2.4.1 Requirements

  • A 5.62 kΩ resistor is connected to the RTUNE pin for USB external tuning and a 1% tolerance voltage divider is placed on USB VBUS to transform the 5V into the PIO voltage for VBUS detection.

    → Refer to section “Typical Connection” in the USB High Speed Device Port (UDPHS) and USB Host High Speed Port (UHPHS) chapters of the SAM9X7 Series data sheet.

  • The TST pin is grounded.
  • The ADVREFN pin is connected to the PCB ground plane.
  • If the design does not need JTAG boundary scan, tie the JTAGSEL pin to GND or leave it floating.
  • A 32.768 kHz crystal is placed between XIN32 and XOUT32.

    → Refer to section “32.768 kHz Crystal Oscillator” in the Electrical Characteristics chapter of the SAM9X7 Series data sheet.

  • A high-frequency clock source is provided either through a crystal placed between XIN and XOUT or through an external clock generator.
  • If the clock generator option is chosen, it is recommended to ground XOUT to improve stability.

    → Refer to section “Main Crystal Oscillator” in the Electrical Characteristics chapter of the SAM9X7 Series data sheet.

  • Clock sources should be chosen with great care. 


    → Refer to section “Crystal Oscillator Design Considerations” in the Electrical Characteristics chapter of the SAM9X7 Series data sheet.