LT4293 datasheet(29/39 Pages) AD

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Data Sheet

LTC9101-2B/LTC9102

APPLICATIONS INFORMATION

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Rev. 0 | 29 of 39

If the PSE is commanded to perform an Autoclass measurement

following a Physical Layer request, the measurement 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). Dur-

ing the Autoclass measurement period, the PSE continuously moni-

tors IPORT and VEE, calculating maximum average power. Following

the Autoclass measurement period, the Autoclass measurements

are reported in the Port Parametric registers.

See the LTC9101-2B Software Interface guide for details on ena-

bling Autoclass, the status of the Autoclass negotiation, reading

Autoclass measurement results and dynamically requesting an

Autoclass measurement.

Port Current Readback

The LTC9101-2B measures the current at each power channel

with per-channel A/D converters. Note channel current is only valid

when the power channel is on and reads zero at all other times.

Samples are taken continuously and are reported as a 100ms

average.

Port Voltage and VEE Readback

The LTC9101-2B/LTC9102 continuously measures the VEE voltage

with a dedicated A/D converter. This global VEE measurement

is fully synchronized to all port current measurements and can

monitor down to the LTC9102 UVLO threshold.

Temperature Readback

In addition to the over temperature fault in the supply event register,

the LTC9101-2B also reports die temperature of each correspond-

ing LTC9102.

Overtemperature Protection

Overtemperature protection automatically removes power from af-

fected ports when LTC9102 temperature exceeds a preset thresh-

old (150°C, typ). Ports are prevented from resuming operation

until the die temperature drops below a preset recovery threshold

(125°C, typ). See the LTC9101-2B Software Interface guide for

details.

Over Supply Shutdown (OSS)

The LTC9101-2B provides a low latency port shedding feature

to quickly reduce the system load when required. By allowing a

preconfigured set of ports to be turned off, the current on an over-

loaded main power supply can be reduced rapidly while keeping

high priority devices powered. An LTC9101-2B can be configured in

either a 1-bit or 3-bit shutdown priority based on the Multibit Priority

field.

In 1-bit priority mode each port can be configured to high or low

priority. Specifically, if Multibit Priority is disabled, then Port Power

Priority are followed for port priority and OSS action (i.e. legacy

1-bit priority). On a rising edge of the OSS pin, the low priority ports

will be shut down within 6.5μs (typical). An OSS event shall set

OSS event and Disconnect interrupt.

In 3-bit priority mode, e.g., Multibit Priority is enabled, each port

can be configured to one of eight Multibit Power Priorities. When

the host system wants a certain group of priority ports to be shut

down, it will send the matching shutdown code on the OSS pin. The

LTC9101-2B compares the shutdown code received on OSS with

the Multibit Power Priority of each port and shuts down ports which

are less than or equal to the flagged shutdown code (see Figure

47).

If a port is turned off via OSS, the corresponding Detection and

Classification Enable bits remain unchanged and the port will re-

sume operation as configured.

Port Remapping

The LTC9101-2B/LTC9102 support the ability to remap ports logi-

cally, which can be achieved by writing the appropriate values into

the port remapping register to achieve the remapping (see Table

17). By default, there is no remapping.

Table 17. Port Remapping

CODE

REMAPPING

00b

Port 1

01b

Port 2

10b

Port 3

11b

Port 4

Within each quad, physical port remapping is unlimited; any physi-

cal port can be mapped to any logical port.

Figure 47. Multibit Priority Port Shutdown of Lower Priority Port

Code Download

LTC9101-2B firmware is field-upgradable by downloading and exe-

cuting firmware images.

Contact Analog Devices for code download procedures and firm-

ware images.

Firmware images are stored in a dedicated flash partition. A fully-

compliant IEEE 802.3bt firmware image is pre-configured on the

LTC9101-2B. The firmware image may be overwritten by the user.

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