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PTC Resettable Fuses Multifuse® PTC Resettable Fuses SOLUTIONS GUIDE REV. 3.3 Updated 9/5/02 Multifuse® Products Introduction Circuit Protection......................................................................................................2 How Multifuse® Resettable Fuses Work ....................................................................2 Applications ..............................................................................................................3 Application Notes Loud Speaker Crossover Networks............................................................................7 Automotive Door Locks............................................................................................9 Circuit Isolation and Protection ............................................................................11 USB Port Protection ..............................................................................................13 Protecting Battery Chargers....................................................................................14 Lithium-ion/Lithium Polymer Battery Pack Protection ........................................15 90V Multifuse® PTC Resettable Fuses in an HFC Network ..................................17 Protecting the Next Generation of Battery Packs..................................................20 The Multifuse® Solution ........................................................................................22 Multifuse® Product Selection Worksheet ....................................................................................23 Product Specifications Radial Leaded Model MF-R Series ........................................................................24 Radial Leaded Model MF-RX Series ......................................................................28 Surface Mount Model MF-SM Series ....................................................................30 R80 0 Surface Mount Model MF-SM/33 Series ................................................................33 S350 Surface Mount Model MF-USMD Series ..............................................................36 0144T Surface Mount Model MF-MSMD Series ..............................................................39 Surface Mount Model MF-ESMD Series ................................................................42 Radial Leaded Telecom Model MF-R/90 Series ....................................................44 R050 Radial Leaded Telecom Model MF-R/250 Series ..................................................46 Surface Mount Telecom Model MF-SM013/250 Series ........................................49 Axial Leaded Battery Strap Model MF-S Series ....................................................51 Axial Leaded Battery Strap Model MF-LS Series ..................................................55 Axial Leaded Battery Strap Model MF-LR Series ..................................................58 Axial Leaded Battery Strap Model MF-VS Series..................................................61 Axial Leaded Battery Strap Model MF-VSN Series ..............................................63 Axial Leaded Battery Strap Model MF-SVS Series................................................65 Reel Battery Cap Model MF-AAA Series ......................................................................68 Disk Model MF-D Series ........................................................................................70 Uppe Tap Tape and Reel Specifications Model MF-R, MF-RX, MF-RX/90 & MF-R/250 Series..........................................71 Lowe Model MF-SM,MF-SM/33 & MF-SM/250 Series ..................................................73 Model MF-MSMD, MF-USMD & MF-ESMD Series ............................................74 190 Model MF-SM013/250 Series ................................................................................75 9K Model MF-S, MF-LS, MF-LR and MF-VS Series ..................................................76 Model MF-AAA Series ..........................................................................................77 Cross Reference Guide Model MF-R and MF-RX Series ............................................................................79 Model MF-SM and MF-SM/33 Series ....................................................................80 Model MF-USMD Series ........................................................................................80 Model MF-MSMD Series........................................................................................80 Model MF-ESMD Series ........................................................................................81 Model MF-R/90 Series ..........................................................................................81 Model MF-R/250 Series ........................................................................................81 Model MF-SM013/250 Series ................................................................................81 Model MF-S and MF-LS Series ..............................................................................82 190 9K Model MF-LR, MF-VS and MF-VSN Series ..........................................................82 Model AAA Series..................................................................................................83 Surface Mount Soldering Recommendations ..............................................................................84 Glossary ................................................................................................................................90 1 Introduction Circuit Protection When it comes to Polymeric Positive Temperature Coefficient (PPTC) circuit protec- tion, you now have a choice. If you need a reli- R 090 ® LS 018 able source, look to MULTIFUSE Resettable 7144T190 0T Fuses from Bourns. RX1100 0180T MULTIFUSE products are made from a con- ductive plastic formed into thin sheets, with elec- R010 trodes attached to either side. The conductive plastic is manufactured from a non-conductive crystalline polymer and a highly conductive carbon black. The electrodes ensure even distribution of power through the device, and provide a surface for leads to be attached or for custom mounting. VS170 S350 0048T The phenomenon that allows conductive plas- 0144T tic materials to be used for resettable over-cur- rent protection devices is that they exhibit a 07 very large non-linear Positive Temperature 5 Coefficient (PTC) effect when heated. PTC is a characteristic that many materials exhibit whereby resistance increases with tempera- ture. What makes the MULTIFUSE conduc- tive plastic material unique is the magnitude of its resistance increase. At a specific transi- How Multifuse Resettable tion temperature, the increase in resistance is Fuses Work so great that it is typically expressed on a log scale. The conductive carbon black filler material in the MULTIFUSE device is dispersed in a poly- mer that has a crystalline structure. The crys- talline structure densely packs the carbon par- 7 10 ticles into its crystalline boundary so they are 106 close enough together to allow current to flow 105 through the polymer insulator via these carbon 104 “chains.” 103 When the conductive plastic material is at normal LOG R OHMS 102 room temperature, there are numerous carbon chains forming conductive paths through the 101 material. 100 Under fault conditions, excessive current flows 0 20 40 60 80 100 120 140 160 through the MULTIFUSE device. I2R heating TEMPERATURE °C causes the conductive plastic material’s tempera- ture to rise. As this self heating continues, the material’s temperature continues to rise 2 Crystalline Amorphous Polymer Polymer Conducting Non-conducting Carbon Chains Carbon Chains VS210 0057T COLD HOT Reset Your Current Thinking ® until it exceeds its phase transformation tem- General Applications perature. As the material passes through this Almost anywhere there is a low-voltage power phase transformation temperature, the densely source and a load, a MULTIFUSE Resettable packed crystalline polymer matrix changes to Fuse can be used. an amorphous structure. This phase change is accompanied by a small expansion. As the con- The fact that these protection devices reset auto- ductive particles move apart from each other, matically sets them apart among circuit most of them no longer conduct current and the protection devices. resistance of the device increases sharply. Circuit designers know there are circumstances The material will stay “hot,” remaining in this they have no control over which can result in high resistance state as long as the power is potentially damaging overcurrent conditions. applied. The device will remain latched, provid- Non-resettable fuses work well, once, and in many ing continuous protection, until the fault is applications, replacement is not an option due cleared and the power is removed. Reversing the to inconvenience, warranty costs or damaged phase transformation allows the carbon chains to reputations. reform as the polymer re-crystallizes. The resis- The benefits of MULTIFUSE Resettable Fuses tance quickly returns to its original value. are being recognized by more and more design engineers, and new applications are being discov- ered every day. The use of MULTIFUSE types 3 of devices have been widely accepted in the following applications and industries: • Personal computers • Laptop computers • Personal digital assistants • Transformers • Small and medium electric motors • Audio equipment and speakers • Test and measurement equipment • Security and fire alarm systems
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