issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 ZXLD1321EV1 user guide description the zxld1321 is an inductive dc-dc converter, with an internal switch, designed for driving single or multiple leds in series up to a total of 1a output current. applications cover commercial environments with input voltages ranging from 1.2v to 12v. the device employs a variable ?on? and ?off? time control scheme with adjustable peak switch current limiting and supports step-up (boost) mode and self- powering bootstrap operating modes, offering higher power efficiency and lower system cost than conventional pfm circuitry. the device includes the dc-dc converter, a high-side current monitor and an npn switching transistor to provide an integrated solution offering small pcb size, competitive cost/performance, high power efficiency of dc-dc conversion and maximum led brightness/reliability. mo re importantly, it retains design flexibility to add cu stomer specific features the feedback control circuitry inside the zxld1321 provides excellent load and current regulation, resulting in very stable led current over the useful life of the battery and over the full operating temperature range. the led current can be adjusted from 100% down to 10% of the set value by applying a dc voltage to the adj pin and down to 1% by applying a pwm signal to the adj pin. an on-chip led protection circuit also allows output current to be reduced linearly above a predetermined threshold temperature using an external thermistor at the tadj pin. external resistors set nominal average led current and coil peak current independently. the device can be shut down by applying a continuous low level dc voltage to the adj pin. features ? 1.2v to 12v input voltage range ? up to 1a output current ? typical efficiency (*) : >85% ? bootstrap operation enable s input voltage down to 1v ? user-defined thermal cont rol of led output current using external thermistor ? 12a typical standby current ? adjustable soft-start ? drives up to 5 white leds in series applications ? high power led flashlights ? led back-up lighting ? general led lighting ordering information order number ZXLD1321EV1 please note evaluation boards are subject to availability and qualified leads. typical application circuit
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 2 reference design the ZXLD1321EV1 is configured to the reference desi gn below. the target application is 700ma/1000ma high current led driver for single or multiple leds with wide input voltage range. if the ZXLD1321EV1 is connected to 1 off-boar d led, the supply voltag e is: vin=2v ~ 3.4v. the ZXLD1321EV1 boards are initially set at led current of around 700ma with150m ? (r3) current sensing resistor. in order to boost the led current to 1000ma, the on-board 300m ? (r3a) could made parallel to r3 by means of soldering jumper pad jp1. for other reference designs or further applications information please refer to the zxld1321 datasheet. schematic diagram materials list ref value package part number manufacturer contact details u1 led driver dfn14 zxld1321dca zetex www.zetex.com d1 schottky diode sot23-6 zhcs2000 zetex www.zetex.com l1 10uh 2a mss7341-103ml npis64d100mtrf 744-777910 coilcraft nic comps. wurth www.coilcraft.com www.niccomp.com www.we-online.com c1 10nf 10v 0603 generic generic c2 2.2uf 25v 1206 grm31mr71e225k murata www.murata.com c3 4.7uf 50v 1206 grm31cr71h475k murata www.murata.com r1 430 ? 0805 generic generic r2 25m ? 0603 generic generic r3 150m ? 0805 generic generic r3a 300m ? 0805 generic generic r4 5.1k ? 0603 generic generic z1 18v 3w zener do-214ac bzg03c18 vishay www.vishay.com
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 3 performance graphs
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 4 ZXLD1321EV1 operation connection diagram ZXLD1321EV1 set-up and test 1. preset the psu to 3v with a current limit of around 1.8a 2. connect led+ and led- to the anode and cathod e repectively, of the off-board high power led . 3. connect v in and gnd to positive and zero volts of the psu supply respectively. 4. set the psu to 3v. 5. turn on the psu. 6. the led should illuminate and be re gulated at 700ma/1000ma +/-5%. 7. the input current should measure between 0.9a and 1.1a for the 700ma option, and between 1.4 a and 1.6a for the 1a option. caution: please make sure the led is properly connected before applying power. a led with an appropriate current rating should be used.
