Download External ORing FET Reference Circuit

External ORing FET Reference Circuit
MVAC Series
DESCRIPTION
ORing isolation is not required to achieve sharing of current between paralleled power supplies, but may be desired for redundancy in case of a
power supply fault. The reference design in the schematic below shows how it may be implemented for the full-power main output, using FETs
for low voltage drop. For the lower current fan (V2) and auxiliary (V3) outputs, ORing is most easily implemented with diodes rated to handle
the reverse voltage, the power required by reverse voltage and diode leakage current at maximum temperature, and the forward current.
Paralleled fan (V2) outputs must be limited to 12W total, paralleled Aux (V3) outputs must be limited to 10W total. If the Aux (V3) outputs are to
be connected in parallel, ORing devices must be used to guarantee start-up of both units.
Customers are invited to contact a Murata Electronics FAE with any questions.
SCHEMATIC
+Remote Sense
J3 pin 5
+12V bus
Q1
+DC out
J2 pins 1-6
Q2
MVAC #1
J2 pins 7-12
C3
Q3
J3 pin 6
as needed
-Remote Sense
Dotted lines:
Optional remote sense connections.
Remote sense lines are attached
at the desired regulation point.
Gate
IN
OUT
U1
LTC4357 Vdd
C1
0.1µF
GND
+Remote Sense
J3 pin 5
+DC out
R1
100R
DC out return
Q4
J2 pins 1-6
Q5
MVAC #2
J2 pins 7-12
Q6
J3 pin 6
-Remote Sense
Gate
IN
U2
OUT
LTC4357 Vdd
GND
R2
100R
C2
0.1µF
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ACAN-42.A01 Page 1 of 2
External ORing FET Reference Circuit
MVAC Series
BILL OF MATERIALS
ORing Circuit Suggested Parts List:
MVAC400-12AFD or
MVAC250-12AFD
MVAC400-24AFD or
MVAC250-24AFD
MVAC400-48AFD or
MVAC250-48AFD
Vendor
U1,2
LTC4357
LTC4357
LTC4357
Linear Technology
Q1-6
RJK0329DPB-01
HAT2139H
HAT2201R
Renesas
R1,2
100 Ohms
100 Ohms
100 Ohms
C1,2
0.1uF, 25V
0.1uF, 50V
0.1uF, 100V
C3
As Required
As Required
As Required
Murata
Notes:
For 12V applications, logic level power MOSFETs must be used. Fewer parallel FETs can be used depending on airflow, allowable operating
temperature, and actual worst case loading conditions. For additional design information, simulation tools, and application notes, please go to:
www.linear.com/product/LTC4357
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to: http://www.murata-ps.com/requirements/
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
notice. © 2012 Murata Power Solutions, Inc.
www.murata-ps.com/support
ACAN-42.A01 Page 2 of 2