基于Si3480設計的PoE電源管理技術

The Si3480 is a power manager intended for use with the Si3452 Power over Ethernet (PoE) controller. The Si3480 enables the use of a smaller, lower cost, and more efficiently-utilized power supply in an unmanaged PoE Power Sourcing Equipment (PSE) system.

The Si3452 is capable of delivering over 30 W per port, which means that, in a typical 8-port system, a 240 W power supply would have to be used to avoid overload. Typically, not all ports are used at full power; so, a smaller power supply in the range of 30 to 150 W can be used along with the Si3480 power management controller.

The Si3480 power management controller is pin programmed. The pins are used to set the power supply capacity, the number of low power (category 1, 15.4 W), and high power (category 2, 30 W) ports, the port priority, and the detection timing (Alternative A or Alternative B). The Si3480 uses the real time overload and current monitoring capability of the Si3452 to manage power for up to eight ports. Power management is based on actual consumption rather than mere classification in order to supply power to the greatest number of ports.

The Si3480 also provides LED drive to indicate port status and drive an LED bar graph display to indicate the power supply capacity in use. If a port is denied power due to power supply capacity limitations, the LED indicators provide a simple and intuitive indication, helping a user recognize and correct the overload situation by rebalancing loads or adding mid-span power injectors to ports that would not otherwise be powered. In case of a port overload, the port is easily re-enabled by disconnecting the Powered Device (PD) and then reconnecting the PD after correcting the overload situation.

Si3480主要特性：

? Enables use of a smaller power supply for a 4 or 8 port PoE system

? Self-contained solution operates without the need for a host for unmanaged operation

??No software required

??No data isolation required

? Fully compliant with IEEE 802.3 clause 33 for Power over Ethernet including the 802.3at amendment for higher power (30 W category 2 ports)

? Pin programmable for overall power supply capacity, port power level, port priority, and detection timing

? LED indication of port status and overall power consumption

? 20-pin Quad flat package (4x4 mm)

??4x4 mm PCB footprint; RoHS compliant

Extended operating temperature range (–40 to +85℃)

圖1。Si3480功能方框圖

圖2。Si3480典型應用電路圖