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DS90UB941AS-Q1: Using a passive mux for cable swapping

Eric Steimle
Expert 2200 points
Part Number: DS90UB941AS-Q1
Other Parts Discussed in Thread: HD3SS460,

I want to use the DS90UB941 over a USB-C cable in a proprietary alternate mode. I'm thinking that I can use the TI HD3SS460 for this.  The HD3SS460 can swap all four pairs and it says it accepts up to a 1.8Vpp signal with 0-2V common mode.  It looks like the 1.8Vpp is okay per the DS90UB941 datasheet, but I did not see anything about the common mode level for the FPDIII signals. I see they are capacitively coupled on the output and the input at the deserializer though.

Does this sound like it should work?

Thank you

  • 0
    TI__Guru* 98415 points

    Hello Eric,

    Based on the s-parameters model for HD3SS460 on the product page, the IL/RL performance looks suitable for muxing DS90UB941AS-Q1. The common mode level can with the FPD-Link devices since they have a common mode of 550mV and a single-ended swing of 600mV max. 

    The channel requirements for FPD-Link can be provided under NDA, so if you would like to discuss that please send me a private E2E message. The main point for FPD-Link is that the full channel s-parameters between SER/DES (insertion loss, return loss, crosstalk) must meet the FPD channel spec which includes PCB on both sides, cables, and connectors in-between. The specs of the HD3SS460 have slightly mode low frequency insertion loss than our usual PCB portion of the loss recommendation, but so long as the cable length/cable type have low insertion loss, the total channel can likely still meet the spec which will ultimately depend on the cable type/quality here.

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Expert 2200 points

    Thank you that makes sense. I'll send a private message.