4.

Application Information

This section describes the application information of the PD69208T4, PD69204T4, and PD69208M devices.

4.1

Connection Check

An additional PD construction detection phase named, connection check, is done to detect which PD configuration is

connected (single-signature or dual-signature) per the IEEE 802.3bt standard.

4.2

PD Detection

The PD detection feature detects a valid IEEE 802.3af, IEEE 802.3at, or IEEE802.3bt. The PD detection is done

based on four different voltage levels to ensure robust detection, as shown in the Typical IEEE 802.3bt Port PoE

Voltage Diagram.

4.3

Legacy Detection

When legacy detection is enabled, the PD detection mechanism detects and powers up the legacy and pre-standard

PDs as well as IEEE 802.3af, IEEE 802.3at and IEEE 802.3bt standard compliant PDs (Classes 0–8).

4.4

Classification

The classification process takes place immediately after PD detection is successfully completed. The goal of the

classification process is to detect PD class as specified in IEEE 802.3 standards.

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

and IEEE 802.3bt modes, the classification mechanism is based on two voltage levels (multiple events) as defined in

IEEE 802.3-2015 Clause 33 and IEEE 802.3bt. In PoH mode, the classification mechanism is based on three events

classification as defined in HDBaseT standard.

Figure 4-1. Typical IEEE 802.3bt Port PoE Voltage Diagram

4.5

Port Start-Up

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

mechanism.

PD69208T4/PD69204T4/PD69208M

Application Information

Datasheet

DS00003428C-page 16