U. Schiller et al., A VOLTAGE-CONTROLLED OSCILLATOR FOR USE WITHIN A PULSE FREQUENCY-MODULATION SYSTEM, International journal of electronics, 84(1), 1998, pp. 37-43
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%. Th
e VCO is based on two grounded capacitors and is implemented in a 2.4
mu m CMOS technology. Owing to positive feedback, no start-up conditio
ns for the oscillator are required.