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Detect a device to load on TPS2549-Q1

Thomas Jung2
Prodigy 50 points
Other Parts Discussed in Thread: TPS2549-Q1, TPS2549, TPS25810

Hi,

we want to use the TPS2549-Q1 device for our new design. We have two main features
1. load a device (Handy, Tablet,...) via USB
2. communicate with the microcontroller 

Due to space issues we have to share one USB connector, so we can either loading or communicating.

So the general structure of the application is similar to a power bank with the additional requirement, that we have to provide a data path to a microcontroller.

The question:

We have to switch the TPS2549 either into "Device Mode" or in one of the "Load Modes" manually via the control pins.

What happens if we switch into "DCP-Mode" but connect an USP-Host Port (like a PC). In this situation i expect that we (TPS2549) drive 5V and the connected Host port also drives 5V. Is there any protection?

Is there any possibility to automatically detect and distinguish between connected Host (for communication) or device (for loading)?

Do you have any other/additional product to make such a decision automatically?

Thanks for Help

Thomas

  • 0
    TI__Intellectual 1710 points
    The TPS2549 has built in current limit and thermal protection so it would be protected against a connection to another host that was also supplying 5V. A better question is will the host have the same protection? The TPS2549 also supports a client mode which will turn off the internal power switch while still having the DP and DM connected. You would have to put the device into client mode prior to connecting the host for programming. I'm not sure how you could get a host to automatically put the TPS2549 into client mode without some kind of sideband signal. USB Type-C with PD could solve these problems by making your device a DRP (dual role port) device.
  • 0 in reply to Lee E Myers
    Prodigy 50 points
    Hi Lee,

    thanks for the fast answer, it was very helpful and it confirms my fear with the planed solution.

    I am not familiar with USB Typ-C and i can´t oversee how this could solve the problem. Could you please provide me some additional sources of information (Links, PDFs,...).
    I guess it is not just the connector that makes the difference, right? I think there are different or additional devices necessary to support DRP. Is this correct? Is there something available in the TI portfolio?


    Again, Thanks for help.
    Thomas
  • 0 in reply to Thomas Jung2
    TI__Intellectual 1710 points

    You can learn more about type-C here http://www.usb.org/developers/usbtypec/ 

    download the USB 3.1 specification zip file. Inside you will find the specs for type-C and USB PD (Power delivery). You can also do a web search for "USB type-C" and you will find a lot of general info on how it works.

    Something like this might work except replace the DPDT switch with a FET circuit that can decide when the port should behave as a DFP (host) vs UFP (device for loading software). The type-C connector is shown on the right side of the picture.

  • 0 in reply to Lee E Myers
    Prodigy 50 points
    Hi Lee,

    thanks. It answeres my question. I found already the TPS25810 and red the datasheet.
    I think this is the correct solution. I will discuss it with my Colleges.

    Thanks
    Thomas