TUSB8041: TUSB8041I: USB_Dx_DNx pins

Hi Marion,

For USB 2 the DP pull-up are presented on downstream ports only when VBUS is present, per the USB 2 spec. Does customer board power VBUS at the downstream connector without powering the hub? 

Hello Malik,

I asked Marion for support with this issue.

Yes, VBUS is powered without powering the hub.

The USB hub is implemented on the module, which unfortunately does not support control of the power switches for the USB ports implemented on the carrier board. In some cases, the USB port (and the device plugged into it) is powered while the USB hub is not.

Can the TUSB8041I be operated in this way without affecting its lifetime? 

Kind regards,

David

Hi David,

Let me check internally. Is this design meant to be USB complaint?

Hi Malik,

yes, the design should be USB compliant.

TUSB8041 has constrains:

• Bus contention while VDD33 is powered up must be limited to 100 hours over the projected life-time of the
device.
• Bus contention while VDD33 is powered down may violate the absolute maximum ratings.

Our case could be the "Bus contention while VDD33 is powered down.

Hi David,

If the Design is to be USB complaint teh downstream VBUS should not be active if the Hub is unpowered. I also did confirm this type of design should not be done for TUSB8041 I/O, sustained ~3V from device when device is unpowered could potentially cause damage. 

Hi Malik,

thank you for the clarification.