For applications that require maximum stability, then chip capacitors based on the C0G/NP0 dielectric are the obvious choice as capacitance does not vary with applied voltage. But what if you want higher capacitance values than the few nF maximum typically available in C0G?
X7R capacitors deliver higher capacitance, as they have a dielectric constant in the region of 2000-4000. With more capacitance per unit volume, they are generally smaller for the comparable capacitance values, and are typically much lower cost than C0G. However, their capacitance variation with temperature can be as much as ±15% over the temperature range from -55°C to +125°C with no voltage applied. In fact no limit at all is specified for X7R with applied voltage, and so significant capacitance loss can occur. This effect is magnified for less stable dielectrics.
But now X7R dielectric MLCCs are available from Syfer with a defined capacitance variation under applied DC voltage, across the full operating temperature range. Derating or using a higher voltage rating can reduce the capacitance drop but where an application requires more stable performance with minimal voltage derating then these parts are particularly suitable. The advantage of devices with a clearly specified limit for the fluctuation is that they give designers the data they need to make an informed choice for their application.
Syfer’s TCC/VCC range of X7R MLCCs is available in two versions. The “B” code dielectric conforms to MIL STD BX dielectric and IECQ-CECC 2X1 standards, while the “R” code dielectric (conforms to MIL STD BZ dielectric and IECQ-CECC 2C1 standards.) The 2X1 (BX) devices, for example, are the most voltage stable of the X7R versions, at +15 to –25% capacitance charge with full rated DC voltage applied across the full temperature range. The 2C1(BZ) offer +20 to -30% capacitance charge.
The 2X1 (BX) range includes devices rated at 50V, 100V and 200V, and with capacitance ranges from 100pF to 4.7nF (50V, 0603), through 2.7nF to 180nF (50V, 1808) up to 15nF to 1µF (50V, 2225). Comparable devices in the 2C1 (BZ) range are 100pF to 5.6nF (50V, 0603), 2.7nF to 220nF (50V 1808), and 15nF to 1.5µF (50V, 2225).
These X7R dielectric MLCC ranges are eminently suitable for use in a wide range of coupling and power supply bypassing applications, while the higher voltage types are particularly sought after in switching power supplies, dc-dc converters, automotive and aerospace equipment.
The devices are available with FlexiCap™ terminations using Syfer’s proprietary flexible termination material, which make them considerably more resistant to damage through bending or flexing, and when under stress and temperature cycling extremes. Alternative terminations are also available.