SI3402B-EVB: Non-Isolated 802.3at Type 1 PoE PD Board

The Si3402B non-isolated evaluation board (Si3402B-EVB Rev 2) is a reference design for a power supply in a Power over Ethernet (PoE) Powered Device (PD) application.

Ethernet data and power are applied to the board through the RJ45 connector (J1). The board itself has no Ethernet data transmission functionality, but, as a convenience, the Ethernet transformer secondary is brought out to the test points. Power may be applied in the following ways:

• Connecting a dc source to pins 1, 2 and 3, 6 of the Ethernet cable (either polarity)

• Connecting a dc source to pins 4, 5 and 7, 8 of the Ethernet cable (either polarity)

• Using an IEEE 802.3-2015-compliant, PoE-capable PSE, such as Trendnet TPE-1020WS

Boards are generally shipped configured to produce +5 V output voltages but can be configured for +3.3 V or other output voltages by changing resistors R5 and R6. Refer to "Application Note 956: Using the Si3402B PoE PD Controller in Isolated and Non-Isolated Designs" for more information. The preconfigured Class 3 signature can also be modified according to Table 3 in AN956. The D8-D15 Schottky type diode bridge bypass is recommended only for higher power levels (Class 3 operation). For lower power levels, such as Class 1 and Class 2, the diodes can be removed. When the Si3402B is used in external diode bridge configuration, it requires that at least one pair of the CTx and SPx pins be connected to the PoE voltage input terminals (to the input of the external bridge).