Rev. 1.0 12/16 Copyright © 2016 by Silicon Labo rato ries Si3402-C
Si3402-C
FULLY-INTEGRATED IEEE 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 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-C is a pin-compatible
replacement of the obsolete Si3402-A. PCB layouts designed for Si3402-A can
be reused with Si3402-C, but some component value changes are required.
The Si3402-C’s functionality is similar to that of the Si3402-B but without the
requirement to make a connection between the Ethernet jack and CT1, CT2,
SP1, or SP2 pins when bypassing the integrated diode bridge with external
Schottky diodes. Further, PLOSS functionality is removed from the Si3402-C.
Pin-compatible replacement for the
obsolete Si3402-A
IEEE 802.3 standard-compliant
solution, including pre-standard
(legacy) PoE support
Highly-integrated IC enables
compact solution footprints
Minimal external components
Integrated diode bridges and
transient surge suppressor
Integrated switching regulator
controller with on-chip power FET
Integrated dual current-limited
hotswap switch
Programmable classification circuit
Incorporates switcher EMI-
reduction techniques.
Supports non-isolated and isolated
switching topologies
Comprehensive protection circuitry
Transient overvo ltage protection
Undervoltage lockout
Thermal shutdown protection
Foldback current limiting
Allows external Schottky diode
bypass of integrated diode bridges
without requiring CT/SP pin
connection
Low-profile 5 x 5 m m 20-pin QFN
RoHS-compliant
Voice over IP telephones and
adapters
Wireless access points
Security cameras
Point-of-sale terminals
Internet appliances
Network devices
High power applications
Ordering Information:
See page 18.
Pin Assignments
5x5mm QFN
(Top View)
Note: Original pin names shown for compatibil-
ity reasons, but SSFT, ISOSSFT, VPOSS,
and VSS1 are not internally connected.
EROUT
SSFT*
RDET
HSO
RCL
SP1
SP2
VPOSF
CT1
NC
ISOSSFT*
VDD
5678910
1
2
3
411
12
13
14
VNEG
VSSA
VPOSS
VSS1
SWO
VSS2
FB
VNEG
(PAD) CT2
151620 19 18 17