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TUSB1002: Designing for SATA, USB & PCIe (multiplexed)

Aaron Mills1
Prodigy 20 points
Part Number: TUSB1002

I have a complicated application requiring USB 3.0, PCIe Gen 3 and SATA support and I'm trying to determine if it is possible to multiplex these three standard protocols through a common buffer system based on TUSB1002.

The TUSB1002 component describes designing for USB 3, PCIe and SATA. Figure 18 illustrates an approach for USB 3.x and Figure 22 for SATA+PCIe. But it's not clear to me if it is possible to create a circuit (capacitors, filters, etc) which can support all three in a multiplexed environment  (e.g. three separate host interfaces multiplexed onto a common outbound bus, terminated on the host side by a buffer such as TUSB1002).

Is TI aware of any hard limitation, either in the part itself or due to differing requirements of the three standards, why the part couldn't be configured to support all three protocols in the same circuit?

 

  • 0
    TI__Guru 64326 points

    Hi Aaron,

    I recommend using TUSB1002A however there is a hard limitation here. SATA AC coupling requirement are very different from PCIe and USB 3.0 (these are similar) making it impossible to implement only one TUSB1002A to accommodate all three interfaces. Please refer tot eh second paragraph of section 8.3.2 Detailed Design Procedure in the TUSB1002A datasheet. 

  • 0 in reply to Malik Barton57
    Prodigy 20 points

    Hi Malik, 

    Thank you very much for pointing this out:

    SATA: 12nf max
    PCIe: 75-265nF
    USB3: ~100nF

    However, I noticed also in that section they described an approach to adding a special pulldown network with an NFET. My guess is that you could design for PCIe & USB (using say 100nF cap) and add the switched pulldown as specified. What's not clear to me is why it's only needed on the device side--it seems like the TX interface back to the host would have the same problem, not "seeing" the proper termination on the receiver.

    Am I misunderstanding something there?

  • 0 in reply to Aaron Mills1
    TI__Guru 64326 points

    Hi Aaron,

    No the external NFETs an pull-downs are only needed for the AC coupling in between TUSB1002A and the miniCard/mSATA socket. The AC coupling (Ctx1) in between the "Host" and TUSB1002A is fixed and not influenced by the 12 nF from the miniCard/mSATA socket.