Ethernet Reference Schematic - Novatel OEM6 Series User Manual

FB100
OEM628_ETH_CENTRETAP
P1502, pin 3
OEM628_ETH_CENTRETAP
P1502, pin 6
ETH_3V3
FB101
OEM628_ETH_TD+
P1502, pin 4
DIFF PAIR (100 ohm)
OEM628_ETH_TD-
P1502, pin 5
OEM628_ETH_RD+
P1502, pin 2
DIFF PAIR (100 ohm)
OEM628_ETH_RD-
P1502, pin 1
C103
0.1μF
D
You must provide 100 Ω ±10% differential pairs over unbroken reference (ground) planes up to the pins
on the Ethernet magnetics. Beneath and beyond the magnetics, there must be no ground plane (no
copper on layers other than the traces shown here). Ensure that the Ethernet differential pairs in the
voided area are also 100 Ω ±10% (the widths/spacing are different).
The transient suppression components must be placed as close to the RJ45 jack as possible. U101 and
U102 protect the OEM628 against differential mode transients. The Ethernet magnetics provide high
voltage isolation and low capacitance TVS devices on the OEM628 card itself protect against common
mode transients.
The spacing between receive and transmit pairs should be at least three times the width of each
differential pair (both traces plus the separation distance) to minimize crosstalk. Avoid more than two
layer changes (single layer routing is best) and ensure that reference planes do not change when
changing layers. If in doubt, contact your PCB vendor for appropriate dimensions for the differential pairs.
Keep vias on the lines to a minimum (ideally, no vias). If a layer change is required, ensure that the
reference plane does not change to prevent increased radiated or conducted emissions.
Ethernet cable type (Cat5/Cat5e/Cat6) does not affect the OEM628 emissions profile with a properly laid
out PCB. The following table gives recommended Ethernet transformer characteristics.
Alternately, use modular jacks with built-in Ethernet magnetics. In that case, run 100 Ω differential pairs
over unbroken reference planes directly to the jack. Ensure the integrated magnetics in the jack meet the
specifications in the table below. Ensure that the jack is no more than 15 cm (6 inches) from the OEM6
connector. Shorter runs are better.
Ethernet cable type (Cat5/Cat5e/Cat6) does not affect the OEM628 emissions profile with a properly laid
out PCB. The following table gives recommended Ethernet transformer characteristics.
An example of a modular jack with integrated Ethernet magnetics is provided in Figure 67. The part and
circuit shown there would be suitable for the OEM628 as well. It is worth noting, however, that
environmentally-sealed versions of the jack with integrated magnetics may not be readily available.
OEM6 Family Installation and Operation User Manual Rev 7
Figure 67: Ethernet Reference Schematic
ETH_3V3
C100 C101 C102
0.1μF 0.1μF 0.01μF
D D D
ETH_3V3
C105 1000pF
1206 2kV
D
FB102
U100
9
T1_N
10
T1_CT
11
T1_P
12
NC1
13
NC2
14
T2_N
15
T2_CT
16
T2_P
HALO TG110-E050N5RL
C104
0.1μF
C106 1000 pF
1206 2kV
D D
Transient Suppression
(near RJ45 connector)
R100
U101
49.9-1%
PLC03-6
ETH_TD+
8
1 8
T1_PS1 IO4
IO1
2 7
GND4
DIFF PAIR GND1 DIFF PAIR
3
6
(100 ohm) (100 ohm)
GND2 GND3
7
4 5
T1_CTS IO2 IO3
ETH_TD-
6
T1_PS2
5
NC3
4
NC4 U102
PLC03-6
ETH_RD+
3 1 8
T2_PS1
IO1 IO4
2 7
DIFF PAIR GND1 GND4 DIFF PAIR
3
6
(100 ohm) (100 ohm)
GND3
GND2
2
4 5
T2_CTS
IO3
IO2
ETH_RD-
1
T2_PS2
R101
49.9-1%
All planes voided beneath these traces!
MODULAR JACK
1
TX+
2
TX-
3
RX+
4
NC1
5
NC2
6
RX-
7
NC3
8
NC4
SHELL1 SHELL2
C107
1000pF
C108
1206 2kV
1000pF
1206 2kV
D
135