一個使用差動對多項式補償技巧之類比式溫度補償晶體振盪器

Abstract

本論文提出一個基於差動對、全類比式的溫度補償技巧以改善溫度補償石英晶體振盪器之頻率隨溫度變化之穩定性。本作品中，我們使用三組差動對將溫度感測電路之輸出電壓進行三次多項式對應，再以對應後之電壓控制一組變容器，藉此補償石英晶體本身頻率隨溫度三次多項式變化之特性。本作提出之技巧被使用於一個以 90 奈米製程實作之 40 兆赫茲溫度補償石英晶體振盪器中。晶片面積為 0.455 平方毫米，於 -40~80°C 溫度範圍內達成 <±2.5 ppm 頻率變異，同時其溫度補償電路僅消耗整體 185 微瓦功耗之 16%。此作品之輸出在 10 千赫茲頻率偏移下量測得 -117.5 dBc/Hz 相位雜訊、4.5 皮秒之時脈抖動，表現上接近於其他溫度補償石英晶體振盪器作品。

In this thesis, we present an all-analog, differential-pair-based technique to improve the frequency stability over temperature for temperature-compensated crystal oscillators (TCXO). By configuring three differential pairs to synthesize a cubic input-output characteristic, the proposed circuit maps the temperature sensor output to control a single varactor, compensating the cubic frequency error intrinsic to the crystal unit. Incorporating the proposed technique, a 40-MHz TCXO, which is fabricated in a TSMC 90-nm CMOS process, is demonstrated in this work. The TCXO occupies an active area of 0.455 mm2 and achieves a <±2.5 ppm frequency variation over the -40~80°C range, with its temperature-compensation blocks only consuming 16% of the overall 185-μW power. In terms of phase noise, the TCXO measures -117.5 dBc/Hz at 10 kHz offset with 4.5 psecrms integrated jitter, a level comparable to prior work.