Abstract

Current-mode ripple-based dc–dc converters have become a widely adopted topology due to their inherent advantages of improved dynamic transient response along with a simple current sensing scheme. However, the switching frequency of such converters is a function of the converter’s duty cycle and inherent circuit delays. In this brief, a novel frequency control of a buck converter is proposed through the implementation of a frequency-to-voltage converter that obviates the need for an external clock, and enables both fixed-switching frequency ( ${F} _{\textbf {SW}}$ ) and spread-spectrum modes of operation. A current-mode ripple-based buck converter is implemented in a 180-nm CMOS process for an input voltage of 2.8–4.2 V, output voltage range of 1.3–2.2 V, and load current range of 40–200 mA. In fixed- ${F} _{\textbf {SW}}$ mode, a peak efficiency of 89.4% was achieved at an input voltage of 3.8 V, load current of 200 mA and 1.8 V output voltage, while in spread-spectrum mode, a peak efficiency of 88.2% was achieved for similar conditions. Additionally, in spread-spectrum mode, a 19-dB reduction in peak noise power is observed in the output at the fundamental frequency.

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