Multilayer ceramic capacitors (MLCCs) are used extensively in modern electronics because they offer high volumetric efficiencies and low equivalent series resistances at attractive prices. These advantages make MLCCs nearly ideal for a wide range of applications, including output capacitors for power supplies and local decoupling capacitors for integrated circuits. The various types of MLCCs are delineated primarily by their temperature coefficient, which is the amount of variation in their capacitance over a specified temperature range. Class I types, given a designation of NP0 or C0G, must vary less than +/–30 ppm over their operating temperature range, while Class II types can change anywhere from +/–15 percent (X7R) to +22 percent /–82 percent (Z5V) .
The temperature coefficient of an MLCC is a direct effect of the materials used in the ceramic that forms the capacitor dielectric. Furthermore, the dielectric material also determines the electrical characteristics of the capacitor. Class II dielectric types (X7R, Z5U, Z5V), often are referred to as “high-k” ceramics because their dielectric materials, have relative permittivities that range from 3000 (X7R) up to 18000 (Z5U). Class I C0G capacitors tend to have relative permittivities in the range of six to 200 . The benefit of increased relative permittivity of the dielectric material is that high-k MLCCs are available in much larger capacitance values and smaller packages than C0G types.
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