LP3382SB6F

Preliminary Datasheet LP3382S High Performance, Constant Current Switching Regulator For 8PCS White LED In Series General Description Features The LP3382S is a 1.2MHz PWM boost switching  High Efficiency: 92 regulator designed for constant- current white LED  1.2MHzFixed-Frequency PWM Operation driver applications. The LP3382S can drive a string of  Maximum Output Voltage up to 29V up to 8 white LEDs in series, ensuring uniform  Operating Range : 2.2V to 5.5V brightness and eliminating several ballast resistors.  The LP3382S implements a constant frequency  Available in SOT23-6 1.2MHz PWM control scheme. The high frequency  Built-in 29V PWM operation also saves board space by reducing  Minimize the External Component external component sizes. To improve efficiency, the  RoHS Compliant and 100% Lead (Pb)-Free feedback voltage is set to 250 mV, 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 Typical Application Circuit Vin Panel 4.7uH Cin 10uF Cout 2.2uF 1 LX 6 LC filters value and low operation current with high efficiency. 4 Vin OVP EN GND FB 2 5 3 LP3382S Order Information R1 2R LP3382S □ □ □ F: Pb-Free Package Type B6: SOT23-6 Marking information Device LP3382S Applications  WLED Backlight driver  OLED Backlight driver  PDA  MID/PTV LP3382S-02 May.-2013 Marking Package Shipping SOT23-6 3K/REEL Y:Production year W:Production week X:Production batch Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 1 of 10 Preliminary Datasheet LP3382S Functional Pin Description Package Type Pin Configurations IN OUT EN 6 5 4 1 2 3 GND FB SOT23-6 LX SOT-23-6 Pin Description Pin Name 1 LX 2 GND 3 FB Description 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 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 over voltage 4 EN 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. 5 OVP Over voltage pin. 6 Vin Supply Input Voltage Pin. Bypass 10uF capacitor to GND to reduce the input noise. LP3382S-02 May.-2013 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 2 of 10 Preliminary Datasheet LP3382S Function Block Diagram Absolute Maximum Ratings  Supply Input Voltage --------------------------------------------------------------------------------------- -0.3V to 6.0V  LX/OVP Pin to GND ----------------------------------------------------------------------------------------- -0.3V to 35V  The Other Pins ----------------------------------------------------------------------------------------------- -0.3V to 5.5V  Power Dissipation, PD @ TA = 25°C SOT-23-6 ------------------------------------------------------------- 0.45W  Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C  Operation Temperature Range ------------------------------------------------------------------------- -20°C to 85°C  Storage Temperature Range --------------------------------------------------------------------------- -65°C to 150°C ESD Susceptibility  HBM(Human Body Mode) --------------------------------------------------------------------------------------------- 2KV  MM(Machine Mode) --------------------------------------------------------------------------------------------------- 200V LP3382S-02 May.-2013 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 3 of 10 Preliminary Datasheet LP3382S Typical Application Circuit Panel Vin Panel Vin 4.7uH 4.7uH Cin 10uF Cin 10uF Cout 2.2uF 1 LX 6 LX 6 Vin OVP EN GND FB 5 4 4 Cout 2.2uF 1 3 Vin OVP EN GND FB 2 2 5 3 LP3382S LP3382S LP3382S for 6pcs Application Circuit Rset 12 Panel Vin LP3382S for 2X6pcs Application Circuit Panel Vin 4.7uH Rset 5.1 4.7uH Cin 10uF Cout 2.2uF 1 Cin 10uF LX 6 4 LX Vin OVP EN GND FB 2 Cout 2.2uF 1 5 6 3 4 Vin OVP EN GND FB 2 LP3382S LP3382S for 7pcs Application Circuit Rset 12 5 3 LP3382S LP3382S for 2X7pcs Application Circuit Rset 5.1 Vin Panel 4.7uH Cin 10uF Cout 2.2uF 1 LX 6 4 Vin OVP EN GND FB 2 5 3 LP3382S Rset 2 LP3382S-02 May.-2013 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 4 of 10 Preliminary Datasheet LP3382S Electrical Characteristics Parameter Symbol Test Condition Min Typ. Max Units 5.5 V System Supply Input Operation voltage Range VDD Under Voltage Lock Out VDD Supply Current IDD Shut Down Current IDD Line Regulation 2.2 1.8 V FB=0.2V, Switch 90 uA VEN < 0.4V 0.1 VIN : 3.0~4.3V 1 uA 2 % 1.2 MHz Oscillator Operation Frequency FOSC Maximum Duty Cycle Feedback Voltage 93 LP3382 235 % 250 265 mV MOSFET On Resistance of MOSFET RDS(ON) 0.3 Ω SW Current Limit ILM 2 A VOVP 29 V 5 μA Protection OVP Threshold OVP Sink Current Shut Down Voltage VEN Enable on Voltage VEN PWM EN Dimming range LP3382S-02 May.