TUSB8041A: USB 3.1 speeds not supported

Sam Harris

Part Number: TUSB8041A

Hello,

I have designed a PCB which contains a TUSB8041A USB 3.1 hub. The PCB is 6-layer with controlled impedance and intra-pair length matching for the USB lines.

The TUSB8041A DFPs are connected to:

a USB Type-C connector which connects to a USB 3.1 camera via a USB 3.1 cable, and
two USB 2.0 devices contained on the PCB.

The TUSB8041A UFP is connected to a USB Type-C connector which is connected to a computer via a USB 3.1 cable.

However, the camera bandwidth is restricted to ~50MB/s which leads me to believe that the TUSB8041A is falling back onto USB 2.0 interface. Looking at the schematics, is there anything amiss?

4130.TUSB8041A.pdf

4152.TUSB8041A-DFP.pdf

7268.TUSB8041A-UFP.pdf

over 6 years ago

0 Brian Zhou over 6 years ago

TI__Guru*** 145550 points

we will review the schematic

0 JMMN over 6 years ago

TI__Guru 60870 points

Hi Sam,

Where are the USB 3.0 signals from the type c connectors that are not routed to the hub routing? Is there an offpage Superspeed switch? The AC capacitors for the superspeed lines are typically 100 nF and only on the TX pair, your design has higher values and they are on both pairs. This may be causing the connection issues.

Regards,
JMMN

0 Sam Harris over 6 years ago in reply to JMMN

Prodigy 170 points

Hello JMMN,

Thank you for your reply.

The UFP and DFP USB Type-C signals go to a MUX, see the attached schematics. Sorry for not including these in the original post! The MUXs are on either side of the TUSB8041A. With regards to the AC capacitors, these values were recommended to me on TI E2E forum post: e2e.ti.com/.../745055

TUSB8041A-DFP-MUX.pdf

TUSB8041A-UFP-MUX.pdf

0 JMMN over 6 years ago in reply to Sam Harris

TI__Guru 60870 points

Hi Sam,

Ok, I'm checking with the engineer who supports muxes on the AC caps. In the meantime, what OS are you running? If you are running microsoft you can download usbview.exe and see if the hub and camera are connecting at superspeed or high speed. You can also do this through Device Manager using the View by Connection mode.

Regards,
JMMN

0 David (ASIC) Liu over 6 years ago in reply to JMMN

TI__Guru**** 176991 points

Sam

The AC coupling capacitor placement is correct.

Thanks
David

0 Sam Harris over 6 years ago in reply to JMMN

Prodigy 170 points

Hello JMMN,

Merry Christmas and a Happy New Year.

Sorry for the delayed reply, just back from the holidays. Using USBView.exe, it looks like the TUSB8041A only connects at high speed - see the attached screenshot. I am using Windows 10.

0 JMMN over 6 years ago in reply to Sam Harris

TI__Guru 60870 points

The TUSB8041A is correctly connected at both High Speed (Generic USB Hub PID 0x8142) and Super Speed (Generic SuperSpeed USB Hub PID 0x8140). I only see one downstream device connected on Port 2 of the USB 2.0 hub though. Are the other devices installed?

0 Sam Harris over 6 years ago in reply to JMMN

Prodigy 170 points

Hello JMMN,

Attaching the USB 3.1 camera (XIMEA USB3.0) to the DFP of the TUSB8041A makes it appear under the "Generic USB Hub". However, it does not appear under the "Generic Superspeed USB Hub". This means the camera bandwidth is severely reduced.

The only other connected device is a FTDI bridge (USB Serial Converter) and it is working. It is only USB 2.0, hence it only appears under "Generic USB Hub".

0 JMMN over 6 years ago in reply to Sam Harris

TI__Guru 60870 points

HI Sam,

Are you ever able to see the camera connect at superspeed, if the system is already running and you do a hard reset tot he camera, which speed does it show up at?

Regards,
JMMN

0 Sam Harris over 6 years ago in reply to JMMN

Prodigy 170 points

Hello JMMN,

Thank you for getting back in touch. The camera never connected at superspeed and, unfortunately, I cannot issue a hard reset to the camera when it is running.

We believe the problem is down to the PCB design and in particular, the differential pairs. I will update this when the redesigned PCB comes back, to see if the problem has been fixed.

0 JMMN over 6 years ago in reply to Sam Harris

TI__Guru 60870 points

Ok, let us know if the problem persists.

Thanks,

JMMN

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TUSB8041A: USB 3.1 speeds not supported