Design of high-performance crystal oscillator and frequency calibration circuit
Bao Yu-we · Modern Electronics Technique · 2014
A high-performance Pierce crystal oscillator and frequency calibration circuit were designed. A depletion mode NMOS transistor is used to obtain 1.5 V output reference circuit with low-power dissipation. Crystal oscillating circuit uses a power supply of 1.5 V reference voltage to reduce the power consumption and improve the output frequency precision of the oscillator. In order to further increase the output frequency precision,fuse trimming circuit is integrated inside chip. The correction of the oscillating circuit output frequency after packaging is realized by adjustment of the crystal oscillator load capacitance. The correction range is-52.216~54.962 ppm,and the maximum correction step is 3.723 ppm. If the correction circuit of digital mode is integrated in the chip,this function can be used to correct temperature-related clock precision variation in system,including temperature detection function. The correction range is-189.1~189.1 ppm,and the correction step is 3.05 ppm. A practical circuit is realized in a 0.5 μm-5 V COMS process. The die size is 0.842 mm×0.996 mm.