DS250DF810: CONFUSION OVER RX TX AND USAGE FOR ETHERNET

Wesley Andrews

Part Number: DS250DF810
Other Parts Discussed in Thread: DP83869

HI there,

I hope you are well,

I have some questions regarding the correct way to connect this device inline with 2 ethernet connectors (RJ45), as if this device was in the middle of a cable or PCB backplane. I have had a look at the EVM schematic and it has thrown some confusion to my normal understanding of RX/TX pairs, as the TX lines from the QSFP device are connected to the TX lines of the DS250F810 and the same fort he RX lines.

Here's a brief overview of my usage scenario:

I have 2 ethernet connectors (RJ45) I currently have connected them pin to pin as a passive Ethernet cable extender, I want to also build a device that will allow me to make an active ethernet extender, with the DS250F810 in the middle of the 2 RJ45 connectors and Pin to pin linked, such that from the perspective of the connected devices it would be like it was just a standard cable connected, just with an inline signal conditioning capability.

Questions

1. Do I connect RX+/- from ethernet RJ45 TO RX +/- of DS250F810 or is it RX+/- of Ethernet RJ45 connector to TX+/- of DS250F810 and vice versa ( I have attached a PDF to illustrate these examples)0652.DS250F810 LAYOUT EXAMPLES.pdf

Please let me know which example (1 or 2) is correct :).

2. is there a programming guide/example code I can use with the VSCode/Arduino environment/STM32, or any code I can port myself?

Thank you in advance for any advice :).

Kind regards

Wes

8 months ago

+1 Drew Miller1 8 months ago

TI__Mastermind 23727 points

Hi Wes,

Example 1 is the correct signal chain.

Is it correct that you are using base-T Ethernet signaling? The DS250DF810 is not designed for base-T Ethernet signaling, I would not recommend using this device for this application. Base-T electrical signaling is different than electrical signaling for 25Gbase-R applications.

Thanks,

Drew

0 Wesley Andrews 8 months ago

Prodigy 60 points

Hi Drew,

Thank you for your response,

Yes I am using Base-T signalling, I didn't realise this part was not suitable. Can you suggest a suitable part number please?

Kind regards

Wes

0 Drew Miller1 8 months ago in reply to Wesley Andrews

TI__Mastermind 23727 points

Hi Wes,

Please allow me to loop in the Ethernet PHY team to better advise on this. I believe that some PHYs can be used in a repeater mode.

Also, can you please share what data rate you are trying to support? Is this 1000Base-T?

Thanks,

Drew

0 Wesley Andrews 8 months ago in reply to Drew Miller1

Prodigy 60 points

Hi Drew,

Thank you, yes application is up to 1000base-T, I need a repeater/redriver for the application, as this will be used in PCB backplane applications for some legacy equipment as well and as cable extension.

Alternatively are there any ICs available that can be used on single differential pairs to buffer/repeat/condition incoming signals?

I was also hoping this device would be protocol agnostic such that it could handle Ethernet/HDMI/DVI/ any differential signal.

Thank you again for your help.

Kind regards

Wes

+1 Drew Miller1 8 months ago in reply to Wesley Andrews

TI__Mastermind 23727 points

Hi Wes,

Wesley Andrews said:
Alternatively are there any ICs available that can be used on single differential pairs to buffer/repeat/condition incoming signals?

I was also hoping this device would be protocol agnostic such that it could handle Ethernet/HDMI/DVI/ any differential signal.

We have a variety of signal conditioning devices, but once a rate in Gbps is reached, these devices are generally application specific rather than general purpose due to specific electrical/termination/coupling requirements associated with different protocols.

I think we have discussed this a bit in the past.

https://e2e.ti.com/support/switches-multiplexers-group/switches-multiplexers/f/switches-multiplexers-forum/1321157/tmux136-application-and-cascade-capability/5050267#5050267

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1324357/tusb501-general-enquiries

Thanks,

Drew

0 Wesley Andrews 8 months ago in reply to Drew Miller1

Prodigy 60 points

Hi Drew,

Thank you again, apologies for asking the same question twice there aha! I'm currently trying to ascertain all the information I can, as the application is for a research project :).

Once again thank you for your help.

Kind regards

Wes

0 Hillman Lin 8 months ago in reply to Wesley Andrews

TI__Mastermind 23175 points

Hi Wesley,

Is this the application what you looking for?

RJ45 connector < -- > PHY < -- > PHY < -- > RJ45 connector

If so, we do have two Gigabits PHYs that could perform this back to back application:

DP83867
DP83869

Regards,

Hillman Lin

0 Wesley Andrews 8 months ago in reply to Hillman Lin

Prodigy 60 points

Hi there,

Thank you for your reply,

I am intending my application to be as follows:

RJ45 <-->PCB TRACE<-->SIGNAL CONDITIONING<-->PCB TRACE<-->RJ45

Kind regards

Wes

0 Hillman Lin 8 months ago in reply to Wesley Andrews

TI__Mastermind 23175 points

Hi Wesley,

May I ask what is the "signal conditioning" you are looking for?

Regards,

Hillman Lin

0 Wesley Andrews 8 months ago in reply to Hillman Lin

Prodigy 60 points

Hi there,

The signal conditioning, is for PCB backplane losses primarily and signal degradation reduction/prevention.

Kind regards

Wes

+1 Hillman Lin 8 months ago in reply to Wesley Andrews

TI__Mastermind 23175 points

Hi Wesley,

If you are looking for repeater mode, the signal boost back when the signal pass through the PHY. This application is mainly used when the signal attenuate more than expected.

Regards,

Hillman Lin

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DS250DF810: CONFUSION OVER RX TX AND USAGE FOR ETHERNET