7
Rev A
DEMO MANUAL DC2685B
DEMONSTRATION CIRCUIT 2683A MOTHER BOARD
capacitance components; these components must be
sized to the final system requirements.
Demonstration circuit 2683A is a 4-Port, 2-channels per
port IEEE 802.3bt PoE PSE motherboard. This board
accepts an IEEE 802.3bt four port PSE daughter card
featuring the LTC4291-1/LTC4292 chipset.
Daughter Card Insertion Precautions
When inserting or removing the daughter card into the
DC2683A motherboard, verify all supplies and LEDs are
off. Push the card straight down for insertion or pull
straight up for removal to avoid bending the connector
pins. Follow the instructions in the Quick Start Procedure
for alignment.
Main V
EE
PoE Supply
The V
EE
supply is the main PoE supply and connects to
the DC2683A with the positive rail to AGND (+) and the
negative rail to V
EE
(–) as shown in Figure 3 of the Quick
Start Procedure. The voltage must be within the range
shown in Table 3 depending on the application PSE type.
For full load testing at each port, choose a power supply
that is set with a current limit higher than the maximum
allowed output power at each port.
Onboard 3.3V Supply
The DC2683A motherboard has an onboard (non-iso-
lated) 3.3V LDO for the LTC4291-1/LTC4292 V
DD
supply
which is generated from the V
EE
supply. This onboard
logic supply is for demonstration purpose to allow for
a single supply connection to the DC2685B kit. DGND
is tied to V
EE
through shunt resistor R42. To isolate the
logic supply from the PoE supply, remove R42 and R41
and apply an external isolated 3.3V supply across V
DD
and DGND. If the DC2685B kit is connected in parallel for
multi-quad port evaluation, verify all ground connections
are correct before applying power.
LED Indicators
V
EE
LED (D5) and V
DD
LED (D7) indicate if a voltage is
present at these supplies. Verify these LEDs are off before
inserting or removing the daughter card.
Each pairset channel (2 per port) has a respective OUTnM
LED to indicate if the channel is powered on with PoE.
The
INT
LED (D6) indicates if the interrupt line is pulled
low by the daughter card. When the interrupt is cleared
(high) via I
2
C interrupt servicing, the LED is turned off.
Digital Connections
The DC590 (USB to I
2
C) controller board is connected
to the DC2683A at J6 through a 14-pin ribbon cable. The
QuikEval software must be previously installed. When
QuikEval is opened, the software will automatically detect
the DC2685B kit and open the LTC4291-1 GUI.
I
2
C address pins AD3 and AD2 are set with a 2-bit switch
SW3 on the DC2683A. Refer to Table 4 for setting the
individual I
2
C address for each DC2685B kit.
Turret digital test points for SCL, SDA, DGND,
INT
,
MSD
,
and
RESET
are provided on the DC2683A.
RJ45 Connections
PDs are connected using an Ethernet cable to any of the
bottom row ports at 2 × 4, RJ45 connector J1 on the
DC2683A. Test points for each channel output OUT1A
through OUT4B, are provided. Optionally, an Ethernet data
source may be connected with an Ethernet cable to any of
the top row ports at J1.
MSD
and
RESET
Pushbuttons
Pushbutton switch SW1, when pressed, pulls the
RESET
pin of the daughter card logic low. The PSE controller
is then held inactive with all ports off. When SW1 is
released,
RESET
is pulled high, and the PSE returns to
the AUTO pin reset state.
Pushbutton switch SW2, when pressed, pulls the mask-
able shutdown input (
MSD
) pin of the daughter card logic
low. When pressed, all ports that have their corresponding
mask bit set in the mconfig register of the PSE controller
will be shutdown. These ports must then be manually
re-enabled via I
2
C or by resetting the PSE.
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from