00940376Z

ELECTRONIC DESIGNER’S GUIDE World Headquarters Littelfuse, Inc. 800 E. Northwest Highway Des Plaines, IL 60016, USA www.littelfuse.com International Sales, Distribution and Engineering Facilities: • Des Plaines, Illinois USA and Irving, Texas USA Technical Assistance Phone: +1 (800) 999-9445 +1 (847) 824-1188 Fax: +1 (847) 391-0459 Europe • Utrecht, The Netherlands Phone: (+31) 30-299-9900 Fax: (+31) 30-299-9800 • Munich, Germany Phone: (+49) 89-552766-0 Fax: (+49) 89-552766-99 • Swindon, United Kingdom Phone: (+44) (0) 1793-720400 Fax: (+44) (0) 1793-720401 Asia/Pacific • Singapore Phone: (+65) 6885-9111 Fax: (+65) 6885-9113 • Taipei, Taiwan Phone: (+886) 2-8751-1234 Fax: (+886) 2-8751-1177 • Shin-Yokohama, Japan Phone: (+81) 45-478-1088 Fax: (+81) 45-478-1089 • Seoul, Korea Phone: (+82) 2-6000-8600 Fax: (+82) 2-6000-8655 • Beijing, China Phone: (+86-10) 8213-6327 Fax: (+86-10) 8213-6343 ELECTRONIC DESIGNER’S GUIDE North America • Hong Kong, China Phone: (+85) 22-810-5099 Fax: (+85) 22-810-5500 • Shanghai, China Phone: (+86-21) 5383-8016 Fax: (+86-21) 5383-9568 • Shenzhen, China Phone: (+86-755) 8207-0760 Fax: (+86-755) 8299-5040 Central and South America • São Paulo, Brasil Phone: (+55) 11-3835-3780 Fax: (+55) 11-3645-0612 Research and Manufacturing Facilities: • Arcola, Illinois USA • Des Plaines, Illinois USA • Irving, Texas USA • Dundalk, Ireland • Grenchen, Switzerland • Lipa City, Philippines • Matamoros, Mexico • Piedras Negras, Mexico • Suzhou, China • Swindon, United Kingdom Other Catalogs Available • Telecom Designer’s Guide • Teccor® Power Thyristor Databook • POWR-GARD™ Electrical Product Catalog • Automotive OEM Catalog • Automotive Aftermarket Catalog FORM NO. EC101-J © April 2005, Littelfuse Inc. Printed in U.S.A. Specifications descriptions and illustrative material in this literature are as accurate as known at the time of publication, but are subject to changes without notice. Visit www.littelfuse.com for the most up-to-date technical information. 1 Resettable PTCs Fuses PulseGuard® Polymeric ESD Suppressors Metal Oxide Varistors TVS Diodes Greentube™ Gas Plasma Arresters (Improved GDTs) Introduction Sample Kits LITTELFUSE® The World’s Leading Provider of Circuit Protection Solutions As the leader in circuit protection, the Littelfuse portfolio of brands is backed by decades of design and manufacturing expertise, plus the industry’s most experienced technical support. Littelfuse products are vital components in virtually every product that uses electrical energy, including: • Automobiles • Computers • Consumer electronics • Handheld devices • Industrial equipment • Telecom/Datacom circuits From fuses to diodes, from GDTs to power thyristors and varistors, Littelfuse not only has the product breadth to be your single-source solution provider, we also offer the technology depth to meet requirements for every application. Choose from diacs, sidacs, triacs, rectifiers, SCRs, varistors, SIDACtor ® devices— even fuses, holders, blocks, clips and much more. Companies around the world have come to rely on Littelfuse’s commitment to providing the most advanced overcurrent and overvoltage solutions and technical expertise. It’s this focus that has enabled Littelfuse to become the world’s leading provider of circuit protection solutions. A comprehensive approach to circuit protection Littelfuse goes well beyond efficient and comprehensive product delivery. We offer an integrated approach that includes: • A very broad, yet deep selection of products and technologies from a single source, so you benefit from a greater range of solutions and make fewer compromises. • Products that meet or exceed all applicable industry and government standards, as well as our own uncompromising and rigorous quality and reliability criteria. • Forward thinking, application-specific solutions that provide the assurance your most demanding requirements will be met. • Dedicated, customer-focused and application-specific technical support services — in the U.S. and around the world. For over 75 years, Littelfuse has maintained its focus on circuit protection. This focus is as strong today as ever. We continue to expand our circuit protection product offering with new, innovative technologies as we also expand our global reach and our level of technical support and expertise. The Littelfuse Quality Policy Littelfuse is committed to being sensitive to customer expectations and to providing quality products and services at a competitive price. In support of this commitment, Littelfuse will: Encourage quality awareness and quality performance in all associates at all levels of the Company through management leadership; Promote the participation of all associates in making individual contributions to the quality improvement process; Support continuous quality improvement by providing our associates with the necessary training, tools, and information feedback to enable enhancement of the quality of our products and services; Develop relationships with suppliers who consistently demonstrate their ability to fulfill quality, price and delivery objectives that are mutually beneficial; and, Build quality into our products and services, striving for zero defects in everything we do, thereby reducing cost and increasing TOTAL CUSTOMER SATISFACTION. Littelfuse and the Environment As members of the global community, we at Littelfuse have always strived to understand the impact of what we do, and of what we create, on the world around us. Because of this, our concern for the environment has always been an integral and fundamental part of our business. We continually work to balance our business objectives with the need to protect and improve the local and global environment. • All lead-free products are marked with the symbol Littelfuse defines lead-free as products which contain less than 1000ppm (0.1%) Lead, measured by weight of the entire product. • All RoHS compliant products are marked with the symbol European Union Directive 2002/95/EC Restriction of the use of Hazardous Substances (RoHS), restricts the use of Lead, Mercury, Hexavalent Chromium, Cadmium and Polybrominated Ethers (PBB’s and PBDE’s). SAMPLE KITS FROM LITTELFUSE® Surface Mount Design Kit Resettable PTC Design Kit This kit provides unsurpassed access to the most advanced surface mount circuit protection devices on the market today. It allows you to have the right product . . . the right size. . . the right rating you need . . . when you need it! This kit provides a wide assortment of Resettable PTC products from Littelfuse, the world leader in circuit protection. The PTC is a unique polymer device that trips during an overload to limit current flow in the circuit and resets after the overload current is removed. A must have for every electronic design Engineering or R&D Department. Complete assortment for every application need. This kit includes both fuses and Resettable PTCs. Part Number: 00940381 This kit contains both surface mount and radial leaded product, of various voltage and current ratings. A must have for everyone interested in this new form of circuit protection. Part Number: 00940463 Complete Electronic Kit PC Mount Kit This kit allows the designer to have a broad range of traditional cartridge style fuses and fuse mounting at their fingertips. Contains over 280 pieces of 3AG, 2AG and 5 x 20 mm fuses in both Fast-Acting and Slo-Blo® fuses in addition to an assortment of fuse clips, in-line fuseholders and International Shock-Safe panel mount fuseholders. This kit allows the designer to have an extensive range of traditional leaded fuses and fuse mountings at their disposal for prototype PCB applications. Contains over 200 pieces of PICO® II Fuses, MICRO™ Fuses, assorted fuseholders and clips in addition to 3AG and 2AG Fast-Acting and Slo-Blo® fuses. Part Number: 00940376 Part Number: 00940378 Economy Kit Complete Automotive Fuse Kit This kit allows one to sample a variety of cartridge style fuses and mounting while on a budget. Contains over 150 pieces of 3AG and 5 x 20 mm fuses in both Fast-Acting and Slo-Blo® fuses in addition to selected fuse clips, in-line fuseholders and International Shock-Safe panel mount fuseholders. This kit puts an assortment of traditional glass cartridge, Autofuse® Fuse blade fuses and in-line fuseholders at your fingertips. Part Number: 00940379 Part Number: 00940377 Representatives: Littelfuse has a worldwide network of manufacturers’ representatives. If you need direction on contacting your local representative, please visit www.littelfuse.com for more information. Other Littelfuse Literature: Please visit www.littelfuse.com or contact our Des Plaines, Illinois headquarters to request other Littelfuse literature including the following items. • Littelfuse POWR-GARD™ Products Catalog covering 13/32" x 11/2" and larger fuses which meet the National Electrical Code and CSA requirements for main, feeder, and branch circuit protection. (PF101) • Littelfuse Automotive OEM Products and Capabilities Brochure which is a reference guide covering fuses, fuseholders, and other special products directed to the automotive market. (OE101) • Littelfuse Electronic Products Selection Guide (EC102) • Littelfuse Telecom Designer’s Guide (EC105) w w w. l i t t e l f u s e . c o m w w w. l i t t e l f u s e . c o m Table of Contents Introduction to Circuit Protection 1 Varistor Products 2 Surface Mount Varistors 3 PulseGuard® Suppressors 4 TVS Diode Arrays 5 Silicon Avalanche Diodes 6 Switching Gas Discharge Tubes 7 Gas Discharge Tubes 8 Resettable PTCs 9 Surface Mount Fuses 10 Axial Lead and Cartridge Fuses 11 Blade Terminal and Special Purpose Fuses 12 Fuseholders 13 Fuse Blocks and Clips 14 Military Fuses and Fuseholders 15 w w w. l i t t e l f u s e . c o m Table of Contents PAGE INTRODUCTION TO CIRCUIT PROTECTION Fuseology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-11 Fuse Facts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4 Fuse selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6 Standrds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8 Packaging Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 PTC