Rainbow-electronics MAX5940B Manual do Utilizador descarregar pdf (Página 11)

MAX5940A/MAX5940B

IEEE 802.3af PD Interface Controller

For Power-Over-Ethernet

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60V

68nF

UVLO

GND

GATE

RCLASS

PGOOD

DC-DC CONVERTER

GND

-48V

WALL

ADAPTER

SUPPLY

GND

V+

VREG

OUT

GATE

DISC

25.5kΩ

SS_SHDN

MAX5014

MAX5940B

LOAD

10kΩ

Typical Application Circuits (continued)

Figure 5. Adding Wall Adapter Input Supply (Wall Adapter Supply Takes Precedence Over Power-Over-Ethernet)

Application Circuit 2

Diode D1 prevents the power-over-ethernet to back

drive the wall adapter. Whenever the wall adapter

power is available, the GATE is pulled low to pinch off

the power-over-ethernet. R3 provides the GATE current

flow path. The wall adapter power pollutes the discov-

ery signature, preventing PSE from detecting this PD.

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Rainbow-electronics MAX5940B Manual do Utilizador Página 11