CX3 custom board: USB-3.0 enumeration issue

[GaK_4661021]

Hi,

We have developed custom hardware based on CX3. We are unable to enumerate our hardware on USB-3.0. We have USB-3.0 pin connection as below,

CX3       --- Connector Micro-B

SSRXM --- Pin9(SSRX-)

SSRXP ---  Pin10(SSRX+)

SSTXP ---  Pin7(SSTX+)

SSTXM ---  Pin6(SSTX-)

I have read in one KBA(USB Differential Pair Pin Inversion - KBA218753 ) that pin inversion is recommended for SSRXM and SSRXP but in our design, it is not followed as you can see above pin mapping. What could be the issue in our case?

[YashwantK_46]

Hello,

The above KBA only gives a suggestion that the pin pair can reversed and it's not mandatory to do so.

As mentioned in the last line of the KBA," In the design of the PCB layout, SSRX_N and SSRX_P (or the TX pairs) may cross with each other. Inversion is recommended to avoid this crossing."

Also, please let me know if you have referred to AN70707 and the Question 8 and 9 of this KBA: CX3 Hardware: Frequently Asked Questions - KBA91295

Please refer to this KBA for MIPI signal guidelines.

Regards,
Yashwant

[GaK_4661021]

Hi,

Thanks for the response.

Yes, We have referred reference schematic to design custom board. What could be the possible issue with USB-3.0 enumeration?

[GaK_4661021]

Hi,

Can you please help us that how can we narrow down the issue so that we can confirm that is this issue from the HW side of on FW side?

[YashwantK_46]

Hello,

From the shared schematics to JayakrishnaT_76, I found that the capacitors are placed on the RX lines instead of TX lines.

The capacitors C44 and C46 need to placed on the SSTXP and SSTXM lines (not on SSRXP and SSRXM) in the U port of FX3S.

Please make this change and test on different host PC with different OS platforms as well and see if there is any change.

Regards,
Yashwant

[GaK_4661021]

Hi,

Thanks for your response.

We have similar changes in our design. I don't know which schematic are you pointing but as I can verify in our schematic we have capacitors connected on SSTXM and SSTXP lines.

[YashwantK_46]

Hello,

Please share your latest schematics so that I can review it.

Regards,
Yashwant

[GaK_4661021]

Hi,

Please find below snapshot for USB-3.0 pin connection in our design,

[YashwantK_46 · Accepted solution]

Hello,

The capacitors look correct.

But i see that's it's mentioned as TX/RX/P/M 1000 Ohm DIff Pairs for the SS lines.

From AN70707, it is recommended to have a 90 Ohm DIfferential Impedence in the HS and SS lines.

Can you please share the entire schematics so that i can review it?

Regards,
Yashwant

[GaK_4661021]

Hi,

I have sent schematic to you.