Linear Technology has been a major player in helping define the PoE specification since its inception and continues to help define the evolving standards. The first stand alone PD controller from Linear Technology, the LTC4257, is based on the original IEEE 802.af specification, which was finalized in 2003 and limited power delivery to 12.95W. This offered the flexibility to select the desired switcher for a given application. Customers who want a more integrated solution with the DC/DC converter on-chip can select from the LTC4267 family of PD controllers with integrated switcher. As applications became more advanced and demanded additional features, more power was clearly needed. Thus began the development of the IEEE 802.3at, or PoE+, specification. While this standard was evolving, Linear Technology supported the need for higher power in proprietary PoE systems with the LTC4264 PD controller and LTC4268-1 PD controller with synchronous flyback switcher to provide up to 35W while still abiding by the IEEE 802.3af specification in all other respects. The LTC4265 PD controller and LTC4269 and LTC4278 PD controllers with integrated switchers are Linear Technology’s 3rd generation supporting the IEEE 802.3at specification and support the 2-event classification mechanism. Benefits of these new PoE+ compliant devices will be highlighted in the following slides.