Rev. 1.0 7/10

Copyright © 2010 by Silicon Laboratories

Si3480

Features

Description

The Si3480 is a power manager intended for use with the Si3452 Power

over Ethernet (PoE) controller. The Si3480 enables the use of a smaller,

lower cost, and more efficiently-utilized power supply in an unmanaged

PoE Power Sourcing Equipment (PSE) system.

The Si3452 is capable of delivering over 30 W per port, which means that,

in a typical 8-port system, a 240 W power supply would have to be used

to avoid overload. Typically, not all ports are used at full power; so, a

smaller power supply in the range of 30 to 150 W can be used along with

the Si3480 power management controller.

The Si3480 power management controller is pin programmed. The pins

are used to set the power supply capacity, the number of low power

(category 1, 15.4 W), and high power (category 2, 30 W) ports, the port

priority, and the detection timing (Alternative A or Alternative B). The

Si3480 uses the real time overload and current monitoring capability of

the Si3452 to manage power for up to eight ports. Power management is

based on actual consumption rather than mere classification in order to

supply power to the greatest number of ports.

The Si3480 also provides LED drive to indicate port status and drive an

LED bar graph display to indicate the power supply capacity in use. If a

port is denied power due to power supply capacity limitations, the LED

indicators provide a simple and intuitive indication, helping a user

recognize and correct the overload situation by rebalancing loads or

adding mid-span power injectors to ports that would not otherwise be

powered. In case of a port overload, the port is easily re-enabled by

disconnecting the Powered Device (PD) and then reconnecting the PD

after correcting the overload situation.

supply for a 4 or 8 port PoE

system

without the need for a host for

unmanaged operation



No software required



No data isolation required

clause 33 for Power over Ethernet

including the 802.3at amendment

for higher power (30 W category 2

ports)

power supply capacity, port

power level, port priority, and

detection timing

overall power consumption

(4x4 mm)



4x4 mm PCB footprint; RoHS

compliant

range (–40 to +85 °C)

Ordering Information:

See Ordering Guide on page 9.

Pin Assignments

(Top View)

2

3

4

5

14

13

12

11

15

SDA

GND

VDD

RST

NC

LED6

LED7

LED8

PRIOCFG

ALTCFG

1

Si3480