25 Jun 2018

Isolated 4-port PoE++ PSE controller delivers up to 71.3W

Analog Devices announces the Power by Linear LTC4291/LTC4292 isolated 4-port power sourcing equipment (PSE) controller chipset designed for use in IEEE 802.3bt (PoE++) Power over Ethernet (PoE) systems.

The LTC4291/LTC4292 provides 4 independent PSE ports comprised of 2 channels each, ensuring fully compliant support for the next generation of IEEE 802.3bt powered devices (PDs). The LTC4291 includes a digital interface to the PSE host, while the LTC4292 implements the high voltage Ethernet power interface. The two ICs intercommunicate using an inexpensive Ethernet transformer. The transformer-isolated communication protocol replaces up to six expensive opto-couplers and a complex isolated 3.3V supply used in traditional designs, resulting in significant BOM cost savings and a more robust and easy to manufacture design.

The LTC4291/LTC4292 chipset operates seamlessly with compliant 802.3bt PD controllers, the LT4294 or LT4295, forming complete end-to-end PoE++, PoE+ and PoE solutions. Up to 71.3W of power can be delivered to single-signature or dual-signature PDs. Users will appreciate the robustness of the 80V pins. Analog Devices is a specialist in low power path dissipation, significantly outperforming PSEs that integrate higher RDS(ON) MOSFETs.

PD discovery is accomplished using a multipoint voltage and current detection mechanism, ensuring the best immunity from false PD detection. Advanced power management includes Autoclass support, prioritized fast shutdown, 14-bit per-port power and current readback, 8-bit programmable power limits and 7-bit programmable overload current limits. Systems can be updated with field-upgradable firmware. A 1MHz I2C interface allows a host controller to digitally configure the chipset or query port status. Power management “C” demonstration libraries are also available to reduce NRE and improve time to market.

The LTC4291/LTC4292 chipset is offered in the industrial temperature range. The LTC4291 digital controller is in a RoHS-compliant 24-pin 4mm x 4mm QFN package, while the LTC4292 analog controller is in a 40-pin 6mm x 6mm QFN package. The LTC4291/LTC4292 is Analog Devices’ first 802.3bt PSE controller and provides an upgrade path from the LTC4266 4-port 802.3at PSE controller.

Summary of Features: LTC4291/LTC4292

  • Four PSE Ports

  • Two Channels per Port

  • Fully Compliant IEEE 802.3bt Type 3 & 4 PSE

  • Compliant Support for Type 1, 2, 3 & 4 PDs

  • Chipset Provides Electrical Isolation

  • Eliminates Optos & Isolated 3.3V Supply

  • Low Power Dissipation

  • 0.15Ω Sense Resistance per Power Channel

  • Enables Extremely Low RDS(ON) External MOSFETs

  • Very High Reliability Multipoint PD Detection

  • Connection Check Distinguishes Single-Signature & Dual-Signature PDs

  • Continuous, Dedicated Per-Port Power & Current Monitoring

  • 1MHz I2C Compatible Serial Control Interface

  • Pin or I2C Programmable Max PD Power up to 71.3W

  • 40-Pin 6mm x 6mm (LTC4292) & 24-Pin 4mm x 4mm (LTC4291) QFN Packages

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The electronics industry has a major role to play in helping to save energy, by enabling better equipment and new ways of working and living that that are more efficient and environmentally friendly. Maintaining the pace of technological progress is key, but improvements become both smaller and harder to achieve as each technology matures. We can see this trend in the development of power semiconductors, as device designers seek more complex and expensive ways to reduce switching energy and RDS(ON) against silicon’s natural limitations.

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