Verdin iMX8M Plus PCIe external clock

Technical Support
1

Hi,

is it possible to use external PCIe Clock for Verdin modules?
from what I found build-in clock generator of iMX8mp is not compatible with Gen3 (jitter is too big).
For new revision of out product we would like to use PCIe and I would like to include external clock generator if possible, to be able to use Gen3 in the future.

If it is possible to add external generator could you provide some reference design?

Best Regards
Paweł

2

Hi, I’m the Toradex AI Assistant. The Toradex Support team will follow up with you shortly!

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Hello Paweł,

Thank you for reaching out with your question about using an external PCIe clock generator with the Verdin iMX8M Plus module. You are correct that the internal clock generator may not meet the jitter requirements for PCIe Gen3, and using an external clock source is indeed a viable solution.

To implement an external PCIe clock generator, you would need to design a custom carrier board that incorporates the external clock circuitry. Here are some key considerations for your design:

  1. Clock Source Selection: Choose a clock generator that complies with PCIe Gen3 specifications, particularly focusing on jitter performance.

  2. Clock Routing: Ensure the clock signal is routed with minimal skew and jitter. Use controlled impedance traces and consider differential signaling if applicable.

  3. Power Supply: Provide a stable power supply for the clock generator to minimize noise and ensure reliable operation.

  4. Integration with SoM: Connect the external clock to the appropriate pins on the Verdin iMX8M Plus module. You may need to consult the module’s datasheet for pin assignments and electrical characteristics.

  5. Software Configuration: Modify the device tree and any relevant software configurations to recognize and utilize the external clock source.

While I don’t have a specific reference design to offer, you can refer to the Verdin iMX8M Plus datasheet and design guides for more detailed information on interfacing with the module. Reviewing existing carrier board designs might also provide useful insights into best practices for integrating external components.

If you have any further questions or need additional guidance, feel free to ask!

Best regards,
Toradex AI Assistant.

Please, also check if these links can help you solve your problem:

Offset in main oscillator in imx7d.

3

Hi @WisniewskiP

Are you designing your own carrier board?

Have you already checked the carrier board design guide page?