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TUSB8020B-Q1: Circuit Design Problems

Jerry Hsueh
Expert 2730 points
Part Number: TUSB8020B-Q1
Other Parts Discussed in Thread: TUSB8041

Hi

1: At present, TUSB8020B-Q1 achieves system-side power supply by system-side, not by USB. Just use the HUB function of basic USB 3.0.

Does the I2C interface of this chip need to be connected? Or is it just floating?

2: PWRCTL pin and OVERCUR1z pin power switch function and over-current protection function I do not need here, is it possible to connect pull-down resistance?

3.Because I don't have external USB, so I don't have 5V voltage when external USB is inserted. So, do I just look for a 5V voltage in the board and use the voltage divider resistance to connect the VBUS_DETECT_TMS pin?

4. This reset pin needs a pull-up resistor for power-up reset, but the pull-up resistor is not added in the user manual. Why is this? If pull-up resistance is needed, what is the recommended resistance value (ground capacitance is 1uf?)

5: I don't quite understand the use of PWRCTL_POL/SS_DN1 pin in the picture below. Can you explain it more specifically?

6. What does the POWER SWITCHING refer to below?

7. I saw the SMBus address settings, but I didn't see the I2C mode chip address settings.

 

Thank you

Jerry

  • 0
    Expert 2730 points
    Is it convenient to reply?

    Thank you
    Jerry
  • 0 in reply to Jerry Hsueh
    TI__Guru 64326 points
    Hi Jerry,

    1. If unused the I2C interface can be left floating.

    2. PWRCTL pins can be left floating if unused. If unused, OVERCURxz pins should pull pin high with 4.7-kΩ pull up resistor to VD33. Over-current reporting required for USB-IF Compliance.

    3. This is a possibility, you can also adjust the resistor values to accommodate a 3.3V source. Resistor divider values may change with Vbus
    to keep voltage seen by USB_VBUS inside 0V to 1.155 V range. Are all port permanently attached? If so some bits will need to be set in the rmbl[3:0] register.

    4. There is an internal pull-up resistor on the GRSTz pin. There for a 1 uF capacitor will provide the appropriate timing for a passive reset. This pull up is connected to VDD33.

    5. PWRCTL_POL/SS_DN1 is used to control the logic of the PWRCTL pins when interfacing to different kinds of power switches. This features allows for both active high and active low enable pins fo the power switch to work with TUSB8020-Q1.

    6. Power switching refer to the ability that TUSB8041 has to control power switches for downstream Vbus power. this is done through the PWRCTL pins. Please read section 8.3.2 USB Power Management of datasheet.

    7. This is because in I2C mode TUSB8020-Q1 acts as an I2C master to read the EEPROM. For a slave configuration mode SMBus mode should be used.
  • 0 in reply to Malik Barton57
    Expert 2730 points
    Hi Malik,

    Thank you very much for your support.
    In addition, I want to make sure that the following ideas.
    I just do a basic HUB function. so MCU doesn't need to configure the HUB chip through SMBUS interface.
    It doesn't need to do any more operation on software.
    It can realize HUB function only by directly power on.
    Is that right?

    Regards,
    Jerry
  • 0 in reply to Jerry Hsueh
    TI__Guru 64326 points

    Hi Jerry,

    This is correct and you should be able to achieve default operation without need for software. If advanced features are needed like the ones below then some firmware will be needed.

    • Changing VID/PID
    • U1 U2 Timer Override
    • Marking permanently attached ports
    • Marking enabled or disabled ports
    • Custom Battery Charging Feature Enable
    • Swap downstream USB2 polarity
    • Edit Manufacture String
    • Edit Product String