Quartz Crystal Oscillator
Vibrating is the abbreviation of quartz crystal oscillator, also known as active crystal oscillator, which can generate the clock frequency signal necessary for the central processing unit (CPU) to execute instructions, and the execution of all instructions of the CPU is based on this, the higher the clock signal frequency, the faster the CPU will usually run.
As long as it is an electronic product that contains a CPU, it contains at least one clock source, and even if the actual oscillation circuit is not visible from the outside, it is integrated inside the chip, which is called the heart of the circuit system.
The nominal frequency of the periodic output signal is the frequency specified in the crystal component specification, and it is also the primary parameter that engineers pay attention to when designing circuits and selecting components. The nominal frequency of crystal oscillator is commonly used between 1~200MHz, such as 32768Hz, 8MHz, 12MHz, 24MHz, 125MHz, etc., and higher output frequencies are also commonly used PLL (phase-locked loop) to multiply the low frequency to more than 1GHz.
The frequency of the output signal will inevitably have a certain deviation, we use the frequency error (FrequencyTolerance) or frequency stability (Frequency Stability), expressed in ppm, that is, parts per million (1/106), is the amount of change relative to the nominal frequency, the smaller this value means the higher the accuracy.
For example, the deviation of the 12MHz crystal oscillator is ±20ppm, which means that its frequency deviation is 12×20Hz=±240Hz, that is, the frequency range is (11999760~12000240Hz)
In addition, there is a temperature frequency difference (Frequency Stability vs Temp), which is the allowable deviation of the operating frequency from the reference temperature over a specific temperature range, and it is also measured in ppm.
