TUSB8044A: Hub appears to put terminations on downstream pins when there is no upstream partner for SS, causing downstream devices to mis-behave

Matt Leacock

Part Number: TUSB8044A

Tool/software:

HI I'm currently debugging an issue where it appears that the hub is putting termination on the downstream port SS pins when there is no upstream SS partner.

The signal chain looks like this TUSB8044A ->TUSB5522PI->TMUXHS4446->Type-c Connector. Would any of these give a false positive to the hub for it to think there is an upstream partner? What conditions would cause the hub to put downstream terminations if there are no upstream connection?

The hub is not generating LFPS pings or jumping into compliance mode, but the downstream device is.

What is happening is on port 4 there is a Realtek RTL8153B connected, it is jumping into compliance mode and not enumerating usb 2.0. The host device is an iPad 10th gen which is USB2.0 only. A USB 2.0 mouse will always work.

Thanks,

5 months ago

0 Brian Zhou 5 months ago

TI__Guru*** 145550 points

If hub upstream is connected to USB2, then downstream port should be USB2 as well, Can you send schematic for review?

Best

Brian

0 Matt Leacock 5 months ago in reply to Brian Zhou

Prodigy 180 points

Hi Brain,

I'll send you the schematic directly, I won't upload it to a public forum.

The hub is set up to support 3.2 and 2.0, It should be able to support both dynamically correct?

0 Brian Zhou 5 months ago in reply to Matt Leacock

TI__Guru*** 145550 points

Matt Leacock said:
The hub is set up to support 3.2 and 2.0, It should be able to support both dynamically correct?

correct.

0 Matt Leacock 4 months ago in reply to Brian Zhou

Prodigy 180 points

This issue has been resolved. There was a patch for the Reatek device that improved the RX detection.

Thanks for the support on this Brian.

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TUSB8044A: Hub appears to put terminations on downstream pins when there is no upstream partner for SS, causing downstream devices to mis-behave