IEEE 802.3-2005 PoE Interface and Isolated Converter and Controller

The TPS23753 is a combined Power over Ethernet (PoE) powered device (PD) interface and current-mode dc/dc controller optimized specifically for isolated converter designs. The PoE implementation supports the IEEE 802.3at standard as a 13 W, type 1 PD. The requirements for an IEEE 802.3at type 1 device are a superset of IEEE 802.3-2008 (originally 802.3af) requirements.

The TPS23753 supports a number of input-voltage ORing options including highest voltage, external adapter preference, and PoE preference.

The PoE interface features an external detection signature pin that can also be used to disable the internal hotswap MOSFET. This allows the PoE function to be turned off. Classification can be programmed to any of the defined types with a single resistor.

The dc/dc controller features a bootstrap startup mechanism with an internal, switched current source. This provides the advantages of cycling overload fault protection without the constant power loss of a pull up resistor.

The programmable oscillator may be synchronized to a higher-frequency external timing reference.