Selasa, 05 Juli 2011


Choosing the best chip multilayer capacitors (MLCC) for an application can involve a difficult trade-offs involving stability, capacitance and cost. European passive component manufacturer, Syfer Technology has introduced various devices that increase choice and reduce the compromise.

For applications that require maximum stability, the capacitor dielectric chip based C0G/NP0 is an obvious choice as the capacitance is not different from the applied voltage. But what if you want to capacitance values ​​higher than the maximum of a few nF usually available in C0G?

X7R capacitors deliver higher capacitance, because they have a dielectric constant in the region 2000-4000. With more capacitance per unit volume, they are generally smaller for comparable values ​​of capacitance, and usually costs much lower than the C0G. However, the variation of capacitance with temperature can be as much as ± 15% over the temperature range from -55 ° C to 125 ° C with no voltage applied. In fact there are no limits at all are determined to X7R with a voltage is applied, and so significant capacitance loss can occur. This effect is magnified for the dielectric is less stable.

But now X7R dielectric MLCCs are available from Syfer with capacitance variation is defined under the DC voltage is applied, at full operating temperature range. Derating or using high-voltage rating may reduce the capacitance drop, but where an application requires a more stable performance with minimal voltage derating the part is perfect. The advantage of the device with clearly defined limits to the fluctuations is that they give designers the data they need to make informed choices for their application.

Syfer range of TCC / VCC X7R MLCCs are available in two versions. "B" dielectric in accordance with MIL STD code BX dielectric and the IECQ-CECC standard 2x1, while the "R" code dielectric (in accordance with MIL STD BZ dielectric and IECQ-CECC standard 2C1.) The 2x1 (BX) devices, for example, is the most stable voltage version of the X7R, at +15 to -25% load capacitance with the full rated DC voltage applied at full temperature range. The 2C1 (BZ) offers to fill 20% -30 capacitance.

The 2x1 (BX) range includes devices rated at 50V, 100V and 200V, and with a capacitance range from 100pF to 4.7nF (50V, 0603), through a 2.7nF to 180nF (50V, 1808) up to 15nF to 1μF (50V, 2225 ). Comparable devices in the range (BZ) 2C1 is 100pF to 5.6nF (50V, 0603), 2.7nF to 220nF (50V 1808), and 15nF to 1.5μF (50V, 2225).

This X7R MLCC dielectrics range is suitable for use in a variety of coupling and power supply through the application, while the high voltage types are particularly sought after in switching power supplies, dc-dc converters, automotive and aerospace equipment.

The devices are available with FlexiCap ™ terminations Syfer cessation using the flexible material it owned, which makes them much more resistant to damage by bending or flexing, and when under pressure and extreme temperature cycling. Termination alternatives are also available.

Surface mount capacitors already in production and available immediately at 8 weeks of lead time from Syfer of Norwich, England manufacturing facility. The device is fully RoHS compliant.

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