Abstract: A digital programmable DC—DC voltage-down converter which can be used in a low voltage and low power digital circuit design is disclosed. The DC—DC voltage-down converter includes at least a digitally controlled oscillator (DCO), a pulse-width modulator (PWM), a gate driver, and a switching-type voltage-down converter. Duty cycle and operating frequency of the modulated signal are controlled by using two digital control signals. Furthermore, combining the pulse-width modulator and the digitally controlled oscillator (DCO), the duty cycle of the generated clock is more robustly stable for different frequencies during process variation.