Research And Design Of Precision CMOS Oscillator With Temperature Compensation

Oscillator has been widely used in electronics, communications, instrumentation, marine, medical equipment, aviation and other fields from its birth. With the development of IC, the mainstream of CMOS manufacturing processes are constantly progressed, the sizes of MOSFET reduced from submicron to tens of nanometers, the consumption and area of power IC are also decreased, oscillator as a core component of the switching power supply, its requirements become more and more high-performance. Thus the designers are facing more and more difficulties in the design, analysis and simulation. In order to meet those requirements, designers need to make power, speed, noise and stability to achieve a balance. The structures of the oscillator are improved continuously. Therefore, in the CMOS process, optimizing the circuit structure and expanding the performance are very meaningful.In this paper, from the point of view, we study the structure and function of the relaxation oscillator. The contents and innovative achievements are described as follows:(1) When the operating temperature is changed, the frequency of the oscillator is also affected. Based on the relaxation oscillator, we analysis the main factors affecting the frequency. At a certain temperature range, respectively, we make the temperature compensation on the charging current circuit and threshold voltage circuit, and by optimization of the comparator, we achieve linearity and frequency jitter reasonable compromise. In this way, we get the oscillator highly accurate and highly stable.(2) Base on the temperature compensation structure, we expand its capabilities, the expanding features include external synchronization feature, the function of reduced frequency and spread spectrum. When the chip is in the external synchronous working state, on the one hand it generates a stable signal to enable the other circuits, on the other hand it generates the synchronous clock signal to make the whole system work in the external clock frequency; when the chip work in the short circuit state, the frequency is reduced automatically, thus we can not only reduce the dissipation in the short-circuit state, but also short the time recovering from short circuit state to the normal operation state; Finally we use two ways to spread spectrum by changing the charging capacitor and threshold voltage periodically. By spreading the spectrum, the electromagnetic interference is suppressed.