Facts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Overcurrent Selection Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Transientology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-23 Overvoltage Suppression Facts and Overvoltage Selection Guide . . . . . . . . . . . . . . . . . . . . . .11-21 ESD Suppressor Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Overvoltage Application Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22-23 VARISTOR PRODUCTS Varistor Products Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25-26 TMOV® and iTMOV® High Surge Current Radial Lead, Thermally Protected Metal Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27-35 UltraMOV™ High Surge Current Radial Lead Metal Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . .36-47 C-III Series High Energy Radial Lead Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48-55 LA Series Radial Lead Metal-Oxide Varistors for Line Voltage Operation . . . . . . . . . . . . . . . . . . . .56-66 ZA Series Radial Lead Metal-Oxide Varistors for Low to Medium Voltage Operation . . . . . . . . . . .67-80 BA/BB Series Industrial High Energy Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81-85 DA/DB Series Industrial High Energy Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86-89 HA Series Industrial High Energy Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90-94 TMOV34S® High Energy, Thermally Protected Metal Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . .95-100 HB34, HF34 and HG34 Series Industrial High Energy Metal-Oxide Varistor . . . . . . . . . . . . . . .101-108 DHB34 Series Industrial High Energy Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . .109-113 CA Series Industrial High Energy Metal-Oxide Disc Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . .114-121 NA Series Industrial High Energy Metal-Oxide Square Disc Varistor . . . . . . . . . . . . . . . . . . . . .122-126 MA Series Axial Lead Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127-131 PA Series Base Mount Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132-136 RA Series Low Profile Metal-Oxide Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137-144 High Reliability Varistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145-154 SURFACE MOUNT VARISTORS Surface Mount Varistors Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156 RoHS Pb MHS Series Multilayer High-Speed Surface Mount ESD Voltage Suppressor . . . . . . . . . . . . . .157-160 RoHS Pb MLE Series Multilayer Surface Mount ESD Suppressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161-167 RoHS Pb ML Series Multilayer Surface Mount Transient Voltage Surge Suppressor . . . . . . . . . . . . . . . .168-178 ™ RoHS Pb MLN SurgeArray Four Line Multilayer Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . .179-185 RoHS Pb AUML Series Multilayer Surface Mount Automotive Transient Surge Suppressor . . . . . . . . . . .186-194 RoHS Pb CH Series Monolithic Chip Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195-199 PULSEGUARD® SUPPRESSORS RoHS Pb PGB1 Series Lead-Free 0603, Single Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . .202-203 RoHS Pb PGB1 Series Lead-Free SOT23, Two Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . .204-205 RoHS Pb PGB1 Series Lead-Free 0805, Four Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . . .206-207 PGB Series 0603, Single Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . . . . . . . . . . .208-209 PGB Series SOT23, Two Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . . . . . . . . . . . .210-211 PGB Series 0805, Four Line Surface Mount ESD Suppressor . . . . . . . . . . . . . . . . . . . . . . . . . .212-213 PGD Series Connector Array, Surface Mount ESD Suppressor. . . . . . . . . . . . . . . . . . . . . . . . . . . . .214 TVS DIODE ARRAYS SPUSB1 Series, TVS Protection with Filter and Termination for USB Ports . . . . . . . . . . . . . . . .217-219 SP05x Series TVS Avalanche Diode Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220-227 SP720 Series High Voltage Rail Clamp SCR/Diode Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228-233 SP721 Series High Voltage Rail Clamp SCR/Diode Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . .234-239 SP723 Series High Voltage Rail Clamp SCR/Diode Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240-245 SP724 Series High Voltage Rail Clamp SCR/Diode Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246-251 SILICON AVALANCHE DIODES RoHS SMAJ Series, 400W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . .254-257 RoHS P4SMA Series, 400W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . .258-261 RoHS SMBJ Series, 600W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . .262-265 RoHS P6SMBJ Series, 600W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . .266-269 RoHS 1KSMBJ Series, 1000W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . .270-273 RoHS SMCJ Series, 1500W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . .274-277 RoHS 1.5SMC Series, 1500W Surface Mount Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . .278-281 RoHS P4KE Series, 400W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . .282-285 RoHS SA Series, 500W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . . . .286-289 RoHS P6KE Series, 600W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . .290-293 RoHS 1.5KE Series, 1500W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . .294-297 RoHS 5KP Series, 5000W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . .398-301 RoHS 15KP Cells, 15000W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . .302-304 RoHS SLD Series, Axial Leaded Transient Voltage Suppressor for Automotive Applications . . . . . . . .305-306 RoHS AK6 Series, 6000W Transient Voltage Suppressor for AC Line Protection . . . . . . . . . . . . . . . . .307-308 RoHS AK10 Series, 1000W Transient Voltage Suppressor for AC Line Protection . . . . . . . . . . . . . . . .309-310 w w w. l i t t e l f u s e . c o m Table of Contents PAGE SWITCHING GAS DISCHARGE TUBES RoHS RoHS RoHS GAS DISCHARGE TUBES RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS RoHS Pb RoHS RESETTABLE PTCs SURFACE MOUNT FUSES RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS RoHS RoHS RoHS RoHS RoHS RoHS RoHS AXIAL LEAD & CARTRIDGE FUSES RoHS RoHS RoHS RoHS RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb LCE Series, 1500W Axial Leaded Transient Voltage Suppressor . . . . . . . . . . . . . . . . . . . . . . . .311-314 LT Series, Voltage Switch Designed for HID Lighting Systems . . . . . . . . . . . . . . . . . . . . . . . . . .316-317 VS Series, Voltage Switch Designed for Fuel Ignition Circuits . . . . . . . . . . . . . . . . . . . . . . . . . .318-319 XT Series, Voltage Switch Designed for Xenon HID Circuits in Automobiles . . . . . . . . . . . . . . .320-321 Greentube™Broadband Optimized™ SL1002 Minitube Series . . . . . . . . . . . . . . . . . . . . . . . . . .323-325 Greentube™ SL1003 Minitube Series, 3 Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326-328 Greentube™ SL1011A Medium Duty Arrester Series, 2 Terminal . . . . . . . . . . . . . . . . . . . . . . . .329-331 Greentube™ SL1011B Heavy Duty Arrester Series, 2 Terminal . . . . . . . . . . . . . . . . . . . . . . . . . .332-334 Greentube™ SL1021A Medium Duty Arrester Series, 3 Terminal 8.0mm diameter . . . . . . . . . . .335-337 Greentube™ SL1021B Heavy Duty Arrester Series, 3 Terminal 8.0mm diameter . . . . . . . . . . . .338-340 Greentube™ SL1024A Medium Duty Arrester Series, 3 Terminal 8.0mm diameter . . . . . . . . . . .341-343 Greentube™ SL1024B Heavy Duty Arrester Series, 3 Terminal 8.0mm diameter . . . . . . . . . . . .344-346 Greentube™ SL1122A Hybrid Arrester Series, 3 Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347-348 Greentube™ SL1026 Maximum Duty Arrester Series, 3 Terminal . . . . . . . . . . . . . . . . . . . . . . . .349-350 Greentube™ HV Series High Voltage Arrester, 2 Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351-352 1206L Series 1206 Surface Mount Resettable PTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354-355 1812L Series 1812 Surface Mount Resettable PTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .356-357 30R Series 30 Volt Radial Lead Resettable PTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358-359 60R Series 60 Volt Radial Lead Resettable PTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .360-361 466 Series, SlimLine™ Lead-Free 1206, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . .364-365 433 Series, SlimLine™ 1206, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366 429 Series, High Current Lead-Free 1206, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . .367 468 Series, SlimLine™ Lead-Free 1206, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368 430 Series, 1206, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 467 Series, SlimLine™ Lead-Free 0603, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . .370-371 434 Series, SlimLine™ 0603, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372 435 Series, SlimLine™ Lead-Free 0402, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 451/453 Series, NANO2® Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 452/454 Series, NANO2® Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .375 455 Series, NANO2® UMF Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 154 Series, SMF OMNI-BLOK® Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .377 464 Series, NANO2® 250V UMF Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .378 465 Series, NANO2® 250V UMF Time Lag Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .379 461 Series, TeleLink® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .380-382 459/460 Series, PICO® SMF Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .383 202 Series, FLAT-PAK® Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .384 203 Series, FLAT-PAK® Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 446/447 Series, EBF Fuse Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .386 251/253 Series, PICO® II, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388 263 Series, PICO® II 250 