A coupled sawtooth oscillator combining low jitter and high control linearity

A new type of current controlled oscillator (CCO) is presented that combines excelllent control linearity with low timing jitter. The problem of overshoot in traditional relaxation oscillators is solved by using an alternative for the Schmitt-trigger. Circuits realised in a 0.8µm CMOS process show a HD2 < -65dB and HD3 < -85 dB (Δf=500 kHz). The measured phase noise is smaller than -100dBc/Hz at 10kHz carrier offset frequency at FOSC=1.5 MHz for a supply current of 360µA.