PEM3100 SERIES

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30W Power Over Ethernet Plus (POE+) PD Module

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PEM3100_13F_R1-1

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Part F.5. – AT Detection (ATD Pin)

In case of Layer 2 (link layer) classification, in order to extract more than 15.4W power from the PSE the

host board controller has to confirm back to the PSE through the data link layer (Layer 2) that it is a Type-2

PD. Full details are available in the IEEE 802.3at standards document.

ATD Pin can be connected to host board through an opto-coupler as shown in figure 4.

The opto-coupler (U1) is connected across the isolation barrier. When a Type-2 PSE is connected to the

PEM3100, the ATD pin goes High and turns on the opto-coupler. The collector pin of U1 to be connected to

the host board controller, using a pull-up resistor. When the ATD pin goes High, U1 output goes Low. Then

the host board controller can understand that the PSE can deliver more than 15.4W and confirm back that

this is a Type-2 PD.

If the PEM3100 detects a 1 – Event Physical Layer classification, U1 remains OFF and the output collector

remains high (via pull-up resistor). The host board then understands that the PSE is not Type-2.

In case the Physical Layer classification is not supported by the PSE, then U1 remains OFF.

Figure 4 – ATD Pin Connection

AT Detect

+VDC

-VDC

VIN-

To Host Board Controller

470uF

C1

C2

470uF

R1

Isolation

U1

LTV357 or PC817 or equivalent

PEM3100

Figure 4

Part F.6. – Remote Shutdown (RSD)

The PEM3100 series is featured with Remote Shut Down option, which can be used in case the host board

need to shut down PEM3100. This feature is helpful with host boards having auxiliary power supply.

Using the remote shut down feature the designer can decide the priority of POE power or auxiliary power.

For example, when the auxiliary power supply is live, the host board can shut down the PEM3100 output.

Similarly the RSD feature can be used to initiate a hardware reset.

The RSD pin can be connected to host board through an opto-coupler as shown in Figure 5. The opto-

coupler is required in order to maintain the 1500V isolation barrier.

To shut down the PEM3100 the host board needs to pull the RSD pin from Zero to High. When the RSD pin

is activated, the output of the PEM3100 will switch off. RSD is a current-mode pin, the ratings are as per

Table 2 below.