Design of A Controllable and Adjustable Spread Spectrum Clock Signal Generator

With the rapid development of the internet industry, higher demands are placed on the power management chips, the core drivers of electronic devices, with particular emphasis on reducing electromagnetic interference (EMI). Clock generators typically represent the largest contributors to EMI within power management chips. This paper presents a design of a controllable and adjustable spreading signal generator capable of operating under a low voltage power supply of 3V. The spreading function can be enabled or disabled via an external enable signal. When the spreading function is disabled, the converter operates in fixed frequency mode, whereas when enabled, it operates in spreading mode. The center frequency of the oscillator can be adjusted by varying external resistances, while the spreading range and depth can be tuned by adjusting external reference voltage and charging capacitance. Simulation results using CMOS 0.18um technology indicate that spreading technology widens the spectrum of the system output signal, distributing energy more uniformly across a wider frequency band, resulting in a 56% reduction in peak energy of the fundamental wave. By controlling the spreading function's switch, a trade-off can be made between EMI and output voltage stability to accommodate different application scenarios, thereby enhancing system immunity to interference and achieving efficient energy conversion and stable power output.