PD interface

PM8803

20/34

Doc ID 018559 Rev 2

A low T2P signal after the turn-on phase of the POE means that the PD is connected to a

Type2, 2-event physical layer classification PSE which may allocate power either through

further LLDP negotiation or directly feedthe PD with the required power.

In isolated applications, the main circuits and the PM8803 are at both sides of the galvanic

isolation. The T2P signal is normally connected to an optocoupler to pass the

Type 2, 2-event PSE detection information to the main circuit in the PD system.

Figure 7.

T2P signal when connected to PSE supporting 1-event classification

Figure 8.

T2P signal when connected to PSE supporting 2-event classification

Time

Idle or Mark Range

Classification Range

On range

Detection

Time

OUTPUT VOLTAGE

Soft Start

V

Time

T2P (802.3af)

V

T2P stable before

output soft-start

AM045097v1

Time

Idle or Mark Range

Classification Range

On range

Detection

Time

OUTPUT VOLTAGE

Soft Start

V

Time

T2P (802.3at)

V

T2P stable before

output soft-start

AM045098v1