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
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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