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TUSB8042A: Downstream Port Configuration

Tess Chen
Intellectual 2675 points
Part Number: TUSB8042A

Hi,

The application use TUSB8042A as a hub for 3 downstream USB ports:  2 USB3.0 and 1 USB2.0 port. Please find the schematic in the below.

1. Could you please help review the connection in the schematic?

2. In datasheet, P22  In table 4.  TUSB8042A Downstream Port Configuration Examples  which is shown below.  For 3 port application , the physical port is 2,3 and 4. Does the physical port 1,2 and 3 can be used under this configuration which is aligned with the schematic?

3. Does device can realize the application with default configuration which may not need EEPROM or  any I2C operation?

 Thanks a lot.

 

  • 0
    TI__Guru 60865 points

    Hi Tess,

    By default, the hub will work at both USB 3.0 and USB 2.0 speeds on all ports.  The different port configurations and mappings are for cases such as  if you only use 3 ports, you can configure the hub to report that it only has 3 ports.  Functionally this is not required, but USB-IF requires that end products getting official certification mark non-removable ports, USB 2.0 only ports or unused ports accordingly.

    Schematic feedback.

    1. GRSTz has an internal pull-up already.
    2. Downstream SS TX lines need AC caps.
    3. SCL / SDA seem to have both pullups and pulldowns installed.  Neither is needed if the EEPROM is not installed.
    4. Please note that installing a blank EEPROM connected to the hub will cause the hub to automatically enter programming mode at power on reset.
    5. GANGED and FULLPWRMGMTz should be pulled low or left unconnected in your system (since your power switches are not ganged and you are implementing power management).  The status outputs on these lines will only work if configured over I2C / SMBUS. 

    Regards,

    JMMN