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A 16 MHz CMOS RC Frequency Reference With ±90 ppm Inaccuracy From −45 ◦Ct o8 5 ◦C
本文介绍了一种16 MHz RC频率参考电路，采用180nm CMOS工艺，通过数字温度补偿实现±90 ppm的精度。
16 MHz, 180nm CMOS, 1.8V, 220 µA, ±90 ppm
频率参考CMOS温度补偿Wien桥数字控制振荡器
▸创新点1：频率锁定环路（FLL）的创新设计，通过将数字控制振荡器（DCO）的输出频率锁定到Wien桥RC滤波器的频率-相位特性，实现了高精度的频率参考。该方法避免了传统晶体振荡器的体积和成本问题，同时提供了良好的频率稳定性。
▸创新点2：数字温度补偿技术的创新应用，通过结合Wien桥RC滤波器的输出相位数字化和Wheatstone桥温度传感器的数字输出，实现了对温度依赖性的有效补偿。这一技术使得在-45°C至85°C的温度范围内，频率参考的不准确性仅为±90 ppm。
▸创新点3：Wien桥RC滤波器的创新使用，作为频率参考的核心元件，其频率-相位特性被用于锁定DCO的输出频率。这种设计利用了片上电阻和电容的温度依赖性，通过数字补偿技术实现了高精度的温度稳定性。
▸创新点4：低功耗和高性能的系统设计，频率参考在1.8V电源下仅消耗220 µA电流，具有0.12%/V的电源敏感性和320-ppb的Allan Deviation floor（10秒步长）。这一设计在功耗和性能之间取得了优异的平衡。
Abstract
This article presents a 16-MHz RC frequency reference implemented in a standard 180-nm CMOS process. It consists of a frequency-locked loop (FLL) in which the output frequency of a digitally controlled oscillator (DCO) is locked to the frequency-phase characteristic of a Wien bridge RC filter. Since it is made from on-chip resistors and capacitors, the filter’s characteristic is temperature dependent. To compensate for this, the control signal of the DCO is derived by digitizing the filter’s output phase and combining it with the digital output of a Wheatstone bridge temperature sensor. After a two-point trim, this digital temperature compensation scheme achieves an inaccuracy of ±90 ppm from −45 ◦Ct o8 5 ◦C. The frequency reference draws 220 µA from a 1.8-V supply, with a supply sensitivity of 0.12%/V and a 320-ppb Allan Deviation floor for a 10-s stride.