PAM2803 3W High Power White LED Driver General Descriptio n Features n LED Power Efficiency: up to 90% n Current Accuracy: ± 5%(V IN=3.6V to 1.8V @V F=3.7V) n Low Start-Up Voltage: 0.9V(I LED=270mA) n Low Hold Voltage:0.75V(I LED=200mA) n 1MHz Switching Frequency n Uses small, Low Profile External Components n Low RDS(ON) : 100mΩ (TYP.) n Open LED Protection n Over Temperature Protection n Low Profile SOT-23-6 Package n Pb-Free Package The PAM2803 is a set-up DC-DC converter that delivers a regulated output current. The device switches at a 1.0MHz constant frequency, allowing for the use of small value external inductor and ceramic capacitors. The PAM2803 is targeted to be used for driving loads up to 1A from a two-cell alkaline battery. The LED current can be programmed by the external current sense resistor, Rs, connected between the feedback pin (FB) and ground. A low 95mV feedback voltage reduces the power loss in the Rs for better efficiency. With its internal 2A, 100 mΩ NMOS switch, the device can provide high efficiency even at heavy load. During the shutdown mode, the feedback resistor Rs and the load are completely disconnected and the current consumption is reduced to less than 1uA. Applications n n n n n n White LED Torch (Flashlight) White LED Camera Flash DSC(Digital Still Camera)Flash Cellular Camera Phone Flash PDA Camera Flash Camcorder Torch(Flashlight) Lamp The PAM2803 is available in the 6-lead SOT-23-6 package. Typical Application Block Diagram VOUT 2.2uH 95mV Reference + A1 - 1 SW 6 VIN VOUT 5 A2 + Rc C IN V IN PAM2803 OFF ON 4 SHDN 3W WLED FB 3 GND PWM Logic And Driver Cc FB 10uF SW VIN Comparator Σ CO RS + Ramp Generator 10uF 2 SHDN I LED=750mA, R S=0.127 Ω Shutdown And Soft-start 1.0MHz Oscillator GND Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 1 PAM2803 3W High Power White LED Driver Pin Configuration& Marking Information Top View SOT - 23 - 6 6 5 XX: Product Code V: Voltage Code Y: Year W: Weekly 4 XX V Y W 1 2 3 Pin Number Name Function 1 SW Switch 2 GND Ground 3 FB Feedback 4 SHDN Shut Down 5 VOUT Output 6 VIN Input Absolute Maximum Ratings These are stress ratings only and functional operation is not implied . Exposure to absolute maximum ratings for prolonged time periods may affect device reliability . All voltages are with respect to ground . Operating Temperature Range .........-40 ° C to 85 ° C Storage Temperature Range......... –65 ° C to 125 ° C Lead Temperature (Soldering, 5 sec) ...........300 ° C Input Pin Voltage...............................–0.3V to 6V SW Pin Voltage..................................–0.3V to 6V SHDN, FB Pin Voltage.........................–0.3V to 6V Recommended Operating Conditions Junction Temperature ............... - 40 ° C to 125 ° C Ambient Temperature .................. - 40 ° C to 85 ° C Thermal Information Parameter Thermal Resistance (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Package Symbol Maximum SOT-23-6 θJC 130 Unit ℃/W SOT-23-6 θJA 250 SOT-23-6 PD 400 mW Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 2 PAM2803 3W High Power White LED Driver Electrical Characteristic T A=25 ℃ , V IN=2.4V, I LED=750mA, V SHDN = V IN, L=2.2uH, C ΙΝ=10uF, C O=10uF, unless otherwise noted. Parameter Symbol Conditions Min Input Voltage Range VIN 0.9 Feedback Voltage VFB 90 VIN: 0V→3V Start-up Voltage VSTART Hold Voltage VHOLD Oscillator Frequency FOSC SHDN Input High VSH VIN=1.8V SHDN Input Low VSL VIN=1.8V ILED=270mA VIN: 3V→0V ILED:750mA→200mA 0.85 Typ Max VF-0.2 (note 1) 95 100 Unit V mV 0.9 V 0.75 V 1.0 1.15 1.0 MHz V 0.4 V Over Temperature Shutdown OTS 150 ℃ Over Temperature Hysteresis OTH 15 ℃ Maximum Output Current Range IO(MAX) Quiescent Current IQ Shutdown Current ISD Switch on Resistance 750 ILED=0mA, VO=3.4V, mA 1 Device Switching at 1MHz Shutdown mode RDSON VO=3.4V 0.1 Current Limit ILIM VO=3.4V Efficiency η ILED=750mA 2 3 mA 1 uA Ω A 90 % Note1: V F - LED Forward Voltage Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 3 PAM2803 3W High Power White LED Driver Typical Performance Characteristics T A=25 ℃ , L=2.2uH , C ΙΝ=10uF, C Ο=10uF, unless otherwise noted. 