I'm just getting started with an LS2 and was wondering what the intent
of the spare pair connections on the RJ45 ... it looks like one is
grounded and the other goes to AVDD33. Is it intended to be used as a
supply connection (in which case how can the 1v8 supply be derived) or
is it for biasing/powering some other circuit on the other end of the
twisted pairs ?
I recognize the jack used on the LS1 was larger and more expensive but
it did give a couple options for using POE, it seems like it would have
been useful to have left the spare pairs unconnected ... I was going to
disconnect the AVDD33 at the ferrite bead but noticed it also supplies a
pin on U4 (eth phys), will need to review the datasheets for it.
Insights appreciated, thanks.
All the signals you see on the schematic are going to the board side
of the transformers, and the supplies there are just for biasing.
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