Features and Benefits

  • Allows Safe Board Insertion and Removal from a Live –48V Backplane
  • Floating Topology Permits Very High Voltage Operation
  • Programmable Analog Current Limit with Circuit Breaker Timer
  • Fast Response Time Limits Peak Fault Current
  • Improved Ruggedness Shunt Regulator
  • Programmable Timer
  • Programmable Undervoltage/Overvoltage Protection
  • Low Profile 6-Lead SOT-23 (ThinSOT) Package

Product Details

The LTC4251B/LTC4251B-1/LTC4251B-2 negative voltage Hot Swap controllers allow a board to be safely inserted and removed from a live backplane. Output current is controlled by three stages of current limiting: a timed circuit breaker, active current limiting and a fast feedforward path that limits peak current under worst-case catastrophic fault conditions.

Programmable undervoltage and overvoltage detectors disconnect the load whenever the input supply exceeds the desired operating range. The supply input is shunt regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial start-up and controls the circuit breaker’s response time.

The LTC4251B UV/OV thresholds are designed to match the standard telecom operating range of –43V to –75V. The LTC4251B-1 UV/OV thresholds extend the operating range to encompass –36V to –72V. The LTC4251B-2 implements a UV threshold of –43V only. The LTC4251B improves the ruggedness of the LTC4251 shunt regulator.

LTC4251 –43V/–75V
LTC4251-1 –36V/–72V
LTC4251-2 –43V UV Only
LTC4251B –43V/–75V
LTC4251B-1 –36V/–72V
LTC4251B-2 –43V UV Only


  • Hot Board Insertion
  • Electronic Circuit Breaker
  • –48V Distributed Power Systems
  • Negative Power Supply Control
  • Central Office Switching
  • Programmable Current Limiting Circuit
  • High Availability Servers
  • Disk Arrays

Product Lifecycle icon-recommended Recommended for New Designs

This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.

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