Design of Sub-microwatt Oscillators with Temperature Compensations

這篇論文的主題主要分為兩個部分，第一個部分是設計一個低於微瓦且低溫度係數的弛張振盪器。此電路運用電晶體工作在次臨界區，電流模式的比較器以及汲取電流式反向器來減少消耗的功率，且利用不同閘極氧化層厚度的電晶體來實做低溫度係數的電流源，再以曲度電流源和分段式電流源補償使得振盪器有低溫度係數。在0.18-μm CMOS 的製程中，實現了振盪頻率為1.1MHz 的振盪器，在1.2 伏特供給電壓的操作下，振盪器消耗功率為420nW，在-20~80°C 平均的量測溫度係數為49.7ppm/°C 計算的第一優值、第二優值和第三優值分別為124.2dB、-136.7dB 和101dB。 第二部分則是以主動電組取代弛張振盪器中被動電組的使用，使得操作在低於微瓦的弛張振盪器可以小布局面積實現。在此電路中，我們以正比於絕對溫度與反比於絕對溫度的電流源實現參考電流源，且利用不同閘極氧化層厚度的電晶體來實做電壓產生器，再以分段式曲度電流源補償來減少振盪器溫度的變異。1.6MHz 的振盪器，在1 伏特供給電壓的操作下，振盪器消耗功率為631nW，在-20~80°C 平均的量測溫度係數為66ppm/°C 計算的第一優值、第二優值和第三優值分別為124.1dB、-155.2dB 和114dB。This thesis consists of two parts. The first part aims to design a submicrowatts and low temperature coefficient (TC) relaxation oscillator. In this oscillator, the transistors in the subthreshold region, the current-mode comparator, and the current-starving inverters are used to reduce the power of the relaxation oscillator. The low TC current reference is realized with different gate-oxide thickness mosfets. Besides, we developed the curvature current source and the piecewise current source to compensate the TC of the oscillator. This oscillator is fabricated in a 0.18-μm CMOS process and its power consumption is 410nW with a supply voltage of 1.2V. The measured average TC is 49.7ppm/°C for the temperature of -20~80°C. The calculated FOM1, FOM2 and FOM3 are 124.2dB, -136.7dB and 101dB, respectively. The second part implements a resistor-free oscillator. In this oscillator, we proposed the transistors in the linear region to replace passive resistors. The low TC current reference is realized by PTAT and CTAT current and the voltage generator is implemented with different gate-oxide thickness mosfets. Besides, the piecewise curvature current is used to release the temperature variations. For the 1.6MHz oscillator, its power consumption is 631nW with a supply voltage of 1V. The average temperature coefficient is 66ppm/°C for the temperature of -20~80°C, and the calculated power FOM1, FOM2 and FOM3 are 124.1dB, -155.2dB and 114dB, respectively.1. Introduction………………………………………………………… 1 1.1 On-chip Oscillators………………………………………….. 1 1.2 Overview…………………………………………………….. 2 2. A Nano-watts 1.1MHz CMOS Relaxation Oscillator with Temperature Compensation……………………………………….. 5 2.1 Motivation…………………………………………………… 5 2.2 Circuit Architecture……………………………….…………. 7 2.2.1 Overview of the Approach…….…………………….. 7 2.2.2 Low TC Current Reference……….…………………. 9 2.2.3 Curvature Current Source.…………………...………. 10 2.2.4 Piecewise Current Source…………………..………... 14 2.2.5 Overall Proposed Relaxation Oscillator……………... 15 2.3 Experimental Results………………………………………… 19 2.3.1 Measurement Results..………………………………. 19 2.3.2 Die Photo and Performance Summary......................... 20 2.4 Conclusion………………………………………………..…. 24 3. A 0.005mm2 631nW 66ppm/℃ 1.6MHz CMOS Resistor-free Relaxation Oscillator……………………………………………….. 25 3.1 Motivation…………………………………………………… 25 3.2 Circuit Architecture……………………………….…………. 27 3.2.1 Overview of the Approach…….…………………….. 27 3.2.2 Complementary TC Bias Current Sourc….…………. 28 3.2.3 Proposed PVT Tracking Voltage Generator....………. 32 3.2.4 Piecewise Curvature Source.………..……..………... 35 3.2.5 Overall Proposed Relaxation Oscillator……………... 36 3.3 Experimental Results………………………………………… 40 3.3.1 Measurement Results..………………………………. 40 3.3.2 Die Photo and Performance Summary......................... 41 3.4 Conclusion………………………………………………...…. 46 4. Conclusion and Future Work……………………………………… 47 4.1 Conclusion…………………………………………………… 47 4.2 Future Work……………………………………………….…. 48 Bibliography ……………………………………………………………….. 4