Relaxation oscillator with low phase noise

摘要

A relaxation oscillator includes a first capacitor at the terminals of which there is a first voltage V1, a circuit to charge the first capacitor from a power supply voltage, a circuit to discharge the first capacitor, and a switch which alternately charges and discharges the first capacitor responsive to a control signal. The relaxation oscillator also includes a relaxation circuit to generate the oscillation signal and the control signal from the first voltage. The oscillator also includes a regulation circuit to cause the first voltage applied to the relaxation circuit to be approximately equal to a reference voltage. The circuit for charging the first capacitor includes a resistance R1. The relaxation oscillator is particularly applicable to phase locked loops.