• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 32 subscribers
  • Views 883 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS25820: Using TPS25820 for dual role support with legacy OTG uc

Chris Hamilton
Intellectual 270 points
Part Number: TPS25820
Other Parts Discussed in Thread: TUSB320, TPS25910

Hi, I have an STM32 that I would like to use with USB-C.  I have built a design using the TPS25820 to negotiate and provide power to USB C devices. I plan to use the uc OTG capabilities for USB 2.0 host and device negotiation, and kick on the TPS25820 for any devices detected with no 5V on the USB and maybe gain future proofed downstream capabilities with the TPS25820.

However, when a USB host/downstream port connects on Type C from a Type C (A->C works), no power is sent to the board in device mode.  It appears the CC lines on the TPS25820 are interferring (EN is uc controlled so high-z dead or low once powered).  Is it EN being high-z when the board is unpowered?  How would I work around it if so?

Thanks!

  • 0
    TI__Mastermind 27545 points

    Hello Chris,
    Have a few questions to help get a better understanding of this problem.
    Are you only using the TPS25820 for when you are trying to source power to an external device, or is the board the TPS25820 is on acting as the device and you are sinking power from an external host?

  • 0 in reply to Adam Mc Gaffin
    Intellectual 270 points

    The TPS25820 was designed to supply power as a DFP.  I am using it for power in a DRP role.  So I am trying to understand what I can do to get the correct response when the board it is on is a sink with the board/TPS25820 powered off.  I assumed the TPS25820 would leave the CC high-Z at a minimum, ie. the board would act as a device on CC until the TPS25820 is enabled.

  • 0 in reply to Chris Hamilton
    TI__Mastermind 27545 points

    So the TPS25820 itself is designed only for DFP applications. From what I understand, you are not using the TPS25820 itself as a sink, but will instead will be a powered off while the board is acting as a UFP. While you are not using the TPS25820 as a sink, because this is not an intended application, you may experience abnormalities in your design such as the high impedance and CC lines.

    What I would recommend is switching to a port that has capabilities of being a DRP like the TUSB320. This can replace the TPS25820, and should remove the problem of CC line errors as well as potential impedance issues.

    If this doesn't help you, would you be able to include a block diagram of your design?

  • 0 in reply to Adam Mc Gaffin
    Intellectual 270 points
    OK, I picked the TPS25820 in the hope that the VBUS switching would be based on CC or the uc OTG. Is there a VBUS switch that you would recommend paired with the TUSB320 for DRP Type C? Thanks!
  • 0 in reply to Chris Hamilton
    TI__Mastermind 27545 points

    The Vbus switch used on the EVM for the TUSB320 is the TPS25910

    http://www.ti.com/tool/tusb320evm

    However, what I would recommend is to close this thread and to open up a new one but have the part in question be the TUSB320. You'll be put in touch with another Texas Instruments engineer who has been assigned that specific part. Tell them what you told me, and they can help you pick a specific VBUS switch for you. The TPS25910 may be the one they recommend, or after hearing your application they could recommend something else. Just explain your application like you did to me, but focus on how you are using this part as a DRP. Also, if you have a block diagram  of your design, include that as it will help paint a clearer picture of what you are trying to accomplish.

    If this answers your question, PLEASE select  This resolved my issue