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TUSB2046B: USB Power Surge

Kamran
Intellectual 270 points
Part Number: TUSB2046B
Other Parts Discussed in Thread: TPS2042

Hello E2E community,

I used TUSB2046 to design a hub with one upstream port (USB type B), 2 downstream port (USB type A), and one port connected to an MCU. When I plug the upstream port to a PC, I get an error message “Unknown USB Device needs more power than the port can supply”. There are no devices connected to the down stream ports, but port 3 of the hub chip is connected to the MCU. I have done some troubleshooting and this is what I found:

PWRON1 & PWRON2 (pins 9 & 13) are both high (this disables the power-distribution switches TPS2042) although OVRCUR1 & OVRCUR2 are both high (no over-current condition)

I realised that we don't have 15k pulldown on DM3 DP3 lines, could this cause Power-Surge Error and deactivate all ports?

We left the unused OVRCUR3 & OVRCUR4 open, should they be pulled high?

Is there any error in this design?

Thank you for your help!

Hub_Schematic.pdf

  • 0
    Intellectual 270 points

    Troubleshooting update.

    PWRON1 & PWRON2 (pins 9 & 13) are low if no device connected to downstream port. They go high as soon as we connect a device and disable the power-distribution switches.

    Even with no device connected, we are not able to communicate with the MCU.

    We still have the Power Surge Error message.

    We still did not install 15k pulldown on DM3 DP3 lines.

    The unused OVRCUR3 & OVRCUR4 are still no connect.

    Any hint?

  • 0 in reply to Kamran
    Intellectual 270 points

    Troubleshooting update:

    I have added 15k pulldown on DM3 DP3 lines. I don't get USB Surge error anymore.

    PWRON1 & PWRON2 (pins 9 & 13) are good now, They are both Low now even when I connect a device on downstream port.

    I have connected the upstream to PC and optical mouse on one of the downstream port. However, downstream device (optical mouse) does not get recognized... The MCU is not programmed yet. But since the downstream device is connected through the hub chip, shouldn't work regardless of firmware??

    Any help on that please?

  • 0 in reply to Kamran
    Intellectual 270 points

    Hi All,

    I finally resolved the issue. The 15k pulldown resistors did the trick.

    Hope my post will help someone having similar issues.