Feasibility of monolithic and 3D-stacked DC-DC converters for microprocessors in 90nm technology generation

Abstract

Rapidly increasing input current of microprocessors resulted in rising cost and motherboard real estate occupied by decoupling capacitors and power routing. We show by analysis that an on-die switching DC-DC converter is feasible for future microprocessor power delivery. The DC-DC converter can be fabricated in an existing CMOS process (90nm-180nm) with a back-end thin-film inductor module. We show that 85% efficiency and 10% output voltage droop can be achieved for 4:1, 3:1, and 2:1 conversion ratios, area overhead of 5% and no additional on-die decoupling capacitance. A 4:1 conversion results in 3.4/spl times/ smaller input current and 6.8/spl times/ smaller external decoupling.