Volt, Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .389 471 Series, PICO® II, Time Lag Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390 473, Series, PICO® II, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 265/266/267 Series, PICO®, Very Fast-Acting Fuse (High-Reliability) . . . . . . . . . . . . . . . . . . . . . . . .392 262/268/269 Series, MICRO™ Very Fast-Acting Fuse (High-Reliability) . . . . . . . . . . . . . . . . . . . . . . .393 272/273/274/278*279 Series, MICRO™ Very Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . .394 2AG, Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395-396 2AG, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .397-398, 399-400 3AG Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401-402 3AG, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .403-404 3AB, Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405-406 3AB, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .407-408 5 x 20 mm, Medium-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409-410, 422-423, 426-427, 428-429 5 x 20 mm, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . .411-412, 413-414, 417-418, 419, 420-421 5 x 20 mm, Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .415-416, 424-425 3.6 X 10 mm, Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .432, 434, 436 3.6 X 10 mm, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .433, 435, 437 322 Series, 3AB, Very Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .438 322P Series, 3AB, Very Fast-Acting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .439 662 Series, LT-5, Fast-Acting- for New Designs use the Wickmann 370 series TR5® fuse . . . . . . . . . . . 663 Series, LT-5, Time Lag Fuse- for New Designs use the Wickmann 372 series TR5® fuse . . . . . . . . 664 Series, LT-5, Time Lag Extended Breaking Capacity- for New Designs use the Wickmann 382 series TR5® fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665 Series, LT-5, Time Lag- for New Designs use the Wickmann 374 series TR5® fuse . . . . . . . . . . . . . KLK Series, AC, Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .440 KLKD Series, DC, Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441 w w w. l i t t e l f u s e . c o m Table of Contents AXIAL LEAD & CARTRIDGE FUSES (CONT.) BLADE TERMINAL AND SPECIAL PURPOSE FUSES RoHS RoHS RoHS RoHS RoHS RoHS RoHS RoHS RoHS RoHS FUSEHOLDERS FUSE BLOCKS AND CLIPS RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb RoHS Pb MILITARY FUSES AND FUSEHOLDERS RoHS Pb FLA, FLM and FLQ Series, Midget, Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .442-443 KLK, KLKD, BLS, BLF, and BLN Series, Midget, Fast-Acting Fuse . . . . . . . . . . . . . . . . . . . . . .444-445 Midget, KLQ and FLU Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .446 CCMR Series, Class CC Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .447-448 257 Series, ATO® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .450 297 Series, MINI® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .451 997 Series, MINI® 42V Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452 299 Series, MAXI™ Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .453 999 Series, MAXI™ 42V Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .454 298 Series, MEGA® Slo-Blo® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .455 498 Series, MIDI® Fuse and Fuseholder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .456 995 Series, JCASE® 42V Slo-Blo® Cartridge Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .457 496 Series, Cable Pro® Cable Protector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458 242 and 259 Series, Hazardous Area Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .459 481 Series Alarm Indicating Fuse for Telecom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .460 482 Series Alarm Indicating Fuseholder for Telecom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .461-462 LVSP Surge Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .463-464 International Shock-Safe (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .467-468 Flip-Top Shock-Safe (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .469 Shock-Safe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .470-471 Low Profile (Snap Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .472 Blown-Fuse Indicating (Snap Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .472 RF-Shielded (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .473 Traditional (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .474 Blown-Fuse Indicating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .475 Watertight (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .476 RF Shielded/Watertight (Panel Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .476 Micro™ or PICO® II Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .477 LT-5™ Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .477 In-Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .478-479 ATO® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .479 MINI® Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .480-481 OMNI-BLOK® Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .484-486 Midget Fuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .487 3AG Screw Terminal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .488 Clips (Rivet/Eyelet Mount) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .489 Clips (PCB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .490-491 Automatic Insertion Clips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .491 Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .494-495 Fuseholders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .496 European Union Directive 2002/95/EC Restriction of the use of Hazardous Substances(RoHS), restricts the use of Lead, Mercury, Hexavalent Chromium, Cadmium and Polybrominated Ethers (PBB’s and PBDE’s). Littelfuse defines lead-free as products which contain less than 1000ppm (0.1%) Lead, measured by weight of the entire product. w w w. l i t t e l f u s e . c o m 1 Introduction To Circuit Protection PAGE Fuseology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Fuse Facts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 Fuse Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6 Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8 Packaging Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 PTC Facts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Overcurrent Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Transientology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-23 Overvoltage Suprression Facts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-19 Overvoltage Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-21 ESD Suppressor Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Overvoltage Application Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-23 w w w. l i t t e l f u s e . c o m 1 Introduction to Circuit Protection Fuseology Fuse Facts The application guidelines and product data in this guide are intended to provide technical information that will help with application design. Since these are only a few of the contributing parameters, application testing is strongly recommended and should be used to verify performance in the circuit/application. In the absence of special requirements, Littelfuse reserves the right to make appropriate changes in design, process, and manufacturing location without notice. The purpose of the Fuseology Section is to promote a better understanding of both fuses and common application details. The fuses to be considered are current sensitive devices which are designed as the intentional weak link in the electrical circuit. The function of the fuse is to provide protection of discrete components, or of complete circuits, by reliably melting under current overload conditions. This fuseology section will cover some important facts about fuses, selection considerations, and standards. FUSE FACTS The following fuse parameters or application concepts should be well understood in order to properly select a fuse for a given application. AMBIENT TEMPERATURE: Refers to the temperature of the air immediately surrounding the fuse and is not to be confused with “room temperature.” The fuse ambient temperature is appreciably higher in many cases, because it is enclosed (as in a panel mount fuseholder) or mounted near other heat producing components, such as resistors, transformers, etc. BREAKING CAPACITY: See Interrupting Rating. CURRENT RATING: The nominal amperage value of the fuse. It is established by the manufacturer as a value of current which the fuse can carry, based on a controlled set of test conditions (See RERATING). Catalog Fuse part numbers include series identification and amperage ratings. Refer to the FUSE SELECTION GUIDE section for guidance on making the proper choice. RERATING: For 25°C ambient temperatures, it is recommended that fuses be operated at no more than 75% of the nominal current rating established using the controlled test conditions. These test conditions are part of UL/CSA/ANCE (Mexico) 248-14 “Fuses for Supplementary Overcurrent Protection,” whose primary objective is to specify common test standards necessary for the continued control of manufactured items intended for protection against fire, etc. Some common variations of these standards include: fully enclosed fuseholders, high contact resistances, air movement, transient spikes, and changes in connecting cable size (diameter and length). Fuses are essentially temperature-sensitive devices. Even small variations from the controlled test conditions can greatly affect the predicted life of a fuse when it is loaded to its nominal value, usually expressed as 100% of rating. The circuit design engineer should clearly understand that the purpose of these controlled test conditions is to enable fuse manufacturers to maintain unified performance standards for their products, and he must account for the variable conditions of his application. To compensate for these variables, the circuit design engineer who is designing for trouble-free, long-life fuse protection in his equipment generally loads his fuse not more than 75% of the nominal rating listed by the manufacturer, keeping in mind that overload and short circuit protection must be adequately provided for. The fuses under discussion are temperature-sensitive devices whose ratings have been established in a 25°C ambient. The fuse temperature generated by the current passing through the fuse increases or decreases with ambient temperature change. The ambient temperature chart in the FUSE SELECTION GUIDE section illustrates the effect that ambient temperature has on the nominal current rating of a fuse. Most traditional Slo-Blo® Fuse designs use lower melting temperature materials and are, therefore, more sensitive to ambient temperature changes. DIMENSIONS: Unless otherwise specified, dimensions are in inches. 