LT4295 datasheet(18/50 Pages) AD

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LTC9101-1/

LTC9102/LTC9103

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

In LTC9101-1 2-pair mode, exactly one LTC9102/LTC9103

channel is associated with each port in a quad. As such it

is required that the LTC9102/LTC9103 power channel is

connected to either Alternative A or Alternative B of the

associated RJ45 connector. (See Figure 10)

In 2-pair mode the IEEE 802.3bt standard limits delivered

power to 25.5W and supports PD Classes 0 to 4.

In LTC9101-1 4-pair mode, two LTC9102/LTC9103 chan-

nels are associated with each port. As such it is required

that power channels are connected to Alternative A and

Alternative B, respectively (see Figure 11). In 4-pair mode

the host is responsible for deciding if both power channels

will be utilized to power a given PD. Thus 2-pair powering

in 4-pair mode can be used to power single-signature

Class 0 to 4 PDs. For higher power Class 5 to 8 PDs and

for all dual-signature PDs, both power channels must be

utilized, also referred to as 4-pair power (see Figure 12).

In 4-pair mode the IEEE 802.3bt standard supports delivered

power to 71.3W, supporting all existing single-signature PD

Classes 0 to 8 and dual-signature PD Classes 1 to 5.

Mixes of 2-pair and 4-pair quads are available using a con-

figuration package. See Stored Configurations for details.

backwards-compatibility with LTC4291 drivers, ultralow

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

pins, and improvements to cable surge ride through.

Each LTC9102/LTC9103 power channel is implemented

with dedicated detection and classification hardware. This

allows all ports and channels to detect, classify and power

on simultaneously, drastically reducing power on latency

across a switch. Other less advanced PSEs are subject to

visible delays as PDs, e.g. LED lights, power on a port-

by-port basis.

VEE and port current measurements are performed simul-

taneously, enabling coherent and precise per-port power

monitoring.

2-PAIR VS 4-PAIR MODE

The LTC9101-1 includes up to 12 groups of four identical

ports. Each group of four ports is referred to as a quad. In

the LTC9101-1 architecture, each quad contains register

configuration and status for exactly four ports, regardless

of whether the ports are in 2-pair mode or 4-pair mode.

1000BASE-T

TX1

TX2

TX3

TX4

RJ45

1000BASE-T

TX1

TX2

TX3

TX4

VEE

GATEn

AGND

LTC9101-1/

LTC9102/LTC9103

I2C

–55V

9101123 F10

–

VOUT

DATA PAIRS

Figure 10. 2-Pair, Alternative A (Endpoint), Power over Ethernet Single-Signature PD System Diagram

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