PAM2803SHDNAF095

3W High Power White LED Driver F eatures 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 PAM2803 General Descriptio n 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. The PAM2803 is available in the 6-lead SOT-23-6 package. 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 Typical Application 2.2uH 1 Block Diagram VOUT 95mV Reference VIN SW + A1 - Comparator Rc Cc SW 6 VIN VOUT 5 FB A2 + PWM Logic And Driver C IN V IN 10uF OFF ON PAM2803 4 3W WLED CO Σ + - SHDN FB 3 RS GND 2 10uF SHDN Ramp Generator Shutdown And Soft-start 1.0MHz Oscillator I LED=750mA, R S=0.127 Ω GND Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 1 3W High Power White LED Driver P in Configuration& Marking Information Top View SOT - 23 - 6 PAM2803 6 5 4 XX V Y W XX: Product Code V: Voltage Code Y: Year W: Weekly 1 2 3 Name SW GND FB SHDN VOUT VIN Function Switch Ground Feedback Shut Down Output Input Pin Number 1 2 3 4 5 6 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 . Input Pin Voltage...............................–0.3V to 6V SW Pin Voltage..................................–0.3V to 6V SHDN, FB Pin Voltage.........................–0.3V to 6V Operating Temperature Range .........-40 ° C to 85 ° C Storage Temperature Range......... –65 ° C to 125 ° C Lead Temperature (Soldering, 5 sec) ...........300 ° C 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 SOT-23-6 SOT-23-6 SOT-23-6 Symbol θJC θJA PD Maximum 130 ℃/W 250 400 mW Unit Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 2 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 Input Voltage Range Feedback Voltage Start-up Voltage Hold Voltage Oscillator Frequency SHDN Input High SHDN Input Low Over Temperature Shutdown Over Temperature Hysteresis Maximum Output Current Range Quiescent Current Shutdown Current Switch on Resistance Current Limit Efficiency Symbol VIN VFB VSTART VHOLD FOSC VSH VSL OTS OTH IO(MAX) IQ ISD RDSON ILIM η ILED=0mA, VO=3.4V, Device Switching at 1MHz Shutdown mode VO=3.4V VO=3.4V ILED=750mA 2 90 0.1 750 1 3 1 VIN=1.8V VIN=1.8V 150 15 VIN: 0V→3V ILED=270mA VIN: 3V→0V ILED:750mA→200mA 0.85 1.0 0.4 Conditions Min 0.9 90 95 0.9 0.75 1.0 1.15 Typ Max VF-0.2 (note 1) 100 Unit V mV V V MHz V V ℃ ℃ mA mA uA Ω A % PAM2803 Note1: V F - LED Forward Voltage Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 3 3W High Power White LED Driver Typical Performance Characteristics T A=25 ℃ , L=2.2uH , C ΙΝ=10uF, C Ο=10uF, unless otherwise noted. 100 PAM2803 1. LED Power Efficiency vs Input Voltage 2. LED Current vs Input Voltage 800 750 LED Power Efficiency(%) 90 LED Current(mA) 80 70 60 50 40 3.6 3.3 3 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) ILED=750mA@VF=3.7V 700 650 600 550 500 450 400 3.6 ILED=750mA@VF=3.7V 3.3 3 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) 2300 2100 3. DC Input Current vs Input Voltage Feedback Voltage(mV) 4. Feedback Voltage vs Input Voltage (I LED=750mA@V F=3.7V) 100 95 90 85 80 75 70 65 60 55 50 3.6 3.3 3 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) DC Input Current(mA) 1900 1700 1500 1300 1100 900 700 500 3.6 3.3 3 2.7 2.4 2.1 1.8 1.5 1.2 Input Voltage(V) ILED=750mA@VF=3.7V Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 4 3W High Power White LED Driver Typical Performance Characteristics (continued ) 5. Switching Waveform 6. Start-Up Waveform PAM2803 SHDN SW VO AC Coupling VO IL IL 7. Overvoltage Protection Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 5 3W High Power White LED Driver Application Information I nductor Selection 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. Capacitor 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. 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. LED Current Setting 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 Table 1. Rs Resistor Value Selection Standard Value(Ω) 0.18 0.15 0.12 0.10 ILED(mA) 528 633 792 950 PAM2803 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. Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 6 3W High Power White LED Driver O rdering Information PAM2803 PAM2803 X X X X FB Voltage Number of Pins Package Type Pin Configuration Pin Configuration A Type 1. SW 2. GND 3. FB 4. SHDN 5. VOUT 6. VIN Package Type A: SOT-23-6 Number of Pins F: 6 FB Voltage 095：95mV Part Number PAM2803AAF095 Marking CFAYW Package Type SOT-23-6 Standard Package 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 3W High Power White LED Driver O utline Dimension SOT - 23 - 6 PAM2803 E1 A A e e1 E S E E VIEWS b A2 WITH PLANTING A BASE METAL SECTION A-A A1 0.25 L L1 VIEW B G A U G E P L A NE NE S E A T I N G P L ANE Symbol Spec Symbol Spec A θ A1 A2 1.10±0.2 e1 c b 0.40±0.1 L c D E 2.80±0.2 1.20±0.25 0.10±0.05 E11 1.60±0.1 e 0.95BSC 0.15±0.0.7 2.90±0.1 L1 0.60REF θ 4°±4° 1.90BSC 0.55±0.25 Power Analog Microelectronics , Inc www.poweranalog.com 08/2007 8