Rev. 1.1 11/10 Copyright © 2010 by Silicon Laboratories Si3402
Si3402
FULLY-INTEGRATED 802.3-COMPLIANT POE PD INTERFACE
AND LOW-EMI SWITCHING REGULATOR
Features
Applications
Description
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 non-isolated (buck)
converter topologies. The Si3402 supports IEEE Std 802.3™ 2008 (future
instances are referred to as 802.3) compliant solutions as well as prestandard
products, all in a single IC. Standard external resistors connected
to the Si3402 provide the proper 802.3 signatures for the detection function
and programming of the classification mode. Startup circuits ensure wellcontrolled
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. While the Si3402 is designed for applications up to 10 W, it can be
used for higher power applications (up to approximately 15 W). See also
“AN313: Using the Si3401/2 in High Power Applications” for more
information.
ƒÞ IEEE 802.3 standard-compliant
solution, including pre-standard
(legacy) PoE support
ƒÞ Highly-integrated IC enables
compact solution footprints
ƒÜƒnMinimal external components
ƒÜƒnIntegrated diode bridges and
transient surge suppressor
ƒÜƒnIntegrated switching regulator
controller with on-chip power
FET
ƒÜƒnIntegrated dual current-limited
hotswap switch
ƒÞ Programmable classification
circuit
ƒÞ Incorporates switcher EMIreduction
techniques.
ƒÞ Supports non-isolated and
isolated switching topologies
ƒÞ Comprehensive protection
circuitry
ƒÜƒnTransient overvoltage
protection
ƒÜƒnUndervoltage lockout
ƒÜƒnEarly power-loss indicator
ƒÜƒnThermal shutdown protection
ƒÜƒnFoldback current limiting
ƒÞ Low-profile 5 x 5 mm 20-pin QFN
ƒÞ RoHS-compliant
ƒÞ Voice over IP telephones and
adapters
ƒÞ Wireless access points
ƒÞ Security cameras
ƒÞ Point-of-sale terminals
ƒÞ Internet appliances
ƒÞ Network devices
ƒÞ High power applications
Ordering Information:
See page 19.
Pin Assignments
5 x 5 mm QFN
(Top View)
EROUT
SSFT
RDET
HSO
RCL
SP1
SP2
VPOSF
CT1
PLOSS
ISOSSFT
VDD
5 6 7 8 9 10
20 19 18 17 16 15
1
2
3
4 11
12
13
14
VNEG
VSSA
VPOSS
VSS1
SWO
VSS2
FB
VNEG
(PAD)
CT2