DP83826E: Ethernet PHY In Passthrough

Diang Xing

Mastermind 37101 points

Part Number: DP83826E

Tool/software:

Hi Team,

We are designing a PoE passthrough circuit. Could you help to comment:

1. Is the termination circuit for the PHY correct?

2. Do we need to add any chips to avoid data attenuation. If considering the input and output Ethernet cables are both up to 100m?

3. Could you help to comment the layout for data wires? Any related application notes. Thanks!

Best regards,

Diang

over 1 year ago

0 Gerome Cacho over 1 year ago

TI__Mastermind 39835 points

Hello,

The circuit looks okay, but we don't have much expertise in non-TI PHY Ethernet related circuitry.

The would be a concern of cable reach as most PHYs should reach up to 100m end to end. It appears this is 200m end to end.

Overall, the traces look very sharp, but for further guidance, we do have our layout checklist, located on all of our PHYs product portfolios. As rules of thumb, the MDI should keep its impedance match consistent. There should also be no ground under the magnetics to avoid coupling, while there is GND below the MDI traces to give proper return path.

Sincerely,

Gerome

0 Diang Xing over 1 year ago in reply to Gerome Cacho

TI__Mastermind 37101 points

Hi Gerome,

Thanks for your reply!

This is actually a PoE passthrough / daisy chain circuit. It could be similar to below diagram via (https://cc.cs.1worldsync.com/inlinecontent/mediaserver/stech/811/354/811354494da74443b290af9bda4b705e/original.pdf). Considering the data transmission distance is beyond 100m, and there may be some attenuations or distortions by data transformer, do you recommend to add some circuits to avoid data loss?

Best regards,

Diang

0 Gerome Cacho over 1 year ago in reply to Diang Xing

TI__Mastermind 39835 points

Hi Diang,

We have no passive recommendations to buffer this circuit from our BU side. Perhaps HSSC has some ICs which can help. The only way we can see this possible is a cable repeater application which would require a PHY inside the middle box.

Sincerely,
Gerome

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DP83826E: Ethernet PHY In Passthrough