Linear Technology LTC2874, Demo Manual

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dc2228af
DEMO MANUAL DC2228A
operating information
Status Indicators
Top LED
Table 3. LED0 (Ethernet Link/Active)
STATE DESCRIPTION
Off No link
Green Link
Blinking Green Activity
Bottom LED
Table 4. LED1 (Ethernet Link Speed)
STATE DESCRIPTION
Off 10 Mbps
Green 100 Mbps
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
example, 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.
d. Connect an Ethernet cable between the PoE injector/
switch input and the PC running the Control Tool software.
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 pos-
sible, 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, depend-
ing 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)
Table 5. Classification Resistor Programming
RCLASS +
CLASS PD Type
NOMINAL
ICLASS
PD POWER
AVAILABLE
NOTE
J40
34.8Ω
J41
49.9Ω
J42
118Ω
J43
34.8Ω
---- Open Open ---- 0 Type 1 0.4mA 13W
---- Shunt Open ---- 3 Type 1 28mA 13W
---- Open Shunt ---- ---- Invalid ---- ----
Shunt* Open Open ---- 4 Type 2 40mA 25.5W
---- Open Open Shunt* 4** LTPoE++ 40mA 38.7W
---- Shunt Shunt ---- 4** LTPoE++ 40mA 90W Default
*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.