage range v dd 2.7 16 v under voltage lock out v dd 2.5 v supply current i dd fb=0v, switch 1 2.5 ma shut down current i dd v en < 0.4v 0.1 1 ua line regulation v in : 3.0~4.3v 3 % oscillator operation frequency f osc 0.9 1.0 1.2 mhz maximum duty cycle 90 % dimming frequency 100 10k hz feedback voltage LP3303 191 200 210 mv mosfet on resistance of mosfet r ds(on) 0.5 protection ovp threshold v ovp 29 v ovp sink current 5 a ocp 750 ma shut down voltage v en 0.4 v enable voltage v en 1.5 v
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 4 of 7 typical operating characteristics
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 5 of 7
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 6 of 7 applications information led current control the LP3303 regulates the led current by setting the current sense resistor (rset) connecting to feedback and ground. the internal feedback reference voltage is 200mv. the led current can be set from following equation easily. i led(ma) =200mv/rset in order to have an accurate led current, precision resistors are preferred (1% is recommended). the table for rset selection is shown below. rset resistor value selection iled(ma) rset( ) 20 10 15 13.3 12 16.6 10 20 5 40 inductor selection the recommended value of inductor for 2 to 8 wleds applications are 4.7 to 22h. small size and better efficiency are the major concerns for portable device, such as LP3303 used for mobile phone. the inductor should have low core loss at 1.4mhz and low dcr for better efficiency. to avoid inductor saturation current rating should be considered. dimming control a. using a pwm signal to ctrl pin for controlling the led brightness, the LP3303 can perform the dimming control by applying a pwm signal to ctrl pin. the internal soft-start and wide range dimming frequency from 100hz to 50khz can insignificantly reduce audio noise when dimming. the average led current is proportional to the pwm signal duty cycle. the magnitude of the pwm signal should be higher than the maximum enable voltage of ctrl pin, in order to let the dimming control perform correctly. rset LP3303 2 4 3 6 1 5 gnd ctrl fb vin sw out 10r vin 22uh pwm 1uf 1uf b. using a dc voltage using a variable dc voltage to adjust the brightness is a popular method in some applications. the dimming control using a dc voltage circuit is shown in figure 4. accord ing to the superposition theorem, as the dc voltage increases, the voltage contributed to vfb increases and the voltage drop on rset decreases, i.e. the led current decreases. for example, if the vdc range is from 0v to 2.8v, the selection of resistors in figure 4 sets dimming control of led current from 20ma to 0ma. 10r 1uf rset off vin r2 r1 (0-2.8v) 1uf LP3303 2 4 3 6 1 5 gnd ctrl fb vin sw out 5k on 22uh 90k vdc c. using a filtered pwm signal another common application is using a filtered pwm signal as an adjustable dc voltage for led dimming control. a filtered pwm signal acts as the dc voltage to regulate the output current. the recommended application circuit is shown in the figure 6. in this circuit, the output ripple depends on the frequency of pwm signal. for smaller output voltage ripple (<100mv), the recommended frequency of 2.8v pwm signal should be above 2khz. to fix the frequency of pwm signal and change the duty cycle of pwm signal can get different output current. according to the application circuit of figu re 5, output current is from 20.5ma to 5.5ma by adjusting the pwm duty cycle from 10% to 90%. r2 (0-100khz) LP3303 2 4 3 6 1 5 gnd ctrl fb vin sw out vin 1uf pwm r1 on 22uh 0.1uf 1uf r3 rset off 100k 90k 10r 5k c1
preliminary datasheet LP3303 LP3303 C03 ver. 1.3 datasheet feb.-2009 p age 7 of 7 packing information
|
