LTC4354
1
4354fc
Typical applicaTion
FeaTures DescripTion
Negative Voltage
Diode-OR Controller
and Monitor
The LT C
®
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.
–48V Diode-OR Power Dissipation vs Load Current
applicaTions
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
n
AdvancedTCA
Systems
n
–48V Distributed Power Systems
n
Computer Systems/Servers
n
Telecom Infrastructure
n
Optical Networks
L, LT , LT C , LT M, Linear Technology and the Linear logo are registered trademarks and
Hot Swap, PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
LTC4354
LOAD
DB GADA GB
V
SS
V
B
= –48V
V
A
= –48V
–48V_RTN
FAULT
IRF3710
IRF3710
4354 TA01
V
CC
33k
12k
2k2k
LED
1µF
CURRENT (A)
0
0
POWER DISSIPATION (W)
1
2
3
4
6
5
2
4 6
4354 TA01b
8 10
DIODE (MBR10100)
FET (IRF3710)
POWER
SAVED