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TUSB2036: TUSB2036 + TPS2033B only momentarily powering USB devices, not showing up as a device

Craig Easdale
Expert 2160 points
Part Number: TUSB2036
Other Parts Discussed in Thread: TPS2043B

I have used this pair fo components as recommended by the datasheet to add some extra USB ports to my embedded linux system (schematic below)

There have been difficulties in getting this working. The most obvious issue is shown when I plug in a USB device and it powers for a split second (I can see an LED come on) before then going off again. Secondary to that I have no devices showing up on the connected system that might indicate that the TUSB2036 is working and communicating upstream either.

Any input would be appreciated.

  • 0
    TI__Guru*** 139455 points

    Hi,

    Looking at the schematic, how do you provide the clock to TUSB2036? You would need to use either a 6MHz crystal or 48MHz oscillator to provide a clock to TUSB2036.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Expert 2160 points

    Hello,

    Thanks for your reply, for some reason I had thought that was optional.

    I have now added a 6MHz crystal, with the MODE pin pulled low I'd expect that this should work. Now when the system is powered I see a brief 5.997MHz sine wave appear on the XTAL2 pin, which stops very soon after it begins and the behaviour after that point is the same as before. I'm not sure what that might indicate as a problem?

  • 0 in reply to Craig Easdale
    TI__Guru*** 139455 points

    Hi,

    For self-powered hub which implements the downstream port power switching, you want to pull pin 21 to ground. 

    Also, OC pins of the TPS2043B are open drain pins and you need to have external pullup resistors as shown below.

    Thanks

    David