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TUSB8020B: schematic check

GARETH OU
Guru 11365 points
Part Number: TUSB8020B

Hi 

could you help check the TUSB8020B schematic and any need to adjust ?

Thanks you

6470.TUSB8020B.pdf

  • 0
    TI__Guru 64326 points

    Hi,

    TUSB8020B is not ideal/complaint for bus powered applications. The TUSB8020B will always report as a self powered hub in its descriptors and it exceeds the suspend mode power consumption required by a bus powered device.  Functionally this design can work (with consideration to the below comments) since most USB host ports provide extra power.  Please note that a compliant bus powered hub application would necessarily limit the power available to the attached downstream devices to prevent the power consumption from the host port from exceeding 900 mA / 500 mA total for both the hub and the devices combined.

    I don't think the TUSB8020B is a good fit for this application. What is the main reasoning for using a USB hub here for only one port? It is not a compliant bus powered hub and it would add in considerable power consumption to your application if bus powered.

    • SMBUSz - Should be pulled high or left NC to enter I2C. With pull down device will not automatically enter default mode since not SMBUS host will configure the device. 
    • Downstream port 1, USB 2 pins need to be connected to the device for complaint operation. Is the USB3 going to a SFP module or USB connector?
    • Missing AC coupling Downstream port 1, USB 3 pins 
    • FULLPWRMGMTz is pulled down so BATEN/PWRCTL pins should be left NC.