Lack of Spread Spectrum Support on Jetson Orin Nano Dev Board’s Extperiph Clocks

Issue Overview

Users of the Nvidia Jetson Orin Nano Dev board have reported a lack of spread spectrum (SS) support on the extperiph1 and extperiph2 clocks. This limitation extends to the parent clocks, including PLLP. The absence of spread spectrum capability can potentially impact electromagnetic interference (EMI) management and clock stability in certain applications.

Possible Causes

1. Hardware Design Limitation: The Jetson Orin Nano’s clock generation circuitry may not include dedicated spread spectrum modules for the extperiph clocks.

2. Architectural Decision: Nvidia may have intentionally omitted spread spectrum support for these specific clocks to optimize other aspects of the system’s performance or reduce complexity.

3. Technical Constraints: There might be technical challenges in implementing spread spectrum on these particular clock domains without affecting other critical system timings.

4. Cost Considerations: The decision to exclude spread spectrum support could be related to cost optimization in the hardware design.

5. Use Case Prioritization: Nvidia may have determined that spread spectrum support on these clocks was not a priority for the target applications of the Jetson Orin Nano.

Troubleshooting Steps, Solutions & Fixes

Given that spread spectrum support is not available for the extperiph1/2 clocks or their parent clocks (including PLLP) on the Jetson Orin Nano Dev board, there are no direct fixes or workarounds to enable this feature. However, developers can consider the following approaches to address potential issues related to the lack of spread spectrum:

1. EMI Mitigation Techniques:

   • Implement proper shielding and grounding techniques in your hardware design.
   • Use EMI suppression components such as ferrite beads or EMI filters on critical signal lines.
   • Optimize PCB layout to minimize electromagnetic emissions.

2. Clock Management:

   • Carefully review the clock tree and adjust clock frequencies if possible to avoid problematic harmonics.
   • Consider using external clock generators with spread spectrum capability for sensitive circuits, if feasible within your design constraints.

3. System Design Considerations:

   • Evaluate the impact of the lack of spread spectrum on your specific application.
   • If EMI is a critical concern, consider using additional EMI reduction techniques at the system level.

4. Alternative Clock Sources:

   • Investigate if other clock sources on the Jetson Orin Nano support spread spectrum and whether they can be used for your application.
   • Consult the Jetson Orin Nano Technical Reference Manual (TRM) for a comprehensive list of available clocks and their capabilities.

5. Software-based Solutions:

   • Explore software-based techniques to mitigate potential issues caused by the lack of spread spectrum, such as implementing dithering in digital signal processing applications.

6. Compliance Testing:

   • Conduct thorough EMI/EMC testing of your final product to ensure it meets regulatory requirements despite the lack of spread spectrum on these specific clocks.

7. Nvidia Support:

   • For critical applications where the lack of spread spectrum on extperiph clocks is a significant issue, consider reaching out to Nvidia support for guidance on alternative approaches or potential future hardware revisions.

8. Documentation and Design Notes:

   • Document this limitation in your project specifications and design notes to ensure all team members are aware of the constraint.
   • Update any relevant system documentation to reflect the lack of spread spectrum support on these clocks.

It’s worth mentioning that while these steps can help mitigate potential issues, they do not add spread spectrum capability to the extperiph1/2 clocks. Developers should carefully consider this limitation when designing systems based on the Jetson Orin Nano Dev board, especially for applications where EMI management is critical.