A voltage-controlled oscillator for use within a pulse frequency modulation system

A fully integrated voltage-controlled oscillator (VCO) for use within a pulse frequency modulation (PFM) system is described, that achieves a linear voltage to frequency transfer characteristic over 17 MHz. The output of the VCO is a pulse waveform with a duty cycle below 20%. The VCO is based on two grounded capacitors and is implemented in a 2.4 µm CMOS technology. Owing to positive feedback, no start-up conditions for the oscillator are required.