TUSB8044A: Timing of VBUS

Hailey Chen

Part Number: TUSB8044A

Hi, expert:

In a specific design, we are considering powering up the USB device VBUS (5V) before the Hub's internal rails (1.1V/3.3V) are active (while the Hub's USB_VBUS pin is still unpowered). What potential impact would this power sequence have on the Hub's operation or reliability?"

1 month ago

0 Vishesh Pithadiya 1 month ago

TI__Guru 54776 points

Hi,

Why are we doing this? This will mean that the device will be powered before the hub is powered. This does not speed up enumeration or operation as we will need to wait for the USB hub to enumerate anyway.

0 Hailey Chen 1 month ago in reply to Vishesh Pithadiya

TI__Expert 3520 points

Hi, Vishesh:

Due to power rail design, VBUS 5V is not always could be controlled power up later than Hub's internal rails, so want to know the potential impact on Hub's operation.

0 Brian Zhou 1 month ago in reply to Hailey Chen

TI__Guru**** 158835 points

Hi Haily:

USB_VBus is normally connected to host Vbus, is this embedded system?

Best

brian

0 Vishesh Pithadiya 29 days ago in reply to Brian Zhou

TI__Guru 54776 points

Hello,

Closing thread due to inactivity. If you have any follow-up questions or concerns, feel free to reply.

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TUSB8044A: Timing of VBUS