The difference between both versions of the LTC4269 lies in the different switchers being used. The LTC4269-1 integrates a high efficiency synchronous flyback controller. The synchronous flyback converter provides a low part count design with the advantage that additional outputs can be obtained by simply adding windings. Synchronous rectification offers the benefit of higher output power, increased conversion efficiency and improved cross regulation in applications with multiple outputs. The LTC4269-1 offers the flexibility of programmable switching frequency from 50kHz to 250kHz for optimized power supply design. In low-noise system designs, the controller can be synchronized to an external oscillator. The LTC4269-1 incorporates Linear Technology’s patented No-Opto feedback topology to provide full IEEE 802.3 isolation without the need for optoisolator circuitry. The traditional optocoupler and shunt regulator used in the feedback loop are replaced with an additional winding on the existing transformer for improved regulation, efficiency and a simpler circuit. A high absolute maximum voltage rating of 100V along with the field-proven PD controller front end provides worry-free use in hostile PoE environments.