Preliminary Datasheet LP3302 High Performance, Constant Current Switching Regulator For White LED General Description Features The LP3302 is a 1.1MHz PWM boost switching regulator High Efficiency: 88% designed for constant current white LED driver applications. 1.1MHz Fixed-Frequency PWM Operation The LP3302 can drive a string of up to 8 white LEDs from a Maximum Output Voltage up to 29V 3.2V supply or 21 white LEDs from a 5V supply in series, Operating Range : 2.7V to 6V ensuring uniform brightness and eliminating several ballast Shutdown Supply Current:<1uA resistors. The LP3302 implements a constant frequency Available in SOT23-6 Package 1.1MHz PWM control scheme. The high frequency PWM Built-in Over Voltage Protection operation also saves board space by reducing external Minimize the External Component component size. To improve efficiency, the feedback RoHS Compliant and 100% Lead Pb-Free 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 Pin Configurations 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 B6：SOT23-6 LP3302B6F-00 Version 1.0 Datasheet May.-2013 Applications WLED Backlight driver OLED Backlight driver PDA DSC Camera Flash WLED driver www.lowpowersemi.com Page 1 of 13 Preliminary Datasheet LP3302 Typical Application Circuit Vin 10uH SS14 4 EN OVP 2 PWM Vin GND 6 LX 1 Cin 10uF FB Cout 1uF 5 3 LP3302B6F 0-100KHz R1 12 Marking information Device Marking Package Shipping LP3302B6F LPS SOT23-6 3K/REEL F3XXX LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 2 of 13 Preliminary Datasheet LP3302 Application Circuit Vin Vin Panel Panel 10uH 10uH + + + 1 2.2uF Vin 6 Vin 5 OVP GND 4 2 EN EN 3 FB 2 4 LP3302 Rset 12 LP3302 for 4pcs Application Circuit Vin Panel 5 OVP GND 6 2.2uF LX 2.2uF LX 2.2uF 1 + 3 FB LP3302 Rset 5.1 LP3302 for 2X6pcs Application Circuit Vin Panel 10uH 10uH 6 3 4 LX 5 LP3302 Rset 12 LP3302 for 7pcs Application Circuit 2.2uF Vin OVP GND FB + 2.2uF EN 2 EN OVP 2 4 Vin GND 6 2.2uF LX 2.2uF + 1 + 1 + FB 5 3 LP3302 Rset 5.1 LP3302 for 2X7pcs Application Circuit Vin Panel 10uH + 1 + Vin EN OVP 2 4 2.2uF GND 6 LX 2.2uF FB 5 3 LP3302 LP3302 for 21pcs Application Circuit LP3302B6F-00 Version 1.0 Datasheet May.-2013 Rset 2 www.lowpowersemi.com Page 3 of 13 Preliminary Datasheet LP3302 Functional pin description SOT-23-6 Pin Name 1 LX 2 GND Pin Function Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track area to reduce EMI. Ground Pin Feedback Reference Voltage Pin. Series connect a resistor between WLED 3 FB and ground as a current sense. Sense the current feedback voltage to set the current rating. Chip Enable (Active High). Voltage sensing input to trigger the function of 4 EN over voltage protection. Note that this pin is high impedance. There should be a pull low 100kΩ resistor connected to GND when the control signal is floating. OVP Pin. Overvoltage Sense. When VOUT is greater than 29V, the internal 5 OUT N-channel MOSFET turns off until VOUT drops below 29V, then the IC reenters start. Connect a 1uF capacitor from OUT to GND. 6 LP3302B6F-00 VIN Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input noise. Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 4 of 13 Preliminary Datasheet LP3302 Function Block Diagram IN OUT LX 250mV FB PWM_COMP. Q R PWM S 1 4mS DELAY EN SLOPE ENABLE 1.1MHz OBCILLATOR GND Absolute Maximum Ratings Supply Input Voltage---------------------------------------------------------------------------------------------------−0.3V to 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 = 25°C SOT-23-6 ------------------------------------------------------------------------0.455W Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------------ 260°C Operation Temperature Range -------------------------------------------------------------------------------------−40°C to 80°C Storage Temperature Range --------------------------------------------------------------------------------------−65°C to 150°C LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 5 of 13 Preliminary Datasheet LP3302 Electrical Characteristics Parameter Symbol Test Condition Min Typ. Max Units 6 V System Supply Input Operation voltage Range VDD 2.7 Under Voltage Lock Out VDD Supply Current IDD FB=0V, Switching 0.8 1.3 mA Shut Down Current IDD VEN < 0.4V 0.1 1 uA 2.4 Line Regulation VIN : 3.0~4.3V V 3 % 1.1 MHz Oscillator Operation Frequency FOSC 0.8 Maximum Duty Cycle 92 Dimming Frequency Feedback Voltage 100 LP3302 235 250 % 500k Hz 265 mV MOSFET On Resistance of MOSFET RDS(ON) 0.3 Ω 29 V 5 μA 1200 mA Protection OVP Threshold VOVP Rising OVP Sink Current OCP Shut Down Voltage VEN Enable Voltage VEN LP3302B6F-00 Version 1.0 Datasheet 0.4 1.5 May.-2013 www.lowpowersemi.com V V Page 6 of 13 Preliminary Datasheet LP3302 Typical Operating Characteristics LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 7 of 13 Preliminary Datasheet LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com LP3302 Page 8 of 13 Preliminary Datasheet LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com LP3302 Page 9 of 13 Preliminary Datasheet LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com LP3302 Page 10 of 13 Preliminary Datasheet LP3302 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. 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. Inductor Selection According to the Superposition Theorem, as the DC The recommended value of inductor for 2 to 6 WLEDs voltage increases, the voltage contributed to VFB applications are 4.7 to 22µH. Small size and better increases and the voltage drop on R2 decreases, i.e. efficiency are the major concerns for portable device, the LED current decreases. For example, if the VDC such as LP3302 used for mobile phone. The inductor range is from 0V to 2.8V, the selection of resistors in should have low core loss at 1.1MHz and low DCR for Figure 4 sets dimming control of LED current from better efficiency. To avoid inductor saturation current 20mA to 0mA. 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 control perform correctly. LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 11 of 13 Preliminary Datasheet 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 LP3302 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%. PWM signal. For smaller output voltage ripple (<100mV), the recommended frequency of 2.8V PWM LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 12 of 13 Preliminary Datasheet LP3302 Package Information LP3302B6F-00 Version 1.0 Datasheet May.-2013 www.lowpowersemi.com Page 13 of 13