AL8806EV6 USER GUIDE Performance Introduction • • • • This evaluation circuit demonstrates the AL8806 High Efficiency 30V 1.5A Buck LED Driver operating in a circuit providing 1.1A LED current in MR16 form intended to drive 1 to 3 high brightness LEDs in series with a total load voltage drop up to 10V. The circuit includes a 470µF reservoir capacitor to prevent flicker for 50Hz or 60Hz AC input power. EMC filtering is included to meet international standards including the radiated emission requirements of EN55015 and EN55022 Class B. • 12VDC and 12VAC input 1.1A LED current Drives 1 to 3 LEDs in series 2% current regulation 9V to 30VDC (with 2 LEDs) Ambient temperature range -40°C to +105°C Ordering Information Order Number AL8806EV6 The switching frequency is approximately 440kHz when driving 2 Osram Dragon Diamond LEDs. The construction uses a double-sided FR4 printed circuit board, 17 x 20 x 0.8 mm with 2oz/sq ft copper (70µm). Components are mounted on both sides. Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 1 of 8 AL8806EV6 Quick Start Guide Suitable Test Equipment Count Description 1 Adjustable Power Supply, 12V 2A 2 Digital Multimeter 1 Digital Storage Oscilloscope 2 LED, high brightness, “Dragon Diamond”, series connected on suitable heat conducting PCB Manufacturer Part Number Thurlby Thandar CPX400A Fluke 179 Tektronix TDS2024B Osram CAUTION: The LEDs are very bright. Ensure they are hidden from direct view, or covered with a dispersing filter. The lid from an aerosol can is convenient for this. Also the LEDs are very hot. Do not touch!! Lamp Operation 1. Set the power supply to 12.0V but do not switch on. Set the current limit to 2.0A. 2. Connect up the AL8806EV6 board to the equipment as in Figure 1 below. Set DMM1 and DMM2 to measure current up to 2A. Figure 1: Test Schematic using VDC Input 3. Cover the LEDs to avoid dazzling. 4. Switch on the power supply. This should illuminate the LEDs. Note that the input current (DMM1) is approximately 690mA. The output current (DMM2) is approximately 1.12A. The input voltage can be varied from approximately 9VDC to 30VDC and the current regulation observed is typically within ±2%. Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 2 of 8 AL8806EV6 Observe Switching Waveform 5. The switching waveform can be observed on an oscilloscope. 6. Set the oscilloscope as follows: Channel 1 sensitivity: Time base: Trigger Source: Trigger Mode: 2V/div (at probe tip) 1µs/div CH1 Auto 7. Connect the ground lead of a 10x probe to the supply negative terminal near P2 of the AL8006EV2, and touch the probe tip onto the anode of D1 as in Figure 2 below. On the oscilloscope, press RUN/STOP to capture the waveform. The cursor readout indicates a switching frequency of 440kHz approximately. Figure 2: Figure 3: Oscilloscope Waveform Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 3 of 8 AL8806EV6 AL8806EV6 Schematic Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 4 of 8 AL8806EV6 PCB Copper Layout & Silk Screen – Top PCB Copper Layout & Silk Screen –Bottom Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 5 of 8 AL8806EV6 Parts List Count Designator Description Package 1 C1 Capacitor, 470uF, 25V Aluminium Electrolytic Radial, 10 x 12.5mm Manufacturer Part Number Rubycon 25ZLH470M 1 C2 Capacitor, 4.7µF 10% 50V X7R 1210 Kemet C1210X475K5RAC 3 C3 C9 C10 Capacitor, 100nF 10% 50V X7R 0805 Kemet NIC NMC0805X7R104K50TRPF 1 C4 Capacitor, 100nF 10% 50V X7R 1206 Kemet NIC NMC1206X7R104K50TRPF 4 C5 - C8 Capacitor, 1.5nF 10% 50V or 100V, COG 0805 generic 1 L1 Inductor, shielded, 15µH 20% 6.6 x 6.6mm Coilcraft NIC Würth MSS7341-153ML NPIS64D150MTRF 744777115 