Linear Technology's LTC4352 is a 0V to 18V ideal diode controller that enables low loss ORing of multiple power sources with minimal disturbance to supply voltages.

The LTC4352 regulates the forward voltage drop across an external N-channel MOSFET to ensure smooth current transfer between supplies in diode-OR applications.

In low voltage systems a slow handoff between controllers results in a voltage droop during supply switchover. The fast 500ns turn-on time LTC4352 ensures smooth switchover from one path to the other without oscillation. In the event the input supply fails or is shorted, a fast turn-off minimizes reverse current. In addition to redundant power supply ORing, the LTC4352 makes an excellent diode replacement in supply holdup applications where momentary collapse of supply voltage is isolated from the load.

Fast turn-on is achieved via charge stored on an external capacitor for immediate sourcing of gate pull-up current. The LTC4352 provides under/overvoltage monitoring and a Fault# pin to indicate when the input supply is outside of proper levels or an open MOSFET fault has occurred, while a Status pin indicates the MOSFET on state. The ideal diode behaviour may be overridden to allow reverse current if desired. Furthermore, the LTC4352 can be used for inrush current control in applications where the input supply is hot-plugged.

In contrast to a standard diode, the LTC4352 can prevent out of range input voltages from affecting the load voltage, using back-to-back MOSFETs and resistive dividers on the UV and OV pins to set the allowable input voltage operating range. The controller operates with supplies from 2.9V to 18V, and offers additional flexibility to control voltages down to 0V by applying an external supply.

The level of monitoring and control provided by the LTC4352 is aimed at paralleled and redundant supplies in high-availability systems. The device is offered in space-saving 12-pin MSOP and 3mm x 3mm DFN packages and is specified over commercial and industrial temperature ranges. Pricing starts at $2.50 each in 1,000 piece quantities.

Summary

• Low loss replacement for power diode in multiple power supply or supply holdup applications
  
• Controls external N-Channel MOSFET for high-current capability
  
• 0V to 18V supply ORing or holdup
  
• 500ns turn-on and turn-off fime
  
• Input undervoltage and overvoltage protection 
  
• Open MOSFET detect 
  
• Status and Fault outputs for monitoring
  
• Hot swappable
  
• Reverse current enable input
  
• Available in 12-pin MSOP & DFN (3mm x 3mm) packages