Dynamic voltage scaling is an efficient technology for the low power design in the deep submicron IC. The frequency controlled fully on chip DC-DC converter is implemented by using the variable reference voltage generator (VRVG) scheme with a supply voltage of 1.2V. The output of the converter is well regulated from 0.6V to 1.2V Therefore, the output voltage is adaptive to the operation frequency. The maximum variation with temperature range from -40°C to -140°C is 5mV. We use a frequency detector to control the reference voltage, and there are four modes which are the high performance mode (425-316MHz at Vdd=1.2V), normal mode (315-207MHz at Vdd=lV), standby mode (206-97MHz at Vdd=0.8V) and idle mode (below 97MHz at Vdd=0.6V). The on-chip DC-DC converter is simulated by TSMC 0.13um CMOS Technology. The applications of on-chip DC-DC converter with frequency detector are widely used in the datapath of the DSP processors.