Hello, my name is Taro.
I am writing about frequency accuracy of clock generators.
Frequency accuracy is not mentioned in the datasheet of clock generators.
However, crystal resonator and crystal oscillator generally have frequency accuracy listed in the PPM.
Why isn't it there, since it should be important for clock generators and oscillators to be substituted?
The frequency accuracy of a clock generator depends on the frequency accuracy of the reference.
Many clock generators use a reference input as a source for frequency division/multiplication and other adjustments.
The frequency accuracy of the PLL output depends on the frequency accuracy of the reference clock signal because the clock is synchronized once by the PLL inside the clock generator.
Although the specifications of the Jitter depend on each clock generator, the frequency accuracy can be considered equal to the source oscillation.
This is the reason why frequency accuracy is not mentioned in the datasheets of clock generators.
Frequency Accuracy of Quartz Crystals
The frequency accuracy listed in the datasheet of a crystal resonator unit is that of a matched state.
Therefore, a crystal resonator that is not matched may not meet the frequency accuracy listed on the data sheet.
In addition, the frequency accuracy listed in the datasheet of the crystal resonator is divided into Initial / Temp / Aging.
Initial describes the frequency characteristics of the crystal resonator. This depends on the purity of the crystal and the cutting process.
The output frequency of the crystal also changes with temperature.
Temp indicates how much the frequency accuracy varies with respect to the crystal's guaranteed operating temperature.
It means that the frequency accuracy of the data sheet is satisfied at the stated temperature, so if the temperature changes, the frequency accuracy will also change.
Aging is the physical vibration of the crystal blank to produce the clock signal. As a result, the crystal blank wears out and deteriorates over time.
Aging describes the change in frequency accuracy due to aging.
Come to think of it, Bee, who used to join Synchronous, bought an RTC crystal resonator and lamented that it was not clocked (lol).
Please take a look at my previous article on RTC.
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