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TUSB2E11: application issues

Nanpeng Chen
Prodigy 10 points
Part Number: TUSB2E11

Tool/software:

Hi team, Could you please help to check two questions as follow：

1、From the databook of TUSB2E11, I see that this device should only have supplies power-on time requirements, but no power-on-reset sequence requirements. No matter RESETB is de-asserted high before or after all power supplies are stable，it is ok？Please help confirm.

2. After the device has done its POR, what is the status of DP/DM? If the repeater completes the POR first, but the SOC's eUSB PHY has not yet completed initialization, so the SOC's eUSB PHY and eUSB repeater's 
handshake has not yet completed, what is the status of the DP/DM at this time？I'm concerned about whether there will be unexpected status on DP/DM at this time, causing the repeater to start interacting with the PC.
  • 0
    TI__Mastermind 27925 points

    Hi Nanpeng,

    1. There is no power on sequencing between the 3.3V rail and 1.8V rail, except for the 2ms ramp-up time listed in the electrical specification.  RESETB will not be deasserted when power supplies are not stable as described in the datasheet seciton 11.3.1:
    "Internal power on reset circuit along with the external RESETB input pin allows for proper initialization when RESETB is de-asserted high prior to the power rails being valid. If RESETB de-assert high before the power supplies are stable, internal power on reset circuit holds off internal reset until the supplies are stable."

    2. After a repeater is powered on.  It is in the default state, meaning it does not forward any messaging between eUSB2 and USB 2.0, and waits to be configured by the peripheral or host through the eUSB2 interface.  DP/DM are low as it is not been configured yet. 

    After it is configured as a peripheral as suggested in your screenshot, then it will begin to present a USB 2.0 "J" idle state just as any normal USB 2.0 device would.  After a USB 2.0 host detects the "J" state on the USB 2.0 interface it will begin regular USB 2.0 communication and begin enumeration.

    Regards,

    Nicholaus

  • 0 in reply to Nicholaus_Malone
    Prodigy 10 points

    Hi Nicholaus,

    Thanks for your reply. As you mention, DP/DM are low as it is not been configured yet. May I know what's value of the pull-down resister? 

  • 0 in reply to Nanpeng Chen
    TI__Mastermind 27925 points

    Hi Nanpeng,

    Based on the datasheet.  It is likely a 390kohm impedance to GND when not configured. 

    Regards,

    Nicholaus

  • 0 in reply to Nicholaus_Malone
    Prodigy 10 points

    Hi Nicholas，

        I get it，Thank you very much！