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Original question:

TUSB8020B: New PCB design doesn't connect to upstream

TUSB8020B: USB 3.0 part doesn't connect to the PC

KIRILL LINKOV
Prodigy 20 points
Part Number: TUSB8020B

Hi,

We use open source USB 3.0 hub schematic based on TUSB8020B. When we tested the board USB 2.0 part has successfully detected by the PC and works. But USB 3.0 part of the device does not work and is not detected by the UsbTreeView software.

open source USB 3.0 hub schematic based on TUSB8020B

1. Upstream connected to PC USB2.0 port:
- current consumption: ~ 80 mA;
- board detected in USBTreeView as USB2.0 hub;
- board works correct and doesn't heating;
- signal on TX line presents below.

board detected in USBTreeView as USB2.0 hub

USB2.0 port, signal on TX line

2. Upstream connected to PC USB3.0 port (has been checked usb3.0 function):
- current consumption: ~ 260 mA;
- board detected in USBTreeView as USB2.0 hub;
- board works correct as USB2.0 hub and heating over 60C;
- signal on TX line not stable. Variations presents below.

Upstream connected to PC USB3.0 port

       

We've read topic where Justin Y describe similar problem and then checked thermal pad connection of our board by X-ray. It was uncertain and we made new board with good thermal pad contact (X-ray checked too), but behavior was the same with the first board.

We used the shortest cable we have, checked two samples of board and two different PCs. What else should we do to make USB 3.0 part of the device work.

We would greatly appreciate your help in creating this design.

  • 0
    TI__Guru 60870 points

    Hi Kirill,

    It looks like a capacitor is missing for GRSTz.  The hub requires a power on reset, since it is missing that PLL may not be locking correctly for USB 3.0 operation.

    You can use a 1uF or 2 uF capacitor on GRSTz or an active reset.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 20 points

    Hi JMMN,

    Thank you very much for your reply.

    Firstly, we put a 1uF ceramic capacitor on GRSTz, and secondly, we used a manual reset (active reset). The TX waveform is shown below.

    Otherwise, nothing has changed: the chip is still very hot and the board is defined in UsbTreeView only as a USB2.0 hub.

  • 0 in reply to KIRILL LINKOV
    TI__Guru 60870 points

    Hi Kirill,

    What type of USB connectors are you using?  I noticed both upstream port and downstream ports receptacles have the same port pin numbering.  Can you confirm that there is a cross between SS TX to SS RX and SS RX to SS TX between the host and the hub?

    How many layers is the PCB?  With just 260 mA of current consumption, I wouldn't expect the hub to get hot.

    Regards,

    JMMN

    UPDATE:  Another E2E user confirmed that swapping the upstream TX and RX lines fixed his issue with a similar schematic.

  • 0 in reply to JMMN
    TI__Guru 64326 points

    Response from :

    Since the original topic is already locked and there is no way to answer there, I will write here about the solution I found. Hope admins can combine these topics.

    We checked the pinout of the connectors, and it turned out to be non-standard. When using an adapter that swapped the upstream RX and TX, everything is in working order. Many thanks for the help.
    It also matches the answer given by JMMN. Unfortunately, I read it a little bit later )

    So be careful if you use this open source USB 3.0 hub schematic based on TUSB8020B.