Post-Manufacturing Process and Temperature Calibration of a 2-MHz On-Chip Relaxation Oscillator

In this work, the design methodology of the relaxation oscillator with the post-processing trimming option for frequency and temperature coefficient is presented. A novel oscillator core is introduced, which ensures good control linearity and insensitivity to CMOS variations of the output frequency as a prerequisite for frequency and temperature calibration. The proposed oscillator operates at 2 MHz and consumes typically about $I_{DD}=97.8\,\,\mu \text{A}$ at the nominal temperature of 42.5°C and nominal supply voltage of $V_{DD}=1.8$ V. The oscillator is verified experimentally with 10 samples manufactured in 180 nm CMOS process, each covering an area of 0.075 mm ² . The frequency and temperature calibration was performed based on the two-point temperature measurements, resulting in a significant improvement in frequency stability. The temperature calibrated oscillator has a temperature variation ±0.30% in the temperature range from −40°C to 125°C, and the variation with the power supply ±0.07% in the supply range from 1.62 V to 1.98 V.