A 3-Ratio 85% Efficient Resonant SC Converter With On-Chip Coil for Li-Ion Battery Operation

This letter introduces a fully integrated hybrid multiratio resonant dc-dc converter implemented in a 130-nm BCD process. With a 3.0-4.5 V input voltage range it is fully compatible with Li-ion batteries. It provides output voltages of 1.5-1.8 V with an output current range of 500 μA-120 mA, suitable for wearable applications. The proposed switch conductance regulation (SwCR) achieves a flat converter efficiency across the full load range together with a small output voltage ripple of <; 35 mV. The converter achieves 85% peak efficiency with a total flying capacitance of 2 nF, a 9-nH spiral inductance and 10-nF output capacitance (all onchip). With a small external 10-nH SMD inductance mounted on top of the die, 88.5% peak efficiency is achieved.