A DC-DC converter providing a DC output voltage at an output node. The DC-DC converter comprises an output stage, a digital controller, and a controller. The output stage comprises a pull-up circuit having a control terminal and coupled between a first fixed voltage and a internal node, a pull-down circuit coupled between the internal node and a second fixed voltage, and a low pass filter coupled between the internal node and the output node. The digital controller is powered by the DC output voltage and adjusts the DC output voltage by controlling the output stage. The controller controls a connection of a feedback path, comprising the digital controller, between the output node and the control terminal according to the DC output voltage.