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DS90UB953-Q1: PoC design about inverting signal termination

Fumiyasu Seino
Prodigy 30 points
Part Number: DS90UB953-Q1

Tool/software:

Hi team

I have looked at datasheets and videos regarding PoC circuits, but in the layout of a single PoC circuit, what is the significance of extending the transmission line of the inverted signal (the one not connected to the connector) up to the vicinity of the connector and terminating it to GND?

If it is going to be connected to GND, I thought it could be done anywhere, not necessarily near the connector, so I would like to know the reason.

Reference:Power over Coax (PoC) Design | Video | TI.com　Power Over Coax Design Guidelines for DS90UB953-Q1

Regards,

Seino

  • 0
    TI__Guru** 107670 points

    Hello seino,

    The only advantage of that approach when routing both P & N traces as differential pairs, is to cancel the common-mode noise, which can help improving immunity and EMC performance. If you think that is not required on your design, feel free to make the N trace as short as possible and terminate near the device.

  • 0 in reply to Hamzeh Jaradat
    Prodigy 30 points

    Dear Jaradat san,

    Thank you for your response.

    If there are benefits in the case of differential pairs, does that mean there is no particular significance in bringing the P and N lines close to the connector when the P side is connected to the connector and the N side is connected to GND?

    Regards,

    Seino

  • 0 in reply to Fumiyasu Seino
    TI__Guru** 107670 points

    Hello,

     

    The team is out due to a public Holiday in the US. Responses will be delayed until Monday.

    Thank you for your patience.

  • +1 in reply to Fumiyasu Seino
    TI__Guru** 107670 points

    Hello Seino-san,

    As I said, the only advantage when you route the N line as differential to the P line and length match them is only to cancel the common mode noise. Correct, if these two traces are just equal in length but not routed as differential pair, then there is no actual benefit.