LT4293 datasheet(16/44 Pages) AD

16 / 44 page

LTC9101-2/LTC9102

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

Table 1. PSE Maximum Delivered Power, Per-Port

DEVICE

PSE

STANDARD

802.3at

802.3bt

TYPE

802.3at

13W

13W*

25.5W

802.3bt

13W*

25.5W*

51W

13W*

25.5W*

51W*

71.3W

*Indicates PD allocated less power than requested.

The LTC9101-2 further supports 802.3af compliant port

operation. In the rare event an 802.3af PD is incompatible

with 802.3bt operation, a 15W, No CC mode is supported

in the

cfg2p4p register.

Note that an 802.3at PSE will not pass an 802.3bt PSE

compliance test, and an 802.3bt PSE will not pass an

802.3at PSE compliance test. This is by design of the

respective standards. 802.3at and 802.3bt devices are

designed to be interoperable. Key features of 802.3at and

802.3bt standards are contrasted in Table 2.

Table 2. 802.3at Type 1 vs 802.3bt Features

FEATURE

802.3at TYPE 1

802.3bt

First Class Event

Short

Long

First Mark Event (15W Mode) No

Yes

Limit Timer

No (Uses Cutoff Timer) Yes

Connection Check

Yes

Active Alternative(s)

2-Pair: A

4-Pair: A and B

Maximum Class Events

Maximum Available Power

Class 3

2-Pair: Class 4

4-Pair: Class 8

Short MPS

Yes

Autoclass

Yes

PoE BASICS

Common Ethernet data connections consist of two or four

twisted pairs of copper wire (commonly known as Ethernet

cable), transformer-coupled at each end to avoid ground

loops. PoE systems take advantage of this coupling arrange-

ment by applying voltage between the center-taps of the data

transformers to transmit power from the PSE to the PD with-

out affecting data transmission. Figure 10 and Figure 11 show

high level PoE system schematics.

Each LTC9102 power channel is implemented with dedi-

cated 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

simultaneously, enabling coherent and precise per-port

power monitoring.

802.3bt 4-PAIR OPERATION

The LTC9101-2 includes up to 12 groups of four identical

channels. Each group of four channels is referred to as a

quad. In the LTC9101-2 architecture, each quad contains

and provides control for two 802.3bt ports, composed of

two channels each.

To support 802.3bt 4-pair operation, two LTC9102 chan-

nels (1,2 and 3,4) are associated with each port. As

such it is required that power channels are connected

to Alternative A and Alternative B, respectively (see

Figure 10). 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 11).

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

ered power to 71.3W, supporting all existing single-sig-

nature PD Classes 0 to 8 and dual-signature PD Classes

1 to 5.

802.3at Type 1 Mode

All 802.3bt-compliant PSEs are fully backwards compat-

ible with existing 802.3at Type 1 and Type 2 PDs as shown

in Table 1.

In addition to full compatibility, 802.3bt PSEs extend sup-

port for lower standby power, enhanced current limit tim-

ing, and dynamic power management to all PD Types (as

supported by the PD application).

LT4293 Datasheet(PDF) 16 Page - Analog Devices

LT4293 Datasheet(HTML) 16 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL