On 15/12/05, Olin Lathrop <olin_piclist@embedinc.com> wrote:
> kravnus wolf wrote:
> > What kind of ethernet transformer can be used with
> > this
> > IC? I am not familiar with the function of an ethernet
> > transformer.
>
> Anything sold as a "ethernet transformer" should work as their
> characteristics are specified in the ethernet standard, at long as one side
> of the windings are center tapped since the ENC28J60 requires that.  I'm
> using Pulse Engineering H2019.  This has center tapped windings on both
> sides which I need since this device can also be powered over ethernet.  if
> yours doesn't, you can get away with center tapped on one side only.
>
>
> ******************************************************************
> Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC

Olin,

Isn't the turns ratio also important (but maybe not critical)   I
spent a fair bit of time looking for an ethernet transformer with the
correct turns ration and tapping for a previous project. IIRC the
turns ratio is different depending on whether you are using 5V or 3.3V
supplies, as well as different chip requirements (presumably related
to the output drive circuit).

Or is it something that works regardless and a matched source &
termination isn't really that critiacl once cable losses are included
in the calculation?

RP

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