2 w w w. l i t t e l f u s e . c o m The fuses in this catalog range in size from the approx. 0402 chip size (.041"L x .020"W x .012"H) up to the 5 AG, also commonly known as a“MIDGET” fuse (13/32" Dia. x 11/2" Length). As new products were developed throughout the years, fuse sizes evolved to fill the various electrical circuit protection needs. The first fuses were simple, open-wire devices, followed in the 1890’s by Edison’s enclosure of thin wire in a lamp base to make the first plug fuse. By 1904, Underwriters Laboratories had established size and rating specifications to meet safety standards. The renewable type fuses and automotive fuses appeared in 1914, and in 1927 Littelfuse started making very low amperage fuses for the budding electronics industry. The fuse sizes in the chart below began with the early “Automobile Glass” fuses, thus the term “AG”. The numbers were applied chronologically as different manufacturers started making a new size: “3AG,” for example, was the third size placed on the market. Other non-glass fuse sizes and constructions were determined by functional requirements, but they still retained the length or diameter dimensions of the glass fuses. Their designation was modified to AB in place of AG, indicating that the outer tube was constructed from Bakelite, fibre, ceramic, or a similar material other than glass. The largest size fuse shown in the chart is the 5AG, or “MIDGET,” a name adopted from its use by the electrical industry and the National Electrical Code range which normally recognizes fuses of 9/16" x 2" as the smallest standard fuse in use. SIZE 1AG 2AG 3AG 4AG 5AG 7AG 8AG FUSE SIZES DIAMETER (Inches) 1/4 .250 — .177 1/4 .250 9/32 .281 13/32 .406 1/4 .250 1/4 .250 LENGTH (Inches) 5/8 — 11/4 11/4 11/2 7/8 1 .625 .588 1.25 1.25 1.50 .875 1 TOLERANCES: The dimensions shown in this catalog are nominal. Unless otherwise specified, tolerances are applied as follows: ± .010" for dimensions to 2 decimal places. ± .005" for dimensions to 3 decimal places. The factory should be contacted concerning metric system and fractional tolerances. Tolerances do not apply to lead lengths. FUSE CHARACTERISTICS: The characteristic of a fuse design refers to how rapidly the fuse responds to various current overloads. Fuse characteristics can be classified into three general categories: very fast-acting, fast-acting, or Slo-Blo® Fuse. The distinguishing feature of Slo-Blo® fuses is that these fuses have additional thermal inertia designed to tolerate normal initial or start-up overload pulses. FUSE CONSTRUCTION: Internal construction may vary depending on ampere rating. Fuse photos in this catalog show typical construction of a particular ampere rating within the fuse series. Introduction to Circuit Protection Fuseology Fuse Facts TEST SAMPLING PLAN: Because compliance with certain specifica- holders. These fuses and their associated fuseholders are not intended for operation as a “switch” for turning power “on” and “off ”. tions requires destructive testing, these tests are selected on a statistical basis for each lot manufactured. INTERRUPTING RATING: Also known as breaking capacity or short TIME-CURRENT CURVE: The graphical presentation of the fusing circuit rating, the interrupting rating is the maximum approved current which the fuse can safely interrupt at rated voltage. During a fault or short circuit condition, a fuse may receive an instantaneous overload current many times greater than its normal operating current. Safe operation requires that the fuse remain intact (no explosion or body rupture) and clear the circuit. characteristic, time-current curves are generally average curves which are presented as a design aid but are not generally considered part of the fuse specification. Time-current curves are extremely useful in defining a fuse, since fuses with the same current rating can be represented by considerably different time-current curves. The fuse specification typically will include a life requirement at 100% of rating and maximum opening times at overload points (usually 135% and 200% of rating). A time-current curve represents average data for the design; however, there may be some differences in the values for any one given production lot. Samples should be tested to verify performance, once the fuse has been selected. Interrupting ratings may vary with fuse design and range from 35 amperes AC for some 250V metric size (5 x 20mm) fuses up to 200,000 amperes AC for the 600V KLK series. Information on other fuse series can be obtained from the factory. Fuses listed in accordance with UL/CSA/ANCE 248 are required to have an interrupting rating of 10,000 amperes, with some exceptions (See STANDARDS section) which, in many applications, provides a safety factor far in excess of the short circuit currents available. NUISANCE OPENING: Nuisance opening is most often caused by an incomplete analysis of the circuit under consideration. Of all the “Selection Factors” listed in the FUSE SELECTION GUIDE, special attention must be given to items 1, 3, and 6, namely, normal operating current, ambient temperature, and pulses. For example, one prevalent cause of nuisance opening in conventional power supplies is the failure to adequately consider the fuse’s nominal melting I2t rating. The fuse cannot be selected solely on the basis of normal operating current and ambient temperature. In this application, the fuse’s nominal melting I2t rating must also meet the inrush current requirements created by the input capacitor of the power supply’s smoothing filter. The procedure for converting various waveforms into I2t circuit demand is given in the FUSE SELECTION GUIDE. For trouble-free, long-life fuse protection, it is good design practice to select a fuse such that the I2t of the waveform is no more than 20% of the nominal melting I2t rating of the fuse. Refer to the section on PULSES in the FUSE SELECTION GUIDE. RESISTANCE: The resistance of a fuse is usually an insignificant part of the total circuit resistance. Since the resistance of fractional amperage fuses can be several ohms, this fact should be considered when using them in low-voltage circuits. Actual values can be obtained from the factory. Most fuses are manufactured from materials which have positive temperature coefficients, and, therefore, it is common to refer to cold resistance and hot resistance (voltage drop at rated current), with actual operation being somewhere in between. Cold resistance is the resistance obtained using a measuring current of no more than 10% of the fuse’s nominal rated current. Values shown in this publication for cold resistance are nominal and representative. The factory should be consulted if this parameter is critical to the design analysis. Hot resistance is the resistance calculated from the stabilized voltage drop across the fuse, with current equal to the nominal rated current flowing through it. Resistance data on all Littelfuse products are available on request. Fuses can be supplied to specified controlled resistance tolerances at additional cost. SOLDERING RECOMMENDATIONS: Since most fuse constructions incorporate soldered connections, caution should be used when installing those fuses intended to be soldered in place. The application of excessive heat can reflow the solder within the fuse and change its rating. Fuses are heat-sensitive components similar to semi-conductors, and the use of heat sinks during soldering is often recommended. UNDERWRITERS LABORATORIES: Reference to “Listed by Underwriters Laboratories” signifies that the fuses meet the requirements of UL/CSA/ANCE 248-14 “Fuses for Supplementary Overcurrent Protection”. Some 32 volt fuses (automotive) in this catalog are listed under UL Standard 275. Reference to “Recognized under the Component Program of Underwriters Laboratories” signifies that the item is recognized under the component program of Underwriters Laboratories and application approval is required. VOLTAGE RATING: The voltage rating, as marked on a fuse, indicates that the fuse can be relied upon to safely interrupt its rated short circuit current in a circuit where the voltage is equal to, or less than, its rated voltage. This system of voltage rating is covered by N.E.C. regulations and is a requirement of Underwriters Laboratories as a protection against fire risk. The standard voltage ratings used by fuse manufacturers for most small-dimension and midget fuses are 32, 63, 125, 250 and 600. In electronic equipment with relatively low output power supplies, with circuit impedance limiting short circuit currents to values of less than ten times the current rating of the fuse, it is common practice to specify fuses with 125 or 250 volt ratings for secondary circuit protection of 500 volts or higher. As mentioned previously (See RERATING), fuses are sensitive to changes in current, not voltage, maintaining their “status quo” at any voltage from zero to the maximum rating of the fuse. It is not until the fuse element melts and arcing occurs that the circuit voltage and available power become an issue. The safe interruption of the circuit, as it relates to circuit voltage and available power, is discussed in the section on INTERRUPTING RATING. To summarize, a fuse may be used at any voltage that is less than its voltage rating without detriment to its fusing characteristics. Please contact the factory for applications at voltages greater than