Rainbow Electronics MAX5940B - Manual (Page 11)

MAX5940A/MAX5940B
IEEE 802.3af PD Interface Controller
For Power-Over-Ethernet
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60V 68nF
UVLO GND
V EE
GATE
RCLASS PGOOD
PGOOD
DC-DC CONVERTER
GND
-48V
WALL
ADAPTER
SUPPLY
R
CL
D1
GND
V+
VREG
OUT
1
2
3
4 5
6
7
8 C OUT
C GATE
R DISC
25.5k Ω
SS_SHDN
MAX5014
MAX5940B LOAD
R3
10k Ω
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.