TUSB2077A: BUSPWR pin switching

Gert-Jan van Noort

Part Number: TUSB2077A

Hello,

Recently I found out an issue with switching from buspowered to selfpowered mode.The hub works fine in most cases, however when I
connect the hub to the host, connect a device on one of the downstream ports above number 4 (the exclusively self powered ones) and then connect the hub on a external power supply, the
HUB is not resetting and the downstream port won't work before a manual reset. I expected if there is a logic change on the BUSPWR pin that there will be a reset.

The strangest thing is when I connect the external power supply quickly after connecting the host, it will work fine. It needs to be at least 10 seconds or something to not work anymore.

Anyone familiar with this issue?

Kind regards,

Gert-Jan

over 1 year ago

0 Brian Zhou over 1 year ago

TI__Guru*** 127625 points

Gert:

Do you have overcurrent protection for every downstream ports? can you send schematic for review?

Regadrs

Brian

0 Gert-Jan van Noort over 1 year ago in reply to Brian Zhou

Prodigy 10 points

Yes, PWRONx does not recover after about 6 seconds without external power supply. before the 6 seconds the PWRONx works fine. the red PORTPWR Led turns on aswell.

0 Gert-Jan van Noort over 1 year ago in reply to Gert-Jan van Noort

Prodigy 10 points

apparently SUSPND is the problem here. During SUSPND mode, a change in PORTPWR is not noticed by the hub.

0 Brian Zhou over 1 year ago in reply to Gert-Jan van Noort

TI__Guru*** 127625 points

Please check this E2E, in bus powered mode, port 5-7 are disabled.

(+) TUSB2077A: /BusPwr signal causes three highest-numbered ports to disable when low! - Interface forum - Interface - TI E2E support forums

Regards

Brian

0 Gert-Jan van Noort over 1 year ago in reply to Brian Zhou

Prodigy 10 points

Yes, but what if the HUB is in SUSPEND, after that I connect external power supply to go into selfpower mode. Will the HUB go out of suspend if I connect something on port 5 - 7? Or will the HUB go out of suspend after a change on BUSPWR? for me it does neither of those.

Thanks for your help so far, I appreciate it!

0 Brian Zhou over 1 year ago in reply to Gert-Jan van Noort

TI__Guru*** 127625 points

Even in self-powered mode, once the hub into suspend mode, it may not get out of suspend mode until a USB device is connected.

Main issue here is that port5-7 are disabled in bus-powered mode then PORTPWR will not functional as expected for port 5-7.

Regadrs

Brian