POEPHYTEREV-I / -E User
Guide
National Semiconductor
Application Note 1521
Youhao Xi Bradley Kennedy
April 4, 2008
Introduction
The POEPHYTEREV-I/-E evaluation board is a seamless de-
sign demonstrating National’s LM5072 PoE product (capable
of up to 24W) and DP83848I (single port 10/100Mb/s) Ether-
net PHYTER® product. While both the LM5072 and the
DP83848 Ethernet PHY device have many advanced and
enticing features, this specific board is designed to demon-
strate a subset of those features, specifically Power over
Ethernet. Two versions of this board are available. The –I
version has an RJ-45 connector that with integrated Ethernet
magnetics. The –E version has discrete RJ-45 connector and
Ethernet magnetics. The schematics of the board are avail-
able with this kit for duplication into an end application prod-
uct.
For additional features of the PoE and PHY devices, individ-
ual device evaluation boards are separately available. For
detailed information about the complete functions and fea-
tures of the LM5072 or DP83848 devices, refer to the relevant
datasheets. For applications where IEEE 802.3af must be
complied with and the power level is below 12.95W, refer to
Application Note AN-1455 (www.national.com/an/AN/
AN-1455.pdf). For detailed information about the Ethernet
PHYTER® circuit, refer to Application Note AN-1469
(www.national.com/an/AN/AN-1469.pdf).
This evaluation kit contains:
•
POEPHYTEREV-I or –E Evaluation board
•
Printed copy of this User's Guide
•
Board schematic
•
End User Licensing Agreement (EULA)
Scope of Applications
The POEPHYTEREV-I/-E evaluation kit (EK) is designed for
high power PD (PoE terminology - Powered Device) applica-
tions in which the maximum power exceeds the IEEE
802.3af’s 12.95W limit. The evaluation board features
National’s DP83848 10/100 Mb/s PHYTER® Ethernet Phys-
ical Layer Transceiver, so any equipment that provides a
standard IEEE 802.3, Clause 22 MII DTE interface; e.g.
SmartBits/Netcom box, is required as a data source for the
Ethernet device. The LM5072 is a 100V, high power PoE PD
and PWM controller. The evaluation board is capable of op-
erating with both PoE and auxiliary (AUX) power sources. The
dc-dc converter stage of the power supply is implemented in
the versatile flyback converter topology.
Important Note on Circuit Board
Versions
There are two versions of PCBs being built, which can be
identified by the PCB serial number printed along the left edge
of the top side the circuit board. One version is labelled
551012916-001 Rev A, the other 551013040-001 Rev A. The
first version cannot modify the 3.3V output to higher voltages
because it is directly connected to the PHY through inner lay-
ers. It is modified on the second version such that higher
output voltage can be produced without damaging the PHY
circuit. The factory default output setting for both versions is
3.3V. Contact National on support to modify the latter version
to other output voltage.
In the following, descriptions apply to both versions of the cir-
cuit boards unless specifically indicated.
Features of the Evaluation Board
Seamless design solution, incorporating DP83848
PHYTER® single port 10/100 Mb/s Ethernet physical layer
transceiver and LM5072 High Power PoE PD and PWM con-
troller.
Ethernet
•
Integrated or External magnetics and RJ45
•
Minimum configuration requirements:
2 PHY Addresses - 01h (default) or 03h
Status LEDs – board power, others dependant on LED
mode selected
Limited Strap Options – MDIX_EN, LED_CFG,
PWR_DWN/INT, MII/RMII Sel
RESET_N jumper
PWR_DWN/INT jumper
•
Connections for the following interfaces:
MIl/RMII Interface (IEEE 802.3 standard)
RJ-45 Cat-V Ethernet cable connector
JTAG header
25MHz_OUT header
Header for “ribbon cable” connection to MII/RMII
•
On-board clock – Crystal/Oscillator Dual Footprint
Power Over Ethernet
•
Isolated output voltage: 3.3V
•
Maximum output current: 7.3A
•
Maximum output power: 24W
•
Input voltage ranges:
PoE input voltage range: 39 to 57V
AUX input voltage range: 22 to 57V
•
Measured maximum efficiency:
DC to DC converter efficiency: 90% at 6A
Overall efficiency (including the input diode bridge):
86% at 6A
•
Overall Board Size: 5.50” x 3.96” x 0.70”
•
Switching frequency: 250 kHz
•
Optional input common-mode filter
PCB Layout Considerations
•
FR4 material
•
Trace symmetry within differential pair (±0.5")
•
Differential impedance 100 ohms, ±5%
•
Adjacent differential pairs spacing > 2X distance within a
differential pair, to minimize cross-talk and EMI
•
Trace length matching between differential pairs not
required
•
Uniform supply & ground plane
•
Void planes under magnetics, except for Chassis GND (at
RJ-45 edge only)
•
Combination of through-hole and surface mount
technology
•
Trace/space will be 0.007”/0.008” minimum
© 2008 National Semiconductor Corporation
202052
www.national.com
POEPHYTEREV-I / -E User Guide
AN-1521
