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DS90UB954-Q1: Alternating between coax and STP mode

Simon Wright
Prodigy 20 points
Part Number: DS90UB954-Q1

Hi

we are currently using the DS90UB954-Q1 on one of our boards with input 0 (RIN0) connected to a coax connector. Input 1 (RIN1) is currently not used.

We are looking into extending our board to offer both coax and STP inputs. For this we would like to connect the currently unused RIN1 input to a STP connector. As the DS90UB954-Q1 has to be configured for coax or STP only one input can be active at the same time which is fine for us. We are using power-over-coax and will provide the same voltage over STP.

Can you confirm that this approach works? Are there any pitfalls we should consider?

Many thanks

  • 0
    TI__Genius 10475 points
    Hello,
    Just to confirm you are trying to set up your board to support either STP or coax or together? As you said the settings would need to be set differently for the two modes - strap settings, reg 0x6D[2] etc.
    It is possible to use power over STP with the 953/954 with some modifications.
  • 0 in reply to Palaniappan Manickam
    Prodigy 20 points

    Hi

    the board has to support STP _and_ coax if possible.

    However, only one of the two inputs will be active at the same time.

    - Serializer is connected to the coax input (connected to RIN0) -> configure deserializer for coax mode in register 0x6D, set PORT0_EN to 1 and PORT1_EN to 0 in register 0x0C

    - Serializer is connected to the STP input (connected to RIN1) -> configure deserializer for STP mode in register 0x6D, set PORT0_EN to 0 and PORT1_EN to 1 in register 0x0C

    Can you confirm that this is possible?

    What modifications are you referring to regarding power over STP? Our STP connector has dedicated power and ground lines which we plan to connect to the same DC voltage used for power over coax.

    Regards

  • 0 in reply to Simon Wright
    TI__Expert 8135 points
    Hello-

    That is possible.

    I believe my colleague was referring to the use case with only a single twisted pair (the power sent over the same TP as the data). In that case, there is a need for extra circuitry (PoTP filter similar to PoC filter). In your case, the power and data are sent over separate twisted pairs, so there is no need for the extra circuitry.

    Regards,
    Davor