LTC4354

Features:

Controls N-Channel MOSFETs
Replaces Power Schottky Diodes
1µs Turn-off Time Limits Peak Fault Current
80V Operation
Smooth Switchover Without Oscillation
No Reverse DC Current
Fault Output
Selectable Fault Thresholds
Available in 8-Pin (3mm * 2mm) DFN and 8-Pin SO
   Packages


Application

AdvancedTCA® Systems
48V Distributed Power Systems
Computer Systems/Servers
Telecom Infrastructure
Optical Networks


Pinout




Specifications

ICC (100µs duration) ............................................. 50mA
Output Voltages
GA, GB....................................... ...... 0.3V to VCC + 0.3V
FAULT ........................................................... 0.3V to 7V
Input Voltages
DA, DB.................................................. ......0.3V to 80V
Input Current
DA, DB, Reverse Current ....................................... 20mA
(Note 1)
Operating Temperature Range
LTC4354C ............................................... 0°C to 70°C
LTC4354I............................................. 40°C to 85°C
Storage Temperature Range ............ 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)............... 300°C



Description

The LTC®4354 is a negative voltage diode-OR controller that drives two external N-channel MOSFETs. It replaces two Schottky diodes and the associated heatsink, saving power and area. The power dissipation is greatly reduced by using N-channel MOSFETs as the pass transistors. Power sources can easily be ORed together to increase total system power and reliability.

When first powered up, the MOSFET body diode conducts the load current until the pass transistor is turned on. The LTC4354 servos the voltage drop across the pass transistors to ensure smooth transfer of current from one transistor to the other without oscillation.

The MOSFETs are turned off in less than 1µs whenever the corresponding power source fails or is shorted. Fast turnoff prevents the reverse current from reaching a level that could damage the pass transistors.

A fault detection circuit of LTC4354 with an open drain output capable of driving an LED or opto-coupler indicates either MOSFET short, MOSFET open or supply failed.