Negative Voltage Hot Swap Controllers in SOT-23

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

UV/OV

LTC4251

-43V / -75V

LTC4251-1

-36V / -72V

LTC4251-2

-43V UV Only

LTC4251B

-43V / -75V

LTC4251B-1

-36V / -72V

LTC4251B-2

-43V UV Only

Applications

* 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

* Allows Safe Board Insertion and Removal from a Live –48V Backplane

* Floating Topology Permits Very High Voltage Operation

* Low Profile (1mm) ThinSOT™ Package

* Programmable Analog Current Limit with Circuit Breaker Timer