The processing systems on an integrated circuit require clock signals for timing and synchronization. Crystal oscillators or ceramic resonators are widely used for obtaining these clock signals. A crystal oscillator includes a crystal that implements a piezoelectric effect of converting mechanical vibrations to electrical impulses. When alternating currents or voltages are applied to the crystal, it will vibrate at a resonant frequency, and harmonic modes thereof. To initiate and amplify the piezoelectric effect, an oscillator circuit is coupled to the crystal. A frequency of the generated oscillator signal is governed by multiple factors including a type of crystal.
The ceramic resonators are variable frequency oscillators that include a piezoelectric ceramic material. When an oscillator circuit is coupled to the ceramic material, the resonant mechanical vibrations in the device generate an oscillator signal of a specific frequency. Different types of crystals and ceramics are used to generate multiple oscillator signals based on the application domain.
However, the oscillator circuit coupled to a crystal or ceramic material for initiating and amplifying the oscillation varies with the type of crystal or ceramic material. Thus, an oscillator circuit used with a quartz crystal is not compatible with certain ceramic material. An integrated circuit generally requires multiple oscillator circuits to support multiple integrated devices functioning at different clock frequencies. Therefore, multiple pads are provided on these integrated circuits to support multiple oscillator circuits. This increases a number of pins used on the integrated circuit.