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TUSB8020B: TUSB8020B with TPS2561A

David Dionisopoulos
Prodigy 20 points

Part Number: TUSB8020B
Other Parts Discussed in Thread: TPS2561A,

Hello,

I have boards manufactured and I'm trying to debug the USB interface. The issue I'm seeing is the  TPS2561A is not getting the enable signal from the TUSB8020B. I don't know if the Hub is in a sleep state or if I incorrectly configured the standalone mode.

I have verified I am getting all of the correct voltages at the VDD and VDD33 pins.
I do see voltage at XI from my external oscillator.
Pins 2 and 3 (SCL and SDA) I had them floating, but I also tried pulling down to ground
Pin 22 (SMBusZ) I had pulled down to ground and I tried it floating
Pin 9 (Usb VBUS) I'm getting around .5V
Pin 11 (GRST_In) I'm getting around 3.2V

I'm not sure what else to check or what would be causing the TUSB8020B Not to send the enable signals to turn power to my downstream devices.

Thanks
David


  • 0
    TI__Guru 58186 points

    HI David,

    Can you probe these pins on startup?

    1) FULLPWRMGMTz/ SMBA1/SS_UP

    2) PWRCTL_POL/SS_DN1

    3) PWRCTL1/BATEN1 

    4) PWRCTL2/BATEN2

  • 0 in reply to Vishesh Pithadiya
    Prodigy 20 points

    Hi Vishesh,

    I measured those pins and they're all at 3.3V.


    I might've figured out the issue. I was only supply power to USB_VBUS. I didn't have the uplink DP and DM pins connected to the host. Once I did that and I set pin 22 to floating ( i had it pulled down to ground , that didn't seem to work) it allowed the TPS2561A to enable and my downstream devices were turning on.



  • +1 in reply to David Dionisopoulos
    TI__Guru 58186 points

    Hi David,

    I see. Yes, the DP and DM pins must be connected to the upstream host for proper operationn.

    Pin 22 (SMBUSz/SS_DN2) places the part into SMBus, I2C, or GPIO modes. 

    - in SMBus mode a register must be written to enable the hub

    - in I2C mode the part will be expecting a configuration from an external EEPROM

    - when floating the part goes default mode and operates on the sampled pins.