When it comes to input filtering, ceramic capacitors are a great choice. They offer high ripple current rating and low ESR and ESL. Also, ceramic capacitors are not very sensitive to over voltage and can be used without derating the operating voltage. However, designers must be aware of a potential overvoltage condition that is generated when input voltage is applied abruptly. After applying an input voltage step, typical input filter circuits with ceramic capacitors can generate voltage transients twice as high as the input voltage. This document describes how to efficiently use ceramic capacitors for input filters and how to avoid potential problems due to input voltage transients.
Applying a voltage step to a ceramic capacitor causes a large current surge that stores energy in the inductances of the power leads. A large voltage spike is created when the stored energy is transferred from these inductances into the ceramic capacitor. These voltage spikes can easily be twice the amplitude of the input voltage step.
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