A 1-MHz Relaxation Oscillator Core Employing a Self-Compensating Chopped Comparator Pair

An improved relaxation oscillator core is designed and fabricated in 0.35-μm CMOS process, occupying the area of 0.032 mm
²
and consuming around 160 μW while running at 1 MHz. Employing a self-compensating chopped comparator structure, the designed oscillator exhibits a significant improvement in the frequency stability and control linearity, at the same time retaining a fast start-up and having a minimal overhead in the power consumption and area. Measured on 8 test chips, the frequency variation against temperature is ±0.26% in the temperature range from -40 to 125 °C, and the line sensitivity is ±0.08 %/V with the supply voltage changing from 3.0 to 4.5 V. The typical distortion parameters of the control characteristic are HD
₂
= -61.7 dB and HD
₃
= -93.2 dB at △f
_osc
= 500 kHz. The measured jitter and phase noise at 10 kHz carrier offset are 235 ppm and -92 dBc/Hz, respectively, while the Allan deviation floor is 15 ppm.