LTC4354_15 Datasheet, PDF (1/14 Pages) Linear Technology – Negative Voltage Diode-OR Controller and Monitor

Features
n _{Controls N-Channel MOSFETs}
n _{Replaces Power Schottky Diodes}
n _{Less Than 1µs Turn-off Time Limits Peak}
Fault Current
n _{80V Operation}
n _{Smooth Switchover without Oscillation}
n _{No Reverse DC Current}
n _{Fault Output}
n _{Selectable Fault Thresholds}
n _{Available in 8-Lead (3mm × 2mm) DFN and}
8-Lead SO Packages
Applications
n _{AdvancedTCA Systems}
n _{–48V Distributed Power Systems}
n _{Computer Systems/Servers}
n _{Telecom Infrastructure}
n _{Optical Networks}
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LTC4354
Negative Voltage
Diode-OR Controller
and Monitor
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 heat sink, 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
turn-off prevents the reverse current from reaching a level
that could damage the pass transistors.
A fault detection circuit with an open-drain output capable
of driving an LED or opto-coupler indicates either MOSFET
short, MOSFET open or supply failed.
Typical Application
–48V_RTN
–48V Diode-OR
12k
V_A = –48V
V_B = –48V
V_CC
LTC4354
FAULT
DA DB
GA
2k 2k
GB
V_SS
IRF3710
IRF3710
33k
LOAD
LED
1µF
4354 TA01
Power Dissipation vs Load Current
6
5
DIODE (MBR10100)
4
3
POWER
SAVED
2
1
FET (IRF3710)
0
0
2
4
6
8
10
CURRENT (A)
4354 TA01b
4354fc
1