Document
Si3402-B
FULLY-INTEGRATED 802.3-COMPLIANT POE PD INTERFACE AND LOW-EMI SWITCHING REGULATOR
Features
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 EMIreduction techniques.
Supports non-isolated and isolated switching topologies
Comprehensive protection circuitry Transient overvoltage protection Undervoltage lockout Early power-loss indicator Thermal shutdown protection Foldback current limiting
Low-profile 5 x 5 mm 20-pin QFN RoHS-compliant
Applications
Voice over IP telephones and adapters
Wireless access points Security cameras
Description
Point-of-sale terminals Internet appliances Network devices High power applications
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 802.3at Type 1 Powered Device applications. 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 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 is designed for IEEE 802.3at Type 1 (Class 3 and below) applications. 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.
Ordering Information: See page 18.
Pin Assignments 5 x 5 mm QFN (Top View)
FB VSS2 SWO VSS1 VPOSS VSSA
20 19 18 17 16 15
EROUT 1 SSFT* 2 VDD 3
ISOSSFT* 4
VNEG (PAD)
14 CT1 13 CT2 12 VPOSF 11 SP1
5 6 7 8 9 10
PLOSS RDET HSO RCL VNEG SP2
Note:
Original pin names shown for compatibility reasons, but SSFT, ISOSSFT, VPOSS, and VSS1 are not internally connected.
Rev. 1.0 11/15
Copyright © 2015 by Silicon Laboratories
Si3402-B
Si3402-B
Functional Block Diagram
VPOSF VPOSS* RDET RCL
SSFT* VDD
IS O S S FT *
CT1 CT2 SP1 SP2
Rectification &
Protection
D ete ctio n &
C lassificatio n
H otsw ap S w itch &
C u rre nt lim it
H otsw ap C ontrol
& Com m on
B ias
P W M C ontrol and EMI L im itin g
S w itching FET
EROUT FB
SW O
VNEG
HSO
PLOSS VSSA
VSS1* VSS2
N o te : O rig in a l p in n a m e s s h o w n fo r c o m p a tib ility re a s o n s, b u t S S F T , IS O S S F T , V P O S S , a n d V S S 1 a re n o t in te rn a lly co n n e cte d.
2 Rev. 1.0
TABLE OF CONTENTS
Si3402-B
Section
Page
1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2. Typical Application Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 3. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. PD Hotswap Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. Switching Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Recommended Land Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. Device Marking Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .