一种高精度高稳定性的片内振荡电路设计

Design of a high precision and high stability on⁃chip oscillator circuit

作为系统时钟源,振荡电路的频率特性会影响芯片工作性能。为提高片内振荡器输出时钟的精度及稳定性,设计一种基于RC结构的振荡电路。该振荡电路采用带隙基准产生电容充电电流及基准电压,通过调整镜像管比例进行频率粗调校正,通过调整基准电压大小和温度系数以实现频率细调校正及温度特性校正。电路基于55 nm CMOS工艺设计实现,仿真结果表明,典型条件下电路工作输出为30 MHz,50%占空比时钟,在1.6~5.5 V、-40~125℃工作范围内,振荡频率偏移位0.6%以内,中心校准精度为0.5%,可作为片内高精度时钟源或参考时钟。

As the clock source of the system,the frequency characteristics of the oscillation circuit can affect the operational performance of the chip.In order to improve the precision and the stability of on-chip oscillator output clock,an oscillation ciruit based on RC structure is designed.The bandgap reference is used in the oscillation circuit to generate capacitor charging current and reference voltage,and the mirror tube ratio is adjusted for the frequency coarse adjustment correction.By adjusting the reference voltage size and temperature coefficient,the frequency fine adjustment correction and temperature characteristic correction are achieved.The circuit is designed based on the 55 nm CMOS process,and the simulation results prove that,under typical conditions,the working output of the circuit is 30 MHz,with a 50%duty cycle clock.It operates within the range of 1.6 V to 5.5 V and-40℃to 125℃,with an oscillation frequency offset of 0.6%and a center calibration accuracy of 0.5%.The circuit can be used as a high-precision on-chip clock source or reference clock.