Abstract
Voltage scaling is a technique for high energy-efficiency operation. However, the voltage scaling technique requires a adaptive power-supply regulator, which is difficult and complex to implement by analog control. Digitally controlled dc-dc converters inherently have the characteristics of flexibility, robust and programmable, but its efficiency may be lower because of power waste in mixed signal data conversion. This thesis demonstrates a complete design of a digitally controlled buck converter for dynamic voltage systems. The converter senses the voltage error by a windowed ADC which consumes less power than a conventional ADC. A nonlinear digital controller is proposed to improve the tracking performance. A power MOS width slicing technique further increase the power efficiency. This design is fabricated in a 0.18-um CMOS process. The chip area is 2.9mm^2. The switching frequency is 5 MHz. The measurement result shows the power efficiency can achieve 93% and the tracking behavior could be several times improved by the proposed nonlinear control.