Digitally controlled oscillator with variable capacitive loading

A Digitally controlled oscillator (DCO) designed with digital programming using binary coded capacitor load is presented. The Digitally Controlled Oscillator is basically designed based on the ring oscillator, where delay of the ring oscillator is controlled digitally. The delay cell is implemented to synthesize digital input. The oscillation frequency is controlled digitally with control bits applied to the input of binary coded capacitive load. The nine-bit DCO implemented using the 45nm technology at 1 V supply voltage shows oscillation frequency variation in the range of 1.2486-1.2523 GHz, with a change in control bits. The design implementation has better stability against supply voltage variation compared to the conventional voltage controlled oscillator (VCO).