Analog Devices LINEAR TECHNOLOGY LTC2874 Demo Manual page 6

operating information
Status Indicators
Top LED
Table 3. LED0 (Ethernet Link/Active)
STATE
Off
Green
Blinking Green
Bottom LED
Table 4. LED1 (Ethernet Link Speed)
STATE
Off
Green
Power over Ethernet (PoE)
The DC2228A optionally operates using power supplied
over an Ethernet connection, eliminating the need for a
local power supply. To use this mode:
a. Set the power source selector (S1) to the PoE position.
b. Connect a PoE injector (Figure 3), PoE switch, or other
Power Sourcing Equipment capable of 90W (for exam-
ple, an LTPoE ++ demo board, DC1814A-D) to its power
adapter or supply.
c. Connect an Ethernet cable between J1 and the PoE
injector/switch output.
Table 5. Classification Resistor Programming
RCLASS
J40 J41
34.8Ω 49.9Ω
---- Open
---- Shunt
---- Open
Shunt* Open
---- Open
---- Shunt
*Jumper not provided. Requires addition of 2-pin header to PC board.
**LTPoE ++ PD will be classified as Class 4 Type 2 by an IEEE 802.3 compliant PSE.
DESCRIPTION
No link
Link
Activity
DESCRIPTION
10 Mbps
100 Mbps
RCLASS++
J42 J43
118Ω 34.8Ω
Open ----
Open ----
Shunt ----
Open ----
Open Shunt*
Shunt ----
DEMO MANUAL DC2228A
d. Connect an Ethernet cable between the PoE injector/
switch input and the PC running the Control Tool soft-
ware.
Because the DC2228A is nominally classified as a 90W
LTPoE ++ PD (Powered Device), it requires a PSE rated at
this power level for unrestricted operation.
Limited operation with a PSE rated for less power is possi-
ble, but the classification must be changed using Table 5.
For example, to operate using a 13W PoE injector, remove
the J42 shunt (keeping the J41 shunt in place) and restrict
the total power consumption accordingly.
A PSE rating below 90W might easily be adequate,
depending on the actual power consumed by devices
connected to eight ports. This consideration must take
into account whether the C/Q lines will drive DC loads
(e.g., in SIO mode) or only connect with IO-Link devices.
For additional guidance regarding PoE classification set-
tings, refer to the LT4275 data sheet.
Figure 3. 90W LTPoE ++ Injector (Allnet ALL048900)
NOMINAL
CLASS PD Type
0 Type 1
3 Type 1
---- Invalid
4 Type 2
LTPoE ++
4**
LTPoE ++
4**
PD POWER
ICLASS AVAILABLE
0.4mA 13W
28mA 13W
---- ----
40mA 25.5W
40mA 38.7W
40mA 90W
NOTE
Default
dc2228afa
5