Figure 1-2. Typical PoE Voltage Timing Diagram

1.2.2

Legacy (Capacitor) Detection

In cases where pin 24 is set to 0, the PD69101's detection mechanism is configured to detect and power-up legacy

PDs, as well as AF/AT compliant. This mechanism also detects and powers up Cisco legacy PDs.

1.2.3

Classification

The classification process takes place right after the resistor detection, is successfully completed. The main goal of

the classification process is to detect the PD class, as specified in the IEEE802.3af and IEEE 802.3at standards. In

IEEE 802.3af mode, the classification mechanism is based on a single voltage level (single class event). In IEEE

802.3at mode, the classification mechanism is based on two voltage levels (dual class event) as defined in IEEE

802.3at 2009. In IEEE 802.3at mode, when the PD is class 0–3, the PD69101 generates a single class event. When

the PD is class 4, the PD69101 generates two class events.

1.2.4

Port Start Up

Upon a successful detection and classification process, power is applied to the load through a controlled start-up

mechanism. During this period, current is limited to 425 mA for a typical duration of 65 mS, which enables the PD

load to charge and enter a steady state power condition.

1.2.5

Over-Load Detection and Port Shut Down

After power-up, the PD69101 automatically initializes its internal protection mechanisms to monitor and disconnect

power from the load in cases where extreme conditions (such as over-current or short port terminal scenarios) occur,

as specified in the IEEE 802.3af/at standard.

1.2.6

Disconnect Detection

The PD69101 supports the DC disconnect function as per the IEEE 802.3af/at standard. This mechanism

continuously monitors the load current and disconnects power in cases where the load current is below 7.5 mA

(typical) for more than 322 mS.

1.2.7

Overtemperature Protection

The PD69101 has internal temperature sensors that continuously monitor junction temperature and disconnect load

power when the junction temperature exceeds 200 °C. This mechanism protects the device from extreme events

such as high ambient temperature or other thermo-mechanical failures that might damage the PD69101 device.

1.2.8

valuable feature that protects the load, if the main power source is faulty or damaged.

PD69101

Functional Description

and its subsidiaries

Datasheet

DS00004280A-page 7