LT4351CMS Linear Technology, LT4351CMS Datasheet - Page 13

• Manufacturer Part Number: LT4351CMS
• Description: IC CTRLR MOSFET DIODE-OR 10MSOP
• Manufacturer: Linear Technology

Specifications of LT4351CMS

• Applications: Paralleled/Redundant Power Supplies
• Fet Type: N-Channel
• Number Of Outputs: 1
• Internal Switch(s): No
• Delay Time - Off: 600ns
• Voltage - Supply: 1.2 V ~ 18 V
• Current - Supply: 1.4mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Delay Time - On: -

APPLICATIONS INFORMATION
The gate drive amplifier will attempt to regulate the voltage
across the MOSFETs to 15mV. Regulation will be achieved if:
This requires very low R
by paralleling MOSFETs, but be careful to keep intercon-
nection trace resistance low. In the event that regulation
cannot be achieved, the gate drive amplifier will drive GATE
to its clamp and achieve the best R
STATUS
The STATUS pin sinks current when the input (V
above output (OUT) by 15mV and GATE is above V
0.7V. This will normally indicate that power is being passed
though the MOSFETs.
In the event of a nonfunctional MOSFET, the GATE voltage
will be driven high (to the GATE clamp voltage). If V
greater than OUT by more than 0.21V, the FAULT pin will
sink current to signal the potential problem.
There is no direct measurement or confirmation of cur-
rent flowing in the MOSFETs. Current is shared between
sources based on their voltage and series resistance. If
precision load sharing is desired, the LTC4350 may be a
more suitable part.
Redundant Supplies
The LT4351 is an improved solution for ORing redundant
supplies because of its lower forward drop versus con-
ventional diodes. The lower forward drop significantly
improves overall efficiency, improves the voltage tolerance
R
R
DS
DS
<
<
15mV
2 • I
I
LOAD
15mV
LOAD
for a single MOSFET
for two MOSFETs and
DS
values. This may be achieved
DS
possible at that level.
IN
IN
IN
) is
by
is
at the load and provides for a more accurate transition
from supply to supply and more accurate load sharing
between supplies.
ORing can be done either at the load or at the source.
Figure 9 shows some examples. ORing at the load is usu-
ally the safest method since it protects against shorts in
interconnects.
The LT4351 tighter forward-voltage tolerance makes it
easier to balance current between similar supplies using
the droop method. The droop method uses the supply
voltage and series resistance in the power path to provide
load sharing. In this case, size the MOSFET’s R
to allow for regulation.
BACKPLANE
BACKPLANE
Figure 9. Redundant Backplane Supplies
SOURCE 1
SOURCE 2
SOURCE 1
SOURCE 2
LT4351
LT4351
LT4351
LT4351
BOARD
BOARD
LOAD
LT4351
LOAD
4351 F09
DS(ON)
13
4351fc
low