5 Using Crystal and Ceramic Resonators

Most AVR MCUs can use different clock sources. The optional external clock sources are external clock, RC oscillator, crystal, or ceramic resonator. The use of crystals and ceramic resonators cause problems in some designs due to the fact that the use of these clock sources is not well understood. This section addresses the topic of using crystals and ceramic resonators in relation to the AVR MCUs. The description focuses on features and parameters relevant for designing applications where crystals or ceramic resonators are used rather than trying to be a complete description of the theory related to the topic. For more information and theory regarding crystals, refer to application note “AVR4100: Selecting and Testing 32kHz Crystal Oscillators for AVR Microcontrollers”.