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Daisy chaining TSB83AA23

Elvis Mota1
Prodigy 80 points
Other Parts Discussed in Thread: TSB83AA23

Hi,

I'm designing a custom board that will use three TSB83AA23 PHY devices as shown in the inserted image:

2235.ieee-phy.ppt

I understand the termination and connection for the taps that will be connecting the PHY to the 1394 connectors. I also understand that the PHY that will only have one active tap will need to have the other two ports properly terminated.

My question is in regarding the connection of ports between PHY devices. Should the pairs be terminated the same way as if they were connecting to a cable?

Regards,

Elvis

  • 0
    TI__Guru* 76130 points

    Hello,

    Yes, both sides need to be terminated.

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 80 points


    Hi Elias,

    Thank you for your response. Could you please be a bit more specific?

    If I understood you correclty, the pairs connecting to PHY#1 are terminated. These pairs are then routed to PHY#2 where they will again be terminated.

    I want to make clear that these PHY devices will be on the same PCB next to each other.

    Regards,

  • 0 in reply to Elvis Mota1
    Guru 316940 points

    The datasheet says:

    The line drivers are designed to work with external 112-Ω termination resistor networks to match the 110-Ω cable impedance. One termination network is required at each end of a twisted-pair cable.

    Even without an actual cable, you must pretend that there is a (very short) cable between these ports.

    Please note that the PIL-FOP interface is essentially a connection between two adjacent PHY chips; see section 9.3.8.3 of IEEE1394-2008, and especially figure 9-24.