ZXSC400EV3 ZXSC400EV3 USER GUIDE DESCRIPTION The ZXSC400 is voltage mode boost converter in SOT23-6 package. Its low feedback voltage allows the current in a chain of LEDs to be set and accurately monitored with a single resistor with minimal losses. The ZXSC400EV3 is configured as a boost converter to drive a 1W LED from two NiCd/NiMH batteries. FEATURES • Drives a 1W white LED at 350mA • Typical efficiency of 80% APPLICATIONS • LED torches • High Power LED driving ORDERING INFORMATION ORDER NUMBER ZXSC400EV3 Please note evaluation boards are subject to availability and qualified leads. REFERENCE DESIGN ZXSC400EV3 is configured to the reference design below. The target application is a 1W white LED Driving from two NiCd/NiMH battery input for torches and high powered LED driving. The supply voltage for ZXSC400EV3 is: VIN=3V ~ 1.8V. For other reference designs or further applications information please refer to the ZXSC400 datasheet. Schematic Diagram L1 D1 22uH ZHCS1000 VIN Q1 ZXTN25012EFH U1 1 3 C1 2 C2 ZXSC400 VCC VDRIVE STDN ISENSE GND VFB 100uF/6V3 6 LED1 LXHL-PW01 4 5 100uF/6V3 R1 R2 22mohm 0.82ohm GND ZXSC400EV3 ISSUE 4 – January 2008 1 ZXSC400EV3 Suggested components: Ref Value Package Part Number Manufacturer Notes ZXSC400E6 ZXTN25012EFH ZHCS1000 DO3316P-223 NPI31W220MTRF Boost converter Low sat NPN transistor 40V/1A Schottky diode 22uH/2.5A Inductor U1 Q1 D1 L1 N/A N/A 40V/1A 22uH/2.5A SOT23-6 SOT23 SOT23 N/A R1 22mΩ 0805 Zetex Zetex Zetex Coilcraft NIC Components Generic R2 0805 Generic 0805 5% tolerance C1 0.82Ω 100µF/6V3 100uF/6V3/X5R C2 100µF/6V3 1812 LED1 PCB 1W N/A Murata NIC Components Murata NIC Components Lumileds Zetex 1812 GRM43SR60J107ME20L NMC1812X5R107M6.3F GRM43SR60J107ME20L NMC1812X5R107M6.3F LXHL-PW01 ZDB250R2 0805 5% tolerance 100uF/6V3/X5R 1W white LED emitter Note: Components are continually being developed and improved. Please check each manufacturer’s data for current products. 1W LED DRIVER ZXSC400EV 3 a L1 D2 VIN D1 Q1 U1 3V m ax. k GND C1 R1 R2 C2 ZD B250R3 C opy rightZetex PLC 2006 ZXSC400EV3 Set-up and Test 1. Connect VIN and GND to positive and zero volts of PSU supply respectively. 2. Set the PSU to 3V. 3. Turn on PSU. 4. The LED should illuminate and be regulated at 350mA. 5. Input current should measure between 0.5A ~ 0.6A - THIS IS A FUNCTIONAL EVAL. BOARD. Layout considerations PCB tracks should be kept as short as possible to minimise 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 minimise parasitic resistance and inductance, which will degrade efficiency. The FB pin is a high impedance input, so PCB track lengths to this should also be kept as short as possible to reduce noise pickup. Excess capacitance from the FB pin to ground should be avoided. Manufacturer’s datasheets must be consulted regarding proper mounting and thermal management of the LED device. The evaluation board is intended as a demonstration of the functionality of the driver circuitry, and is not intended to represent a final solution for the OEM. ZXSC400EV3 ISSUE 4 – January 2008 2 ZXSC400EV3 PERFORMANCE Increasing efficiency On ZXSC400EV3, R1 is set to 22mΩ to ensure that the LED current is regulated over the full input voltage range of 3V ~ 1.8V. For improved efficiency R1 can be changed to a 33mΩ resistor but LED current will not be regulated below 2V. See performance graphs. Graphs 100 VSTDN=VIN LED Current (mA) Efficiency (%) 90 400 VSTDN=VIN ILED=350mA R1=33mohms 80 70 R1=22mohms 60 50 3.0 2.8 2.6 2.4 2.2 2.0 380 R1=22mohms 360 340 R1=33mohms 320 300 3.0 1.8 2.8 2.6 2.4 2.2 2.0 1.8 Input voltage (V) Input Voltage (V) Efficiency vs Input Voltage LED Current vs Input Voltage 4.0 VSTDN=VIN 3.8 800 R1=22mohms R1=33mohms 600 400 3.0 LED Voltage (V) Input Current (mA) 1000 VSTDN=VIN 2.8 2.6 2.4 2.2 2.0 1.8 Input Voltage (V) R1=33mohms 3.6 3.4 R1=22mohms 3.2 3.0 3.0 2.8 2.6 2.4 2.2 2.0 1.8 Input Voltage (V) Input Current vs Input Voltage ZXSC400EV3 ISSUE 4 – January 2008 3 LED Voltage vs Input Voltage ZXSC400EV3 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. 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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. 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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. ZXSC400EV3 ISSUE 4 – January 2008 4