PM8801 datasheet(21/37 Pages) STMICROELECTRONICS

Part #	PM8801

Description	High-efficiency, IEEE 802.3at compliant, integrated PoE-PD interface and PWM controller

PDF	37 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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21 / 37 page

DocID018560 Rev 2

21/37

PM8801

PD interface

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

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

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

In isolated applications, the main circuits and the PM8801 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

Time

T2P (802.3af)

T2P stable before

output soft-start

AM045039v1

Time

Idle or Mark Range

Classification Range

On range

Detection

Time

OUTPUT VOLTAGE

Soft Start

Time

T2P (802.3at)

T2P stable before

output soft-start

AM045040v1

PM8801 Datasheet(PDF) 21 Page - STMicroelectronics