DP83867E: How does this part interface to RJ45 integrated magnetics?

John11513

Part Number: DP83867E
Other Parts Discussed in Thread: DP83TG720EVM-MC, DP83TC812EVM-MC

Hi team,

The datasheet of this part says it can interface with integrated or discrete magnetics. However, the center tap of 1000M Ethernet integrated Magnetics always have single center tap pinout, all center taps of 4 coils have been connected together in RJ45. Does not meet the requirements of this part.

I am thinking this special requirements of DP83867 maybe is due to the mismatched common mode output voltage from each port. If so, is it possible to connect PHY signal to magnetics through AC coupling caps? With this AC coupling caps, is it possible to use this kind of integrated magnetics? (common center tap) If the answer is YES, how should the common center tap be connected? Connected to GND directly?

Thank you!

John

over 2 years ago

0 Gerome Cacho over 2 years ago

TI__Mastermind 39775 points

Hi John,

There are numerous 1G Mag-Jacks in the market in many different flavors; not just center tap short. For example, our DP83TC812EVM-MC (which has DP83867) has a 1G mag-jack which is compatible; AR11-4647. DP83TG720EVM-MC (also has DP83867) has 7499111614A.

Sincerely,

Gerome

0 John11513 over 2 years ago in reply to Gerome Cacho

TI__Expert 5720 points

Hi Gerome,

Thank you!

Yes we can find different magnetics, thank you for proposal.

I am just curious Why some device has such requirement, while some others not. Such as our device requires isolated center taps, while RT8211 does not have such requirement (RT8211 is also voltage mode MDI). This question is also from my customer.

Additionally, I am also curious, if the center taps have been shorted together, how about grounded the center tap and feed the signal from PHY to transformer through DC blocking caps?

Regards,

John

+1 Gerome Cacho over 2 years ago in reply to John11513

TI__Mastermind 39775 points

John,

We have tested our PHY with these configurations in the datasheet only. Any case that deviates from this configuration is solely on the customer to validate.

Sincerely,

Gerome

0 John11513 over 2 years ago in reply to Gerome Cacho

TI__Expert 5720 points

Ok, understand.

Thank you!

John

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DP83867E: How does this part interface to RJ45 integrated magnetics?