ZXSC400EV4 ZXSC400EV4 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 ZXSC400EV4 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 ZXSC400EV4 TYPICAL APPLICATION CIRCUIT L1 D1 22uH ZHCS1000 VIN Please note evaluation boards are subject to availability and qualified leads. Q1 FMMT617 U1 ZXSC400 VCC C2 LED1 100uF/6V3 LWW5SG VDRIVE ST DN ISENSE GND C1 VFB 100uF/6V3 R1 R2 22mohm 0.82ohm GND ZXSC400EV4 ISSUE 1 - June 2005 1 ZXSC400EV4 REFERENCE DESIGN ZXSC400EV4 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 ZXSC400EV4 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 FMMT617 U1 ZXSC400 VCC VDRIVE STDN ISENSE GND C1 C2 LED1 100uF/6V3 LWW5SG VFB 100uF/6V3 R1 R2 22mohm 0.82ohm GND Materials List Ref Value Package Part Number Manufacturer Notes U1 Q1 D1 L1 R1 SOT23-6 SOT23 SOT23 N/A 0805 UZXSC400E6 UFMMT617 UZHCS1000 DO3316P-223 Zetex Zetex Zetex Coilcraft Generic Boost converter Low sat NPN transistor 40V/1A Schottky diode 22uH/2.5A SMT Inductor 0805 5% tolerance Generic 0805 5% tolerance Murata Murata Osram Opto Semiconductors 100uF/6V3/X5R/1812 100uF/6V3/X5R/1812 TM 1W Golden Dragon WLED R2 C1 C2 LED1 N/A N/A 40V/1A 22uH/2.5A 22mΩ 0.82Ω 100µF/6V3 100µF/6V3 1W 0805 1812 1812 N/A GRM43SR60J107ME20L GRM43SR60J107ME20L LW W5SG-GYHY-5K8L ZXSC400EV4 ISSUE 1 - June 2005 2 ZXSC400EV4 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 ZXSC400EV4 ISSUE 1 - June 2005 3 LED Voltage vs Input Voltage ZXSC400EV4 ZXSC400EV3 OPERATION Connection diagram 1W LED DRIVER ZXSC400EV4 ZDB263 L1 VIN D1 Q1 LED1 U1 OSRAM Opto Semiconductors GND C1 R1 R2 C2 Copyright Zetex plc ZXSC400EV4 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. ZXSC400EV4 ISSUE 1 - June 2005 4 ZXSC400EV4 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. Below is the recommended layout of the ZXSC400EV4. 1W LED DRIVER ZXSC400EV4 ZDB263 L1 VIN D1 Q1 LED1 U1 OSRAM Opto Semiconductors GND C1 R1 R2 C2 Copyright Zetex plc Top Silk Top Copper Bottom Copper Drill File ZXSC400EV4 ISSUE 1 - June 2005 5 ZXSC400EV4 © Zetex Semiconductors plc 2005 Europe Zetex GmbH Streitfeldstraße 19 D-81673 München Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 email: [email protected] The Americas Zetex Inc 700 Veterans Memorial Hwy Hauppauge, NY 11788 USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 email: [email protected] Asia Zetex (Asia) Ltd 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 email: [email protected] Corporate Headquarters Zetex Semiconductors plc Zetex Technology Park, Chadderton, OL9 9LL United Kingdom Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 email: [email protected] These offices are supported by agents and distributors in major countries world-wide. This publication is 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. The Company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. For the latest product information, log on to www.zetex.com ZXSC400EV4 ISSUE 1 - June 2005 6