Power Over Ethernet – Sync Flyback Reference Design
Model Number – PMP411 – This reference design describes an easy-to-use, low cost isolated power supply to be used in Power-over-Ethernet Powered Devices (PD's). Power-over-Ethernet is an emerging new capability to deliver data and power to internet appliances over existing CAT-5 Ethernet cables. Power-over-Ethernet is rapidly gaining in popularity with manufacturers and users of devices such as VoIP phones, wireless access points, security cameras and point-of-sale terminals. The TPS2370 is a PoE Interface Switch used to control the input power in accordance with the IEEE802.3af governing standard.
The UCC3809 is a current-mode PWM controller for a continuous mode synchronous flyback regulator. Depending on load current, the synchronous rectifier achieves 5-15% better efficiency than a schottky rectifier. The main output is 3.3V at 3.1A. A second winding is added to the transformer to create a semi-regulated 5.5V output.
All control circuitry and the power switch are internal to the IC. The only external parts required are an inductor, rectifier, input/output capacitors, and feedback resistors. Bias voltage for the DSP core is generated from the 3.3V output with a TPS62201 synchronous buck controller. All control circuitry and both power switches are internal to the IC. The only external parts required are an inductor and input/output capacitors. This converter will deliver 1.5V at up to 300mA.
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