Features

• Ideal Diode-OR and Inrush Current Control for Redundant Supplies
• Low Loss Replacement for Power Schottky Diodes
• Enables Safe Board Insertion into a Live Backplane
• 9V to 14V Operation
• Current Monitor Output
• Controls N-Channel MOSFETs
• Limits Peak Fault Current in ≤ 1μs
• Adjustable Current Limit with Foldback
• Adjustable Current Limit Fault Delay
• 0.5μs Ideal Diode Turn-On and Turn-Off Time
• Smooth Switchover without Oscillation
• Fault and Power Good Outputs
• LTC4235-1: Latch Off After Fault
• LTC4235-2: Automatic Retry After Fault
• 20-Pin 4mm x 5mm QFN Package

Typical Application

Description

The LTC®4235 offers ideal diode-OR and Hot Swap^TM functions for two 12V power rails by controlling external N-channel MOSFETs. MOSFETs acting as ideal diodes replace two high power Schottky diodes and the associated heat sinks, saving power and board area. A Hot Swap control MOSFET allows a board 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 foldback current limit and circuit breaker.

The LTC4235 regulates the forward voltage drop across the 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 switchover. If the input supply fails or is shorted, a fast turn-off minimizes reverse-current transients.

A current sense amplifier translates the voltage across the sense resistor to a ground referenced signal. The LTC4235 allows turn-on/off control, and reports fault and power good status for the supply.