Temperature calibration of an on-chip relaxation oscillator

This work investigates the calibration procedure of a conventional relaxation oscillator. First, the numerical analysis is performed in MATLAB in order to evaluate the sensitivity of the procedure to the noise generated inside the chip and measurement system. Next, the theory is experimentally verified by calibrating four test chip samples designed and manufactured in 0.35-μm CMOS technology. The test chips are calibrated with two different test methods: the first method measures the output frequency in the entire temperature range from -40 to 150°C during 12 hours; the second method measures the output frequency from 30 to 60°C during 30 seconds. The proposed calibration methods exhibit the reduction of the frequency error by 18× and 8×, having the total post-calibration precision of ±0.1 % and ±0.22 %, respectively.