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DS90UB953-Q1: Vpoc recommendation for cable with different length

Hao Wang14
Expert 4415 points
Part Number: DS90UB953-Q1

Hi Team,

For the power over cable, is there any recommendation for the power supply voltage if the cable with different length is used?

It's also found that the EMI performance is better when higher voltage is used for a fixed length cable, could you please advise the possible reason?

Thanks and Best Regards!

Hao

  • 0
    TI__Mastermind 18755 points

    Hello Hao,

    Typically a higher PoC voltage will lead to less current draw and therefore less EMC issues with the SERDES link.  We usually recommend a PoC voltage high enough to meet the PoC noise requirements found in the datasheet but not so high as to damage your devices.  Depending on the ratings of LDOs being used and the ratings of passive components I have seen PoC voltages of tens of volts with very little current draw.  As I said the higher voltage usually results in lower current so the maximum allowable voltage is usually dependent on what the system can handle.

    Regards,

    Nick

  • 0 in reply to Nicholas Darash
    TI__Expert 4415 points

    Hi Nick,

    Thanks for the detailed explanation. How about the relationship between the cable length and PoC voltage? For example, if the cable length is increased, should PoC voltage also be increased or unchanged?

    Thanks and Best Regards!

    Hao

  • 0 in reply to Hao Wang14
    TI__Mastermind 18755 points

    Hello Hao,

    I don't believe it will make much of a difference to increase PoC voltage with the length of the cable.  I understand why it make sense to do so but the cables are generally pretty short and typically a maximum length is 15m.  I would say a higher PoC voltage typically leads to less noise but what the voltage should be is really system dependent. 

    Regards,

    Nick