LT4351
1
4351fd
TYPICAL APPLICATION
DESCRIPTION
MOSFET Diode-OR
Controller
The LT
®
4351 creates a near ideal diode using external
single or back-to-back N-channel MOSFETs. This ideal
diode function permits low loss ORing of multiple power
sources. Power sources can easily be ORed together to
increase total system power and reliability with minimal
effect on supply voltage or efficiency. Disparate power
supplies can be efficiently ORed together.
The IC monitors the input supply with respect to the load
and turns on the MOSFET(s) when the input supply is
higher. If the MOSFET’s R
DS(ON)
is sufficiently small, the
LT4351 will regulate the voltage across the MOSFET(s)
to 15mV. A STATUS pin indicates the MOSFET on-state.
An internal boost regulator generates the MOSFET gate
drive voltage. Low operating voltage allows for ORing of
supplies as low as 1.2V.
The LT4351 will disable power passage during undervolt-
age or overvoltage conditions. These voltages are set by
resistive dividers on the UV and OV pins. The undervoltage
threshold has user programmable hysteresis. Overvoltage
detection is filtered to reduce false triggering.
The LT4351 is available in a 10-pin MSOP package.
Dual 5V Redundant Supply
FEATURES
APPLICATIONS
n
Low Loss Replacement for ORing Diode in Multiple
Sourced Power Supplies
n
External N-Channel MOSFETs for High Current
Capability
n
Internal Boost Regulator Supply for MOSFET
Gate Drive
n
Wide Input Range: 1.2V to 18V
n
Fast Switching MOSFET Gate Control
n
Input Under and Overvoltage Detection
n
STATUS and FAULT Outputs for Monitoring
n
Internal MOSFET Gate Clamp
n
Available in a 10-pin MSOP Package
n
Paralleled Power Supplies
n
Uninterrupted Supplies
n
High Availability Systems
n
N + 1 Redundant Power Supplies
LOADC
LOAD
GATE OUTV
IN
V
DD
SW
LT4351
UV
OV
STATUS
1µF
24.9k
1%
232Ω
1%
1.47k
1%
10µF
5V
POWER
SUPPLY
1
4.7µH
MBR0530
MBR0530
FAULT
GND
Si4862DYSi4862DY
1× 1×
GATEOUT
5V COMMON
V
IN
V
DD
SW
LT4351
UV
OV
4351 TA01
GND
POWER
SUPPLY
2
1µF
24.9k
1%
232Ω
1%
1.47k
1%
10µF
5V
4.7µH
MBR0530
MBR0530
STATUS
FAULT
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