LT4295 datasheet(35/50 Pages) AD

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LTC9101-1/

LTC9102/LTC9103

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

7. The PSE measures the Autoclass response of the PD.

If class signature 0 is measured, the PD is requesting

Autoclass. When the measurement is complete the first

class event is ended.

8. The PD continues holding the class signature selected

in step 6 until the end of the first class event.

Following the Autoclass negotiation procedure, PSE and

PD continue Physical Layer classification and power up

as normal. Regardless of Autoclass, the PD is required

to operate below the negotiated power allocation corre-

sponding to PD assigned Class.

Autoclass Measurement Procedure

Autoclass measurements may be requested by the PD

through Physical Layer classification or, following power

on, through LLDP. Although the LTC9101-1/LTC9102/

LTC9103 is compatible with LLDP-based Autoclass

requests, it cannot receive LLDP Autoclass requests

directly since it does not have access to the data path.

If the PSE is commanded to perform an Autoclass mea-

surement following a Physical Layer request, the mea-

surement typically begins tAUTO_PSE1 (1.5s typical) after

port inrush is successfully completed. For LLDP-based

Autoclass requests, the measurement begins immediately.

The Autoclass measurement period is tAUTO_PSE2 –

tAUTO_PSE1 (1.8s typical) using a sliding window of tAUTO_

WINDOW (0.23s typical). During the Autoclass measure-

ment period, the PSE continuously monitors IPORT and

VEE, calculating maximum average power. Following the

Autoclass measurement period, the Autoclass measure-

ments are reported in the Port Parametric registers.

See the LTC9101-1 Software Programming documen-

tation for details on enabling Autoclass, the status of

the Autoclass negotiation, reading Autoclass measure-

ment results and dynamically requesting an Autoclass

measurement.

Autoclass Negotiation Procedure

A PSE may receive an Autoclass request from the PD by

Physical Layer classification or LLDP (by way of the PSE

host). For Physical Layer requests, the Autoclass negotia-

tion procedure listed below is shown in Figure 25.

tACS_MAX (87.5ms)

tACS_MIN (75.5ms)

tCLASS_ACS_MIN

tCLASS_PD_MAX (5ms)

tCLASS_MIN

tCLASS_LCE_MAX

tLCE_MIN

tLCE_MAX

VOUTn

VCLASS

VMARK

IOUTn

CLASS_SIG_4

CLASS_SIG_0

9101123 F25

Figure 25. Autoclass Negotiation, Voltage and Current

1. PSE begins issuing the long first class event. The PD

class signature is allowed to settle during this time.

2. The PD responds with a class signature corresponding

to its Class. The class signature during this time period

is unrelated to the Autoclass negotiation.

3. The PSE measures the PD class signature during this

time and uses the result for the normal Multi-event

Classification.

4. The PD continues presenting its class signature.

5. The PSE continues the long class event and does not

measure the class signature current at this time.

6. The PD, if requesting Autoclass, transitions to class

signature 0. If the PD is not requesting Autoclass it

continues presenting its class signature.

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