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TUSB8020 Vbus application question?

Chen Bogey8
Mastermind 9990 points
Other Parts Discussed in Thread: TUSB8020B, TIDA-00287

Dear Sir

My customer use TUSB8020 in M.2 application(no 5V power) , may we know how to connect VBUS_DETECT_TMS pin?

                                      Best regards,

                                                   Bogey

  • 0
    TI__Guru 60865 points

    Per the USB specification the TUSB8020B uses VBUS_DETECT to determine if the upstream connection is powered on.  If you have an embedded application, where the upstream connection will always be there, you can pull VBUS_DETECT high.  You can connect it to 3.3V and adjust the 5V resistor divider (90.9K / 10K) accordingly.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Mastermind 9990 points
    Dear JMMNthanks for your reply ~
    and another question, DS page 8 "td2:VDD and VDD33 stable before deassertion of GRSTZ. "
    and we have reference reference TIDA-00287, GRST# direct connect 1uF to GND.
    if we use the way to set up Td2 fuction or have any advice?
    Best regards,
    Bogey
  • 0 in reply to Chen Bogey8
    TI__Guru 60865 points

    Hi Bogey,

    You will need to know the expected ramp times of VDD33 and VDD in your system.  If they ramp quickly, using a 1 uF capacitor to complete the RC circuit along with the internal pull-up resistor is sufficient for GRSTz.  If the ramp times are slower, you may need to increase the size of the capacitor.  Many systems use 2.2 uF.  If the ramp times are extremely slow or unpredictable, then an active reset circuit is required.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 10 points
    Hello - not sure if anyone is still monitoring this thread; but I would like to know the threshold on this VBUS_DETECT signal (USB_VBUS, pin 9). The datasheet really only says a maximum voltage of 1.155 V. I've currently set it to ~0.5 (3.3V with 56.2K/10K).
  • 0 in reply to Matt Ferraro
    TI__Guru* 76130 points
    Hello,
    Threshold: 300mV~450mV