A temperature compensated fully trimmable on-chip IC oscillator

The design of an IC on-chip oscillator, including temperature compensation circuitry, a robust spread reduction technique and digital trimming is described. The IC oscillator provides a 12.8 MHz clock signal with a frequency spread of /spl plusmn/25% before the 8 bit digital trimming. After centering the oscillator at the target frequency, a temperature compensated voltage and current reference circuit allows for less than /spl plusmn/5 % frequency variation when operating from 3 to 5 V power supply and from -40 to 125 /spl deg/C of temperature range. The oscillator is implemented in a 0.5 /spl mu/m CMOS technology, occupies an area of 420/spl times/440 /spl mu/m/sup 2/ and dissipates less than 400 /spl mu/W at 3 V supply without requiring any external reference or components.