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TUSB4041I: VBUS capacitor for each downstream port

K.Yaita
Guru 29720 points
Part Number: TUSB4041I

Hi Team,

The datasheet shows the following about VBUS capacitor for each downstream port.



On the other hand, USB 2.0 specification required downstream facing port VBUS power lines must be bypassed with no less than 120 μF (CHPB).
Is the datasheet typo?

Best Regards,
Yaita

  • 0
    TI__Guru 60870 points

    Hello Yaita,

    The requirement for 120 uF is a "per hub' requirement, not per port.  Larger capacitors provide more stability against in-rush currents and are recommended but not required.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Guru 29720 points

    Hi JMMN-san,

    Thank you for your kind support.

    If 120uF is a "per hub' requirement, I think 22uF x 4port (=88uF) doesn't meet 120uF.
    How should we consider it?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru 60870 points

    Hello Yaita-san,

    22 uF capacitance minimum is needed to be meet the functional requirements of the per port power switching of the hub.  You are correct that to meet the expected USB specification, a larger capacitor should be used to be meet the 120 uF per hub requirement.  If battery charging is enabled, I would recommend 100 uF per port.

    Regards,

    JMMN