the voltage rating. Lead-Free Soldering Parameters: Wave Solder — 260°C, 10 seconds max Reflow Solder — 260°C, 30 seconds max w w w. l i t t e l f u s e . c o m 3 1 INTRODUCTION TO CIRCUIT PROTECTION FUSEHOLDERS: In many applications, fuses are installed in fuse- Introduction to Circuit Protection Fuseology Fuse Facts and Fuse Selection Guide DERIVATION OF NOMINAL MELTING I2t: Laboratory tests are conducted on each fuse design to determine the amount of energy required to melt the fusing element. This energy is described as nominal melting I2t and is expressed as “Ampere Squared Seconds” (A2 Sec.). A pulse of current is applied to the fuse, and a time measurement is taken for melting to occur. If melting does not occur within a short duration of about 8 milliseconds (0.008 seconds) or less, the level of pulse current is increased. This test procedure is repeated until melting of the fuse element is confined to within about 8 milliseconds. The purpose of this procedure is to assure that the heat created has insufficient time to thermally conduct away from the fuse element. That is, all of the heat energy (I2t) is used, to cause melting. Once the measurements of current (I) and time (t) are determined, it is a simple matter to calculate melting I2t. When the melting phase reaches completion, an electrical arc occurs immediately prior to the “opening” of the fuse element. Clearing I2t = Melting I2t + arcing I2t. The nominal I2t values given in this publication pertain to the melting phase portion of the “clearing” or “opening”. FUSE SELECTION GUIDE The application guidelines and product data in this guide are intended to provide technical information that will help with application design. Since these are only a few of the contributing parameters, application testing is strongly recommended and should be used to verify performance in the circuit/application. Selection Factors 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Normal operating current Application voltage (AC or DC) Ambient temperature Overload current and length of time in which the fuse must open. Maximum available fault current Pulses, Surge Currents, Inrush Currents, Start-up Currents, and Circuit Transients Physical size limitations, such as length, diameter, or height Agency Approvals required, such as UL, CSA, VDE, METI, MITI or Military Considerations: mounting type/form factor, ease of removal, axial leads, visual indication, etc. Fuseholder features: clips, mounting block, panel mount, p.c. board mount, R.F.I. shielded, etc. NORMAL OPERATING CURRENT: The current rating of a fuse is typically derated 25% for operation at 25°C to avoid nuisance blowing. For example, a fuse with a current rating of 10A is not usually recommended for operation at more than 7.5A in a 25°C ambient. For additional details, see RERATING in the previous section and AMBIENT TEMPERATURE below. VOLTAGE: The voltage rating of the fuse must be equal to, or greater than, the available circuit voltage. For exceptions, see VOLTAGE RATING. CHART SHOWING EFFECT OF AMBIENT TEMPERATURE ON CURRENT-CARRYING CAPACITY (TYPICAL) KEY TO CHART: Curve A: Thin-Film Fuses and 313 Series (.010 to .150A) Curve B: FLAT-PAK®, TeleLink®, Nano2®, PICO®, Blade Terminal and special purpose and other Leaded and catridge fuses (except 313.010-.150A) Curve C: Resettable PTC’s C 140 PERCENT OF RATING* Many of the factors involved with fuse selection are listed below: 120 A B 100 B 80 A 60 25°C 40 C 20 -60°C -76°F -40°C -40°F -20°C -4°F 0°C 20°C 40°C 60°C 80°C 32°F 68°F 104°F 140°F 176°F AMBIENT TEMPERATURE 100°C 212°F 120°C 248°F *Ambient temperature effects are in addition to the normal rerating, see example. AMBIENT TEMPERATURE: The current carrying capacity tests of fuses are performed at 25°C and will be affected by changes in ambient temperature. The higher the ambient temperature, the hotter the fuse will operate, and the shorter its life will be. Conversely, operating at a lower temperature will prolong fuse life. A fuse also runs hotter as the normal operating current approaches or exceeds the rating of the selected fuse. Practical experience indicates fuses at room temperature should last indefinitely, if operated at no more than 75% of catalog fuse rating. 4 Example: Given a normal operating current of 2.25 amperes in an application using a 229 series fuse at room temperature, then: Normal Operating Current 0.75 or Catalog Fuse Rating = 2.25 Amperes 0.75 w w w. l i t t e l f u s e . c o m = 3 Amp Fuse (at 25°C) Introduction to Circuit Protection Fuseology Fuse Selection Guide Catalog Fuse Rating = Nominal Operating Current critical to the design analysis. The following example should assist in providing a better understanding of the application of I2t. EXAMPLE: Select a 125V, very fast-acting PICO®II fuse that is capable of withstanding 100,000 pulses of current (I) of the pulse waveform shown in Figure 1. The normal operating current is 0.75 ampere at an ambient temperature of 25°C. 0.75 x Percent of Rating Step 1 — Refer to Chart I (page #6) and select the appropriate pulse waveform, which is waveform (E) in this example. Place the applicable value for peak pulse current (ip) and time (t) into the corresponding formula for waveshape (E), and calculate the result, as shown: or 2.25 Amperes = 3.15 Amp Fuse (at 80°C) 0.75 x 0.95 OVERLOAD CURRENT CONDITION: The current level for which protection is required. Fault conditions may be specified, either in terms of current or, in terms of both current and maximum time the fault can be tolerated before damage occurs. Time-current curves should be consulted to try to match the fuse characteristic to the circuit needs, while keeping in mind that the curves are based on average data. 1 1 I2t= 5 (ip) = I2t = 5 (ip)2t MAXIMUM FAULT CURRENT: The Interrupting Rating of a fuse This value is referred to as the “Pulse I2t”. must meet or exceed the Maximum Fault Current of the circuit. Step 2 — Determine the required value of Nominal Melting I2t by referring to Chart II (page 6). A figure of 22% is shown in Chart II for 100,000 occurrences of the Pulse I2t calculated in Step 1. This Pulse I2t is converted to its required value of Nominal Melting I2t as follows: Nominal melting I2t is a measure of the energy required to melt the fusing element and is expressed as “Ampere Squared Seconds” (A2 Sec.). This nominal melting I2t, and the energy it represents (within a time duration of 8 milliseconds [0.008 second] or less and 1 millisecond [0.001 second] or less for thin film fuses), is a value that is constant for each different fusing element. Because every fuse type and rating, as well as its corresponding part number, has a different fusing element, it is necessary to determine the I2t for each. This I2t value is a parameter of the fuse itself and is controlled by the element material and the configuration of the fuse element. In addition to selecting fuses on the basis of “Normal Operating Currents”, “Rerating”, and “Ambient Temperature” as discussed earlier, it is also necessary to apply the I2t design approach. This nominal melting I2t is not only a constant value for each fuse element design, but it is also independent of temperature and voltage. Most often, the nominal melting I2t method of fuse selection is applied to those applications in which the fuse must sustain large current pulses of a short duration. These high-energy currents are common in many applications and are described by a variety of terms, such as “surge current”, “start-up current”, “inrush current”, and other similar circuit “transients” that can be classified in the general category of “pulses.” Laboratory tests are conducted on each fuse design to determine its nominal melting I2t rating. The values for I2t given in this publication are nominal and representative. The factory should be consulted if this parameter is 5 x 82 x .004 = 0.0512 A2 Sec. Nom. Melt I2t = Pulse I2t/.22 = 0.0512/.22 = 0.2327 A2 Sec. 10 Current (Amperes) PULSES: The general term “pulses” is used in this context to describe the broad category of wave shapes referred to as “surge currents”, “start-up currents”, “inrush currents”, and “transients”. Electrical pulse conditions can vary considerably from one application to another. Different fuse constructions may not react the same to a given pulse condition. Electrical pulses produce thermal cycling and possible mechanical fatigue that could affect the life of the fuse. Initial or start-up pulses are normal for some applications and require the characteristic of a Slo-Blo® fuse. Slo-Blo® fuses incorporate a thermal delay design to enable them to survive normal start-up pulses and still provide protection against prolonged overloads. The start-up pulse should be defined and then compared to the time-current curve and I2t rating for the fuse. Application testing is recommended to establish the ability of the fuse design to withstand the pulse conditions. 