A digital-trim controlled on-chip RC oscillator

In this paper, a high-accuracy RC Oscillator (OSC) circuit is demonstrated using trimming control. The OSC uses a 7-bit binary-weighted resistor array as the trimming object. Using a 0.5 /spl mu/m CMOS process, the final output frequency can be achieved within 0.5% error while the original OSC without trimming has as much as 40% output variation due to process variations. Temperature variation and power supply variation are also considered and resolved. Detailed circuit design and SPICE simulation results are presented. The final die size of the test chip is 130 /spl mu/m x 145 /spl mu/m excluding bonding pad.