A New Adaptive Mode-Switching Mechanism with Current-mode CMOS DC-DC Converter

In this paper, presented is a new adaptive mode-switching mechanism for a synchronous, self-oscillating, fully integrated CMOS dc-dc converter. The proposed adaptive mode-switching mechanism employs a current sensing technique to enable the automatic mode switching between CCM and DCM according to the level of the load current, thus maintaining a high conversion efficiency even though the load current of an application may change during normal operation. Moreover, the level of the load current for mode switching is programmable depending on the applications. The efficiency of the resulting dc to dc converter is up to 92% while the maximum peak-to peak output voltage ripple is 18 mV and the output current ranges between 50 mA and 500 mA. The dc to dc converter operates at a switching frequency from 250 to 3 MHz from a supply voltage ranging from 2.4 to 4.2 V. The new DC-DC converter was fabricated in TSMC 0.35-mum 2P4M CMOS process with die size was 0.85 mm2. Except the external inductor and capacitor, all the devices including the power switches are on chip.