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 www.murata-ps.com/support 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