A Ripple-Based DC-DC Buck Converter with Random Switching Frequency

In general, the step-down switching power converter is prone to excessive electromagnetic interference on the input side. The constant on-time controlled buck converter with random switching frequency proposed in this paper is mainly characterized by not using external components. In this case, the spread spectrum mechanism is used to reduce the electromagnetic interference (EMI) of the converter itself, and the power stage output capacitor of the converter can use the ceramic capacitor of the low equivalent series resistance to reduce the output voltage ripple. The chip was realized with TSMC 0.18μm 1P6M CMOS process, and the chip area including the PAD is 1.2 × 1.15 mm². The input voltage range is 2.9~3.3V and the output voltage is 1.8V. The switching convertor operated at 1-MHz switching frequency and performed spread-spectrum modulation. The external inductor and capacitor are 3.3μH and 10μF, respectively.