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TPS25820: Use as Powered USB C Dock

Ben Adamson
Prodigy 100 points
Part Number: TPS25820
Other Parts Discussed in Thread: TPS25751

Tool/software:

I'm trying to get the TPS25820 to work as a USB Hub PD controller. I want to supply 1.5A output current to charge the attached cell phone, while allowing the cell phone to access the LAN9512 USB hub.

As far as I can tell this means the TPS25820 is an upstream facing port (upstream / master being the cell phone). But given it is meant to be supplying power not receiving power, also somewhat is acting as a 'downstream facing port' in the sense of power?

With the prototype PCB if we connect to the USB port with a USB A to C cable (no CC pins) the LAN9512 and downstream ports can be detected - but of course no charging. If we connect with a C to C cable, charging is negotiated however the LAN9512 does not appear as a device. 

I've tried enabling and disabling the EN and CHG pins but the LAN9512 is not detected - I suppose because the CC pins are being controlled by the TPS25820 still as if it were an upstream port when I need it to act as a downstream port for the data to work.

Is there any way to modify this circuit (do we need any pull up / down resistors on any lines?) 

Is the functionality I'm looking for 'Dual Role Port' controller?

  • 0
    TI__Mastermind 37855 points

    Hi Ben, 

    Are you looking for a PD controller or a Type-C controller. The TPS25820 is Type-C only.

    Thanks and Regards,

    Chris

  • +1 in reply to Christopher Lim1
    TI__Mastermind 37855 points

    Hi Ben,

    Ben Adamson said:
    As far as I can tell this means the TPS25820 is an upstream facing port (upstream / master being the cell phone).

    The TPS25820 is Source/DFP only, and a Type-C device. It is not Type-C PD so does not support Power or Data role swaps. It is not a UFP for Data.

    Ben Adamson said:
    With the prototype PCB if we connect to the USB port with a USB A to C cable (no CC pins) the LAN9512 and downstream ports can be detected - but of course no charging.

    A type-A to Type-C cable has internal biasing of the CC lines. The Type-A side will act as the Power Source/Data DFP and Type-c side the Power Sink/Data UFP. You may still be detecting the data as the TPS25820 does not directly affect the D+/D- lines, but the CC defined role does not support being a UFP.

    Ben Adamson said:
    If we connect with a C to C cable, charging is negotiated however the LAN9512 does not appear as a device. 

    This is what is expected. The TPS25820 advertised the port as Source/DFP only, and will not attempt or support Data role swaps to UFP(device).

    Ben Adamson said:

    Is there any way to modify this circuit (do we need any pull up / down resistors on any lines?) 

    Is the functionality I'm looking for 'Dual Role Port' controller?

    I don't think there is a way to modify this circuit, the TPS25820 exposes the CC-line pullup resistors and to have conflicting Power and Data roles, USB-C PD is required.

    You are looking for DRP functionality, but maybe not the full capabilities.

    On connect, a port can only be Power Source, Data DFP or Power Sink, Data UFP. After connection, if USB-C PD messaging is supported and both ports support role swaps, you can swap Power and Data roles independently. In your case, it sounds like you want to be Power Source and Data UFP, which requires a USB-C PD controller and some level of DRP.

    If you only need USB 2.0 or USB 3.0 data, I would recommended looking into the TPS25751.

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    Prodigy 100 points

    Thanks Chris for your detailed response, we will look at TPS25751 for the next revision. We do indeed need to be a power source and data UFP, which I clumsily explained without knowing the exact technical terms. On our existing prototype boards we will remove TPS25820 and add pull down resistors on CC pins so that we do at least get USB data with a C-C cable.

  • 0 in reply to Ben Adamson
    TI__Mastermind 37855 points

    Hi Ben,

    No worries, Type-C PD can be a bit much when first looking into it. Here is an App note that may help better understand Type-C PD.

    https://www.ti.com/lit/wp/slyy109b/slyy109b.pdf?ts=1729261789381&ref_url=https%253A%252F%252Fwww.google.com%252F

    Closing this thread now.

    Thanks and Regards,

    Chris