ZXLD1320EV1 USER GUIDE DESCRIPTION The ZXLD1320 is an inductive DC-DC converter, with an internal switch, designed for driving single or multiple LEDs in series up to a total of 1.5A output current. The feedback control circuitry inside the ZXLD1320 provides excellent load and current regulation, resulting in very stable LED current over the full operating voltage and temperature range. Applications cover both commercial and automotive environments with input voltages ranging from 4V to 18V. Depending upon supply voltage and external components, this can provide up to 24W of output power. 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. 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. The device employs a variable ‘on’ and ‘off’ time control scheme with adjustable peak switch current limiting and operates in the step-down (Buck) operating mode, 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. More importantly, it retains design flexibility to add customer specific features. FEATURES • Step Down LED Driver • 4V to 18V Input Voltage Range • Up to 1.5A output current • Typical efficiency *> 85% • User-defined thermal control of LED output current using external thermistor • 12μA typical standby current • Adjustable Soft-Start • Power ‘OK’ flag output • Capable of driving 4 LEDs in series ORDERING INFORMATION External resistors set nominal average LED current and coil peak current independently. The ‘Power-OK’ (POK) output flag remains high during normal operation, but switches low if the switch transistor remains on for more than 500us. This provides indication of a low battery, or fault condition. The POK output may be used to drive an LED or the input of an MCU. The device can be shut down by applying a continuous low level dc voltage to the ADJ pin. APPLICATIONS • Low voltage halogen lamp replacement with LEDs • High Power LED flashlights • LED back-up lighting • General LED lighting • Automotive Lighting TYPICAL APPLICATION CIRCUIT ORDER NUMBER ZXLD1320EV1 Please note evaluation boards are subject to availability and qualified leads. Issue 2 - February 2008 © Zetex Semiconductors plc, 2008 www.zetex.com ZXLD1320EV1 REFERENCE DESIGN The ZXLD1320EV1 is configured to the reference design below. The target application is 1A/1.5A high current LED driver for single or multiple LEDs with wide input voltage range. The supply voltage for ZXLD1320EV1 is: VIN=4V ~ 18V. The ZXLD1320EV1 boards are initially set at LED current of 1A with100mΩ (R3) current sensing resistor. In order to boost the LED current to 1.5A, on-board 200mΩ (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 ZXLD1320 datasheet. SCHEMATIC DIAGRAM Materials List Ref Value U1 LED Driver D1 Schottky Diode Package DFN14 SOT23-6 L1 C1 C2 C3 R1 R2 R3 R3A R4 0603 1206 1206 0805 0603 0805 0805 0603 10uH 2A 10nF 10V 4.7uF 50V 2.2uF 25V 430Ω 25mΩ 100mΩ 200mΩ 5.1KΩ Part Number ZXLD1320DCA ZHCS2000 MSS7341-103ML NPIS64D100MTRF 744-777910 Generic GRM31CR71H475K GRM31MR71E225K Generic Generic Generic Generic Generic Issue 2 - February 2008 Manufacturer Zetex Zetex Coilcraft NIC Comps. Wurth Generic Murata Murata Generic Generic Generic Generic Generic Contact Details www.zetex.com www.zetex.com www.coilcraft.com www.niccomp.com www.we-online.com www.murata.com www.murata.com www.zetex.com © Zetex Semiconductors plc, 2008 2 ZXLD1320EV1 PERFORMANCE Graphs Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 3 ZXLD1320EV1 ZXLD1320EV1 OPERATION Connection diagram ZXLD1320EV1 Set-up and Test 1. Preset the PSU to 8V with the current limited to around 1.5A. 2. Connect LED+ and LED- to the Anode and Cathode, respectively, of an off-board high power LED. 3. Connect VIN and GND to positive and zero volts of the PSU supply respectively. 4. Turn on the PSU. 5. The LED should illuminate and be regulated at 1A/1.5A +/-5%. 6. The input current measured should be between 0.5A and 0.7A for the 1A option and between 0.8A and 1A for the 1.5A option. Caution: A LED with an appropriate current rating should be used. Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 4 ZXLD1320EV1 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 particularly 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 the VIN pin. Input decoupling capacitor C2, between VIN and GND, should be kept as close as possible to the device. Enough copper should be attached to the GND pin (exposed pad) for heat-sinking purposes. In this evaluation board, the copper area is on the bottom layer, connected to the exposed pad through several vias. Below is the recommended layout of the ZXLD1320EV1. Top Silk Top Copper Bottom Copper Drill File Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 5 ZXLD1320EV1 Notes Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 6 ZXLD1320EV1 Notes Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 7 ZXLD1320EV1 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 ideas. It is the responsibility of the user to ensure that the circuit is fit for the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, 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 critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Zetex 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 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 expected to cause the failure of the life support device or to affect its safety or effectiveness. Reproduction The product specifications contained in this publication are issued 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 representation relating to the products or services concerned. Terms and Conditions All products are sold subjects to Zetex’ terms and conditions of sale, and this disclaimer (save in the event of a conflict between 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 conditions and prices, please contact your nearest Zetex sales office. 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 directly 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 whatsoever in respect of any parts purchased through unauthorized sales channels. ESD (Electrostatic discharge) Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices. The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. Devices suspected of being affected should be replaced. Green compliance Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding regulatory requirements with respect to the use of hazardous substances. Numerous 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” “Active” “Last time buy (LTB)” “Not recommended for new designs” “Obsolete” Datasheet status key: “Draft version” Future device intended for production at some point. Samples may be available Product status recommended for new designs Device will be discontinued and last time buy period and delivery is in effect Device is still in production to support existing designs and production Production has been discontinued This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice. “Provisional version” “Issue” Europe Americas Asia Pacific Corporate Headquarters Zetex GmbH Kustermann-park Balanstraße 59 D-81541 München Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 [email protected] Zetex Inc 700 Veterans Memorial Highway Hauppauge, NY 11788 USA Zetex (Asia Ltd) 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Zetex Semiconductors plc Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 [email protected] Telephone: (852) 26100 611 Fax: (852) 24250 494 [email protected] Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 [email protected] © 2006 Published by Zetex Semiconductors plc. Issue 2 - February 2008 www.zetex.com © Zetex Semiconductors plc, 2008 8