IEEE 802.3af PD Interface Controller

For Power-Over-Ethernet

______________________________________________________________________________________

13

60V

68nF

UVLO

GND

GATE

RCLASS

PGOOD

PGOOD

DC-DC CONVERTER

GND

-48V

WALL

ADAPTER

SUPPLY

D1

GND

V+

VREG

OUT

1

2

3

4

5

6

7

8

25.5k

Ω

SS_SHDN

MAX5014

MAX5940B

MAX5940D

LOAD

Typical Application Circuits (continued)

Application Circuit 4

If the wall adapter supply comes up first, it provides

power to the load and pollute the discovery and classi-

fication signatures. If the power-over-ethernet comes

up first, it powers the load until taken over by a wall

adapter with higher output voltage.

Figure 7. Adding Wall Adapter Input Supply (the One with Higher Voltage Provides Power to the Load)