Power over Ethernet IC delivers 123W over 1Gbps CAT5e cable
Demand for higher power delivery comes from many devices, including LTE picocell base stations, LED signage, security monitoring systems, home automation and machine vision systems. The LTC4279 delivers power to a wide variety of powered devices (PDs). This includes all legacy (<13W), IEEE 802.3at Type 1 (13W) and Type 2 (25.5W) PDs, Linear’s proprietary LTPoE++ (up to 90W), and custom (<123W) PDs. 2-pair and 4-pair output topologies are supported, as well as single-signature and dual-signature architectures. Resistor-adjustable power selection allows the LTC4279 to be configured for multiple sockets, simplifying design and bill of materials.
The LTC4279 provides fully autonomous operation for a wide variety of PSE applications, including endpoints and midspan power injectors. A low power sense resistor and external MOSFET simplify thermal design; traditional PSEs utilize less robust MOSFETs with higher RDS(ON). PD discovery is accomplished using a high reliability 4-point detection mechanism that ensures optimum immunity from false PD detection. The LTC4279 provides a set of PD classification mechanisms to enable wide system compatibility. Robustness is reinforced with classification-dependent current cutoff and limit thresholds, short-circuit protection and ±80V cable surge protection.
The LTC4279 is offered in the industrial temperature grade (–40°C to 85°C) and is available in 4 x 5 mm QFN-20 and SO-16 packagesfor $3.45 (1,000). The LTC4279, combined with the LT4275 and LT4276 PD controllers, enable up to 123W end-to-end design.
Linear Technology; www.linear.com/product/LTC4279
next page; feature list
Summary of Features: LTC4279
Compliant with IEEE 802.3at Type 1 & 2
Supports LTPoE++ up to 90W
UltraPWR mode supports custom PDs up to 123W
Supports single-signature & dual-signature PDs
Very low power dissipation
◦ 0.1Ω sense resistance
◦ Low RDS(ON) external MOSFET
Very high reliability 4-Point PD detection
Pin-selectable detection backoff timer for midspans
Pin-programmable power selection
Status LED pin
Available in 20-pin QFN & 16-pin SO packages
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