QUALCOMM Incorporated
Resistor-capacitor oscillator (RCO) with digital calibration and quantizaton noise reduction

Abstract:

An oscillator including a switched capacitor configured to generate a sawtooth or ramp voltage in response to a switched capacitor drive signal; a low pass filter (LPF) configured to filter the sawtooth or ramp voltage to generate a filtered voltage; a reference voltage generator configured to generate a reference voltage; an integrator configured to integrate a difference between the sawtooth or ramp voltage and the reference voltage to generate a frequency control signal; a voltage controlled oscillator (VCO) configured to generate a first clock based on the frequency control signal; a frequency divider configured to frequency divide the first clock to generate a second clock; and a switched capacitor driver configured to generate the switched capacitor drive signal in response to the second clock. The oscillator may also include a switched capacitor sampler to sample the sawtooth or ramp voltage, wherein the filtered voltage is based on the sampled voltage.