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TPS25762-Q1: How can the CC lines control the selection between the SS pairs?

Adithya Anil
Prodigy 150 points
Part Number: TPS25762-Q1
Other Parts Discussed in Thread: TUSB4041I-Q1, TUSB542

Tool/software:

Hi,

I have TUSB4041I-Q1 Hub controller, an MCU(on a different board), TPS25762-Q1 PD controller and a USB type C Connector. The SS signals of an MCU is connected to the type C connector requiring USB 3.0 support. The data lines D+ and D- from the MCU is connected to the upstream of TUSB4041I-Q1 Hub controller and one of the downstream port's D+ and D- lines is connected to the D+ and D- lines of the same Type C connector.

I don't want to use any USB 3.0 Hub, so, I am planning to take the SS signals required for 1 type C connector of 3.0 from the MCU of another board and the rest of the signals like D+ and D- from the Hub Controller. (PS the same MCU's D+ and D- reaches the upstream port of the Hub).

I have two options on my board for powering the Type C port. Either I will use the PD controller or I will use the power switch. If I am using the PD Controller, the power switch will be DNP and I will have the CC lines of the PD Controller connected to the CC lines of the downstream Type C connector. But, how will the selection between SS_1 and SS_2 take place as I am not using any MUX here. I cannot give any signal to the MCU on the other board as well. So, how will the selection be carried out by the PD controller? 

Please note that all the SS1_TX, SS1_RX, SS2_TX and SS2_RX signals are connected with each other on all the type C connectors.

Regards,
Adithya

  • 0
    TI__Genius 11385 points

    Hi Adithya,

    My team works on the TPS25762-Q1 PD controller.  We do not directly play a role in the USB3 datapath, so I am not a complete expert in this regard.  I suggest contacting a local FAE if you need additional resources for the USB3 datapath.  I can try to find a contact for you if you don't already have one.

    Here is my understanding of the problem: you have directly routed SSTX1/2 and SSRX1/2 from the downstream facing Type-C port to the upstream facing Type-C port (which then routes to your MCU).  The cable that connects the MCU board to the intermediary board could be flipped in either orientation.  Additionally, the cable connected to the DFP Type-C port could be flipped in either orientation.  Therefore, there's no guarantee the SSTX/RX signal path is continuous from USB host to device.  Even if the cable from MCU to intermediary board is in a known/fixed orientation, we still need to consider that the cable at the DFP could be flipped.

    To my knowledge, the only solution here is to add a USB3 MUX.  TPS25762-Q1 checks the CC1 and CC2 pin, and based on which one is pulled down, this tells us which way the cable is oriented.  We can use this information to assert a GPIO, which controls the MUX to route the SSTX/RX path correctly.  Again, there may be a better resource to point you to the right part, but on initial search, something like TUSB542 or a would work (https://www.ti.com/product/TUSB542).

    Regards,
    Eric