Magnetics for ENC28J60

[avishay]

Hello all,
I would like to know if I can use an RJ45 socket+transformer combo I
ripped off a board that used Realtek 8139 for making some experiments
with ENC28J60. Are all Ethernet transformers alike? I have noticed that
in 8139 reference design, there are four 75 ohm resistors connected
between all the Ethernet lines to the groud. The ENC28J60 doesn't
specify them. In the socket I have, it seem like these resistor are
already assembled. Should I try to remove them?

Thanks,
Avishay

 

[Deefoo]

Hello all,
I would like to know if I can use an RJ45 socket+transformer combo I
ripped off a board that used Realtek 8139 for making some experiments
with ENC28J60. Are all Ethernet transformers alike? I have noticed that
in 8139 reference design, there are four 75 ohm resistors connected
between all the Ethernet lines to the groud. The ENC28J60 doesn't
specify them. In the socket I have, it seem like these resistor are
already assembled. Should I try to remove them?

Thanks,
Avishay

The resistors are for line termination (if there are caps as well it may be
a "Bob Smith Termination"), Don't bother trying to remove them.

Some time ago I've looked a bit at Ethernet transformers and found that
there are quite a lot of them. They all do the same job, but some do it
better than others.

--DF