SLVSAF7C September 2010 – April 2019 TPS61251
Multilayer ceramic capacitors are an excellent choice for input decoupling of the step-up converter as they have extremely low ESR and are available in small form factors. Input capacitors should be located as close as possible to the device. While a 10-μF input capacitor is sufficient for most applications, larger values may be used to reduce input current ripple on the supply rail without limitations. Although low ESR tantalum capacitors may be used.
DC Bias effect: High capacitance ceramic capacitors have a DC Bias effect, which has a strong influence on the final effective capacitance. Therefore, the right capacitor value has to be chosen very carefully. Package size and voltage rating in combination with material are responsible for differences between the rated capacitor value and the effective capacitance. A 10-V rated 0805 capacitor with 10 µF can have an effective capacitance of less 5 µF at an output voltage of 5 V.