1 L2 Inductor, ferrite bead, 6A, 30ohms @100MHz 0805 TDK MPZ2012S300A 1 R1 Resistor, 0.15ohms 1% 250ppm 125mW 0805 generic 1 R2 0805 generic 1 D1 4 D2 - D5 1 U1 Resistor, 0.2ohms 1% 250ppm 125mW Diode, schottky, 30V 2A DFLS230 (alternatives: DFLS230L or LH) Diode, Super Barrier Rectifier, 30V 2A SBR2U30 IC, LED Driver, AL8806 C1210X475K5RAC C1206104K5RAC7800 PowerDi123 Diodes Inc DFLS230-7 PowerDi123 Diodes Inc SBR2U30P1-7 MSOP-8EP Diodes Inc AL8806MP8-13 I/O Count Designator Description Function 1 Manufacturer P1 Solder pad VDC, VAC Input 1 P2 Solder pad VDC, VAC Input 1 A Solder pad LED Anode load 1 K Solder pad LED Cathode load Part Number Recommended Operating Conditions Symbol Parameter Min Max Units VDC Input Supply Voltage, VDC 8 30 V VAC Input Supply Voltage, VAC 8 20 Vrms VOUT Load voltage ( 1 to 3 LEDs) 0 10 V TA Operating Ambient Temperature -40 +105 °C Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 6 of 8 AL8806EV6 Current Setting The LED current is set by the sense resistor value, RSENSE. On this PCB, there are two resistors in parallel. RSENSE = R1 * R2 / (R1 + R2) For the schematic values this gives a resistance of 0.15 * 0.2 (0.15 + 0.2) = 0.0857 ohms. The LED current flows through RSENSE. The sense voltage is 100mV, so the LED current is simply ILED = 0.1/ RSENSE For the schematic values this gives an LED current of 0.1/0.0857 = 1.167 A nominally. In practice there is a slight reduction in current partly due to the resistance of the PCB copper, depending on the PCB layout. At 1.1A this reduction is typically about 5% using AL8806EV6. The following table gives commercially available resistor values for typical current requirements, allowing a current error of 3% maximum not including the effect of PCB copper. A power limit of 125mW is assumed for the 0805 size resistors with 50% de-rating. LED Current 150mA 300mA 380mA 500mA 660mA 1A 1.1A R1, ohms 0.68 0.33 0.51 0.2 0.15 0.2 0.15 R2, ohms DO NOT FIT DO NOT FIT DO NOT FIT DO NOT FIT DO NOT FIT 0.2 0.2 Performance The performance of the AL8806EV6 demonstrated shows the capability to regulate LED current. The LED current of 1.1A is approximately 5% lower than the calculated value. This is partly due to copper resistance. With a load of 2 LEDs, the current changes by less than ±2% over the input voltage range from 9VDC to 30VDC. With 2 LEDs and a supply of 12VDC, the switching frequency is approximately 440kHz. For further advice, please contact your local Diodes Field Applications Engineer, or one of our sales offices listed on the back page of this document. Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 7 of 8 AL8806EV6 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channels. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably be expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2011, Diodes Incorporated www.diodes.com Sales offices The Americas Europe Taiwan Shanghai Shenzhen Korea 3050 E. Hillcrest Drive Westlake Village, Kustermannpark Balanstraße 59, 7F, No. 50, Min Chuan Road Rm. 606, No.1158 Changning Road Room A1103-04, ANLIAN Plaza, #4018 6 Floor, Changhwa B/D, 1005-5 Yeongtong-dong, CA 91362-3154 D-81541 München Hsin-Tien Shanghai, China Jintian Road Yeongtong-gu, Suwon-si, Tel: (+1) 805 446 4800 Fax: (+1) 805 446 4850 Germany Tel: (+49) 894 549 490 Taipei, Taiwan Tel: (+886) 289 146 000 Tel: (+86) 215 241 4882 Fax (+86) 215 241 4891 Futian CBD, Shenzhen, China Gyeonggi-do, Korea 443-813 Tel: (+82) 312 731 884 Fax: (+49) 894 549 4949 Fax: (+886) 289 146 639 Tel: (+86) 755 882 849 88 Fax: (+82) 312 731 885 Fax: (+86) 755 882 849 99 Issue 1 – June 2011 www.diodes.com © Diodes Incorporated 2011 8 of 8