CMOS Integrated PFM DC-DC Converter with Digitally-Controlled Frequency Selector

This paper proposes a new digital control circuit for PFM (pulse frequency modulation) DC-DC buck converter that operates at light load application. Unlike the conventional PFM circuit, the proposed feedback circuit uses a digitally-control circuit to obtain low-noise and high efficiency converter. In order to achieve low power dissipation with high power efficiency, folding-interpolating ADC is applied in the output stage of the converter. High performance frequency selector is applied in the PFM circuit. The selector is realized by multi-stage frequency divider and multiplexer. The digitally-controlled PFM is incorporated into the voltage-mode DC-DC buck converter which is integrated with 0.18 mu m CMOS process. Post-layout simulation shows that the converter operates in the frequency range of 0.2 similar to 1.5 MHz with power efficiency of 82%. A well-regulated output voltage is obtained from the digitally-controlled PFM circuit.