Hot swap for communications infrastructure

Our telecommunications infrastructure runs 24/7 and much of it uses 48 V rack-based systems that are permanently live. So the boards and components that drive these systems must be able to be ‘hot-swapped’ to allow for upgrades and maintenance without ever needing to power down the equipment.

Block diagram

Highlighted components are Nexperia focus products

Design considerations

  • When a board is plugged into a live system, it is important the in-rush current is carefully controlled to protect the components on the board and ensure other parts of the system do not experience any power disruption.
  • MOSFETs with a strong linear mode performance and enhanced safe operating area (SOA) are required to manage this current effectively and reliably
  • Once the replacement board is safely installed, the MOSFET is turned fully ON. In this mode of operation, a low RDS(on) value is of primary importance, helping to keep temperatures down and system efficiency at a maximum

Nexperia in action

A full evaluation kit of Analog Devices latest LTC4286 High Power Positive Hot-Swap Controller uses Nexperia's 100 V, 2.3 mOhm PSMN2R3-100SSE ASFET with enhanced SOA in LFPAK88 in the hot-swap power path.

The importance of SOA - Quick Learning

When a MOSFET is selected for a high power designs, engineers often select a device based on its on-resistance. Lower on-resistance results in MOSFETs with lower power loss, which in turn indicates less heating and safer operation for the device.

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