1 8 6 4 2 w w w. l i t t e l f u s e . c o m l2 t Pulse Energy .001 Normal Operating Current .002 .003 .004 .005 Time (Seconds) .006 Figure 1 5 1 INTRODUCTION TO CIRCUIT PROTECTION Similarly, if that same fuse were operated at a very high ambient temperature of 80°C, additional derating would be necessary. Curve “B” of the ambient temperature chart shows the maximum operating “Percent of Rating” at 80°C to be 95%, in which case; Introduction to Circuit Protection Fuseology Fuse Selection Guide CHART I WAVESHAPES FORMULAS i=k I2t = ip2 t ip A TESTING: The above factors should be considered in selecting a t ib i = ip -kt I2t = (1/3)(ip2 + ipib + ib2) t ip B Step 3 — Examine the I2t rating data for the PICO® II, 125V, very fastacting fuse. The part number 251001, 1 ampere design is rated at 0.256 A2 Sec., which is the minimum fuse rating that will accommodate the 0.2327 A2 Sec. value calculated in Step 2. This 1 ampere fuse will also accommodate the specified 0.75 ampere normal operating current, when a 25% derating factor is applied to the 1 ampere rating, as previously described. fuse for a given application. The next step is to verify the selection by requesting samples for testing in the actual circuit. Before evaluating the samples, make sure the fuse is properly mounted with good electrical connections, using adequately sized wires or traces. The testing should include life tests under normal conditions and overload tests under fault conditions, to ensure that the fuse will operate properly in the circuit. t CHART II i = ip sin t I2t = (1/2) ip2 t ip C 100,000 10,000 1,000 100 t 100000 ip D I2t = (1/3) ip2 t t 10000 OR t t ip F t1 i = kt2 OR i = ip (1-kt)2 I2t = (1/5) ip2 t Number of Pulses ip E PULSE CYCLE WITHSTAND CAPABILITY Pulses Pulse I2t = 22% of Nominal Melting I2t Pulses Pulse I2t = 29% of Nominal Melting I2t Pulses Pulse I2t = 38% of Nominal Melting I2t Pulses Pulse I2t = 48% of Nominal Melting I2t i = ipe–kt) I2t ≅ (1/2) ip2 t1 1000 100 10% 100% Pulse I 2 t / Average Melting I 2 t Note: Adequate time (10 seconds) must exist between pulse events to allow heat from the previous event to dissipate. FUSEHOLDER SELECTION GUIDE RERATING: For 25°C ambient temperatures, it is recommended that fuseholders be operated at no more than 60% of the nominal current rating established using the controlled test conditions specified by Underwriters Laboratories. The primary objective of these UL test conditions is to specify common test standards necessary for the continued control of manufactured items intended for protection against fire, etc. A copper dummy fuse is inserted in the fuseholder by Underwriters Laboratories, and then the current is increased until a certain temperature rise occurs. The majority of the heat is produced by the contact resistance of the fuseholder clips. This value of current is considered to be the rated current of the fuseholder, expressed as 100% 6 of rating. Some of the more common, everyday applications may differ from these UL test conditions as follows: fully enclosed fuseholders, high contact resistance,air movement, transient spikes, and changes in connecting cable size (diameter and length). Even small variations from the controlled test conditions can greatly affect the ratings of the fuseholder. For this reason, it is recommended that fuseholders be derated by 40% (operated at no more than 60% of the nominal current rating established using the Underwriter Laboratories test conditions, as previously stated). w w w. l i t t e l f u s e . c o m Introduction to Circuit Protection Fuseology Standards Fuse ratings and other performance criteria are evaluated under laboratory conditions and acceptance criteria, as defined in one or more of the various fuse standards. It is important to understand these standards so that the fuse can be properly applied to circuit protection applications. UL/CSA/ANCE (Mexico) 248-14 FUSES FOR SUPPLEMENTARY OVERCURRENT PROTECTION (600 Volts, Maximum) (Previously UL 198G and CSA C22.2, No. 59) UL UL LISTED A UL Listed fuse meets all the requirements of the UL/CSA 248-14 Standard. Following are some of the requirements. UL ampere rating tests are conducted at 100%, 135%, and 200% of rated current. The fuse must carry 100% of its ampere rating and must stabilize at a temperature that does not exceed a 75°C rise. ® The fuse must open at 135% of rated current within one hour. It also must open at 200% of rated current within 2 minutes for 0-30 ampere ratings and 4 minutes for 35-60 ampere ratings. The interrupting rating of a UL Listed fuse is 10,000 amperes AC minimum at 125 volts. Fuses rated at 250 volts may be listed as interrupting 10,000 amperes at 125 volts and, at least, the minimum values shown below at 250 volts. Ampere Rating Interrupting Rating of Fuse In Amperes 0 to 1 35 1.1 to 3.5 100 3.6 to 10 200 10.1 to 15 750 15.1 to 30 1500 Recognized Under the Component Program of Underwriters Laboratories Voltage Rating 250 VAC 250 VAC 250 VAC 250 VAC 250 VAC INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC) Publication 60127, Parts 1, 2, 3, 4, 6 The IEC organization is different from UL and CSA, since IEC only writes specifications and does not certify. UL and CSA write the specifications, and are responsible for testing and certification. Certification to IEC specifications are given by such organizations as SEMKO (Swedish Institute of Testing and Approvals of Electrical Equipment) and BSI (British Standards Institute) , as well as UL and CSA. IEC Publication 60127 defines three breaking capacity levels (interrupting rating). Low breaking capacity fuses must pass a test of 35 amperes or ten times rated current, whichever is greater, while enhanced breaking capacity fuses must pass a test of 150 amperes and high breaking capacity fuses must pass a test of 1500 amperes. 60127 Part 2 Sheet 1 – Type F Quick Acting, High Breaking Capacity Sheet 2 – Type F Quick Acting, Low Breaking Capacity Sheet 3 – Type T Time Lag, Low Breaking Capacity Sheet 4 – Style Fuses 1/4 x 1 1/4 Sheet 5 – Type T Time Lag, High Breaking Capacity Sheet 6 – Type T Time Lag, Enhanced Breaking Capacity The letters ‘F’ and ‘T’ represent the time-current characteristic of the fast-acting and time delay fuses. One of these letters will be marked on the end cap of the fuse. UL/CSA/ANCE (Mexico) 248-14 vs. IEC 60127 Part 2 FUSE OPENING TIMES vs. METI B / MITI B Percent UL & CSA of Rating STD 248-14 IEC TYPE F Sheet 1 (*) IEC Type F Sheet 2 (*) IEC Type T Sheet 3 (*) IEC Type T Sheet 5 (*) 4 Hr. Min. — — — — 130 — — — — — 135 60 Minutes Max. — — — — — 60 Minutes Min. 60 Minutes Min. 60 Minutes Min. 60 Minutes Min. 160 — — — — — 1 Hr. Max. UL Listed 200 2 Minutes Max. — — — — 2 Minutes Max. UL ampere ratings tests are conducted at 110%, 135%, and 200%. Interrupting rating tests are not required. 210 — 30 Minutes Max. 30 Minutes Max. 2 Minutes Max. 30 Minutes Max. ® The Recognized Components Program of UL is different from UL Listing. UL will test a fuse to a specification requested by the manufacturer. The test points can be different from the UL Listed requirements if the fuse has been designed for a specific application. Application approval is required by UL for fuses recognized under the Component Program. UL 275 AUTOMOTIVE GLASS TUBE FUSES (32 Volts) ® CSA Certification CSA Certification in Canada is equivalent to UL Listing in the United States. The Component Acceptance Program of CSA is equivalent to the Recognition Program at UL. ® METI APPROVAL METI approval in Japan is similar to UL Recognition in the United States. METI B has its own design standard and characteristics. MITI APPROVAL MITI approval in Japan is similar to UL Recognition in the United States. MITI B has its own design standard and characteristics. 110 150 METI/MITI B 1Hr. Min. (*) Note: The IEC Specification is only written up to 6.3A (8 and 10A will be added soon), any components above these ratings are not recognized by the IEC (although the fuses may have those opening characteristics). IEC also has requirements at 275%, 400% and 1000%; however, the chart is used to show that fuses with the same ampere rating made to different specifications are not interchangeable. According to the IEC 60127 Standard, a one ampere-rated fuse can be operated at one ampere. A one ampere-rated fuse made to UL/CSA/ANCE 248-14 should not be operated at more than .75 ampere (25% derated — See RERATING section of FUSEOLOGY). METI B covers only one characteristic i.e. there are no ‘delay’ definitions on other performance variants. w w w. l i t t e l f u s e . c o m 7 1 INTRODUCTION TO CIRCUIT PROTECTION Littelfuse is at your service to help solve your electrical protection problems. When contacting Littelfuse sales engineers, please have all the requirements of your applications available. Requests for quotes or assistance in designing or selecting special types of circuit protection components for your particular applications are also welcome. In the absence of special requirements, Littelfuse reserves the right to make appropriate changes in design, process, and manufacturing location without prior notice. Introduction to Circuit Protection Fuseology Standards and Packaging Information MILITARY/FEDERAL STANDARDS See Table of Contents for Military Product Section. Publication IEC 60127-4 (Universal Modular Fuse-Links [UMF] ) This part of IEC 60127 covers both PCB through-hole and surface mount fuses. This standard covers fuses rated 32, 63, 125, and 250 volts. This standard will be accepted by UL/CSA making it the first global fuse standard. This specification uses different fusing gates than IEC 60127-2; the gates used here are 125%, 200%, and 1000%. The fuses must not open in less than one hour at 125% of rated current and open within two minutes at 200% of rated current. The 1000% overload is used to determine the fuse characteristic. The opening time for each rating is listed below. Type FF: Type F: Type T: Type TT: MIL-PRF-15160 and MIL-PRF-23419 These specifications govern the construction and performance of fuses suitable primarily for military electronic applications. MIL-PRF-19207 This specification governs the construction and performance of fuseholders suitable for military applications. DSSC Drawing #87108 Less than 0.001 sec. From 0.001 - 0.01 sec. From 0.01 - 0.1 sec. From 0.1 - 1.00 sec. This drawing governs the construction and performance of .177" x .570" (2AG size) cartridge fuses and axial lead versions suitable for military applications. DSSC #87108 designation is included in the fuse end cap marking. These characteristics correlate to the terminology used in IEC 60127-1. Breaking capacity (interrupting rating) varies based on voltage rating. Parts rated at 32 & 63 volts must pass a test of 35 amperes or ten times rated current, whichever is greater.Parts rated at 125 volts must pass a test of 50 amperes or ten times rated current, whichever is greater. Parts rated at 250 volts are further defined as either low, intermediate or high breaking. The low breaking capacity fuses must pass a test of 100 amperes or ten times rated current, while intermediate breaking capacity fuses must pass a test of 500 amperes and, high breaking capacity fuses must pass a test of 1500 amperes. Packaging Suffixes R A/X V T H U M D P E W Y N K RT1 RT2 RT3 Fuses and holders approved to the following Military specifications are on the Qualified Products List (QPL) for that