Depending on the device variant (see Section 6), the device with USS module supports a high-frequency crystal on the USSXT pins. External bypass capacitors for the crystal oscillator pins are required. A 22-Ω resistor is required to be serially connected closely to the USSXTOUT pin as shown in Figure 10-4. The USSXT does not support bypass mode, so it is not possible to apply digital clock signals to the USSXTIN pin. Never connect the USSXTIN pin to a power supply line (AVCC, DVCC, or PVCC). If the USSXT pins are not used, terminate them according to Section 7.6.
Figure 10-4 shows a typical connection diagram.
Consider the following items for the USSXT layout:
Figure 10-5 shows recommended PCB layout.