Datasheet

3-1

Capacitor Selection

For the maximum output current and best performance, capacitors placed on

the EVM are recommended. For lower currents or higher allowed output

voltage ripple, other capacitors can also be used. It is recommended that the

output capacitor has a minimum value of 0.22 µF. This value is necessary to

assure a stable operation of the system. However, output ripple and noise are

going to be much larger with such a low output capacitor. With lower flying

capacitors then 1 µF the maximum output power will decrease.

The best performance of the charge pumps can be seen with ceramic

capacitors. To reduce the spikes during turnover from the transfer phase

(charging of the output capacitor) of one charge pump to that of the other one,

a ceramic capacitor is recommended at the input and output. Tantalum

capacitors are not able to filter these spikes because their equivalent series

resistance (ESR) is too high. When using tantalum capacitors as input or

output capacitors connect a ceramic capacitor in parallel to reduce voltage

spikes.

Chapter 3