Si3404 Data Sheet
Fully-Integrated IEEE 802.3 Type 1-Compliant POE PD Interface
and High-Efficiency Switching Regulator with Compact Footprint
The Si3404 integrates the power management and control functions required in a Pow-
er-over-Ethernet (PoE) powered device (PD) application. These devices convert the
high voltage supplied over the 10/100/1000BASE-T Ethernet connection to a regulated,
low-voltage output supply. The optimized architecture of this device minimizes the solu-
tion footprint and external BOM cost and enables the use of low-cost external compo-
nents while maintaining high performance. The Si3404 integrates a transient surge
suppressor. The switching power FET and associated functions are also integrated.
The integrated, current mode controlled switching regulator supports isolated or non-
isolated flyback and buck converter topologies. The switching frequency for the regula-
tor is tunable with a simple external resistor value to help avoid unwanted harmonics
for better emissions control.
This device fully supports the IEEE 802.3at specification for Type 1, single-event classi-
fication. Standard external resistors provide the proper IEEE 802.3 signatures for the
detection function and programming of the classification mode, and internal startup cir-
cuits ensure well-controlled soft-start initial operation of both the hotswap switch and
the voltage regulator.
The Si3404 is available in a low-profile, 20-pin, 4 x 4 mm QFN package.
KEY FEATURES
• Type 1 (PoE) power
•
IEEE 802.3at Type 1 compliance
• Current mode dc-dc converter
• Tunable switching frequency
• Transformer bias winding support
• Auxiliary adapter capability
• Integrated hotswap FET and switching FET
• 120 V Absolute Max voltage performance
• Extended –40 to +85 °C temperature
• Compact ROHS-compliant 4 mm x 4 mm
QFN Package
APPLICATIONS
• Voice over IP telephones
•
Wireless access points
• Security and surveillance IP cameras
• Point-of-sale terminals
• Internet appliances
• Network devices
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