Abstract
Clock signal plays an important role in nearly all consumer electronics. Electronic platforms ranging from communications, instruments to smart phone need clock generation to work properly. Additionally, most of these circuits require crystal oscillators (XO) serving as the frequency reference. Nevertheless, quartz crystal possesses some disadvantages such as large area, high power consumption and cannot be integrated into microelectronic process technology. For these reasons, researchers had been devoting themselves to exploiting technologies to replace quartz over the past thirty years. Recently, several methods have been proposed to solve above mentioned problems, including MEMS oscillators (MOs), QMEMS, LC oscillators and relaxation oscillator with voltage average feedback circuits. However, MOs and QMEMS remain the challenge in process integration; LC oscillators consume too much power and chip area; relaxation oscillator is subject to mismatch caused by manufacturing process which would induce inaccurate duty cycle. Considering these defects collectively, we aimed to develop an integrated frequency source with accurate duty cycle and low power consumption. In this paper, we proposed a method to avoid mismatch in relaxation oscillator, that is, to simplify the two charging and discharging paths as one single path. Furthermore, we improved the accuracy of duty cycle by employing a divider in the oscillator. The chip in this work was fabricated in the TSMC 0.18 μm 1P6M process. Both of the simulation and measurement results show that such approach efficiently enhances the accuracy of duty cycle to 50%, achieves small chip area and low power dissipation, and can be realized with standard CMOS processes.