在過去幾十年，石英振盪器在大多數電子產品被廣泛用作參考時脈產生器，因為它們可以提供穩定的操作時脈來與各種應用系統晶片（SoC）的電路。值得注意的是，一個石英振盪器不僅在正常的環境下提供了一個穩定的運行時脈，重點是當晶片處在操作環境的變異下，石英振盪器仍可以提供一個精準與穩定的輸出，這是石英振盪器的主要優勢。通常集成在SoC的電路需要不同操作頻率的時脈，但這些時脈卻需要由不同的振盪器產生。因此，提供一個廣泛頻道使用的時脈產生器設計已於近日成為無晶體時脈產生器中一個突出的設計考量。 本文提出了一種新的控制機制來產生較寬的輸出頻率範圍，而此機制僅需要一對25MHz差動輸入訊號的責任週期變異。當這些責任週期由數位控制脈衝寬度調變設置後，送入責任週期電壓轉換器，由呈現反比成長的責任週期控制係數產生雙控制電壓VP和VN，分別管理電壓控制振盪器的延遲以提供一個寬頻輸出範圍的頻率。本文所提出的時脈產生器可以提供一個穩定35MHz至138MHz的頻率輸出時脈，並以較小的供應電壓以及面積，提供給寬頻需求的應用做為使用。 In previous decades, quartz oscillators were widely used as reference clock generators in most electronic products, because they can supply a stable operating clock to system-on-a-chip (SoC) circuits with various applications. Notably, a quartz oscillator not only supplies a stable operating clock in normal situation, but can also provide accuracy and stability against the environment variations, which is the main advantage of quartz oscillator. Circuits integrated on a SoC usually require diverse operating frequencies, which are generated by various clock generators. Therefore, supplying a wide range of frequency channels has recently become a prominent design consideration for crystal-less clock generators. This paper presents a new control mechanism to generate wide range frequencies, which requires only the duty cycle variation of the differential 25-MHz input signals. When these duty cycles are set by digitally controlled pulse width modulation and fed into the duty-cycle-to-voltage converter, dual control voltages, namely VP and VN with positive and negative control duty cycle coefficients, respectively, are produced to manage the delay of the voltage-controlled ring oscillator and supply a wide range of frequency channels. The proposed clock generator can supply a stable output clock with a wide range of frequencies from 35MHz to 138MHz, and can be used in wideband applications with low supply voltages and small areas.
