以0.18微米CMOS製程設計一高精準度低功率之溫度補償石英震盪器

Abstract

本論文提出一工作頻率為16MHz的數位控制石英振盪器和一時域溫度感測器之電路設計，其用於在低功耗的行動裝置內實現一高精準度之溫度補償石英振盪器。數位控制石英振盪器是基於皮爾斯振盪器的電路架構，並內含兩個8位元的切換式電容陣列。數位控制石英振盪器的溫度感測是藉由量測由本論文提出之延遲單元的延遲時間對溫度的變化達成，其稱為時域溫度感測器。數位控制石英振盪器和時域溫度感測器的電源電壓是透過使用兩組低壓降穩壓器穩壓在1.2V。本論文所設計的電路已使用台積電0.18微米CMOS製程下線製作成功，其總面積為0.516平方毫米。量測到的8位元數位控制石英振盪器的啟動時間約為0.35毫秒，並且在環境溫度為25度的條件下，於1kHz頻率偏移測得的相位雜訊為-119.93dB/Hz。在溫度變化範圍從-40度至85度的情況下，量測到補償後的頻率漂移介於+/-0.08ppm的範圍內。時域溫度感測器在10Hz轉換速度條件下，量測到的溫度感測解析度為0.45°C/LSB，以及溫度感測誤差範圍為-6.3度至7.1度之間。晶片測得的電流消耗大約為2毫安培。

This thesis presents a 16-MHz digital-controlled crystal oscillator and a time-domain temperature sensor design to achieve a high precision temperature-compensated crystal oscillator in a low-power mobile device. The digital-controlled crystal oscillator is based on Pierce topology with two 8-bit switched-capacitor arrays. The temperature of it is measured with the temperature-dependent delays of proposed delay cell, called time-domain temperature sensor. The supply voltage of digital-controlled crystal oscillator and time-domain temperature sensor are regulated at 1.2 V by using two on-chip low-dropout regulators. The designed circuit has been successfully fabricated by using TSMC 0.18-μm CMOS process, where the active area is 0.516 mm*mm. The measured start-up time of implement 8-bit digital-controlled crystal oscillator is about 0.35 ms and the measured phase noise of 1 kHz offset at 25°C is -119.93 dB/Hz. The frequency deviation over -40°C to 85°C is within +/- 0.08 ppm after compensation. The measured effective temperature resolution of time-domain temperature sensor is 0.45 °C/LSB and the measured error is within -6.3°C to 7.1°C at 10 Hz conversion rate. The measured current consumption of chip is about 2 mA.