LT4293 datasheet(19/39 Pages) AD

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Data Sheet

LTC9101-2B/LTC9102

APPLICATIONS INFORMATION

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Rev. 0 | 19 of 39

802.3at Type 1 Mode

All 802.3bt-compliant PSEs are fully backwards compatible with

existing 802.3at Type 1 and Type 2 PDs as shown in Table 5.

In addition to full compatibility, 802.3bt PSEs extend support for

lower standby power, enhanced current limit timing, and dynamic

power management to all PD Types (as supported by the PD

application).

The LTC9101-2B further supports 802.3af compliant port operation.

In the rare event an 802.3af PD is incompatible with 802.3bt opera-

tion, 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 6.

Table 5. PSE Maximum Delivered Power, Per-Port1

DEVICE

PSE

STANDARD

802.3at

802.3bt

TYPE

3 (2-

Pair)

3 (4-

Pair)

802.3at

13W

13W1

25.5W

802.3bt

13W1

25.5W1

51W

13W1

25.5W1

51W1

71.3W

1 Indicates PD may be allocated less power than requested (demoted).

Table 6. 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)

Yes

Limit Timer

No (Uses Cutoff Timer)

Yes

Connection Check

2-Pair: No

4-Pair: Yes

Active Alternative(s)

A or B

2-Pair: A or B

4-Pair: A and B

Maximum Class Events

2-Pair: 2

4-Pair: 5

Maximum Available Power

Class 3

2-Pair: Class 4

4-Pair: Class 8

Short MPS

Yes

Autoclass

Yes

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