Murata Manufacturing Co has released the NFM18P series three-terminal multilayer ceramic capacitors, with dimensions of 1.6 x 0.8 x 0.8 mm. The devices can be used as decoupling capacitors for high-speed LSI, and are intended for use in mobile phones, PDAs and other equipment.
A decoupling capacitor functions as a filter to bypass high frequency components in power sources to the ground. In general, capacitors with two terminals are used for this purpose. However, large inductance components, generated between the two-terminal filters and the ground, have posed problems. Further inductance components become dominant in high frequency band ranges above the self-resonating frequency, largely degrading filter properties.
Designers have tried to solve this problem by combining several capacitors with different self-resonating frequencies, to obtain sufficient filter performance in wide frequency band ranges. This solution, however, demands increased packaging and adds to costs.
Murata’s feed-through capacitors feature small inductance components between capacitors and the ground. For this reason, their self-resonating frequencies are high, attenuating degradation of filter performance even in high frequency band ranges. Therefore, one feed-through capacitor will often be sufficient.
Whereas conventional feed-through capacitors are quite large in size (the smallest measuring 2.0 x 1.25 mm) and cannot carry large currents, the NFM18P series solves these problems with a thin ceramic layer and a polar structure designed to reduce resistance values.
The rated current of the NFM18P capacitor is up to 2A. “2A is sufficient for applications with LSI power source lines,” says Hironobu Kinoshita of the First Product Technology Section, EMI Products Division of Fukui Murata Manufacturing.
The capacitor shows impressive performance on an LSI power source line. In a test using capacitors with the same electrostatic capacity, a two-terminal capacitor inserted in an LSI line reduced voltage fluctuation from ±456 mV to ±165 mV. The feed-through capacitor reduced fluctuation on the same line to ±38 mV.
The price of the capacitor will be higher than conventional two-terminal devices but, as Hironobu Kinoshita stresses, “Operating costs will be reduced compared to using a case with several two-terminal capacitors.”
Murata Manufacturing CoFax (81) 44-433-0798
www.murata.com
