Circuit models for the simulation of charge pumps facilitate design of integrated circuits containing charge pumps. Such models facilitate accurate simulation of actual charge pump behavior without the need to rigorously simulate the multiple capacitive stages of an actual charge pump and the dedicated oscillator clocking the charge pump. The various embodiments utilize a charge pump model having multiple pull-up stages. At lower output voltages, the pull-up stages each provide an output current. These output currents are added together as the output current of the charge pump. Each pull-up stage automatically shuts off when the output voltage approaches a dedicated voltage source for that pull-up stage. As the output voltage increases, less current is output due to the deactivation of pull-up stages.