VBUS disconnected

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aldoc_3474881
Level 1
Level 1

Hi. I'm currently designing using the CYUSB3304 hub. The VBUS comes from US. The 1.2V and 3.3V are generated from a separate power source.

Is there a problem if the USB 3.0 lines are connected along with 1.2V and 3.3V, but I disconnect the VBUS line?

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1 Solution
Anonymous
Not applicable

Hi Alin,

There will be no issue in disconnecting the VBUS while the rest of the USB lines are connected on the upstream, with 1.2V and 3.3V supplies of Hub are powered.

Since the Hub IC core is not powered with 1.2V and 3.3V, connection of VBUS and USB lines doesn't make any difference compared to un-powered state.

Regards,
Anil  

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5 Replies
Anonymous
Not applicable

Hi Alin,

The VBUS on the US port which is coming from the Host is connected to VBUS_US to indicate the connect/disconnect status to the Hub.

When the VBUS is disconnected (assuming US is disconnected), HX3 Hub will be in suspend with 1.2V and 3.3V connected.

What is the scenario in which the USB3.0 lines are connected and VBUS is disconnected in your case? Is it an embedded application?

Please provide more details.

Regards,
Anil

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I plan on putting a switch on the VBUS line and turn it off during certain scenarios. That's the scenario when VBUS is not present and the USB lines are.

I have a new question too. What happens if VBUS and the USB lines are available, but the 1.2V and the 3.3V are not?

Thank you.

Alin

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Anonymous
Not applicable

Hi Alin,

There will be no issue in disconnecting the VBUS while the rest of the USB lines are connected on the upstream, with 1.2V and 3.3V supplies of Hub are powered.

Since the Hub IC core is not powered with 1.2V and 3.3V, connection of VBUS and USB lines doesn't make any difference compared to un-powered state.

Regards,
Anil  

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Anil,


Thanks for the response.

Is VBUS an interrupt only line? Is there any power drawn from it? Datasheet does not indicate any...

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Anonymous
Not applicable

Alin,

Yes, the VBUS_US pin is an interrupt only line and it will not draw any power.

Regards,
Anil

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