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LTC9101-1/

LTC9102/LTC9103

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

may be characterized and extrapolated from the VEE mea-

surement in a user-defined manner.

Masked Shutdown

The LTC9101-1/LTC9102/LTC9103 provides a low latency

port shedding feature to quickly reduce the system load

when required. By allowing a pre-determined set of ports

to be turned off, the current on an overloaded main power

supply can be reduced rapidly while keeping high pri-

ority devices powered. Each port can be configured to

high or low priority; all low-priority ports will shut down

within 6.5μs after MSD is pulled low, high priority ports

will remain powered. If a port is turned off via MSD, the

corresponding Detection and Classification Enable bits are

cleared, so the port will remain off until the host explicitly

re-enables detection.

In the LTC9101-1/LTC9102/LTC9103 chipset, the active

level of MSD is register configurable as active high or low.

The default behavior is active low.

4-Pair Valid

The IEEE 802.3bt standard leaves room for interpretation

in the single-signature and dual-signature PD definitions.

Strictly speaking the 802.3bt standard defines only single-

signature and dual-signature PDs.

A strict interpretation limits valid PDs to single-and dual-

signature PDs which are connected to both PSE pair-

sets. PDs which do not have valid detection signatures

on both pairsets are treated as invalid PDs. To enable

a port’s 4-Pair Valid mode, set 4PVALID low or set the

port’s 4-Pair Valid configuration register. With 4-Pair Valid

mode enabled, a port will only apply power if there is a

valid detection signature on both pairsets. See Table 14.

Table 14. 4-Pair Valid Enabled

PAIRSET

DETECTION

SIGNATURE

ALTERNATIVE A

INVALID

ALTERNATIVE A

VALID

ALTERNATIVE B

INVALID

Port Unpowered

ALTERNATIVE B

VALID

Port Unpowered

Power A and B

Port Current Readback

The LTC9101-1/LTC9102/LTC9103 measures the current

at each power channel with per-channel A/D converters.

Channel current is only valid when at least one power

channel of a port is on and reads zero at all other times.

The converter has two modes:

• 100ms mode: Samples are taken continuously and the

measured value is updated every 100ms

• 1s mode: Samples are taken continuously; a moving

1 second average is updated every 100ms

VEE Readback

The LTC9101-1/LTC9102/LTC9103 continuously mea-

sures 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/LTC9103 UVLO threshold.

Temperature Readback

In addition to the over temperature fault in the supply

event register, the LTC9101-1 also reports die temperature

of each corresponding LTC9102/LTC9103.

Overtemperature Protection

Overtemperature protection automatically removes power

from affected ports when LTC9102/LTC9103 temperature

exceeds a preset threshold (150°C, typ). Ports are pre-

vented from resuming operation until the die temperature

drops below a preset recovery threshold (125°C, typ). See

LTC9101-1 Software Interface guide for details.

Port Power Readback

The LTC9101-1/LTC9102/LTC9103 provides fully con-

tinuous and synchronized port power measurements. The

LTC9101-1/LTC9102/LTC9103 calculates the port power

by multiplying the port current and VEE measurements.

PPORT = IPORT • VEE

The Port Power measurements replace the Port Voltage

measurements provided in prior ADI PSEs. Port voltage

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