Abstract
Clock signal is essential for any electronic circuits that require timing control. How to generate an accurate and stable clock signal becomes one of the most important issues. Nowadays most clock signals are generated by crystal oscillators primarily because of their excellent stability. However, in view of the drawbacks of quartz crystal such as large size, high power consumption, and being unable to be integrated into microelectronic process technology, for several decades, researchers had been exploring other technologies in order to replace quartz oscillators. Recently, some methods such as MEMS, FBAR and CMOS oscillators were proposed. Unfortunately, MEMS and FBAR oscillators need complex and costly processes to realize and they still cannot be integrated with CMOS circuits. The characteristics of Si devices are easily influenced by the changing variables of the environment, leading the frequency of CMOS oscillators to be sensitive to temperature and supply voltage. These are the reasons why crystal oscillators still cannot be replaced so far. For CMOS oscillators, luckily, we can add some proper compensation to improve their stability. Thus, we tried to develop a CMOS oscillator with low power consumption and high temperature stability. In this paper, a CMOS relaxation oscillator which is nearly insensitive to temperature variation is proposed. In addition, by using single charging and discharging path and a frequency divider, low jitter and nearly 50% duty cycle were achieved. This chip has been realized in the TSMC 0.18 μm 1P6M process.