SPRACI9A October   2018  – July 2021 AM6526 , AM6528 , AM6546 , AM6548

 

  1.   Trademarks
  2. 1Introduction
  3. 2Recommendations Specific to the AM65x/DRA80x
    1. 2.1  EVM versus Data Sheet
    2. 2.2  Power
    3. 2.3  Reset
    4. 2.4  Boot Modes
    5. 2.5  Unused Signals
    6. 2.6  Clocking
    7. 2.7  System Issues
    8. 2.8  Low Power Considerations
    9. 2.9  DDR
    10. 2.10 MMC
    11. 2.11 OSPI and QSPI
    12. 2.12 GPMC NAND
    13. 2.13 I2C
    14. 2.14 CPSW Ethernet
    15. 2.15 ICSSG
    16. 2.16 USB
    17. 2.17 SERDES - USB3
    18. 2.18 SERDES - PCIe
    19. 2.19 JTAG and EMU
  4. 3References
  5. 4Revision History

2.16 USB

  • Have you planned for the routing in the USB interface? For detailed recommendations on proper USB signal connection and routing, see the High-Speed Interface Layout Guidelines Application Report. Add appropriate constraints or routing requirements to your schematic. This will vary from tool to tool.
  • Have you included the correct VBUS decoupling for your configuration? USB device operation requires decoupling capacitance of less than 10 µF connected to the USB VBUS. USB host operation requires decoupling capacitance of greater than 120 µF connected to the USB VBUS. VBUS decoupling capacitance should be connected close to USB connector.
  • Have you connected the USBx_DP and USBx_DM signals directly to the connector? USBx_DP and USBx_DM should never have any series resistors or capacitance on these signals. These signals should be routed with traces that do not include stubs or test points. These traces should be connected directly between the AM65x and the connector, unless EMI control is needed.
  • If you are including a USB device, have you connected the USB signals correctly? USBx_DP and USBx_DM should be routed with traces that do not include stubs or test points. These traces should be connected directly between the AM65x and the connector unless EMI control is needed. The connector ID pin can be left unconnected. The USBx_DRVVBUS is not used and can be left unconnected.
  • If you are including a USB host, have you connected the USB signals correctly? USBx_DP and USBx_DM should be routed with traces that do not include stubs or test points. These traces should be connected directly between the AM65x and the connector unless EMI control is needed. Connector ID should be grounded. The USBx_DRVVBUS should be connected to the enable of the 5-V VBUS power source. The VBUS pin on the USB connector should be connected to the output of the 5-V VBUS power from the power switch controlled by USBx_DRVVBUS
  • If you are including a USB hub, have you connected the USB signals correctly? USBx_DP and USBx_DM should be connected directly to the USB hub upstream port. The hub then distributes these signals to the downstream ports as needed. The connector ID should be grounded to enable host mode. The USBx_DRVVBUS should be unconnected. The USBx_VBUS should be connected to the output of the 5-V VBUS power source. It is also connected to the VBUS detect on the hub, which then allows the hub to selectively enable or disable, typically through a power switch to each downstream port.
  • Do you need components for EMI and ESD protection? Common-mode chokes may be needed for EMI/EMC control. These may reduce the signal amplitude and degrade performance. In addition, ESD suppression may also be required. If necessary, these components should be included in the design.