![]() above only two electrodes and three ground planes are shown. All these measures mean more effective filtering at higher frequencies. A further inductance reduction is achieved by the opposite current direction in opposed electrodes that is possible by the inserted ground planes. The inserted ground planes reduce the current loop in comparison to standard MLCCs thus decreasing the inductance of the device. These EMI filters are mostly used in lower voltage applications but larger sized X2Y devices can be designed also for mains applications where they for safety reasons require test voltages far above 1 kV. X and Y capacitors in an X2Y device reflect the patented design shown in Figure 15. ![]() Schematic of the construction of the four terminal X2Y capacitor. The device is called X2Y.Ī principle sketch of the construction looks like as shown in Figure 15.įig ure 15. Electrical connections are through via and edge terminations.Īnother EMI filter, also consisting of integrated ceramic capacitors, is built of a matched and balanced pair of Y capacitors (line to ground) together with an X capacitor (between the lines) connected to a four-terminal device4 as shown in Figure 14. An example of such a design is shown in Figure 13.įilters in connectors are constructed in the same way but in shape of circular discs with discoidals arranged around the pin feedthroughs. This type of capacitor arrays is preferably used in EMI suppression applications. Moreover, we will increase the electrical filtering capability due to reduced inductance in shorter internal conductors. If we by means of multilayer technology build a number of ceramic capacitor elements into a ceramic block in a planar array construction we may save a considerable board space (see more in next LTCC filters chapter). An EMI filter example of SMD design and corresponding circuit diagram. In the following sequence of figures it is shown which basic style that has to be used in different impedance conditions in order to reduce the mismatch.įigure 13. The LC filters are built up by their elements in certain basic configurations. In the practical circuit, however, the attenuation generally is poorer. Moreover it is necessary to use shielded cables, correct connectors and test fixtures supplied with shielding walls. ![]() If the attenuation characteristics are to be correctly established it is important that the generator side is effectively shielded from the receiver side. Note therefore in catalogues and specifications if the I.L. Maximum DC current – full load operation – impairs inductor inductance. The attenuation of the filter in its turn depends among other things on the DC current. If we apply a load in the circuit that differs from the line impedance, the I. ![]() Measurement of insertion loss according to MIL-STD-220 ![]()
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