How to Calculate the 12MHz Frequency Deviation of the Crystal Oscillator?

Calculation Method

12MHZ=12000000Hz, which is the center frequency of the crystal oscillator. We are also based on the value 12000000Hz as a reference to calculate the actual frequency deviation of the XTAL is how much PPM . Conversely, the specific frequency deviation range of the crystal oscillator can be calculated according to the PPM value in the crystal oscillator parameters. It is inferred from this whether the crystal frequency accuracy meets the requirements of the chip.

If the frequency deviation of the crystal (12MHz) is ± 10ppm, the frequency deviation is converted to an actual 120Hz. By analogy, if the crystal oscillator is 12MHz and the frequency deviation is ±20ppm,

the normal frequency deviation range of the crystal oscillator is: 11999760Hz~12000240 Hz (11.999760 MHz~12.0000240 MHz).

If the frequency deviation of the crystal oscillator ( 12MHz) is ±30ppm, the normal frequency deviation range of the crystal oscillator is: 11999640Hz~12000360 Hz (11.999640 MHz~12.0000360 MHz).

It can be concluded from the above that if the ±10ppm accuracy of the crystal oscillator (12MHz) you need, and the crystal oscillator is tested at room temperature (25℃±2℃), its output frequency should be in the frequency range of 11.999880 MHz to 12.0000120 MHz. Otherwise, it should be treated as frequency deviation.