一种基于斩波拓扑的高精度RC振荡器

A High Precision RC Oscillator Based on Chopper Topology

设计了一种采用0.18μm CMOS工艺制作的基于斩波拓扑的高精度RC振荡器。该结构对比较器失调有较好的抑制效果,并补偿了比较器传输延时对输出时钟频率的影响,达到了较好的温度特性。同时使用LDO对振荡器的主体电路供电,有效抑制了电源电压波动对输出频率的影响。另外该振荡器使用电容修调网络,减小了工艺漂移对中心频率的影响。仿真结果表明,所设计的振荡器在不同工艺角下均可以通过修调将频率校准至典型值2 MHz。在-40~125℃的温度范围内,输出频率的波动仅为0.87%。在3~6 V的电源电压范围,输出频率的波动仅为0.21%。与同类型的片上RC振荡器相比,该电路对温度、电源电压和工艺的漂移有更好的抑制作用。

A high precision RC oscillator with chopper topology was designed in a 0.18μm CMOS process.The structure had a better suppression effect on comparator's offset,and compensated for the effect of comparator transmission delay on the output clock frequency to achieve better temperature characteristics.At the same time,the use of LDO power supply to the main circuit of the oscillator effectively suppressed the impact of power supply voltage fluctuations on the output frequency.In addition,the oscillator used a capacitive trimming network to reduce the impact of process drift on the center frequency.Simulation results show that the designed oscillator can be trimmed to calibrate the frequency to the nominal value of 2 MHz under different process corners.The fluctuation of the output frequency is only 0.87%in the temperature range of-40 to 125℃,and 0.21%in the power supply voltage range of 3 to 6 V.Compared with the same type of on-chip RC oscillator,the proposed circuit's drift of temperature,supply voltage and process is better suppressed.