The voltage pump for generating a boosted output voltage has a switch-on control circuit. The switch-on control includes a transistor that is connected between a terminal for feeding in a supply voltage and the terminal for tapping off the boosted output voltage. After the voltage pump has started to operate, the boosted output voltage is decoupled from the supply voltage by the transistor. A changeover switch forwards the respective higher of the output voltage or supply voltage to the substrate terminal and gate terminal of the transistor. The switch-on control enables early provision of a boosted output voltage in conjunction with reliable start-up operation of the voltage pump, while the additional outlay on circuitry is minimized.