specification. = Taped & reeled fuses = 1 unit per bag = 5 units per box = 10 units per box = 100 units per box = 500 units per box = 1000 units per box = 1500 units per box = 2000 units per box = 2500 units per box = 3000 units per box = 4,000 units per box = 5000 units per box = 10,000 units per box = Taped & reeled. Spacing (x) = 2.062 inches (52.4 mm) = Taped & reeled. Spacing (x) = 2.50 inches (63.5 mm) = Taped & reeled. Spacing (x) = 2.874 inches (73 mm) Tape and Reel packaging per EIA-296: • Tape spacing is defined as the width of the tape and reeled fuse (x) as measured from inside tape to inside tape. • Pitch is defined as the space between two tape and reeled fuses (y) as measured from lead to lead. FEDERAL SPECIFICATION W-F-1814 This specification governs the construction and performance of fuses with high interrupting ratings that are approved for federal applications. Fuses approved to these specifications are on the Federal Qualified Products List. Write to the following agencies for additional information on standards, approvals, or copies of the specifications. Underwriters Laboratories Inc. (UL) 333 Pfingsten Road Northbrook, IL 60062 Att: Publications Stock Canadian Standards Association (CSA) 178 Rexdale Boulevard Rexdale, Ontario, Canada M9W 1R3 Att: Standard Sales International Electrotechnical Commission (IEC) 3, Rue de Varembe 1211 Geneva 20 Switzerland Att: Sales Department Naval Publications and Military Standards Form Center (for Military and Federal Standards) 5801 Tabor Avenue Philadelphia, PA 19120 Att: Commanding Officer Defense Supply Center Columbus (DSCC) 3990 East Broad Street Columbus, OH 43216-5000 Ministry of Economy Trade and Industry (METI) Kasumigaseki Chi-Youda-Ku Tokyo 100, Japan x y 8 w w w. l i t t e l f u s e . c o m Introduction to Circuit Protection Fuseology PTC Facts The most obvious difference is that the PTC is resettable. The general procedure for resetting after an overload has occurred is to remove power and allow the device to cool down. There are several other operating characteristics that differentiate the two types of products. The terminology used for PTCs is often similar but not the same as for fuses. Two parameters that fall into this category are leakage current and interrupting rating. TEMPERATURE RATING: The useful upper limit for a PTC is generally 85°C while the maximum operating temperature for fuses is 125°C. The following temperature rerating curves that compare PTCs to fuses illustrate that more rerating is required for a PTC at a given temperature. Additional operating characteristics can be reviewed by the circuit designer in making the decision to choose a PTC or a fuse for overcurrent protection. Key to chart: Curve A: Thin-Film Fuses and 313 Series (.010 to .150A) Curve B: FLAT-PAK®, TeleLink®, Nano²®, PICO®, Blade Terminal and special purpose and other Leaded and catridge fuses (except 313.010-.150A) Curve C: Resettable PTCs C 140 transitioned from the low resistance state to the high resistance state due to an overload. PERCENT OF RATING* LEAKAGE CURRENT: The PTC is said to have “tripped” when it has 120 A B 100 B 80 A 60 25°C Log resistance (ohms) 40 C 20 -60°C -76°F 0°C 20°C 40°C 60°C 80°C 100°C 32°F 68°F 104°F 140°F 176°F 212°F AMBIENT TEMPERATURE • Ambient temperature effects are in addition to the normal derating. Trip Point Temperature (C) Protection is accomplished by limiting the current flow to some low leakage level. Leakage current can range from less than a hundred milliamps at rated voltage up to a few hundred milliamps at lower voltages. The fuse on the other hand completely interrupts the current flow and this open circuit results in no leakage current when subjected to an overload. INTERRUPTING RATING: The PTC is rated for a maximum short circuit current at rated voltage. This fault current level is the maximum current that the device can withstand keeping in mind that the PTC will not actually interrupt the current flow (see LEAKAGE CURRENT above). A typical PTC short circuit rating is 40A. Fuses do in fact interrupt the current flow in response to the overload and the range of interrupting ratings vary from tens of amperes up to 10,000 amperes at rated voltage. The circuit parameters may dictate the component choice based on typical device rating differences. OPERATING VOLTAGE RATING: General use PTCs are not rated above 60V while fuses are rated up to 600V. CURRENT RATING: The operating current rating for PTCs can be up to 11A while the maximum level for fuses can exceed 20A. -40°C -40°F -20°C -4°F 120°C 248°F AGENCY APPROVALS: PTCs are Recognized under the Component Program of Underwriters Laboratories to UL Standard 1434 for Thermistors. The devices have also been certified under the CSA Component Acceptance Program. Approvals for fuses include Recognition under the Component Program of Underwriters Laboratories and the CSA Component Acceptance Program. In addition, many fuses are available with full “Listing” in accordance with the new Supplementary Fuse Standard UL/CSA/ANCE (Mexico) 248-14. RESISTANCE: Reviewing product specifications indicates that similarly rated PTCs have about twice (sometimes more) the resistance of fuses. TIME-CURRENT CHARACTERISTIC: Comparing the time-current curves of PTCs to time-current curves of fuses show that the speed of response for a PTC is similar to the time delay of a Slo-Blo® fuse. SUMMARY: Many of the issues discussed become a matter of preference, but there is an important area of application where the use of resettable PTCs is becoming a requirement. Much of the design work for personal computers and peripheral devices is strongly influenced by Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the Plug and Play SCSI (Small Computer Systems Interface) Specification for this large market includes a statement that “. . . must provide a self-resetting device to limit the maximum amount of current sourced”. The PTC / fuse discussion provides some insight as to when PTCs may be the appropriate choice for providing overcurrent circuit protection. A selection guide worksheet appears on the following page as an aid in choosing the best circuit protection component. w w w. l i t t e l f u s e . c o m 9 1 INTRODUCTION TO CIRCUIT PROTECTION Overcurrent circuit protection can be accomplished with the use of either a traditional fuse or the more recently developed resettable PTC. Both devices function by reacting to the heat generated by the excessive current flow in the circuit. The fuse melts open, interrupting the current flow, and the PTC changes from low resistance to high resistance to limit current flow. Understanding the differences in performance between the two types of devices will make the best circuit protection choice easier. Introduction to Circuit Protection Fuseology Overcurrent Selection Guide Worksheet 1. Define the circuit operating parameters (Complete the following form). Normal operating current in amperes: Normal operating voltage in volts: Maximum interrupt current: Ambient Temperature: Typical overload current: Required opening time at specified overload: Transient pulses expected (Quarterly) Resettable or one-time: Agency Approvals: Mounting type/form factor: Typical resistance (in circuit): 2. 3. Select the proper circuit protection component. Determine the opening time at fault. Consult the Time-Current (T-C)Curve to determine if the selected part will operate within the constraints of your application. If the device opens too soon, the application may experience nuisance operation. If the device does not open soon enough, the overcurrent may damage downstream components.To determine the opening time for the chosen device, locate the overload current on the X-axis of the appropriate TC Curve and follow its line up to its intersection with the curve.At this point read the time tested on the Y-axis.This is the average opening time for that device. If your overload current falls to the right of the curve the device will open. If the overload current is to the left of the curve, the device will not operate. 4. Verify ambient operating parameters. Ensure that the application voltage is less than or equal to the device’s rated voltage and that the operating temperature limits are within those specified by the device. 5. Verify the device’s dimensions. Using the information from the Designer’s Guide page, compare the maximum dimensions of the device to the space available in the application. 6. Test the selected product in an actual application. Overcurrent Selection Guide: Surface Mount PTC 30V PTC Leaded 60V PTC Leaded Lead-Free Available Pb RoHS N/A N/A 0.200Operating 0.900 - 0.100 2.6A Current Range 9A 3.75A 15V Maximum Voltage (*) 30V 60V Maximum Interupting 40A 40A 40A Rating (**) -40°C to -40°C to -40°C to Temperature Range 85°C 85°C 85°C High Thermal Rerating High High Opening time at Slow Slow Slow 200% of Amp Rating Transient Withstand Resistance 0402 SMF Pb RoHS 0.250 2A 24V 35A -55°C to 90°C Medium Fast Low Low Low Low Medium Medium Medium Low 0603 SMF Pb 1206 SMF RoHS Pb RoHS Nano2® Telelink SMF Fuse PICO® 0402,0603, 3.6 x10mm TR5®/TE5® II Fuse 1206 TFF Fuses RoHS RoHS Pb RoHS N/A Pb RoHS Pb 10 RoHS Midgets N/A 35-59A 35-63A 25-100A 10,000A 10,000A 10,000A 200,000A -55°C to -55°C to -55°C to -55°C to -55°C to 90°C 125°C 125°C 90°C 90°C Medium Low Low Medium Medium Fast to Fast to Fast to Fast to Fast Medium Medium Medium Medium Low to Low to Low to Low to Low Medium Medium Medium Medium -55 to +125° Low Fast to Medium Low to Medium -40 to 85°C Low Fast to Slow Low to Medium -55°C to 125°C Low Fast to Medium Low to High -55°C to 125°C Low Fast to Slow Low to High -55°C to 125°C Low Fast to Slow Low to High -55°C to 125°C Low Fast to Slow Low to High Low Low Low Low Low Low UL, CSA, MITI UL, CSA 50A 50A 50A 50A Low Low Low Low Low UL, UL,CSA, UL, CSA UL, CSA UMF, UL, CSA, MITI CSA, MITI UL,VDE UL,CSA, Senko,METI, VDE, CCC MITI,CCC,CSA One Time One Time One Time One Time One Time One Time One Time One Time Surface Surface Surface Surface Leaded Surface Leaded Leaded Mount Mount Mount Mount Mount RoHS Pb 24-125V 0.250-7A Multiple Surface Mount (*) (**) (***) RoHS 0.03215A 250V 