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LTC9101-2/LTC9102

Rev. 0

For more information www.analog.com

OVERVIEW

Power over Ethernet, or PoE, is a standard protocol for

sending DC power over copper Ethernet data wiring.

The IEEE group that administers the 802.3 Ethernet data

standards added PoE powering capability in 2003. This

original PoE standard, known as 802.3af, allowed for 48V

DC power at up to 13W. 802.3af was widely popular, but

13W was not adequate for some applications. In 2009,

the IEEE released a new standard, known as 802.3at or

PoE+, increasing the voltage and current requirements

to provide 25.5W of delivered power. IEEE 802.3af and

802.3at are commonly known as PoE 1. In 2018, the IEEE

released the latest PoE standard, known as 802.3bt or

PoE 2. 802.3bt maximizes PD delivered power at 71.3W.

The IEEE standard also defines PoE terminology. A device

that provides power to the network is known as a PSE,

or power sourcing equipment, while a device that draws

power from the network is known as a PD, or powered

device. PSEs come in two types: endpoints (typically net-

work switches or routers), which provide data and power;

and midspans, which provide power but pass through

data. Midspans are typically used to add PoE capabil-

ity to existing non-PoE networks. PDs are typically IP

phones, wireless access points, security cameras, and

similar devices.

PoE++ Evolution

Even during the development of the IEEE 802.3at (PoE 1)

25.5W standard, it became clear there was a significant

and increasing need for more than 25.5W of delivered

power. In 2013, the 802.3bt task force was formed to

develop a standard capable of increasing delivered

PD power.

The primary objective of the task force is to use all four

pairs of the Ethernet cable as opposed to the two pair

power utilized by 802.3at. Using all four pairs allows for

at least twice the delivered power over existing Ethernet

cables. Further, the amount of current per two pairs

(known as a pairset) has been increased while maintain-

ing the Ethernet data signal integrity. 802.3bt increases

PD delivered power from 25.5W to 71.3W, enabling IEEE-

compliant high power PD applications.

APPLICATIONS INFORMATION

The LTC9101-2/LTC9102 delivers power over one or two

power channels. Each pairset is driven by a dedicated

power channel. In this data sheet, the term “channel”

refers to the PSE circuitry assigned to a corresponding

pairset. For the purposes of this document, the terms

channel and pairset may be considered interchangeable.

In addition, IEEE 802.3bt enables substantially lower

Maintain Power Signature (MPS) currents, resulting in

significantly lower standby power consumption. This

allows new and emerging government or industry standby

regulations to be met using standard PoE components.

LTC9101-2/LTC9102 Product Overview

The LTC9101-2/LTC9102 is a sixth generation PSE con-

troller that implements up to 24 (71.3W) 4-pair PSE ports

in either an endpoint or midspan application. Virtually all

necessary circuitry is included to implement an IEEE

802.3bt compliant PSE design, requiring a pair of exter-

nal power MOSFETs and sense resistors per port; these

minimize power loss compared to alternative designs with

onboard MOSFETs, and increase system reliability.

The LTC9101-2/LTC9102 chipset implements an optional

proprietary isolation scheme for inter-chip communica-

tion. This architecture substantially reduces BOM cost

by replacing expensive opto-isolators and isolated

power supplies with a single low-cost transformer. A

single LTC9101-2 is capable of controlling a bus of up

to 4 LTC9102s over this transformer-isolated interface.

Direct connection of the LTC9101-2 and the associated

LTC9102s is also possible.

The LTC9101-2/LTC9102 offers a configurable interrupt

signal triggered by per-port events, per-channel power

on control and fault telemetry, per-port current monitor-

ing, VEE monitoring, and one second rolling current, and

voltage averaging.

The LTC9101-2/LTC9102 also offers advanced sixth-gen-

eration PSE features including internal eFlash for storage

of firmware updates and custom user configuration pack-

ages, 802.3bt-compliant mode, I2C quad virtualization for full

backwards-compatibility with quad-based IC drivers, ultralow

100mΩ sense resistors, +80V/–20V tolerant port-facing pins,

and improvements to cable surge ride through.

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