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The Bourns Multifuse PPTC device will deactivate any port that is not protected by the power management circuit due to a temporary or permanent fault and thereby prevent any further system failures. An overcurrent condition is detected when the current drawn from the power sourcing equipment (PSE) at the power interface (PI) is greater than the overload current limit for any duration greater than the overload time limit. Bourns ® Multifuse ® Model MF-SMDF050 The Bourns Multifuse Model Model MF-SMDF050 is an ideal current limiting PPTC resettable fuse for PoE applications. With a maximum operating voltage of 57V, the MF-SMDF050 is suitable for the full voltage range of the PoE circuit, 44V to 57V. The MF-SMDF050 has an operating current of 500mA at room temperature and 360mA at 70°C, which is an excellent fit for the 350mA output current as specified in IEEE 802.3AF. Being a resettable PPTC fuse, the MF-SMDF050 has an obvious benefit of being resettable which is useful in the area of port protection. The fact that a PPTC resets itself automatically once the fault clears substantially reduces the need for costly service calls for service technicians. The MF-SMDF050 has been designed with a symmetrical design, making it ideal for high volume surface mount production runs. With a maximum package height of 1.09mm and a 2018 footprint, the MF-SMDF050 is suitable for the densely packed telecom circuits that are now commonplace. | 32 | As the IEEE 802.3AF standard for Power over Ethernet is one of the first truly global power providing standards—its applications are vast. The technology is not just limited to powering wireless LANs or providing back-up power capabilities to IP phones, but may be used to provide power to many other devices, which cannot be powered by regular power sources for physical or financial reasons. As many companies begin powering such devices as credit card scanners, mobile phone and PDA chargers, security cameras, and security card scanners remotely over the network, the IEEE 802.3AF standard makes it possible. When power is being transmitted to remote devices, there will always be a need to limit it within an accepted safety level. The Bourns Multifuse Model MF-SMDF050 is an ideal current limiting PPTC resettable fuse for such applications, designed specifically for Power over Ethernet installations. Conclusion