Energy-monitoring hot swap controller safeguards 100A PCBs

October 02, 2015 // By Graham Prophet
LTC4282 is an energy monitoring hot swap controller with dual MOSFET drive to enable 100A, and higher, current board designs. The LTC4282 ensures safe board insertion and removal from live 2.9V to 33V backplanes by controlling external N-channel MOSFETs to gently power up capacitors, avoiding sparks, connector damage and system glitches.

High current hot-pluggable boards use parallel MOSFETs to reduce voltage drop, but all of these MOSFETs require large safe operating area (SOA) to ride through overcurrent faults. By controlling two matching current limited paths, the LTC4282 halves each path’s SOA requirements, reducing MOSFET costs in high current applications (over 50A). Further cost savings come from a staged start configuration employing a low SOA MOSFET in one path and low RDS(ON) MOSFETs in the other path. The LTC4282 provides a rugged, compact solution for hot plugging and monitoring, especially in high power circuit boards in servers, network routers and switches, and enterprise data storage systems.

Sitting at the gateway to board power, the LTC4282’s ±0.7% accurate ADC reports board voltage, current, power and energy consumption through an I²C/SMBus digital interface. During overcurrent conditions, the LTC4282 folds back its 2% accurate current limit to maintain constant MOSFET power dissipation for an adjustable timeout period. Digitally configurable current limit enables dynamic adjustment with load changes and eases selection of low value sense resistors. Minimum and maximum values of the monitored electrical parameters are recorded, with alerts raised when they exceed 8-bit thresholds. Internal EEPROM provides nonvolatile storage for register configuration and fault log data. To prevent catastrophic damage to the board, the MOSFETs are continuously monitored for abnormal conditions such as low gate voltage and drain-to-source short-circuit or large voltage drop.

Specified over the 0°C to 70°C commercial and -40°C to 85°C industrial temperature ranges, the LTC4282 occupies a 32-pin 5 x 5 mm QFN package, for $5.95 (1000).

Linear Technology;

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