Regardless of the application—from cell phones to wireless LAN cards—height, size, and efficiency are important features for components used with AAT115X converters. With this in mind, the recommended output capacitor for the AAT115X family of buck converters is presented in this Application Note. The design procedure for determining the capacitor value and calculating stresses is also examined. Surface mount ceramic X5R or X7R capacitors are ideally suited for AnalogicTech's buck converter (Figure 1). X5R ceramic capacitors have a CV product with a temperature and voltage coefficient that is ideal for low voltage, high frequency, and high density switching regulators. Figure 2 shows the voltage and temperature characteristics for a 22µF, 6.3V, 0805, X5R ceramic capacitor. The graph illustrates the strong voltage coefficient typical of an X5R capacitor. From the graph, it can be seen that the applied voltage must be considered when determining the actual capacitor value. The impedance and equivalent series resistance (ESR) characteristics shown in Figure 3 are both typical of an X5R ceramic capacitor and ideal for achieving low output ripple at a high switching frequency.