Evaluation for power over Ethernet controller ICs

Edited by the Electronicstalk editorial team Sep 1, 2004

Two new power over Ethernet (POE) powered device evaluation boards from Solid State Supplies are designed to provide a complete IEEE802.3af compliant power solution.

Two new power over Ethernet (POE) powered device evaluation boards from Solid State Supplies are designed to provide a complete IEEE802.3af compliant power solution.

The boards, one isolated and the other nonisolated, include a low cost POE signature and classification circuit, an EMI filter, an isolated (or nonisolated) flyback DC/DC convertor using a MIC2196 (nonisolated) or MIC9130 (isolated) control IC which is a 400kHz current mode PWM DC/DC controller which is housed in a small and low pin count SO8 package.

When a powered Ethernet cable is connected to the board, the front end handshaking circuit applies the correct signature and classification impedances to accept power from the power sourcing equipment (PSE).

As power, with input voltages between 36 and 57V, is applied from the PSE, the DC/DC flyback convertor engages and generates a 3.3V output with up to 2.5A of output current.

The boards have been designed for use with IEEE802.3af enabled switch/routers which provide power to the Ethernet cable as defined in IEEE802.3af PSE requirements.

To comply with IEEE802.3af it is mandatory to provide a 25kohm resistance and 100nF capacitance across the power line to receive power from the PSE.

A MOSFET is used to hold off the input capacitance of the DC/DC convertor during the signature detection phase.