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Community Manager
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Termination of unused pairs when interfacing a I219LM to a 10/100 PHY.

When interfacing a I219LM to a 10/100 PHY, is it acceptable to leave the unused pairs as no connects, or is some manner of termination (Bob Smith?) required?

I'd originally asked this question on the wired Ethernet forum, and was referred here.

https://communities.intel.com/thread/114521 Termination of unused pairs when interfacing a ... |Intel Communities

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Moderator
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Hello, etk:

Thank you for contacting Intel Embedded Community.

Based on the cited thread and in order to be on the same page, could you tell us if your design has been reviewed by Intel? In case that you answer is negative, please follow the steps stated at the https://edc.intel.com/Tools/Design-Review/Default.aspx?language=en Design Review Services website and let us know the results.

Thanks in advance for your cooperation.

Best regards,

Carlos_A.

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Community Manager
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No, the Intel Phy is on a third party "System On Module", which I don't have the design files for. I'm just asking a generic question of what to do with the unused data-pairs of your GBE Phy. This is information that is typically provided on datasheets for PHY's. Does the Phy require termination, or can I N/C them?

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Moderator
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Hello, etk:

Thanks for your clarification.

The information that may help you is stated in section 13.2.1, on page 246 of the https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/ethernet-connection-i219-dat... Intel(R) Ethernet Connection I219 Datasheet.

We hope that this information is useful to you.

Best regards,

Carlos_A.

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Community Manager
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Are you referring to this?

"Sound engineering practices must be followed with respect to unused inputs by terminating them with pull-up or pull-down resistors, unless otherwise specified in a datasheet, design guide or reference schematic."

I'm not sure how I could take any real meaning from that.

Bob smith termination? 75 Ohm pull-downs? 50 Ohm pull down? 50 Ohm pull up's? 10k pull-ups? Pull up to center tap voltage? Pull up to 3.3V?

Here's an example of a Datasheet that clearly states that (for their chip) these pins can be left as N/C, see section 3.8: http://ww1.microchip.com/downloads/en/DeviceDoc/00002096E.pdf http://ww1.microchip.com/downloads/en/DeviceDoc/00002096E.pdf if I can't leave as N/C for your part , what do I do with them?

Can you please provide a direct answer of how these unused pairs should be treated in a 10/100 application, maybe in a format like this:

"Pull to through ."

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Moderator
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Hello, etk:

Thanks for your reply.

In order to help you, we suggest you provide more details to give you specific information that may help you. Due to this fact, could you please give us at least the portion of your schematics related to this thread?

Thanks again for your cooperation.

Best regards,

Carlos_A.

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