The Art of Hot-Swapping in Telecom Systems: Avoid a Patchwork and Implement a More Effective Solution

By: Hamed Sanogo

Abstract: This application note discusses the important role and optimal circuits for hot-swapping in high-availability systems. It uses a telecom system as an example of an ensemble of embedded microprocessor-based cards plugged into a mid- or backplane. Classified as \"high-availability\" systems, these systems are not supposed to be powered down for service or repair. The article defines the term \"5-NINEs availability,\" which translates to almost zero downtime. This level of availability can only be achieved when the cards are serviced by hot-swapping them in and out without powering down the entire system. The article then describes hot-swap circuits. It shows some patchwork approaches to hot-swapping and explains the deficiencies of these methods. The article concludes with a discussion of newer, more integrated hot-swap controllers that overcome the problems with prior designs.