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TPS25865-Q1: USB data communication od D+ and D- lines

Jan Zastera
Intellectual 260 points
Part Number: TPS25865-Q1

Tool/software:

Dear TI support,

we are planning to use TPS25865-Q1 in our USB-A Host device where we want to support simultaneously BC1.2 protocol and USB data communication with connected USB flash drive. We found, that according to our tests and 10.3.14.1 Dedicated Charging Port (DCP) Mode section in datasheet, this seems not to be possible.

Is there a way how to make it work? For example is there some other part number, that supports these two modes simultaneously or e.g. using multiplexer for D+ and D- lines, or some other way?

Thank you

  • 0
    TI__Mastermind 32891 points

    Jan,

    It is possible with very careful routing to use the TPS25865-Q1 in parallel with a seperate HUB or controller that provides CDP and SDP functionality to fufill the full BC1.2 specification.

    If the USB signals are carefully routed as shown for the port A side, then the TPS25865AQ1 can provide the DCP and current limit portion of the spec while the other device sets the CDP/SDP signaling.

    I drew a quick example on the package footprint that assumed VIA in pad was ok, but the vias can be moved to the left if your design rules require it.  The routing is very critical to make sure that the stub length to connect to the TPS25865AQ1 is a short as possible to minimize the signal degradation.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Intellectual 260 points

    Hello Chuck,

    thank you for fast reply.

    we understand the need for correct routing to avoid signal degradation.

    What I meant was what is noted in chapter 10.3.14.1.

    When we connect flash drive on D+ and D- lines, we are unable to communicate with it.

    Please can you confirm that is because of TPS25865-Q1 connected on those lines, please?

    We can place multiplexer on D+ & D- lines in order to disconnect those from TPS25865-Q1 during the period of time in which connection to flash drive will be needed.

    Thank you

  • 0 in reply to Jan Zastera
    TI__Mastermind 32891 points

    Jan,

    If you add in a MUX, then the TPS25865 will not be able to negotiate any of the DCP modes.

    Can you provide me a scope capture of the DP/DM lines when you attempt to connect the flash drive?  This will help me with the next stage of debug.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Intellectual 260 points

    Hello Chuck, please hold on, we are working on it, we will upload the scopes asap. Sorry it takes so long

  • 0 in reply to Jan Zastera
    TI__Mastermind 32891 points

    Hi Jan,

    I will take a log at this once you have to scope captures.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Intellectual 260 points

    Hello Chuck,

    thank you for waiting, I connected scope to D+ and D- and there are only static voltage levels of approximately 1V on both lines.

    When I cut the lines between TPS25865-Q1 and USB connector, things start to work and my flashdisc starts to communicate with MCU.

    From this behavior I suspect we will need to multiplex USB D+ D- lines to TPS25865-Q1 when BC1.2 needed and to MCU when communication with external flasdisc is needed.

    Thank you

  • 0 in reply to Jan Zastera
    TI__Mastermind 32891 points

    Jan,

    If you have the ability to know when the external flash device is required, then the mux will work well.  If you do not know when it is going to be used, then muxing will cause many system level issues.

    Regards,

    Chuck