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| preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 1 of 13 high performance, constant current switching regulator for white led general description the LP3302 is a 1.1mhz pwm boost switching regulator designed for constant current white led driver applications. the LP3302 can drive a string of up to 8 white leds from a 3.2v supply or 21 white leds from a 5v supply in series, ensuring uniform brightness and eliminating several ballast resistors. the LP3302 implements a constant frequency 1.1mhz pwm control scheme. the high frequency pwm operation also saves board space by reducing external component size. to improve efficiency, the feedback voltage is set to 250mv, which reduces the power dissipation in the current setting resistor. 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. ordering information LP3302 f:pb-free package type b6sot23-6 features ? high efficiency: 88% ? 1.1mhz fixed-frequency pwm operation ? maximum output voltage up to 29v ? operating range : 2.7v to 6v ? 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 pin configurations applications ? ? wled backlight driver ? oled backlight driver ? pda ? dsc ? camera flash wled driver
preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 2 of 13 typical application circuit cout 1uf 10uh cin 10uf r1 12 vin ss14 pwm LP3302b6f gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 0-100khz marking information device marking package shipping LP3302b6f lps f3xxx sot23-6 3k/reel preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 3 of 13 application circuit LP3302 gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 LP3302 gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 LP3302 gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 LP3302 gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 12 5.1 panel 2.2uf 5.1 2.2uf + 2.2uf panel + 10uh LP3302 for 7pcs application circuit 2.2uf rset + rset 2.2uf 10uh + 2 + + LP3302 gnd 2 en 4 fb 3 vin 6 lx 1 ovp 5 10uh LP3302 for 2x6pcs application circuit vin vin rset vin + panel vin panel 2.2uf 2.2uf 2.2uf vin rset + 10uh 10uh rset LP3302 for 21pcs application circuit 2.2uf + + LP3302 for 4pcs application circuit panel LP3302 for 2x7pcs application circuit 2.2uf 12 preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 4 of 13 functional pin description sot-23-6 pin name pin function 1 lx switch pin. connect this pin to inductor and catch diode. minim ize the track area to reduce emi. 2 gnd ground pin 3 fb feedback reference voltage pin. series connect a resistor betwe en wled and ground as a current sense. sense the current feedback volta ge to set the current rating. 4 en chip enable (active high). voltage sensing 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 sig nal is floating. 5 out ovp pin. overvoltage sense. when vout is greater than 29v, the internal n-channel mosfet turns off until vout drops below 29v, then the ic reenters start. connect a 1uf capacitor from out to gnd. 6 vin supply input voltage pin. bypass 1uf capacitor to gnd to reduce the input noise. preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 5 of 13 function block diagram slope 1.1mhz obcillator enable 4ms delay pwm_comp. r s q pwm 1 250mv in out lx fb en gnd absolute maximum ratings supply input voltage------------------------------------------- --------------------------------------------------------?0.3v t o 6.5v lx input voltage ---------------------------------------------- ----------------------------------------------------------?0.3v to 36v ovp voltage---------------------------------------------------- ----------------------------------------------------------?0.3v to 27v the other pins ------------------------------------------------ ----------------------------------------------------------?0.3v to 5.5v power dissipation, pd @ ta = 25c sot-23-6 -------------------- ----------------------------------------------------0.455w lead temperature (soldering, 10 sec.) ------------------------- ----------------------------------------------------------- 260 c operation temperature range ----------------------------------- --------------------------------------------------?40c to 80c storage temperature range ------------------------------------- -------------------------------------------------?65c to 150c preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 6 of 13 electrical characteristics parameter symbol test condition min typ. max units system supply input operation voltage range vdd 2.7 6 v under voltage lock out vdd 2.4 v supply current idd fb=0v, switching 0.8 1.3 ma shut down current idd ven < 0.4v 0.1 1 ua line regulation vin : 3.0~4.3v 3 % oscillator operation frequency fosc 0.8 1.1 mhz maximum duty cycle 92 % dimming frequency 100 500k hz feedback voltage LP3302 235 250 265 mv mosfet on resistance of mosfet rds(on) 0.3 protection ovp threshold vovp rising 29 v ovp sink current 5 a ocp 1200 ma shut down voltage ven 0.4 v enable voltage ven 1.5 v preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 7 of 13 typical operating characteristics preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 8 of 13 preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 9 of 13 preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 10 of 13 preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 11 of 13 applications information led current control the LP3302 regulates the led current by setting the current sense resistor (r2) connecting to feedback and ground. the internal feedback reference voltage is 0.25v. the led current can be set from following equation easily. in order to have an accurate led current, precision resistors are preferred (1% is recommended). the table for r2 selection is shown below. inductor selection the recommended value of inductor for 2 to 6 wleds applications are 4.7 to 22h. small size and better efficiency are the major concerns for portable device, such as LP3302 used for mobile phone. the inductor should have low core loss at 1.1mhz and low dcr for better efficiency. to avoid i nductor saturation current rating should be considered. dimming control a. using a pwm signal to en pin to control the brightness of led, the LP3302 can perform the dimming control by applying a pwm signal to en pin. the internal soft-start and wide range dimming frequency from 100hz to 100khz 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 en pin, in order to let the dimming con trol perform correctly. 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. according to the superposition theorem, as the dc voltage increases, the voltage contributed to vfb increases and the voltage drop on r2 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. preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 12 of 13 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 figure 5, output current is from 20.5ma to 5.5ma by adjusting the pwm duty cycle from 10% to 90%. preliminary datasheet LP3302 LP3302b6f-00 version 1.0 datas heet may.- 2013 www.lowpowersemi.com page 13 of 13 package information |
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