Most of the digital devices we use every day use the DC voltage generated by the AC adapter as the input voltage, and then the voltage is raised and lowered by the power IC. When a semiconductor with a high power consumption is used, a smoothing capacitor of 100 μF or more is particularly used. Further, as semiconductors are reduced in voltage and speed, in order to maintain their operational stability, a low-impedance type smoothing capacitor is required. Therefore, Murata Manufacturing Co., Ltd. (hereinafter referred to as "Murata") has further expanded its lineup of high-capacity multilayer ceramic capacitors above 100μF.
Capacitors are roughly classified into several types in FIG. 2 according to their basic structures and materials. From the figure, we can see that the multilayer ceramic capacitor is slightly insufficient in terms of the temperature dependence of the electrostatic capacity and the effective voltage drop (DC bias characteristic) due to the applied voltage, but its miniaturization, high reliability, and high price competitiveness. The advantages of low impedance/low ESR*1/low ESL*2 are significant. Therefore, in the field of small and large-capacity capacitors today, multilayer ceramic capacitors have become mainstream. However, large-capacity smoothing capacitors exceeding 100 μF must have low impedance. The current mainstream of these products is conductive polymer electrolytic capacitors.
*1. ESR (Equivalent Series Resistance): The actual component of the capacitor's impedance.
*2.ESL (Equivalent Series Inductor): The small inductance component of a capacitor. The impedance of the frequency domain above the resonant frequency is dominated by the ESL.
Nowadays, the technology that supports the large-capacity of multilayer ceramic capacitors is constantly innovating. Murata Electronics has been able to guarantee a high-precision stack of 1000 μm or more with a high-precision dielectric layer of 1 μm or less to produce production technology and thin layer technology. In addition, more than 100 μF Layer ceramic capacitors are also in mass production.
In recent years, semiconductors used in digital devices have been continuously reduced in voltage, and the capacity reduction caused by DC bias characteristics has been decreasing. Therefore, digital devices have begun to use multilayer ceramic capacitors of 100 μF or more as smoothing capacitors.
At present, the products of 2.0x1.25mm/X5R/4V/100μF, 3.2x1.6mm/X5R/6.3V/100μF, 3.2x1.6mm/X5R/4V/220μF have been commercialized. In addition, multi-layer ceramic capacitors (maximum capacity: 300 μF) of 100 μF or more in various projects have also been commercialized.
In Murata's latest product lineup, there are X5R models (operating temperature range: -55 to 85 °C) for general consumer markets, and X6* for applications with high power consumption and high internal temperature. Operating temperature range: -55 to 105 ° C), in addition to the development of larger capacity products are also planned.
At present, in order to ensure the stability of a low-voltage and high-speed semiconductor power supply line used in digital devices, it is necessary to control voltage fluctuations caused by fluctuations in ripple voltage and load. As a smoothing capacitor, it is necessary to achieve a capacity of 100 μF or more and a low impedance. Previously, the market solution was mainly to use a conductive polymer electrolytic capacitor. Murata has expanded its lineup of multilayer ceramic capacitors above 100μF to replace conductive polymer electrolytic capacitors.
Although the multilayer ceramic capacitor has a lower capacity than the conductive polymer electrolytic capacitor, it still has a strong alternative. This is because the multilayer ceramic capacitor has a low impedance and ESR, and responds well to voltage changes. Fig. 5 is an impedance, ESR-frequency characteristic of a representative conductive polymer tantalum electrolytic capacitor and a multilayer ceramic capacitor. The switching frequency of the power IC used in digital equipment is above 100 kHz. As can be seen from the figure, compared with the conductive polymer tantalum electrolytic capacitor, the multilayer ceramic point is easy to not only have the same capacity as the product, but also has a lower capacity, impedance. And ESR is also very low.
In addition, when the resonance frequency is high frequency, the multilayer ceramic capacitor has a very low impedance compared to the conductive polymer tantalum electrolytic capacitor, and is very useful for high frequency squelch.