TUSB8042A: [Consultation] USB HUB Cascade Design Check

Paul Lei

Part Number: TUSB8042A

Tool/software:

Hi TI service team,

For TUSB8042AIRGCR USB HUB application in my system, I have questions about the functional operation want to consult with you.

For my requirements, I might cascade two USB HUB controller like below show.

Is it feasible to do this two USB HUB controller cascade?

Please help to give comments to my USB design.

8 months ago

+1 Brian Zhou 8 months ago

TI__Guru*** 149420 points

This is correct, you need connect upstream port of 2nd hub to any downstream port of 1st hub. up to 5 hubs.

Best

brian

0 Paul Lei 8 months ago in reply to Brian Zhou

Prodigy 170 points

Hi Brian,

Thanks for quick replies, this information is useful and good for my design.

Best Regards,

Paul Lei

0 Paul Lei 8 months ago in reply to Paul Lei

Prodigy 170 points

Hi Brian,

Another question, do we "must" use same "VBUS" sharing from 1st USB HUB controller with 2nd one?

Or it's just a suggestion.

If yes, what's the risk/concern/impact as we don't use this suggestion?

Thanks.

Best Regards,

Paul Lei

0 Brian Zhou 8 months ago in reply to Paul Lei

TI__Guru*** 149420 points

Hi Paul:

I recommend connecting vbus from 1st hub downstream port to USB_DET (pin 48) of 2nd hub. So if 1st hub is off, then 2nd hub will off too.

Best

brian

0 Paul Lei 7 months ago in reply to Brian Zhou

Prodigy 170 points

Hi Brian,

Got it, so if I used more than two USB HUB cascading, you still recommend to connect VBUS from 1st VBUS (pin48, USB_VBUS) to the followings (e.g.: 2nd/3rd/../the last one) ?

Thanks a lot.

Best Regards,

Paul Lei

0 Brian Zhou 7 months ago in reply to Paul Lei

TI__Guru*** 149420 points

Hi Paull:

what I suggested is to connect USB_VBUS from 2nd hub to the downstream port Vbus of 1st hub.

regards

brian

0 Paul Lei 7 months ago in reply to Brian Zhou

Prodigy 170 points

Hi Brian,

Got it, I think you mentioned the Vbus is as below figure.

From 2nd hub to the downstream port Vbus of 1st hub.

Thanks.

0 Paul Lei 7 months ago in reply to Paul Lei

Prodigy 170 points

Hi Brian,

I want to ask that the 2nd HUB VBUS will use the same power net with 1st HUB downstream, which is also 1st HUB VBUS.

Am I correct?

Thanks.

0 Brian Zhou 7 months ago in reply to Paul Lei

TI__Guru*** 149420 points

1st HUB downstream is from host, 1st HUB downstream VBUS is different from 1st HUB USB_VBUS.

Best

Brian

0 Paul Lei 7 months ago in reply to Brian Zhou

Prodigy 170 points

Hi Brian,

OK.

So I think you say that 1st HUB downstream port should connect into 2nd HUB upstream, and also USB_VBUS.

Am I correct?

Thanks.

0 Brian Zhou 7 months ago in reply to Paul Lei

TI__Guru*** 149420 points

Correct.

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TUSB8042A: [Consultation] USB HUB Cascade Design Check