Increased crystal impedance, resulting in reduced oscillation stability

The oscillation stability reduces due to the increase of Crystal Impedance (CI).

When the CI value is significant, the starting or stopping voltage becomes high. That is, even if the voltage increase, it is difficult to start the oscillation. Also, the voltage slightly lower, and the oscillation becomes unstable or stopped.

Besides, the CI value is one of the essential parameters in Crystal. For oscillation instability, no oscillation effects and determines the allowance.

How to solve it?

First, we need to confirm whether the oscillation is stable, and the allowance of the oscillation scale is 5 to 10 times or more. The oscillation circuit of this allowance, negative impedance (r) > CI x (5 ~ 10)

When the allowance is insufficient, there is a delay in starting the oscillation or failure in which the starting voltage becomes high. Moreover, the oscillation is unstable or not start to oscillate.

To improve the allowance, the following two methods recommended by YIC:

  1. Improving the Negative Impedance – In the oscillating circuit, the power consumption and the negative impedance can solve by increasing the oscillating circuit current. However, this method has the disadvantage of increasing power consumption.
  2. Use a quartz crystal with a small CI value