1. LED Power Efficiency vs Input Voltage 2. LED Current vs Input Voltage 800 90 750 LED Current(mA) LED Power Efficiency(%) 100 80 ILED=750mA@VF=3.7V 70 60 50 ILED=750mA@VF=3.7V 700 650 600 550 500 450 400 40 3.6 3.6 3.3 3 2.7 2.4 2.1 1.8 1.5 3.3 3 1.2 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) Input Voltage(V) 2300 4. Feedback Voltage vs Input Voltage (I LED=750mA@V F=3.7V) 3. DC Input Current vs Input Voltage Feedback Voltage(mV) DC Input Current(mA) 2100 1900 1700 1500 1300 1100 900 ILED=750mA@VF=3.7V 700 500 3.6 3.3 3 2.7 2.4 2.1 1.8 1.5 100 95 90 85 80 75 70 65 60 55 50 3.6 1.2 3.3 3 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) Input Voltage(V) Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 4 PAM2803 3W High Power White LED Driver Typical Performance Characteristics (continued) 6. Start-Up Waveform 5. Switching Waveform SHDN SW VO AC Coupling VO IL IL 7. Overvoltage Protection Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 5 PAM2803 3W High Power White LED Driver Application Information Inductor Selection LED Current Setting The PAM2803 can use small value inductors due to its switching frequency of 1 MHz. The value of inductor will focus in the range of 2.2uH to 4.7uH for most PAM2803 applications. In typical high current white LED applications, it is recommended to use a 4.7uH inductor. The inductor should have low DCR (DC resistance) to minimize the I 2R power loss, and it requires a current rating of 2A to handle the peak inductor current without saturating. The LED current is set by the single external Rs resistor connected to the FB pin as shown in the typical application circuit on page 1. The typical FB reference is internally regulated to 95mV. The LED current is 95mV/Rs. It's recommended to use a 1% or better precision resistor for the better LED current accuracy. The formula and table 1 for Rs selection are shown as follows: Rs=95mV/I LED Capacitor Selection Table 1. Rs Resistor Value Selection An input capacitor is required to reduce the input ripple and noise for proper operation of the PAM2803. For good input decoupling, Low ESR (equivalent series resistance) capacitors should be used at the input. At least 2.2uF input capacitor is recommended for most applications. A minimum output capacitor value of 6.8uF is recommended under normal operating conditions, while a 10uF-22uF capacitor may be required for higher power LED current. A reasonable value of the output capacitor depends on the LED current. The ESR of the output capacitor is the important parameter to determine the output voltage ripple of the converter, so low ESR capacitors should be used at the output to reduce the output voltage ripple. The small size of ceramic capacitors is an excellent choice for PAM2803 applications. The X5R and X7R types are preferred because they maintain capacitance over wide voltage and temperature ranges. Standard Value(Ω) ILED(mA) 0.18 528 0.15 633 0.12 792 0.10 950 PCB Layout Guidelines As for all switching power supplies, the layout and components placement of the PAM2803 is an important step in the design; especially at high peak currents and high switching frequencies. The input capacitor and output capacitor should be placed respectively as close as possible to the input pin and output pin of the IC; the inductor and schottky diode should be placed as close as possible to the switch pin by using wide and short traces for the main current path; the current sense resistor should be placed as close as possible between the ground pin and feedback pin. Diode Selection It's indispensable to use a Schottky diode rated at 2A with the PAM2803. Using a Schottky diode with a lower forward voltage drop is better to improve the power LED efficiency, and its voltage rating should be greater than the output voltage. In application, the ON Semiconductor MBRA210LT3G is recommended. Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 6 PAM2803 3W High Power White LED Driver Ordering Information PAM2803 X X X X FB Voltage Number of Pins Package Type Pin Configuration Pin Configuration A Type Package Type Number of Pins FB Voltage A: SOT-23-6 F: 6 095：95mV 1. SW 2. GND 3. FB 4. SHDN 5. VOUT 6. VIN Part Number Marking Package Type Standard Package PAM2803AAF095 CFAYW SOT-23-6 3,000Units/Tape&Reel Please consult PAM sales office or authorized Rep ./ Distributor for detailed ordering information. Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 7 PAM2803 3W High Power White LED Driver Outline Dimension A A E E1 SOT - 23 - 6 e e1 S E E VIEWS c WITH PLANTING A A2 b SECTION A-A 0.25 A1 BASE METAL G A U G E P L A NE NE S E A T I N G P L ANE L1 θ L VIEW B Symbol Spec A A1 1.20±0.25 0.10±0.05 Symbol E11 e Spec 1.60±0.1 0.95BSC A2 b 1.10±0.2 0.40±0.1 e1 L 1.90BSC 0.55±0.25 c D 0.15±0.0.7 2.90±0.1 L1 θ 0.60REF 4°±4° E 2.80±0.2 Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 8