具脈衝寬度調變之弛張振盪器設計實現

21世紀以來，隨著電子產業的發展，具邏輯數位電路的系統晶片因為輕薄與便攜的特性，並且普及於各式的可攜式電子穿戴裝置，也逐漸拓展應用於智能家電以及電動車上，為人們的生活帶來便利。而在數位系統晶片中，時脈產生電路為其中不可或缺的一部分，而振盪器更是時序電路的核心，從推動指令進行的微處理器到維持智能家電及電動車穩定運作，都有不同規格和形式的振盪器存在。在各式振盪器中，石英振盪器因為能供給穩定的時脈頻率，在過去長期作為廣泛使用的振盪器；微機電振盪器同樣擁有穩定、耐用的優勢，在近幾年製程技術進步的加持下，也受到一定程度的應用；無晶體振盪器在設計上，因為體積相對小於石英振盪器及微機電振盪器，作為集成系統晶片的時脈參考較具優勢。不過，在一些特定應用上，可能需要使用相同頻率下不同脈衝寬度的時候，因此，脈衝寬度調變在數位訊號上的使用成為取代類比訊號的方式之一，也可以成為設計振盪器時考量的重點之一。本論文提出以數位控制機制來調變脈衝寬度，並能夠輸出不同脈衝寬度的弛張振盪器。由於弛張振盪器的振盪頻率是以架構內的電阻值及電容值所決定，在低頻表現上較有穩定及控制上的優勢，除此之外，依據電容值輸入的比重不同，也會使弛張振盪器能夠有不同責任週期的頻率輸出。本論文所提出的弛張振盪器可以提供一個穩定25MHz的頻率，並透過數位控制方式，可選擇工作週期20%至80%內特定脈衝寬度的輸出時脈，且以較小的面積及較低的功耗，做為在低頻應用上可切換脈衝寬度的需求作使用。

關鍵字

弛張振盪器；脈衝寬度調變；工作週期；數位控制開關

並列摘要

Since the 21st century, with the development of the electronics industry, system chips with logic digital circuits have been used in electronic wearable devices because of their lightness and portability, and have gradually been applied to smart home appliances and electric vehicles to bring convenience in people's life. In the digital system chip, the clock generation circuit is an important part of it, and the oscillator is the core of the clock generator. Like the microprocessor to drive the instructions, and the stable operation of smart home appliances and electric vehicles, there are different specifications and forms of oscillators in them. Among all oscillators, quartz oscillators have been widely used for a long time because they could provide stable clock frequency; micro-electromechanical oscillators also have the advantages of stability and durability, and they have been applied to a certain extent with the progress of process technology in recent years; the crystal-less oscillators are more advantageous as clock references for integrated system chips because they are relatively smaller than quartz oscillators and microelectromechanical oscillators. However, in some specific applications, it may be necessary to use different pulse widths at the same frequency. Therefore, the use of pulse width modulation on digital signals has become one of the ways to replace analog signals, and it can also become an important part consideration when designing the oscillators. This research proposes a relaxation oscillator that modulates the pulse width with a digital control mechanism and it can output different pulse widths. Since the oscillation frequency of the relaxation oscillator is determined by the resistance value and capacitance value in the structure, it has the advantages of stability and control in low frequency performance. In addition, according to the different proportions of the capacitance, the oscillator can also have frequency outputs with different duty cycles. In addition, according to the different proportions of the capacitance, the oscillator can also have frequency outputs with different duty cycles. The relaxation oscillator proposed in this research can provide a stable frequency of 25MHz, and with the digital control, the output clock with a specific pulse width within 20% to 80% of the duty cycle can be selected, and it can be used as a switchable pulse width in low-frequency applications with a smaller area and lower power consumption.