Linear introduces single-channel PoE controller
Linear Technology
LTC4274
Linear Technology has introduced the LTC4274 single-channel power-over-Ethernet (PoE) controller for power sourcing equipment (PSE) required to provide IEEE 802.3at (25.5W) or higher-power levels.
Next-generation PoE applications call for more power to support demanding features, while increasing power efficiency in an effort to be more 'green' and reduce costs.
The LTC4274 provides up to 100W over four-pair Ethernet cabling and is fully compliant with the new IEEE 802.3at PoE+ standard and backward compatible with the prior IEEE 802.3af PoE standard.
To help conserve power, the LTC4274 delivers low heat dissipation by using low RDS(ON) Mosfets and 0.25ohm sense resistors, eliminating the need for expensive heatsinks and providing a more robust PSE solution, according to the company.
The LTC4274 is suitable for a variety of PSE applications, including next-generation single-port switches, cameras and electronic message boards.
The low power dissipation of the LTC4274 makes thermal design easier than designing with PSEs that integrate more fragile, normally higher RDS(ON) Mosfets.
IEEE 802.3at powered devices (PDs) can request up to 25.5W of power, responding to two-event classification from the LTC4274 and confirming that the PD is indeed a high-power device.
PD discovery is accomplished using a proprietary dual-mode, four-point detection mechanism that ensures the best immunity from false detection.
Advanced power management also includes prioritised fast shutdown, 14.5-bit voltage and current readback, 8-bit programmable current limits and 7-bit programmable overload current limits.
A 1MHz I2C interface allows a host controller to digitally configure the IC or query port readings.
The LTC4274 is offered in commercial and industrial temperature grades and is available in an RoHS-compliant 5 x 7mm QFN-38 package.
It is priced from USD4.95 (GBP3.05) each in 1,000-piece quantities and is available today in production quantities.
The LTC4274 provides an upgrade path from the IEEE 802.3af-compliant LTC4263/-1 and is supported with technical experience in PoE circuit design for a smooth transition to the new PoE+ standard.
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