UG326: Class 2 Non-Isolated Evaluation Board for the Si3406 The Si3406 non-isolated Flyback topology based evaluation board KEY FEATURES is a reference design for a power supply in a Power over Ethernet (PoE) Powered Device (PD) application. IEEE 802.03at Compatible Very Small Application PCB Surface This Si3406-non-ISO-FB EVB maximum output level is Class 2 power ( x 6.5W). High Efficiency The Si3406-non-ISO-FB EVB board is shown below. The Si3406 IC integrates an IEEE High Integration 802.03at compatible PoE interface as well as a current control based dc/dc converter. Optional MPS Function Synchronous Gate Driver The Si3406 PD integrates two diode bridges, which can be used up to 200 mA input cur- Low BOM Cost rent, detection circuit, classification circuit, DC/DC switch, hot-swap switch, TVS over- voltage protection, dynamic soft-start circuit, cycle-by-cycle current limit, syncrhonous Transient Overvoltage Protection gate driver, maintain power signature (MPS), thermal shutdown, and inrush current pro- Thermal Shutdown Protection tection. 5x5 mm 20-pin QFN The switching frequency of the converter is tunable by an external resistor. silabs.com Building a more connected world. Rev. 0.2 UG326: Class 2 Non-Isolated Evaluation Board for the Si3406 Kit Description 1. Kit Description The Si3406-non-isolated Flyback topology based evaluation board is a reference design for power supplies in Power over Ethernet (PoE) Powered Device (PD) applications. The Si3406 device is described more completely in the data sheet and application notes. This document describes the evaluation board. The Si3406-non-ISO-FB EVB board is shown on the cover page. The schematic is shown in Figure 2.3 Si3406 Non-Isolated Flyback EVB Schematic: 5 V, Class 2 PD on page 4, and the layout can be found in 17. Board Layout. The dc output is at connector J2. Boards are shipped configured to produce 5 V output voltage but can be configured for different output voltages, such as 3.3 or 12 V for example, by changing resistor R14 and a few other components. Refer to AN1130: Using the Si3406/Si34061/Si34062 PoE+ and Si3404 PoE PD Controller in Isolated and Non-Isolated Designs for more information. The preconfigured Class 2 signature can also be modified, which is described as well in AN1130. The Si3406 includes integrated diode bridges for both CT and SP connection. The integrated diode bridges can be used up to 200 mA input current. Above 200 mA input current the external diode bridge is required. The external diode bridge can be a Schottky or silicon type. The Si3406 device can operate with CT/SP pins open, but in this configuration the external bridge should be Schottky type diode bridge. To compensate for the reverse leakage of the Schottky type diode bridges at high temperatures, the recommended detection resistor should be adjusted to the values listed in the following table: Table 1.1. Recommended Detection Resistor Values External Diode Bridge R DET Silicon Type 24.3 k Schottky Type 24.9 k silabs.com Building a more connected world. Rev. 0.2 2