Verdin Carrier Board Design Guide
Preliminary
– Subject to Change
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2.3.1.2
Media Dependent Ethernet Reference Schematics
Ethernet connectors with integrated magnetics are preferable. If a design with external magnetics
is chosen, additional care must be taken to route the signals between the magnetics and Ethernet
connector. If only a fast Ethernet (100Mbit/s) is required, some design costs may be saved by using
only 10/100Base-TX magnetics.
The magnetics provide a certain ESD protection which is enough for many designs. However,
especially in Power over Ethernet (PoE) systems, additional transient voltage suppressor diodes
(TVS) are highly recommended to be placed between the module and the magnetics. More
information can be found in the following application note from Microchip:
http://ww1.microchip.com/downloads/en/AppNotes/00002157B.pdf
The LED output signals ETH_1_ACT and ETH_1_LINK are 3.3V tolerant open drain signals with no
pull-up resistor on the module. The pins can be connected directly to the LED of the Ethernet jack
with suitable series resistors. There is no need for additional buffering if the current drawn does
not exceeds 10mA. The ETH_1_ACT signal is used as reference for the ETH_1_MDI2_P signal on
the SODIMM connector and the ETH_1_LINK is a reference for the ETH_1_MDI1_P signal.
Therefore, it is recommended to add a strapping capacitor of 1nF to GND as close as possible to
the SODIMM connector.
2.3.1.2.1 Gigabit Ethernet Schematic Example (Integrated Magnetics)
The Verdin module does not require a center tap voltage. Therefore, add individual 100nF
capacitors to the center taps of the magnetics. Do not connect the center taps together.
The Ethernet connector with integrated magnetics provides a certain amount of protection against
ESD. If a higher level is required, optional ESD protection diodes are recommended.
Figure 11: Gigabit Ethernet with integrated magnetics reference schematic
2.3.1.2.2 Gigabit Ethernet Schematic Example (Discrete Magnetics)
If discrete magnetics are used instead of a RJ-45 Ethernet jack with integrated magnetics, special
care must be taken to route the signals between the magnetics and the jack. These signals are
required to be high voltage isolated from the other signals. Therefore, it is necessary to place a
dedicated ground plane under these signals which has a minimum separation of 2mm from every
other signal and plane. Try to place the magnetics as close as possible to the Ethernet jack. This
reduces the length of the signal traces between the magnetics and jack.
Ethernet Connector
ETH_1_MDI1_P
ETH_1_ACT_C
ETH_1_LINK_C
+V3.3_SW
+V3.3_SW
ETH_1_LINK_GB
1nF
50V
C104
GND
1nF
2KV
C115
GND
GND_CHASSIS
GND
A829-1J1T-KM
CT0
12
D1+
4
D1-
5
D0+
11
D0-
10
CT1
6
C
13
A
14
C
15
A
16
1
2
3
6
yellow
green
orange
4 X 75R
1000pF 2kV
S
S
2
S
S
1
CT2
1
D2+
3
D2-
2
4
5
CT3
7
D3+
8
D3-
9
7
8
C
17
X12
ETH_1_MDI1_N
ETH_1_MDI0_P
ETH_1_MDI0_N
ETH_1_LINK
ETH_1_ACT
ETH_1_MDI3_N
ETH_1_MDI3_P
ETH_1_MDI2_N
ETH_1_MDI2_P
ETH_1_ACT
ETH_1_MDI0_P
ETH_1_MDI0_N
ETH_1_LINK
ETH_1_MDI3_N
ETH_1_MDI3_P
ETH_1_MDI2_N
ETH_1_MDI2_P
ETH_1_MDI1_P
ETH_1_MDI1_N
100nF
16V
C109
GND
ETH_1_CTREF_3
100nF
16V
C107
ETH_1_CTREF_2
100nF
16V
C106
ETH_1_CTREF_1
100nF
16V
C105
ETH_1_CTREF_0
GND
GND
GND
ETH_1_MDI[0..9]
ETH_1_MDI1_P
233
ETH_1_MDI1_N
231
ETH_1_MDI0_P
225
ETH_1_LINK
235
ETH_1_ACT
237
ETH_1_MDI0_N
227
ETH_1_MDI3_N
245
ETH_1_MDI3_P
247
ETH_1_MDI2_N
241
ETH_1_MDI2_P
239
X1J
2309409-2
1M
R163
D3V3F4U10LP -7
8
3
1
2
4
5
D11
D3V3F4U10LP -7
8
3
1
2
4
5
D23
1nF
50V
C111
GND
330R
R71
330R
R72
330R
R87
GND
GND
GND
GND
