What needs to be considered while selecting MLCCs?
Class 1 (e.g.: NP0 = C0G)
In class 1, the material used is titanium oxide. There are smaller capacitance values in this class, which have low dependencies and have smaller tolerances. These types are used for all applications that require a fixed and stable capacitance value (e.g. real-time clock RTC).
Class 2 (e.g.: X7R, X5R, Y5V)
The material barium titanate is used for class 2. Features of this class are larger capacitance values, which have strong environment and application dependencies. This is due to the ferroelectric property of barum titanate and is reflected in capacitance dependencies:
- Capacity vs. Temperature
- DC bias (dependence of the capacity on the applied DC voltage)
- Aging behaviour
In addition, this material structure has piezoelectricity, which can also lead to microphonics.
How much capacitance do you really get? Class 2 examples
The capacitance value changes in an active application. Check the manufacturer's information to evaluate the occurring effects and the resulting capacitance. The following examples give an insight into the calculation of the best and worst case of the capacitance change of class 2 MLCCs.
Example Applications
