A Hybrid, Fully-Integrated, Dual-Output DC–DC Converter for Portable Electronics

This article describes a hybrid, dual-output dc-dc converter suitable for low-power application. It consists of inductor based subconverter providing one output, which is cascaded with a switched-capacitor based subconverter providing the second output. The converter uses bondwire inductance, and on-chip metal-oxide-semiconductor (MOS) capacitance to realize the passive components making it a fully-integrated solution. For target specification of output voltage levels, and input voltage range, the stepped-up output is generated by the inductor-based, high-frequency, voltage-mode boost converter. And, a switched capacitor based, frequency-controlled step-down converter generates the second output. The hybrid converter uses a π-filter to attenuate the switching ripple to an acceptable value. The filter also helps to isolate the internal ground from the noisy power ground connected to boost converter power stage. By the virtue of time-interleaved switching pattern, switching noise induced in its supply rails by the S-C stage is significantly less, which makes the S-C stage an equivalent quiescent load to the boost stage. A prototype of the proposed hybrid converter has been designed, and implemented in 0.18-μm CMOS process. It consumes 0.82 mm2 area, and provides -1.45V, and 3.2V from an input voltage varying from 1.2V to 2.7V at an efficiency > 52% (maximum 77%) for all load conditions.