Vertically stacked ceramic capacitor to filter the power supply


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The continuous development of microelectronics tends to downplay the importance of passive components. In fact, capacitors, resistors, and inductors play an essential role in all electronic systems and have a major influence on the dimensions and overall costs of the final products. The new SV Series from Knowles Precision Devices offers new ceramic capacitors stacked vertically to reduce the impact of PCBs due to electrolytic capacitors. Ceramic capacitors are resistant to very high voltages due to the ceramic materials used for insulation. The series aims to meet filtration requirements for energy sources, and meet high standards for quality and durability. As a division of Knowles, Knowles Precision Devices (KPD) is focused on producing a diverse range of highly engineered capacitors and microwave to mmWave components for use in critical applications in the military, medical, electric vehicle market and the fifth generation chip market. Equivalent series inductor and capacitor resistance The equivalent circuit of the capacitor is composed of capacitance; Equivalent series inductance, or ESL (sum of inductive elements, including terminals); DC high resistance (Rp) path in parallel with capacitance; And equivalent series resistance, or ESR (resistive effects placed in series in capacitance, combined into a single element). ESR and ESL have the effect of increasing the capacitor resistance unnecessarily, as the frequency increases and depends on the capacitor construction. The ESR value varies with frequency, temperature, and component life. The need to reduce the ESR of capacitors mainly stems from reducing the supply voltage of the microprocessors. The need to reduce ESL values ​​is associated with increasing clock frequencies. ESL reduction is pursued primarily at the device architecture level. “By minimizing capacitor losses, lower ESR capacitors have the advantage of making the power source more stable and efficient while lowering the output ripple voltage at the same time,” said Dan Kalin, Product Manager at Knowles Precision Devices. “In high-current applications, ESRs generate heat and can degrade and reduce capacitor life. Additionally, ESL contributes to unwanted current flow and generates electromagnetic interference. [EMI]Which leads to further malfunctions in high-frequency applications. ”Capacitors (especially electrolytic capacitors) can be used as input buffers to provide power when the mains voltage is too low or the power required by load changes, such as in DC / DC converters, But especially to reduce the switching noise in the transformer. When the transformer output, capacitors act as current filters for the inductive elements. In all cases, losses due to the ESR prevent the actual function of the capacitor. At the output, the higher ESR value leads to more ripple, which affects the stability of the loop Control.The ESR value particularly affects applications with low duty cycle and high frequency current pulses. Thanks to the low content of ESR and ESL, ceramic capacitors are widely used in high frequency circuits and are the perfect choice for bypassing power supplies in circuits requiring it. Knowles Precision’s new SV Series capacitors aim to increase the filtering performance of power sources. “The SV Series has been 100% tested to withstand dielectric voltage, insulation resistance and wires. And the waste factor. ” The SV series capacitors offer insulation resistance at 25 ° C minimum 500 m / Fahrenheit, dissipation factor at 25 ° C maximum 5% at 1.0 ± 0.2 VRMS at 120 Hz. The SV series is ideally suited to the input and output stages of switched mode power supplies and DC / DC converters. The X7R dielectric provides high amplitude to volume ratio, providing low ESR and ESL, giving the groups the ability to handle high ripple currents at high frequencies. “In order to have good feedback regarding the final application, equivalent series resistance and effective series induction tests are performed, as well as MIL-STDs for thermal shock, immersion ride, and welding heat resistance,” Kalin said. Since wave currents can cause self-heating losses and capacitor degradation, reducing ESR helps reduce these effects, resulting in reduced energy losses and improved reliability. “The new SV series of capacitor groups from Knowles Precision Devices are built into a vertical stack of ceramic capacitors, resulting in high capacitance reducing the overall circuit board footprint and helping to reduce mechanical and thermal stresses,” Kalin said. “Assemblies can be manufactured with up to 10 strips of the same size with different lead configurations to protect against thermal and mechanical stresses.” The great complexity of the systems leads to an increasingly complex power management architecture, and thus an important use of passive components that must keep pace with the evolution of electronics. The most obvious aspect has to do with miniaturization but also the management of currents during gameplay characterized by relatively high values ​​(due to the low supply voltage) and very sudden changes (due to high clock frequencies). The capacitor should only have capacitive reactance, when in reality, it also has both resistor and inductive reactance. Likewise, real resistors are affected by a certain inductive reactance value, and inductors also have resistivity and capacitive reactance. In order to keep pace with advances in microelectronics, parasitic impedances must be minimized as possible. .


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