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I am using the Novatel OEM729 board for a project, and I need to implement Ethernet in the project.

According to the Novatel OEM7 manual, page 48, the OEM729 does not have Ethernet magnetics, so I have to design my own. According to them, The OEM7 uses the Texas Instruments TKL106 Ethernet PHY. Follow Texas Instruments’ recommendations for transformer selection.

Unfortunately, the TKL106 datasheet contains only a partial list of transformers (only 2), and both of them obsolete. I went back to the OEM7 manual and found the following table, describing the Ethernet transformer characteristics:

Ethernet Transformer Characteristics

So now that I know how these characteristics, how can I find a suitable transformer? I thought that I could use Mouser's filters, for example, but I couldn't find filters that match the parameters in the table.

Please note I cannot use a RJ45 connector.


Another question:

Looking at the TLK106 datasheet, I found this schematic:

TLK106 Reference Schematic

What I don't really understand is the pack of resistors and capacitors on the left. It is said to place them as close to the device, which I assume is the TLK106? But, since that TLK106 is on the Novatel OEM729 board, what can I do? place them as close as possible to the connector (which connects to the Novatel board with a harness) or solder them directly to the wires (on the harness between my board to the Novatel board) so that it would be closer?

Thank you!

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So now that I know how these characteristics, how can I find a suitable transformer?

Just search the vendors like everyone else (such as Farnell): -

enter image description here

The above search found 77 ethernet transformers with a primary inductance of 350 uH.

What I don't really understand is the pack of resistors and capacitors on the left. It is said to place them as close to the device, which I assume is the TLK106? But, since that TLK106 is on the Novatel OEM729 board, what can I do?

Those resistors (or an equivalent circuit) will be on the OEM729 board because, without them being present, the TLK106 won't function correctly - they are line termination resistors and DC biases for the TD and RD outputs and inputs. Appendix F6 of the manual tells you how to make an interface to the magnetics. You don't need to fit these resistors.

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  • \$\begingroup\$ What about the other parameters? Is there a way to filter the search using them or do I have to look at each datasheet until I find what I need? \$\endgroup\$ – Eran Nov 6 '18 at 9:56
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    \$\begingroup\$ Pretty much if you have a magnetization inductance of 350 uH then largely speaking, the other parameters are a given for a similar core dimensions. \$\endgroup\$ – Andy aka Nov 6 '18 at 10:00
  • \$\begingroup\$ Did this answer work for you @Eran? \$\endgroup\$ – Andy aka Dec 13 '18 at 15:05
  • \$\begingroup\$ A little, which is why I upvoted. \$\endgroup\$ – Eran Dec 13 '18 at 21:13
  • \$\begingroup\$ What remains to be answered? Are you able to say? @Eran \$\endgroup\$ – Andy aka Dec 13 '18 at 21:33
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The manual you refer to, in the table 66, recommends the following part:

WE 7499211121A

This is RJ-45 connector with magnetics (transformer) built in, and Digikey says it has 1500 pieces available for shipping.

Related connection circuit is shown in fig. 68, with all required components listed in the table 66.

I can't use an RJ-45 connector, due to lack of space. This is why I have to implement my own magnetics.

You must have stated it in the question.

Update: it seems datasheet you refer to is having a typo: PHY device P/N is TLK106 and not TKL106. And it is not clear if the OEM7 board is having this chip on the board or not apart from stating:

The OEM7 uses the Texas Instruments TKL106 Ethernet PHY

and

The PHY layer is based on the Texas Instruments TKL106 Ethernet PHY.

Second statement assumes that TLK106 is on the board, and your task should be to just attach the components as shown on the figure 68.

You can use any transformer fitting the requirements, for example made by Pulse. This "marketing" sheet lists magnetics with some generic circuit at the last page, you must look into each individual magnetics datasheets to find out the match. For example - H2019NL.

I strongly advise prototyping first - with full diagnosis on the reliability and performance.

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  • \$\begingroup\$ I can't use an RJ-45 connector, due to lack of space. This is why I have to implement my own magnetics. \$\endgroup\$ – Eran Nov 6 '18 at 8:39
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    \$\begingroup\$ You must have stated it in the question. What connector are you going to use? Do you understand the risk of not using standard connector? \$\endgroup\$ – Anonymous Nov 6 '18 at 8:48

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