EUP2539 10 White LED Boost Converter In Thin TSOT-23 Package DESCRIPTION FEATURES The EUP2539 is a constant current step-up converter specifically designed to drive white LEDs. The Step-up converter topology allows series connection of the white LEDs, so the LED currents are identical for uniform brightness. The EUP2539 switches at 1MHz, allowing the use of tiny external components. The output capacitor can be as small as 0.22µF, saving space and cost versus alternative solutions. A low 0.3V feedback voltage minimizes power loss in the current setting resistor for better efficiency. The EUP2539 high-voltage output stage is perfect for driving mid-size and large panel displays containing up to ten white LEDs in series. LED dimming can be done by using a DC voltage, a logic signal, or a pulse width modulation(PWM) signal. The enable input pin allows the device to be placed in shutdown mode with “zero” quiescent current. z z z z z z z z z 2.6V to 5.5V Input Range 38V Output Over Voltage Protection Internal Soft-Start PWM Dimming Control Internal High Power 40V MOSFET Switch Fast 1MHz Switching Frequency Small, Low-Profile Inductors and Capacitors TSOT23-5 Package RoHS Compliant and 100% Lead (Pb)-Free APPLICATIONS z z z z The EUP2539 is available in low profile TSOT23-5 package. GPS Navigation Systems Portable Media Players Handheld Devices, Digital Camera Portable Game Machines Typical Application Circuit Figure 1. White LED Application DS2539 Ver1.1 Apr. 2009 1 EUP2539 Pin Configurations Package Type Pin Configurations TSOT23-5 Pin Description PIN TSOT23-5 SW 1 GND 2 FB 3 EN 4 IN 5 DS2539 Ver1.1 Apr. 2009 DESCRIPTION Switch Pin.This is the drain of the internal power switch. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. Common Ground. Connect the pin to the ground plane. Feedback Pin. Reference voltage is 0.3V. Connect cathode of lowest LED and resistor here. Calculate resistor value according to the formula: RFB=0.3/ILED Chip Enable Pin. Connect it to 1.4V or higher voltage to enable device, 0.3V or less voltage to disable device. Input Supply Voltage 2 EUP2539 Ordering Information Order Number Package Type Marking Operating Temperature Range EUP2539OIR1 TSOT23-5 XXXXX AB00 -40 °C to +85°C EUP2539 □ □ □ □ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type O: TSOT Block Diagram Figure 2. DS2539 Ver1.1 Apr. 2009 3 EUP2539 Absolute Maximum Ratings (1) IN, EN, FB to GND -----------------------------------------------------------------SW to GND --------------------------------------------------------------------------Power dissipation, PD@ TA=25°C TSOT23-5 ----------------------------------------------------------------------------Package Thermal Resistance TSOT23-5,θJA ----------------------------------------------------------------------Maximum Junction Temperature --------------------------------------------------Lead Temperature (Soldering, 10sec.) --------------------------------------------Storage Temperature Range --------------------------------------------------------- -0.3V to 6V -0.3V to 40V 0.4W 220°C/W 125°C 260°C -65°C to +150°C Operating Conditions (2) Operating Temperature Range ---------------------------------------------------- -40°C to +85°C Supply Voltage , VIN----------------------------------------------------------------- 2.6V to 5.5V Note (1): Stress beyond those listed under “Absolute Maximum Ratings” may damage the device. Note (2): The device is not guaranteed to function outside the recommended operating conditions. Electrical Characteristics (VIN =3.6V, VOUT=34V, COUT=0.22µF, CIN=4.7µF, L1=47µH, RFB=15Ω,TA= -40°C to+85°C. Unless otherwise noted. Typical values are at TA= +25°C) Symbol UVLO Parameter Under Voltage