issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 1 of 8 AL8806EV6 user guide performance 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 -40c to +105c ordering information order number AL8806EV6 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 470f 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. 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 (70m). components are mounted on both sides.
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 2 of 8 quick start guide suitable test equipment count description manufacturer part number 1 adjustable power supply, 12v 2a thurlby thandar cpx400a 2 digital multimeter fluke 179 1 digital storage oscilloscope tektronix tds2024b 2 led, high brightness, dragon diamond, series connected on suitable heat conducting pcb osram 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 a s 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 illumina te 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%. 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!!
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 3 of 8 observe switching waveform 5. the switching waveform can be observed on an oscillos cope. 6. set the oscilloscope as follows: channel 1 sensitivity: 2v/div (at probe tip) time base: 1s/div trigger source: ch1 trigger mode: auto 7. connect the ground lead of a 10x probe to the suppl y negative terminal near p2 of the al8006ev2, and touch the probe tip onto the anode o f 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
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 4 of 8 AL8806EV6 schematic
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 5 of 8 pcb copper layout & silk screen C top pcb copper layout & silk screen Cbottom
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 6 of 8 parts list count designator description package manufacturer part number 1 c1 capacitor, 470uf, 25v aluminium electrolytic radial, 10 x 12.5mm rubycon 25zlh470m 1 c2 capacitor, 4.7f 10% 50v x7r 1210 kemet c1210x475k5rac 3 c3 c9 c10 capacitor, 100nf 10% 50v x7r 0805 kemet nic c1210x475k5rac nmc0805x7r104k50trpf 1 c4 capacitor, 100nf 10% 50v x7r 1206 kemet nic c1206104k5rac7800 nmc1206x7r104k50trpf 4 c5 - c8 capacitor, 1.5nf 10% 50v or 100v, cog 0805 generic 1 l1 inductor, shielded, 15h 20% 6.6 x 6.6mm coilcraft nic wrth 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 resistor, 0.2ohms 1% 250ppm 125mw 0805 generic 1 d1 diode, schottky, 30v 2a dfls230 (alternatives: dfls230l or lh) powerdi123 diodes inc dfls230-7 4 d2 - d5 diode, super barrier rectifier, 30v 2a sbr2u30 powerdi123 diodes inc sbr2u30p1-7 1 u1 ic, led driver, al8806 msop-8ep diodes inc al8 806mp8-13 i/o count designator description function manufacturer part number 1 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 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 t a operating ambient temperature -40 +105 c
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 7 of 8 current setting the led current is set by the sense resistor value, r sense . on this pcb, there are two resistors in parallel. r sense = r 1 * r 2 / (r 1 + r 2 ) 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 r sense . the sense voltage is 100mv, so the led current is simply i led = 0.1/ r sense 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 abou t 5% using AL8806EV6. the following table gives commercially available resi stor 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 r1 , ohms r2 , ohms 150ma 0.68 do not fit 300ma 0.33 do not fit 380ma 0.51 do not fit 500ma 0.2 do not fit 660ma 0.15 do not fit 1a 0.2 0.2 1.1a 0.15 0.2 performance the performance of the AL8806EV6 demonstrated shows t he 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 chang es by less than 2% over the input voltage range from 9vdc to 30vdc. with 2 leds and a supply of 12vd c, the switching frequency is approximately 440khz. for further advice, please contact your local diode s field applications engineer, or one of our sales offices listed on the back page of this docum ent.
AL8806EV6 issue 1 C june 2011 ? diodes incorporated 2011 www.diodes.com 8 of 8 sales offices the americas 3050 e. hillcrest drive westlake village, ca 91362-3154 tel: (+1) 805 446 4800 fax: (+1) 805 446 4850 europe kustermannpark balanstra?e 59, d-81541 mnchen germany tel: (+49) 894 549 490 fax: (+49) 894 549 4949 taiwan 7f, no. 50, min chuan road hsin-tien taipei, taiwan tel: (+886) 289 146 000 fax: (+886) 289 146 639 shanghai rm. 606, no.1158 changning road shanghai, china tel: (+86) 215 241 4882 fax (+86) 215 241 4891 shenzhen room a1103-04, anlian plaza, #4018 jintian road futian cbd, shenzhen, china tel: (+86) 755 882 849 88 fax: (+86) 755 882 849 99 korea 6 floor, changhwa b/d, 1005-5 yeongtong-dong, yeongtong-gu, suwon-si, gyeonggi-do, korea 443-813 tel: (+82) 312 731 884 fax: (+82) 312 731 885 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 w arranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve th e right to make modifications, enhancements, improv ements, 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 ap plication or use of this document or any product de scribed herein; neither does diodes incorporated convey any license under i ts patent or trademark rights, nor the rights of ot hers. any customer or user of this document or products described here in in such applications shall assume all risks of s uch use and will agree to hold diodes incorporated and all the companies w hose products are represented on diodes incorporate d website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products pur chased through unauthorized sales channels. should customers purch ase or use diodes incorporated products for any uni ntended or unauthorized application, customers shall indemnify and hold diodes incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any c laim of personal injury or death associated with such unintended or unauthoriz ed application. products described herein may be covered by one or m ore 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 for eign trademarks. life support diodes incorporated products are specifically not a uthorized for use as critical components in life su pport 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 per form when properly used in accordance with instruct ions for use provided in the labeling can be reasonably expecte d 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 c an be reasonably be expected to cause the failure of the life suppor t device or to affect its safety or effectiveness. customers represent that they have all necessary ex pertise 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, regulato ry and safety-related requirements concerning their products and any use of diodes incorporated products in such safety-crit ical, 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 representati ves against any damages arising out of the use of diodes incorporat ed products in such safety-critical, life support d evices or systems. copyright ? 2011, diodes incorporated www.diodes.com
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