A 39.25MHz 278dB-FOM 19µW LDO-Free Stacked-Amplifier Crystal Oscillator (SAXO) Operating at I/O Voltage

📋 论文概要

本文提出了一种39.25MHz无LDO堆叠放大器晶体振荡器（SAXO），工作在I/O电压下，实现了19µW超低功耗和278dB FOM。通过引入低通滤波器，将1kHz偏移相位噪声从-122dBc/Hz降至-139dBc/Hz，解决了传统晶体振荡器在低功耗下相位噪声差的问题。

💡 主要创新点

• 提出堆叠放大器结构（SAXO）实现无LDO操作，直接工作在I/O电压，降低功耗和面积。
• 通过Miller效应和有源电阻倍增技术，实现27MΩ的大电阻（面积仅1800μm²），并利用增益放大实现500pF等效电容，从而集成低通滤波器降低相位噪声。

🏷 关键词

📄 原文摘要

frequency of 12Hz. The active resistor of 27MΩ with a size of 1800μm2 is achieved with a multiplication of RBIAS (= 80kΩ) by (W/L)M1 / (W/L)M3. 500pF is achieved with a multiplication of CLPF (= 50pF) by the gain (≈ 10) of M4. Figure 5.7.4 shows measured phase noise without and with the LPF in the proposed SAXO. By adding the LPF, the phase noise at 1kHz offset is reduced from -122dBc/Hz to -139dBc/Hz, which indicates 17dB noise reduction. University of Tokyo, Tokyo, Japan The target of this work is to develop a low-power 39.25MHz crystal oscillator (XO) with low phase noise for RF applications and to achieve the highest FOM in XO’s. To reduce the supply current at a constant negative resistance (RN) in the XO, a stacked-amplifier crystal oscillator (SAXO) operating at I/O voltage is proposed, eliminating the need for a Low-Dropout Regulator (LDO). By stacking 4 amplifiers, the supply current is reduced by 91%. The developed 3.3V,

👥 作者与机构

Shunta Iguchi, Takayasu Sakurai, Makoto Takamiya, Miller effect is added. The area-efficient LPF with M3 and CLPF achieves a cutoff