SI3402BISO-EVB: Isolated 802.3at Type 1 PoE PD

The Si3402B isolated evaluation board (Si3402BISO-EVB Rev 2) is a reference design for power supplies in Power over Ethernet (PoE) Powered Device (PD) applications. The Si3402B is described more completely in the data sheet and application notes. An evaluation board demonstrating the non-isolated application is described in the Si3402B-EVB User's Guide.

Ethernet data and power are applied to the board through the RJ-45 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 voltage but can be configured for +3.3 V or other output voltages. The preconfigured Class 3 signature also can be modified. 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 at least one pair of the CTx and SPx pins to be connected to the PoE voltage input terminals (to the input of the external bridge).