USB Power Limit Discrepancy in Nvidia Jetson Orin Nano Dev Kit

Issue Overview

Users have identified conflicting specifications regarding the USB power limits for the Nvidia Jetson Orin Nano Dev Kit. The main discrepancy lies in the stated power delivery capabilities of the USB stacks on the carrier board. The official carrier board specification document (Jetson_Orin_Nano_DevKit_Carrier_Board_Specification_SP-11324-001_v1.1.pdf) mentions a 3A limit per stack, which appears to be inconsistent with other documentation and hardware specifications.

The issue impacts users who are planning peripheral connections to their Orin Nano dev kit, as it creates uncertainty about the actual power delivery capabilities of the USB ports. This discrepancy could potentially lead to improper power management or device connection issues if not clarified.

Possible Causes

1. Documentation Error: The most likely cause is an error in the carrier board specification document. The 3A limit mentioned in section 2.1 appears to be a typo or outdated information that was not corrected during document revision.

2. Misinterpretation of Hardware Capabilities: The discrepancy might arise from different interpretations of the AP22811 load switch’s capabilities, which is used in the USB stacks.

3. Inconsistent Specifications Across Documents: Various documents and design files related to the Orin Nano Dev Kit seem to provide different information, leading to confusion.

4. Difference Between Typical and Maximum Ratings: The discrepancy could be due to a mix-up between typical operating conditions and absolute maximum ratings of the components used.

Troubleshooting Steps, Solutions & Fixes

1. Verify Hardware Specifications:

   • Refer to the AP22811 datasheet for accurate power limit information.
   • The datasheet indicates that the recommended operating point is 2A, but the device can potentially deliver up to 3.2A before shutting off.

2. Consult Reference Design Files:

   • Review the P3768_A04_Concept_schematics.pdf and P3768_A04_BOM.xls files in the Jetson_Orin_Nano_DevKit_Carrier_Board_Reference_Design_Files_A04_20230320.zip.
   • These documents consistently mention the AP22811 and its 2A limit, providing more reliable information.

3. Understanding the Actual Power Limits:

   • Assured Performance Limit: 2.2A
   • Maximum Potential Limit: 3.2A
   • Note that the device won’t go into overload/shutdown until at least 2.2A, but there’s a possibility it can deliver up to 3.2A before shutting off.

4. Planning Peripheral Connections:

   • When designing your setup, it’s recommended to adhere to the assured performance limit of 2.2A per USB stack for reliable operation.
   • Consider the USB-C port as one stack, separate from the other USB ports.

5. Reporting the Documentation Error:

   • Report the discrepancy to Nvidia’s support team or through their official channels.
   • Suggest updating section 2.1 of the carrier board specification document to reflect the correct power limits.

6. Best Practices for Power Management:

   • Always design your system with a safety margin below the assured performance limit (2.2A) to account for variations and ensure stable operation.
   • If a peripheral requires more power, consider using powered USB hubs or alternative power delivery methods.

7. Monitoring Power Consumption:

   • Use power monitoring tools or hardware to verify the actual power draw of your USB devices during operation.
   • This can help ensure you’re staying within safe limits and identify any potential issues.

By following these steps and understanding the actual power limitations of the Nvidia Jetson Orin Nano Dev Kit’s USB ports, users can safely plan their peripheral connections and avoid potential power-related issues. It’s worth underlining that while the hardware might support up to 3.2A in some cases, designing for the 2.2A assured limit is the most reliable approach.