LTC4353 データシートの表示（PDF） - Linear Technology
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LTC4353 Datasheet PDF : 16 Pages
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LTC4353
Applications Information
High availability systems often employ parallel connected
power supplies or battery feeds to achieve redundancy
and enhance system reliability. ORing diodes have been
a popular means of connecting these supplies at the point
of load. Diodes followed by storage capacitors also hold
up supply voltages when an input voltage sags or has a
brownout. The disadvantage of these approaches is the
diode’s significant forward-voltage drop and the result-
ing power loss. The LTC4353 solves these problems by
using an external N-channel MOSFET as the pass element
(see Figure 1). The MOSFET is turned on when power is
being passed, allowing for a low voltage drop from the
supply to the load. When the input source voltage drops
below the output common supply voltage it turns off the
MOSFET, thereby matching the function and performance
of an ideal diode.
Power Supply Configuration
The LTC4353 can operate with input supplies down to 0V.
This requires powering the VCC pin with an early external
supply in the 2.9V to 6V range. In this range of operation
VIN should be lower than VCC. If VCC powers up after
VIN and backfeeding of VCC by the internal 5V LDO is a
concern, then a series resistor (few 100Ω) or Schottky
diode limits device power dissipation and backfeeding of
a low VCC supply when any VIN is high. A 0.1µF bypass
capacitor should also be connected between the VCC and
GND pins, close to the device. Figure 2 illustrates this.
If either VIN operates above 2.9V, the external supply at
VCC is not needed. The 0.1µF capacitor is still required
for bypassing.
M1
Si4126DY
12V
C1
56nF
CPO1
EN1
CVCC VCC
0.1µF
GND
VIN1 GATE1 OUT1
D1 R1
2.7k
ONST1
LTC4353
D2 R2
2.7k
ONST2
EN2
CPO2
VIN2 GATE2 OUT2
C2
56nF
12V
D1, D2: GREEN LED LN1351C
M2
Si4126DY
4353 F01
Figure 1. 12V Ideal Diode-OR with Status Lights
OUT
10A
CL
8
M1
0V TO VCC
M1
2.9V TO 18V
(0V TO 18V)
OPTIONAL
2.9V TO 6V
OR
HERE
CVCC
0.1µF
VIN1 GATE1
VCC LTC4353
VIN2 GATE2
VIN1 GATE1
CVCC
0.1µF
VCC LTC4353
VIN2 GATE2
0V TO VCC
0V TO 18V
M2
(2.9V TO 18V)
Figure 2. Power Supply Configurations
M2
4353 F02
4353f
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