Lock Out Maximum Output Voltage Supply Current Quiescent Current Shutdown current ICC1 ICC2 ICC3 Conditions Rising No Switching VCC=5.5V, Continuous Switching VCC=5.5V, FB=1.3V, No Switching VCC=5.5V, VEN<0.4V EUP2539 Min Typ Max. 2.2 2.4 Unit 1.7 130 0.1 2.6 40 2.6 170 1 V V mA µA µA 1 1.3 MHz Oscillator Fosc Operation Frequency Dmax Maximum Duty Cycle 0.8 92 % Reference Voltage VFB Feedback Voltage 285 300 315 mV 1 2 Ω 0.5 0.75 1.6 A 0.4 0.7 MOSFET Rds (on) On resistance of MOSFET ILX Current Limit Control and Protection VEN1 Shutdown Voltage VEN2 Enable Voltage 0.7 1.2 V EN Pin Pull Low Current 0.1 1 µA 38.5 40 V IEN OVP DS2539 OVP Threshold Ver1.1 Apr. 2009 37 4 V EUP2539 Typical Operating Characteristic Quiescent Current vs. VIN (Not Switching) Quiescent Current vs. VIN (Switching) 2 Quiescent Current (mA) Quiescent Current (µA) 150 125 100 75 1.5 1 0.5 0 50 3 3.5 4 4.5 5 3 5.5 3.5 Input Voltage (V) FB PIN Voltage vs. Temperature 4.5 5 5.5 310 304 FB PIN Voltage vs. Output Current FB PIN Voltage (mV) FB PIN Voltage (mV) 306 4 Input Voltage (V) 305 302 300 300 295 298 296 290 -50 0 50 100 150 5 10 Switching Frequency vs. Supply Voltage 20 25 30 LED Current vs. Input Voltage 40 1.1 35 LED Current (mA) Switching Frequency (MHz 15 Output Current (mA) Temperature (℃) 1 0.9 30 25 20 15 10 RFB=10Ω RFB=15Ω 5 0 0.8 3 3.5 4 4.5 5 3 5.5 Ver1.1 Apr. 2009 3.5 4 4.5 Input Voltage (V) Input Voltage (V) DS2539 RFB=20Ω 5 5 5.5 EUP2539 Efficiency vs. Load Current (10 LED) 1 100 0.5 90 Efficiency （%） LED Current Variation (%) Typical Operating Characteristics (continued) LED Current Regulation (10mA) 0 -0.5 80 70 VIN=3.6V -1 VIN=5V 60 3 3.5 4 4.5 5 5.5 5 Efficiency vs. Input Voltage (10LED) 15 20 25 30 Switch On Resistance vs. Input Voltage 100 2 Switch Resistance (Ω) Efficiency （%） 10 LED Current （mA） Input Voltage (V) 90 80 70 ILED=15mA 1.5 1 0.5 ILED=20mA 60 0 3 3.5 4 4.5 5 5.5 3 3.5 Input Voltage （V） 4 4.5 5 5.5 Input Voltage (V) Maximum Output Current vs. Input Voltage Shutdown Voltage vs. Input Voltage 1 120 Shutdown Voltage (V) Output Current (mA) 100 80 60 40 20 0.6 -40℃ 0.4 -25℃ 85℃ 0 3 3.5 4 4.5 5 Ver1.1 Apr. 2009 125℃ 0.2 5.5 3 Input Voltage (V) DS2539 0.8 3.5 4 Input Voltage (V) 6 4.5 5 EUP2539 Typical Operating Characteristics (continued) Light Load Switching Waveform 6LED,VIN=5.5V,ILED＜1mA，L=47µH Open LED Supply Current vs. VIN Supply Current (mA) 5 SW 4 10V/div 3 Inductor Current 2 50mA/div VOUT 1 AC Coupled 20mV/div 0 3 3.5 4 4.5 5 5.5 500ns/div Input Voltage (V) Power-up With 10 LEDs at 20mA Typical Switching Waveforms SW VEN 20V/div 2V/div Inductor VOUT Current 20V/div 50mA/div Input VOUT Current AC Coupled 100mA/div 50mV/div 1.00µs/div 100µs/div Enable to Open LED Waveforms Enable to Open LED Waveforms VEN VEN 2V/div 2V/div VOUT VOUT 20V/div 20V/div SW SW 20V/div DS2539 20V/div 25.0ms/div Ver1.1 Apr. 2009 7 50.0µs/div EUP2539 Application Information Switching Waveform with 1kHz PWM on EN LED Current Control The EUP2539 regulates the LED current by setting the current sense resistor (RFB) connecting to feedback and ground. The internal feedback reference voltage is 0.3V. The LED current can be set from following equation easily. VEN I LED = 0.3 R FB 2V/div VOUT 20V/div --------------------------------------(1) LED Current In order to have an accurate LED current, precision resistors are preferred (1% is recommended). The table for RFB selection is shown below. RFB Resistor Value selection LED Current (mA) RFB (Ω) 5 60 10 30 15 20 20 15 25 12 30 10 20mA/div 250µs/div Figure 4. 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 5. 