0.062 15A 250V Operational Uses Mounting/Form Factor Leaded Pb 0.100 10A 250V 0.062 15A 250V UL, CSA Leaded RoHS 0.40 10A 125-250V 0.125 7A 125V UL, CSA, UL, CSA, UL, CSA, TUV TUV TUV Multiple Pb 3AGs/ 3ABs 0.10010A 250V 0.2505A 32V Agency Approvals Multiple 5x20 mm 2AGs CSA, BSI, UL, VDE, MITI, CSA, MITI SEMKO, UL One Time One Time Leaded or Leaded or Cartridge Cartridge 0.010 35A 250V 0.100 30A 600V One Time One Time Leaded or Cartridge Cartridge Maximum operating voltage in the series, parts may be used at voltages equal to or less than this value. Maximum interrupting rating at specified voltage which may be less than maximum operating voltage. Opening time is in relation to other forms of protection. A fast device will typically operate within three seconds at 200% of rated current. Denotes Lead-Free Product according to Littlefuse standards. Contact factory for availability. Denotes Lead-Free product according to RoHS specification. Contact factory for availability. w w w. l i t t e l f u s e . c o m Introduction to Circuit Protection Transientology Overvoltage Suppression Facts Why are Transients of Increasing Concern? Voltage Transients are defined as short duration surges of electrical energy and are the result of the sudden release of energy that was previously stored, or induced by other means, such as heavy inductive loads or lightning strikes. In electrical or electronic circuits, this energy can be released in a predictable manner via controlled switching actions, or randomly induced into a circuit from external sources. Component miniaturization has resulted in increased sensitivity to electrical stresses. Microprocessors for example, have structures and conductive paths which are unable to handle high currents from ESD transients. Such components operate at very low voltages, so voltage disturbances must be controlled to prevent device interruption and latent or catastrophic failures. Sensitive devices such as microprocessors are being adopted at an exponential rate. Microprocessors are beginning to perform transparent operations never before imagined. Everything from home appliances, such as dishwashers, to industrial controls and even toys, have increased the use of microprocessors to improve functionality and efficiency. Repeatable transients are frequently caused by the operation of motors, generators, or the switching of reactive circuit components. Random transients, on the other hand, are often caused by Lightning (Figure 1) and Electrostatic Discharge (ESD) (Figure 2). Lightning and ESD generally occur unpredictably, and may require elaborate monitoring to be accurately measured, especially if induced at the circuit board level. Numerous electronics standards groups have analyzed transient voltage occurrences using accepted monitoring or testing methods. The key characteristics of several transients are shown below in Table 1. Vp Vp/2 t1 t t2 Figure 1. Lightning Transient Waveform VOLTAGE CURRENT RISE-TIME DURATION 25kV 600V 1kV 15kV 20kA 500A 10A 30A 10µs 50µs 20ns 123 VRMS . 4. 40kA capability depends on applications rated up to 132V RMS . 30kA applies if > 132 VRMS . 5. 40kA capability depends on applications rated up to 97VRMS. 30kA applies if > 97 VRMS. 110 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Industrial DHB34 Varistor Series Device Ratings and Specifications CONTINUOUS SPECIFICATIONS (25 oC) TRANSIENT VRMS VDC ENERGY (2ms) PEAK CURRENT (8/20µs) VARISTOR VOLTAGE AT 1mA DC TEST CURRENT MAXIMUM CLAMPING VOLTAGE (VC) AT 200A (8/20µs) TYPICAL CAPACITANCE f = 1MHz SIZE VM(AC) VM(DC) WTM ITM MIN VN(DC) MAX MODEL NUMBER VC (mm) (V) (V) (V) (A) (V) (V) (V) (V) V391DHB34 34 385 510 550 40,000 545 604 663 1,000 3,500 V421DHB34 34 420 560 600 40,000 610 680 748 1,130 3,000 V441DHB34 34 440 585 630 40,000 622 691 759 1,147 2,900 V481DHB34 34 480 640 650 40,000 670 750 825 1,240 2,700 V511DHB34 34 510 675 700 40,000 735 820 910 1,350 2,500 V551DHB34 34 550 710 755 40,000 778 864 949 1,404 2,390 V571DHB34 34 575 730 770 40,000 805 910 1000 1,480 2,200 V661DHB34 34 660 850 900 40,000 940 1050 1160 1,720 2,000 V681DHB34 34 680 875 925 40,000 962 1068 1173 1,777 1,900 V751DHB34 34 750 970 1050 40,000 1080 1200 1320 2,000 1,800 (pF) NOTE: Ratings are for each individual varistor element in dual assembly. 1. Average power dissipation of transients not to exceed 2.0W per varistor element (2 varistors per device). 2. 40kA capability depends on applications rated up to 115VRMS . 30kA applies if > 115 VRMS . 3. 40kA capability depends on applications rated up to 123V RMS . 30kA applies if > 123 VRMS . 4. 40kA capability depends on applications rated up to 132V RMS . 30kA applies if > 132 VRMS . 5. 40kA capability depends on applications rated up to 97VRMS. 30kA applies if > 97 VRMS. w w w. l i t t e l f u s e . c o m 111 2 VARISTOR PRODUCTS MAXIMUM RATINGS (85 oC) Varistor Products High Energy Industrial DHB34 Varistor Series Power Dissipation Ratings PERCENT OF PEAK VALUE Should transients occur in rapid succession, the average power dissipation result is simply the energy (watt-seconds) per pulse times the number of pulses per second. The power so developed must be within the specifications shown on the Device Ratings and Specifications table for the specific device. The operating values must be derated as shown in Figure 1. 100 90 50 10 O1 T TIME T1 T2 O1 = Virtual Origin of Wave T = Time From 10% to 90% of Peak T1 = Virtual Front time = 1.25 • t T2 = Virtual Time to Half Value (Impulse Duration) Example: For an 8/20µs Current Waveform: 8µs = T1 = Virtual Front Time 20µs = T2 = Virtual Time to Half Value FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM Transient V-I Characteristics Curves 10000 TA = -55 C to 85C Maximum Clamping Voltage DHB34 Series 110 to 750V AC Rating V751 V661 Voltage Volts V511 V551 V681 V571 1000 V481 V141 V131 V111 V441 Current - AMPS 100 0.001 0.01 0.1 1 10 V151 100 1000 10000 V421 V391 V351 V331 V321 V301 V271 V251 V201 V181 FIGURE 3. CLAMPING VOLTAGE FOR DHB34 SERIES 112 w w w. l i t t e l f u s e . c o m 100000 Varistor Products High Energy Industrial DHB34 Varistor Series Mechanical Dimensions Pulse Rating Curves 50,000 DISC SIZE 34mm V131DHB34 - V751DHB34 1 SURGE CURRENT (A) 10,000 2 10 5,000 102 2,000 103 1,000 105 T max 37.5 max 2 106 104 500 VARISTOR PRODUCTS 20,000 56 max 200 100 12.7 typ 50 20 10 3.7 typ INDEFINITE Dia 3.81 +/- 0.08 20 100 1,000 S1 10,000 25.4 +/- 0.5 IMPULSE DURATION ( µs) S2 0.51 typ FIGURE 4. SURGE CURRENT RATING CURVES FOR V131DHB34 - V751DHB34 7.06 +/- 0.2 NOTE: If pulse ratings are exceeded, a shift of VN(DC) (at specified current) of more than ±10% could result. This type of shift, which normally results in a decrease of VN(DC), may result in the device not meeting the original published specifications, but it does not prevent the device from continuing to function, and to provide ample protection. Terminals Configuration: Terminals A & B are connected to one varistor element. Terminals B & C connected to second varistor element. Terminal materials: Tin Plated over copper. TABLE OF DIMENSIONS THICKNESS AND TERMINAL OFFSETS TYPE Ordering Information V 13 1DHB 34 VARISTOR DESIGNATOR MAX AC RMS WORKING VOLTAGE (FIRST SIGNIFICANT DIGITS) V M(AC) DISC SIZE (mm) SERIES DESIGNATOR VM(AC) VOLTAGE DECADE MULTIPLIER T MAX S1 +/- 1.15 mm S2 +/- 2.30mm V111DHB34 7.6 2.65 5.50 V131DHB34 7.8 2.85 5.70 V141DHB34 8.2 3.00 6.00 V151DHB34 8.8 3.15 6.30 V181DHB34 9.0 3.25 6.50 V201DHB34 9.2 3.35 6.70 V251DHB34 7.8 3.00 6.00 V271DHB34 8.7 3.25 6.50 V301DHB34 8.9 3.50 7.00 V321DHB34 9.3 3.66 7.24 V331DHB34 9.5 3.70 7.40 V351DHB34 10.5 4.10 8.20 V391DHB34 11.2 4.45 8.90 V421DHB34 11.3 4.50 9.00 V441DHB34 11.5 4.55 9.10 V481DHB34 12.2 4.80 9.60 V511DHB34 13.4 5.25 10.50 V551DHB34 14.6 5.70 11.40 V571DHB34 14.8 5.80 11.60 V661DHB34 17.20 6.65 13.30 V681DHB34 17.5 7.00 14.00 V751DHB34 18.20 7.35 14.70 w w w. l i t t e l f u s e . c o m 113 Varistor Products High Energy Industrial Disc CA Varistor Series The CA Series of transient surge suppressors are industrial high-energy disc varistors (MOVs) intended for special applications requiring unique electrical contact or packaging methods provided by the customer. The electrode finish of these devices is solderable and can also be used with pressure contacts. Discs of the same diameter may be stacked. This series of industrial disc varistors are available in three diameter sizes of 32, 40, and 60mm, with disc thicknesses ranging from 1.8mm minimum to 32mm maximum. They offer a wide voltage range of from 250 to 2800 VM(AC)RMS . For information on soldering considerations, refer to AN8820 update. “Recommendations for Soldering Terminal Leads to MOV Varistor Discs”. Features • Provided In Disc Form For Unique Packaging By Customer • Solderable Electrode Finish Options • Pressure Contacts and/or Disc Stacking May be Utilized • Standard Disc Sizes 32mm, 40mm, and 60mm Diameter • Available Edge Passivation Insulation • Wide Operating Voltage Range VM(AC)RMS 250V to 2800V • High Peak Pulse Current Range . . . . . . . . . . ITM 20,000A to 70,000A • Very High Energy Capability WTM . . . . . . . . . . . . . . .330J to 10,000J • No Derating Up to 85oC Ambient 114 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Industrial Disc CA Varistor Series For ratings of individual members of a series, see Device Ratings and Specifications chart CA SERIES Continuous: Steady State Applied Voltage: AC Voltage Range (VM(AC)RMS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 to 2800 DC Voltage Range (VM(DC)) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 to 3500 Transient: Peak Pulse Current (ITM) For 8/20µs Current Wave (See Figure 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20,000 to 70,000 Single Pulse Energy Range For 2ms Current Square Wave (WTM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 to 10,000 Operating Ambient Temperature Range (TA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 to 85 Storage Temperature Range (TSTG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 to 85 Temperature Coefficient (αV) of Clamping Voltage (VC) at Specified Test Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .