A DC-DC converter system having at least one DC-DC converter operating in either a PWM mode or a PFM mode is provided. The DC-DC converter system includes a state machine configured to control the switching between the PWM mode and PFM mode. The state machine determines whether an inductor current provided by the DC-DC converter reaches a first specified value for a selective number of clock cycles so switching between the PWM mode and PFM mode is to occur. A pulse generator circuit is connected to the state machine and being configured to provide the appropriate switching period for the PWM mode and the PFM mode at the time of switching. The pulse generator circuit is shared amongst the PWM mode or PFM mode and utilizes a master clock for its operations.