The Si3400 and Si3401 integrate all power management and control functions required in a Power-over-Ethernet (PoE) powered device (PD) application. The Si3400 and Si3401 convert the high voltage supplied over the 10/100/1000BASE-T Ethernet connection into a regulated, low-voltage output supply. The optimized architectures of the Si3400 and Si3401 minimize the solution footprint, reduce external BOM cost, and enable the use of low-cost external components while maintaining high performance. The Si3400 and Si3401 integrate the required diode bridges and transient surge suppressors, thus enabling direct connection of ICs to the Ethernet RJ-45 connector. The switching power FET and all associated functions are also integrated. The integrated switching regulator supports isolated (flyback) and non-isolated (buck) converter topologies. The Si3400 and Si3401 support IEEE STDTM 802.3-2005 (future instances are referred to as 802.3) compliant solutions as well as pre-standard products, all in a single IC. Standard external resistors connected to the Si3400 and Si3401 provide the proper 802.3 signatures for the detection function and programming of the classification mode. Startup circuits ensure well-controlled initial operation of both the hotswap switch and the voltage regulator. The Si3400 and Si3401 are available in low-profile, 20-pin, 5 x 5 mm QFN packages. While the Si3400 is designed for applications up to 10 W, the Si3401 is optimized for higher power applications (up to approximately 15 W). See also "AN313: Using the Si3400/01 in High Power Applications" for more information.