Aspects of this disclosure relate to voltage generators, such as negative voltage generators. In certain configurations, a negative voltage generator includes a charge pump controllable by a clock signal and configured to provide a negative voltage at an output node, an oscillator configured to activate based on an enable signal and to provide the clock signal to the charge pump, a comparator configured to generate the enable signal based on comparing a feedback voltage with a reference value, a voltage divider electrically connected between a positive voltage node and the output node and configured to generate the feedback voltage at a feedback node, and a start-up capacitor electrically connected between the positive voltage node and the feedback node and configured to control a settling time of the feedback voltage.