A coupled sawtooth oscillator combining low jitter with high control linearity

A new type of relaxation oscillator is presented that combines excellent control linearity with low timing jitter. By using an alternative for the Schmitt trigger, the jitter caused by threshold level noise can be significantly reduced compared to a conventional relaxation oscillator, under equal conditions of control linearity. Circuits realized in a 0.8-/spl mu/m CMOS process show a typical measured distortion in the control characteristic of HD/sub 2/ = -67 dB and HD/sub 3/ = -90 dB (/spl Delta/f = 500 KHz), without using any feedback linearization techniques. The measured phase noise is -102 dBc/Hz at 10-kHz offset at f/sub osc/ = 1.5 MHz (65-ppm rms jitter) for a total supply current of 360 /spl mu/A.