Hot Swap Controllers

Hot Swap controllers allow electronic circuit boards and cards to be inserted into live system backplanes, eliminating the need to power them down. Mission critical systems, such as servers and communication equipment, operate continuously as boards are hot plugged in or pulled out, either for system maintenance or to adjust load handling capacity. The basic functions of a Hot Swap controller are inrush current control and fault isolation. When boards are plugged in, the Hot Swap controller detects power first, then ramps up the board’s capacitors gently, avoiding connector sparks, backplane supply glitches and system resets. On a downstream short-circuit fault, the controller’s electronic circuit breaker shuts off power to the card, preventing the fault from propagating upstream to the rest of the system. Being the gateway to board power, Hot Swap Controllers have evolved from these two basic functions to also providing sophisticated board power monitoring via digital measurements of the current and voltage levels by integrated ADCs, accessible through I2C/SMBus interfaces.

Linear Technology’s Hot Swap controllers utilize N-channel MOSFETs to control power flow, which allows a wide range of load currents from 1A to 100A. Operating voltages span 0V to ±80V. Overcurrent protection is provided by a combination of timed electronic circuit breaker and active current limiting with foldback (refer to datasheet for specific scheme). Input undervoltage and overvoltage conditions block power turn-on, while output voltage monitoring provides a powergood signal to enable the downstream DC/DC converter. General purpose controllers serve a wide variety of custom applications in high availability telecom and networking, while standards-friendly controllers ease design of AdvancedTCA, AMC (Advanced Mezzanine Card), MicroTCA, PCI Express and CompactPCI systems.

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