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LTC9101-2/LTC9102

Rev. 0

For more information www.analog.com

Port Current Readback

The LTC9101-2 measures the current at each power chan-

nel with per-channel A/D converters. Channel current is

only valid when the power channel is on and reads zero at

all other times. Samples are taken continuously; a moving

1 second average is updated every 100ms

Port Voltage and VEE Readback

The LTC9101-2/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 LTC9101-2 also reports die temperature

of each corresponding LTC9102.

Overtemperature Protection

Overtemperature protection automatically removes

power from affected ports when LTC9102 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).

SeeLTC9101-2NDASI Software Interface guide for details.

Over Supply Shutdown (OSS)

The LTC9101-2 provides a low latency port shedding fea-

ture to quickly reduce the system load when required. By

allowing a preconfigured set of ports to be turned off,

the current on an overloaded main power supply can be

reduced rapidly while keeping high priority devices pow-

ered. An LTC9101-2 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 HW pin, the low priority ports will be shut

down within 6.5μs. An OSS event shall set OSS event and

Disconnect interrupt.

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.

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 LTC9101-2/LTC9102 is

compatible with LLDP-based Autoclass requests, it can-

not 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 LTC9101-2NDASI Software Programming docu-

mentation for details on enabling Autoclass, the status of

the Autoclass negotiation, reading Autoclass measure-

ment results and dynamically requesting an Autoclass

measurement.

APPLICATIONS INFORMATION

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