LTC9101-3/LTC9103

20

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

LED Power On Self Test

After reset the Supply Overload and all port LEDs will

implement a two phase power on self test. The first phase

lasts four seconds during which the Supply Overload LED

blinks, the port status LED is on, and the port fault LED

is off. The second phase also lasts four seconds during

which the Supply Overload LED blinks, the port status LED

is off, and the port fault LED is on.

Port operation will have already begun during this eight

second period. After the LED power on self test, LED

behaviors will transition to normal system and port status.

System Telemetry

The LTC9101-3 features an interface to control an external

serial LED driver for per-port status and fault LEDs, and

a dedicated pin to control a Supply Overload LED. Using

these features the LTC9101-3 can display complex sys-

tem and port status telemetry. Telemetry is broken up into

two components: port operation and power management.

Port operation is displayed via per-port status and fault

LEDs. The LTC9101-3 displays port power status via that

port's status LED and conveys a list of port faults via blink

codes on that port's fault LED. A list of status and fault

conditions and their factory-default LED responses are

shown in Table 5.

Power management information is displayed via the

Supply Overload LED and secondarily via per-port fault

and status LEDs. The LTC9101-3 conveys conditions such

as system power near-limit warning, system power limit,

and port power revoked via the Supply Overload LED and

blink codes on the corresponding port fault LED(s). A list

of power management conditions and their factory-default

LED responses are shown in Table 6.

LED behaviors are configurable via user-defined settings

in the eFlash-programmable configuration package.

Contact Analog Devices Applications for support with

generating and downloading configuration packages for

use with LTC9101-3/LTC9103.

Overtemperature Protection

Overtemperature protection automatically removes power

from affected ports when LTC9103 temperature exceeds

a preset threshold (150°C, typ). Ports are prevented from

resuming operation until the die temperature drops below

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

Table 5. PoE Operation vs. Port LEDs

CONDITION

LED

PORT STATUS

PORT FAULT

Detect Open

Off

Off

Port Powered

On

Off

Detect Invalid

Off

Blink

Class Invalid

Off

Blink

Inrush Fault*

Off

Blink

PCUT, ICUT and ILIM*

Off

Blink

DC Disconnect*

Off

Blink

* These blink faults persist for 2-3 secs, then a new detection cycle begins and the port LED is

updated based on the latest results..

Notes:

- Supply Overload LED is not affected by PoE Operation conditions.

- Blink rate is 800ms on and 800ms off.

Table 6. Power Management vs. LEDs

CONDITION

LED

SUPPLY

OVERLOAD

PORT STATUS PORT FAULT

Power Available

Off

N/A

N/A

Near Power Limit

On

N/A

N/A

Power Denied

Blink

Blink

Off

Power Revoked

Blink

Blink

Off

Note: Blink rate is 800ms on and 800ms off.

SERIAL DIGITAL INTERFACE

Overview

The serial interface allows configuration downloads but

is not required during normal operation. The LTC9101-3

communicates with the flash programmer using a stan-

dard SMBus/I2C 2-wire interface. The LTC9101-3 is a

slave-only device, and communicates with the flash pro-

grammer master using standard SMBus protocols. The

timing diagrams (Figure 5 and Figure 6) show typical

communication waveforms and their timing relationships.

More information about the SMBus data protocols can be

found at www.smbus.org.