topic i210 Center tap in Embedded Connectivity

i210 Center tap

BenStrawbridge — Tue, 07 Nov 2023 11:58:04 GMT

Hello

Designing using the i210 the reference schematic (Doc number 490115) connects the center tap pins together (see page 4, note and L2 connections). The Datasheet doesn't have any recommendation other than in section 12.5.6.9 (rev 3.7 Jan 2021) to add a capacitor to the centre taps and do not connect to a power rail. can you confirm the correct connection for these please?

Kind regards

Ben Strawbridge

Re:i210 Center tap

Fariz_Intel — Tue, 07 Nov 2023 20:59:08 GMT

Hi BenStrawbridge,

We have a forum dedicated to these specific issues, and we are moving it to the Embedded Connectivity Forum so that it can get answered promptly.

Best regards,

Fariz_Intel

Re: i210 Center tap

Diego_INTEL — Thu, 09 Nov 2023 05:18:25 GMT

Hello @BenStrawbridge,

Thank you for contacting Intel Embedded Community.

I verified it and this is what is being recommended, to connect the pins together as it is shown in the datasheet.

"The I210 includes a voltage mode driver so it doesn’t require an analog powered center tap. The decoupling capacitors for the central tap pins should be placed as close as possible to the magnetic component. This improves EMI compliance."

Best regards,

@Diego_INTEL

Re: i210 Center tap

BenStrawbridge — Thu, 09 Nov 2023 09:02:54 GMT

Hello,

I understand but the evaluation schematic connects all center taps together but this isn't mentioned in the datasheet. can you confirm if I should connect all centre taps together?

Kind regards,

Ben Strawbridge

Re: i210 Center tap

Diego_INTEL — Fri, 10 Nov 2023 01:20:27 GMT

Hello @BenStrawbridge,

Yes, in this topology they are connected together and is what is being recommended, but I read further and found that other vendors recommend to separate the center taps, check this:

https://ww1.microchip.com/downloads/en/Appnotes/VPPD-01740.pdf

In section 3.5:

"To minimize stray current flows between pairs on a cable, the magnetic should route out the transformer center-taps on individual pins so each can be individually AC-coupled. Ganged connections of multiple center-taps, whether connected directly or by chokes, are not recommended. Board designs that require lower pin counts should consider integrated magnetic modules with individually decoupled center taps routed into a single ground pin."

Looking further, in the schematic of the X557 the center taps are separated from each other.

https://www.intel.com/content/www/us/en/content-details/612526/intel-ethernet-connection-x557-at2-with-intel-xeon-processor-d-1500-product-family-b-step-reference-schematic.html?wapkw=x557%20design%20schematic&DocID=612526

The latest version of the schematic for the i210 is from 2015, it is kind of old, in my opinion it may be best to separate center taps from each other but I have not seen any issue reported if they are connected together.

Best regards,

@Diego_INTEL