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Wireless Connectivity

100V MOSFET Switch Targets 802.3 Compliant 48V PoE Systems

23 September 2015

Diodes Inc. has launched the DMN10H120SFG MOSFET, designed as a switch for IEEE 802.3 compliant 48V Power-over-Ethernet (PoE) systems. The switch enables the delivery of power through an Ethernet cable to end-applications such as wireless access points, VoIP phones, point-of-sale terminals, call systems, IP security cameras and building management devices.

In power-sourcing equipment, the 100V N channel MOSFET switches power to the CAT5 (or CAT6) network cable. The cable then provides both power and data, which reduces system costs by eliminating the power supply in the end-equipment. It also protects end-users since PoE operates between 44V to 57V, which meets the 60V Safety Extra Low Voltage (SELV) rating, removing the need for rigorous isolation and certification of end-equipment and easing system maintenance. I2R losses are minimized when operating at these voltage levels, maximizing power delivery to the end-equipment and improving efficiency.

With a 100V BVDSS rating, the DMN10H120SFG MOSFET provides headroom for 48V PoE operation. It offers an extended safe-operating area (SOA) that can withstand power dissipation due to short-circuit fault conditions, such as an Ethernet cable breaking. Once the PSE controller detects the fault it switches off. During this fault condition, the MOSFET goes into linear mode and needs to dissipate 30W for at least 20ms, which is achieved even with a 60°C elevated operating temperature.

The DMN10H120SFG is offered in the PowerDI3333 package. Pricing for the DMN10H series MOSFETs in 10k piece quantities ranges from $0.12 to $0.30 each, dependent on specification and package type.

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