Features

• Power Path and Inrush Current Control for Redundant Supplies
• Low Loss Replacement for Power Schottky Diodes
• Allows Safe Hot Swapping from a Live Backplane
• 2.9V to 18V Operating Range
• Controls N-Channel MOSFETs
• Limits Peak Fault Current in ≤1μs
• 0.5μs Turn-On and Reverse Turn-Off Time
• Adjustable Current Limit with Circuit Breaker
• Smooth Switchover without Oscillation
• Adjustable Current Limit Fault Delay
• Fault and Power Status Output
• LTC4225-1: Latch Off After Fault
• LTC4225-2: Automatic Retry After Fault
• 24-Lead 4mm × 5mm QFN and SSOP Packages

Typical Application

Description

The LTC®4225 offers ideal diode and Hot Swap™ functions for two power rails by controlling external series connected N-channel MOSFETs. MOSFETs acting as ideal diodes replace two high power Schottky diodes and the associated heat sinks, saving power and board area. Hot Swap control MOSFETs allow boards to be safely inserted and removed from a live backplane by limiting inrush current. The supply output is also protected against short-circuit faults with a fast acting current limit and internal timed circuit breaker.

The LTC4225 regulates the forward voltage drop across the back-to-back MOSFETs to ensure smooth current transfer from one supply to the other without oscillation. The ideal diodes turn on quickly to reduce the load voltage droop during supply switch-over. If the input supply fails or is shorted, a fast turn-off minimizes reverse-current transients.

The LTC4225 allows independent on/off control, and reports fault and power good status for the supply. The LTC4225-1 features a latch-off circuit breaker, while the LTC4225-2 provides automatic retry after a fault.