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Original question:

TUSB4041I: Connecting two TUSB4041I USB hubs together

TUSB4041I: USB_VBUS threshold

Geir Pettersen
Prodigy 30 points
Part Number: TUSB4041I

In the datasheet, I can read the following: "The VBUS detection requires a voltage divider. The signal USB_VBUS must be connected to VBUS through a 90.9-kΩ ±1% resistor and to ground through a 10-kΩ ±1% resistor from the signal to ground." The recommended USB_VBUS voltage at pin 16 should be somewhere between 0 V and 1.155 V according to datasheet, but the actual threshold is not stated. What is the actual threshold (voltage) at USB_VBUS (pin 16) to distinguish between USB_HOST_connected / USB_HOST_not_connected?

  • 0
    TI__Guru 64326 points

    Hi,

    The threshold for this pin is ~425mV.

  • 0 in reply to Malik Barton57
    Prodigy 30 points

    Dear Malik.

    Thank you for your answer.

    I understand USB VBUS detection Threshold for TUSB4041 pin 16 could be ~425 mV which corresponds well to the USB 2.0 spec p.173: Must be capable to operate at input VBUS voltage as low as 4.40 V measured at the cable plug end, and taking the 1% resistor (90.9 k and 10 k) tolerance into calculations, and you will get 427 mV.

    But, is the (~) 425 mV the guaranted USB VBUS detection threshold for TUSB4041? How does the ~425 mV threshold value vary with production spread, temperature, etc. ?

    Looking forward to hearing from you soon.

    Best regards

  • 0 in reply to Geir Pettersen
    TI__Guru 64326 points

    Hi,

    425 mV should be the target design spec for any external circuitry to present a high voltage to USB_VBUS pin. Are you seeing any unexpected behavior with the USB_VBUS pin?

  • 0 in reply to Malik Barton57
    Prodigy 30 points

    Dear Malik.

    Thank you for confirming the 425 mV as the *target design spec*. I like to be absolutely sure, even though some times can be difficult. We do not see any unexpected behavior with TUSB4041. Currently re-designing our circuit, because one situation not working as expected. We have two alternative candidate solutions to resolve our prob. One candidate solution must take into consideration the VBUS detection threshold. TUSB4041 is working fine in general. Is a bit early for obtaining the test-results for the re-design. Will do soon. If there are any problem, we will let you know. I resolve this case for now. Thanks for good help. Wish you nice day.

    Best regards

    Geir