Charge pump

Charge pumps use some form of switching device to control the connection of a supply voltage across a load through a capacitor in a two stage cycle.

An external or secondary circuit drives the switching, typically at tens of kilohertz up to several megahertz.

The high frequency minimizes the amount of capacitance required, as less charge needs to be stored and dumped in a shorter cycle.

and generate arbitrary voltages by quickly alternating between modes, depending on the controller and circuit topology.

This means that it can output positive and negative current pulses into the loop filter of the PLL.