Multifuse® PTC Resettable Fuses White Paper: Preventing Component Circuit Damage from Above  Range Current with Reliable Overcurrent Protection

As the demand for electronic components continues to grow in more diverse and complex embedded  systems, it becomes crucial to protect sensitive applications against overcurrent conditions. Reliable  circuit protection is a fundamental design consideration for cost-effective, long-lasting products. Each  time a user plugs in, operates or leaves devices unattended, it is essential that there is a mechanism in  place to ensure no above range current damages the very circuits that allow the device to work. Since  most applications will not be accessible conveniently for replacement, such as with a conventional  fuse or household circuit breaker, the concept of a resettable fuse has been adopted nearly universally.  Some interface standards even require resettable overcurrent protection, recognizing and reminding  designers in advance about the importance of robust circuit protection. The capability of delivering a  smaller, faster, and lighter product than the competition truly begins at the component level, where  parts are pushing the envelope with regard to minimal board space requirements and versatile use  environments.

Overcurrent and overtemperature conditions are a reality that can lead to costly field failures. Ignoring  the need for overcurrent protection is not an option, so the question remains as to how to incorporate  this feature without sacrificing the design constraints or objectives. This white paper will detail  some of the latest advances in circuit protection technology integrated into Bourns’ line of resettable  Multifuse® products that now incorporate a new space-saving freeXpansion™ manufacturing process.

From the inside out, Multifuse® devices are specifically designed to shield a wide range of applications  against the potentially destructive effects of these conditions and provide exceptional protection.  Once system requirements are defined and circuit analysis has determined the operating parameters,  as illustrated by example in this paper, it is straightforward to select the component appropriate for  a given design. A wide range of speed, voltage and current limits among the Multifuse® devices and  specific series for products like USB, which by standard requires resettable overcurrent protection,  ensures that the ideal component can be incorporated in a given design without sacrificing board real  estate.