SI3402-B-GM

The Si3402 integrates all power management and control functions required in a
Power-over-Ethernet (PoE) powered device (PD) application. The Si3402
converts the high voltage supplied over the 10/100/1000BASE-T Ethernet
connection into a regulated, low-voltage output supply. The optimized architecture
of the Si3402 minimizes the solution footprint, reduces external BOM cost, and
enables the use of low-cost external components while maintaining high
performance. The Si3402 integrates the required diode bridges and transient
surge suppressor, thus enabling direct connection of the IC 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 nonisolated (buck) converter topologies. The Si3402 supports IEEE 802.3 Type 1
(Class 3 and below) Powered Device applications. Standard external resistors
connected to the Si3402 provide the proper IEEE 802.3 signatures for the
detection function and programming of the requested power class. Startup circuits
ensure well-controlled initial operation of both the hotswap switch and the voltage
regulator. The Si3402 is available in a low-profile, 20-pin, 5 x 5 mm QFN package.
The Si3402-B is a pin-compatible replacement of the obsolete Si3402-A. PCB
layouts designed for Si3402-A can be reused with Si3402-B, but some component
value changes are required.