-2013 0.4 1.4 100 Email: marketing@lowpowersemi.com www.lowpowersemi.com V V 200K Hz Page 5 of 10 Preliminary Datasheet LP3382S Typical Operating Characteristics LP3382S-02 May.-2013 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 6 of 10 Preliminary Datasheet OVP/UVLO/OTP Applications Information The Over Voltage Protection is detected by a LED Current Control The LP3382S regulates the LED current by setting the current sense resistor (R1) connecting to feedback and ground. LP3382S The internal feedback reference voltage is 250mV. The LED current can be set from following equation easily. junction breakdown detecting circuit. Once VOUT goes over the detecting voltage, LX pin stops switching and the power N-MOSFET will be turned off. Then, the VOUT will be clamped to be near VOVP. As the output voltage is higher than a specified value or input voltage is lower than a ILED=250mV/R1 In order to have an accurate LED current, precision resistors are preferred (1% is recommended). The table for R1 selection is shown below. Power Sequence In order to assure the normal soft start function for suppressing the inrush current the input voltage should be ready before EN pulls high. Soft-Start The function of soft-start is made for suppressing the inrush current to an acceptable value at the beginning of power-on. The LP3382S provides a built-in soft-start function by clamping the output voltage of error amplifier so that the duty cycle of the PWM will be increased gradually in the soft-start period. specified value, the chip will enter protection mode to prevent abnormal function. As the die temperature is higher then 150℃, the chip also will enter protection mode. The power MOSFET will be turned off during protection mode to prevent abnormal operation. Inductor Selection The recommended value of inductor for 2 to 8WLEDs applications are 4.7 to 22µH. Small size and better efficiency are the major concerns for portable device, such as LP3382S used for mobile phone. The inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered. Capacitor Selection Input ceramic capacitor of 10uF and output ceramic Current Limiting The current flow through inductor as charging period is detected by a current sensing circuit. As the value comes across the current limiting threshold, the N-MOSFET will be turned off so that the inductor will be forced to leave charging stage and enter discharging stage. Therefore, the inductor current capacitor of 1uF are recommended for the LP3382S applications for driving 8 series WLEDs. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. will not increase over the current limiting threshold. LP3382S-02 May.-2013 Email: marketing@lowpowersemi.com www.lowpowersemi.com Page 7 of 10 Preliminary Datasheet Dimming control LP3382S Vin a. Using a PWM Signal to EN Pin 4.7uH Cin 10uF For controlling the LED brightness, the LP3382S can SS14 Cout 2.2uF 1 LX perform the dimming control by applying a PWM 6 Vin OVP EN GND FB 5 signal to EN pin. The internal soft-start and wide range dimming frequency from 100Hz to 200KHz can 4 ON/OFF insignificantly reduce audio noise when dimming. R4 100k 2 VFB=250mV LP3382S The average LED current is proportional to the PWM signal duty cycle. The magnitude of the PWM signal 3 VDC R3 R2 56K 6.8K R1 12 should be higher than the maximum enable voltage of EN pin, in order to let the dimming control perform correctly. c. Using a Filtered PWM signal Another common application is using a filtered PWM signal as an adjustable DC voltage for LED dimming Vin control. A filtered PWM signal acts as the DC voltage 4.7uH Cin 10uF SS14 1 to regulate the output current. The suggested Cout 2.2uF application circuit is shown in the Figure 6. In this LX 6 Vin OVP 5 circuit, the output ripple depends on the frequency of PWM 4 R2 100k GND FB EN 2 PWM signal. For smaller output voltage ripple 3 (