Charge Pump Power Dissipation

The peripheral circuit of the MAX829 charge pump is shown in Figure 1. The capacitor C1 in the figure switches between the output voltage UOUT and UIN at a frequency f. The amount of charge transferred in each cycle is

Figure 1 MAX829 charge pump peripheral circuit

The current generated depends on the frequency f, that is,

According to Ohm's law, the equivalent resistance RESR of the switch capacitor is RESR = I/fcl. The higher the operating frequency and the larger the capacitance, the smaller the equivalent resistance RESR and the corresponding loss. In order to reduce the power loss caused by the switch on-resistance and the equivalent series resistance (RESR) of the capacitor itself, it is necessary to select a capacitor with low RESR and a switch with low on-resistance.