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 5 sets dimming control of LED current from 20mA to 0mA. Dimming Control a. Using a PWM Signal to EN Pin For controlling the LED brightness, the EUP2539 can perform the dimming control by applying a PWM signal to EN pin, and the PWM signal frequency range is from 100Hz to 100KHz. 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. Figure 5. DC Voltage Dimming Control 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 6, output current is from 20.5mA to 5.5mA by adjusting the PWM duty cycle from 10% to 90%. Figure 3. Direct PWM Dimming Control DS2539 Ver1.1 Apr. 2009 8 EUP2539 Shutdown Voltage (V) 1 Shutdown Voltage vs. Input Voltage 0.8 0.6 -40℃ 0.4 -25℃ 85℃ 125℃ 0.2 3 Figure 6. Filtered PWM Dimming Control 25 3.5 4 4.5 5 Input Voltage (V) Filtered PWM Dimming (0V to 2.5V) Figure 9. Enable to Open LED Waveforms LED Current (mA) 20 VEN 15 2V/div 10 VOUT 5 20V/div 0 0 10 20 30 40 50 60 70 80 90 100 SW PWM Duty Cycle (%) 20V/div Figure 7. Open Load Shutdown In the event of an “Open LED” fault condition, the EUP2539 will continue to boost the output voltage with maximum power until the output voltage reaches approximately 38V. Once the output exceeds this level, the device will cease operation until the EN pin is cycled off and on. Ver1.1 Apr. 2009 Figure 10. Thermal Shutdown Thermal overload protection circuitry has been included to prevent the device from operating at unsafe junction temperatures above 150ºC. In the event of a thermal overload condition the device will automatically shutdown and wait till the junction temperatures cools to 130ºC before normal operation is resumed. Capacitors Selection A 4.7µF to 10µF ceramic input capacitor (CIN) and a 0.22µF to 4.7µF ceramic output capacitor (COUT) are sufficient for most applications. During Direct PWM Dimming control, a larger output capacitor will significantly reduce audio noise induced by output capacitor, and a smaller will enlarge the audio noise, a 2.2uF COUT is recommended. Under normal condition, a 4.7µF input capacitor is sufficient. For applications with higher output power, a larger input capacitor of 10µF may be appropriate. X5R and X7R capacitor types are ideal due to their stability across temperature range. Figure 8. Open LED Protection DS2539 50.0µs/div 9 EUP2539 Inductor Selection The recommended value of inductor for 2 to 10 WLEDs applications are 4.7µH to 47µH. Small size and better efficiency are the major concerns for portable device, such as EUP2539 used for mobile phone. The inductor should have low core loss at 1MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered. Schottky Diode Selection The current rating of the Schottky diode must exceed the peak current flowing through it. The Schottky diode performance is rated in terms of its forward voltage at a given current. In order to achieve the best efficiency, this forward voltage should be as low as possible. The response time is also critical since the driver is operating at 1MHz. Board Layout Careful PC board layout is required due to fast switching. All components must be placed as close to the device as possible. Keep the path between the inductor L1, diode D1, and output capacitor COUT extremely short for minimal noise and ringing. The feedback components such as the sense resistor RFB must be kept close to the FB pin to prevent noise injection on the FB pin trace. The ground return of CIN and COUT should be tied close to the GND pin. See the EUP2539 demo board layout for reference. DS2539 Ver1.1 Apr. 2009 10 EUP2539 Packaging Information TSOT23-5 SYMBOLS A A1 D E1 E L b e DS2539 Ver1.1 Apr. 2009 MILLIMETERS MIN. MAX. 1.00 0.00 0.15 2.90 1.60 2.60 3.00 0.30 0.60 0.30 0.50 0.95 11 INCHES MIN. 0.000 MAX. 0.039 0.006 0.114 0.063 0.102 0.012 0.012 0.118 0.024 0.020 0.037