DP83TG720S-Q1: DP83TG720S-Q1 Maximum trace length recommended for TRD_P and TRD_M and Maximum cable length

Santhoshwaran Govindaraj

Part Number: DP83TG720S-Q1

Tool/software:

Hi Team,

We are currently in the process of designing our board and need to route the TRD_P and TRD_M (Differential Transmit and Receive) signals. Specifically, we are planning to route these signals for a length of 30 cm on our FR4 PCB.

Could you please confirm if a trace length of 30 cm is acceptable for maintaining signal integrity at 1000Base-T1 (IEEE 802.3bp) standards? Additionally, we would appreciate it if you could provide recommendations for the maximum trace length and any other relevant guidelines for achieving optimal performance with 1000Base-T1.

Furthermore, we are also seeking advice on the recommended cable length for 1000Base-T1. Any specifications or guidelines on this aspect would be greatly beneficial.

Thank you for your assistance. Looking forward to your expert guidance on these matters.

6 months ago

0 Melissa Chang 6 months ago

TI__Genius 14005 points

Hi,

We have an app note available on our layout guidelines here:

https://www.ti.com/lit/an/snla387/snla387.pdf?ts=1725569934151

30 cm is quite long, is there a reason it must be this long? For our devices it must be <5 cm for maintaining signal integrity at 1000Base-T1 (IEEE 802.3bp) standards.

Best regards,

Melissa

0 Santhoshwaran Govindaraj 6 months ago in reply to Melissa Chang

Prodigy 140 points

Hi Melissa,

Can we use SPE cable length up to 40m?

0 Melissa Chang 6 months ago in reply to Santhoshwaran Govindaraj

TI__Genius 14005 points

Hi Santoshwaran,

You should be able to use 40m for type B cabling.

Best regards,

Melissa

0 Santhoshwaran Govindaraj 6 months ago in reply to Melissa Chang

Prodigy 140 points

Hi Melisa,

If I use cable less than 5meters. Can I route the MDI traces little longer?

0 Melissa Chang 6 months ago in reply to Santhoshwaran Govindaraj

TI__Genius 14005 points

Hi Santoshwaran,

Unfortuntely, no. The signal integrity will be directly affected by extending the MDI traces. For instance, you may not pass compliance for Return Loss or Mode Conversion Loss.

Best regards,

Melissa

0 Santhoshwaran Govindaraj 5 months ago in reply to Melissa Chang

Prodigy 140 points

Hi Melissa,

Could you please let us know if there are any link quality (margin) testing tools for SPE, such as an evaluation kit or link quality analyzer? For GMSL, we have a link margin testing kit. Is there a similar kit available for analyzing SPE?

Thanks and Regards,
Santhoshwaran

0 Melissa Chang 5 months ago in reply to Santhoshwaran Govindaraj

TI__Genius 14005 points

Hi Santoshwaran,

Are you asking about a design that has already been printed? If you have already printed the board, you can check the link quality with the DP83TG720 register 0x871. Note that even if the quality is 7/7, it does not necessarily mean you will pass all Open Alliance requirements.

If you want to check whether or not it will pass Open Alliance. you will have to run the tests on the board directly.

Best regards,

Melissa

0 Santhoshwaran Govindaraj 5 months ago in reply to Melissa Chang

Prodigy 140 points

Hi Melissa,

Please let us know how to perform Open alliance test.
We are in the design phase, not yet Fabricated the PCB.

Thanks,
Santhoshwaran

0 Melissa Chang 5 months ago in reply to Santhoshwaran Govindaraj

TI__Genius 14005 points

Hi Santoshwaran,

Which open alliance tests are you trying to qualify your design for?

Best regards,

Melissa

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DP83TG720S-Q1: DP83TG720S-Q1 Maximum trace length recommended for TRD_P and TRD_M and Maximum cable length