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 5 layout considerations the pcb tracks should be kept as short as possible to minimize ground bounce, and the ground pin of the device should be soldered directly to the ground plane. it is par ticularly important to mount the coil and the input/output capacitors close to the device to minimize parasitic resistance and inductance, which will degrade efficiency. precautions should be taken to avoid noise entering t he vin pin. input decoupling capacitor c2, between vin and gnd, should be kept as close as possible to the de vice. enough copper should be attached to the gnd pin (exposed pad) for heat-sinking purposes. in this eval uation board, the copper area is on the bottom layer, connected to the exposed pad through several vias. below is the recommended layout of the ZXLD1321EV1. top silk top copper bottom copper drill file
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 6 notes
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 7 notes
ZXLD1321EV1 issue 1 - february 2008 www.zetex.com ? zetex semiconductors plc, 2008 8 definitions product change zetex semiconductors reserves the right to alter, without notice , specifications, design, price or conditions of supply of any product or service. customers are solely responsible for obtaining the latest relevant information before placing orders. applications disclaimer the circuits in this design/application note are offered as design i deas. it is the responsibility of the user to ensure that t he circuit is fit for the user?s application and meets with the user?s requirements. no r epresentation or warranty is given and no liability whatsoever i s assumed by zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arisi ng from such use or otherwise. zetex does not assume any legal responsibility or w ill not be held legally liable (whether in contract, tort (includ ing negligence), breach of statutory duty, restriction or otherwi se) for any damages, loss of profit, busines s, contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances. life support zetex products are specifically not authorized for use as critic al components in life support devices or systems without the ex press written approval of the chief executive officer of ze tex semiconductors plc. 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 ex pected to result in signif icant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expecte d to cause the failure of the life support device or to affect its safe ty or effectiveness. reproduction the product specifications contained in this publication are i ssued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a repre sentation relating to the products or services concerned. terms and conditions all products are sold subjects to zetex? terms and conditions of sa le, and this disclaimer (save in the event of a conflict bet ween the two when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement. for the latest information on technology, delivery terms and condi tions and prices, please contact your nearest zetex sales off ice. quality of product zetex is an iso 9001 and ts16949 certified semiconductor manufacturer. to ensure quality of service and products we strongly advise the purchase of parts dire ctly from zetex semiconductors or one of our regionally authorized distributors. for a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork zetex semiconductors does not warrant or accept any liability w hatsoever in respect of any parts purchased through unauthorized sales channels. esd (electrostatic discharge) semiconductor devices are susceptible to dam age by esd. suitable precautions should be taken when handling and transporting dev ices. the possible damage to devices depends on the circ umstances of the handling and transporting, and the nature of the device. the ext ent of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. device s suspected of being affected should be replaced. green compliance zetex semiconductors is committed to environm ental excellence in all aspe cts of its operations which includes meeting or exceed ing regulatory requirements with respect to the use of hazardous substances. nu merous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. all zetex components are compliant with the rohs directive, and through this it is supporting its customers in their compliance with weee and elv directives. product status key: ?preview? future device intended for production at some point. samples may be available ?active? product status recommended for new designs ?last time buy (ltb)? device will be discontinued and last time buy period and delivery is in effect ?not recommended for new designs? device is still in production to support existing designs and production ?obsolete? production has been discontinued datasheet status key: ?draft version? this term denotes a very early dat asheet version and contains highly provisional information, which may change in any manner without notice. ?provisional version? this term denotes a pre-release datasheet. it provides a clear indication of anticipated performance. however, changes to the test conditions and specificat ions may occur, at any time and without notice. ?issue? this term denotes an issued datasheet containi ng finalized specifications. however, changes to specifications may occur, at any time and without notice. europe zetex gmbh kustermann-park balanstra?e 59 d-81541 mnchen germany telefon: (49) 89 45 49 49 0 fax: (49) 89 45 49 49 49 europe.sales@zetex.com americas zetex inc 700 veterans memorial highway hauppauge, ny 11788 usa telephone: (1) 631 360 2222 fax: (1) 631 360 8222 usa.sales@zetex.com asia pacific zetex (asia ltd) 3701-04 metroplaza tower 1 hing fong road, kwai fong hong kong telephone: (852) 26100 611 fax: (852) 24250 494 asia.sales@zetex.com corporate headquarters zetex semiconductors plc zetex technology park, chadderton oldham, ol9 9ll united kingdom telephone (44) 161 622 4444 fax: (44) 161 622 4446 hq@zetex.com ? 2006 published by zetex semiconductors plc.
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