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TPS65987D: USB data lines

Laurence Symonds
Intellectual 545 points
Part Number: TPS65987D
Other Parts Discussed in Thread: BQ25703, TPS65987, , TUSB1064

Hi

I am using the TPS65987 as a USB-C controller to control amongst other things the BQ25703 battery charger. I want to use the USB 2 data lines of the USB-C connection for data when a USB-C device that is sending video is connected. When this is not connected, the majority of times, a USB-C PD enabled charger source will be connected. There is an unlikely situation also of connecting a legacy USB charger that could have BC capability.

My question is, will I be compromising the USB data lines at all by connecting the TPS65987 USB BC pins to them? As in will they act like stubs on the differential pair? Having reliable USB data is more important than USB BC capability.

Many thanks

  • 0
    TI__Mastermind 36751 points

    Hi Laurence,

    The USB2 lines cannot be used for Video. Video will not pass through those lines. If you are entering a DisplayPort alternate mode contract with the TPS65987D, the video data will be sent over the USB SuperSpeed lines. 

    If you do connect the USB2 lines to the TPS65987D, you will enable support for BC1.2. If you are expecting to primarily support PD only, then BC1.2 should not be required. You can then choose to not connect the USB2 lines to the TPS65987D.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Intellectual 545 points

    Hi

    Sorry I didn't explain that too well.

    The video will be DP in alt-mode. I have these lines being redriven by a TUSB1064.

    The USB 2 data pair will be used in addition. It is for a touchscreen application, so the USB-C source computer sends DP and has USB-HID over the USB 2 lines.

    I just wanted to know if connecting the USB 2 datalines to the TPS65987, in order to benefit from the USB BC functionality, would risk the signal integrity of those lines?

    Thanks

  • 0 in reply to Laurence Symonds
    TI__Mastermind 36751 points

    Hi Laurence,

    There is a risk of adding a stub to the USB lines. The layout section in the TPS65987D Datasheet has an example layout of how you can route the USB2 lines to the TPS65987D while minimizing the stub that is added.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Intellectual 545 points

    Hi Eric

    That's great, thanks a lot. I had not taken that in when I read through the whole datasheet! My bad.

    Thanks a lot