Switching Regulator with Dynamically Adjustable Supply Voltage for Low Power Vlsi

The paper describes a switching regulator system for adaptive voltage scaling (AVS) where the supply voltage to a digital VLSI chip is dynamically adjusted to the minimum value required for the desired system speed. The control loop includes a variable-frequency Watkins-Johnson switching DC-DC converter and a model of the critical path delay of the application. Simple bang-bang control of the critical path delay allows fast transient response to step changes in speed, and stable operation over a very wide range of system clock frequencies. A chip including the AVS controller and a small digital application has been fabricated in a standard CMOS process. Experimental results demonstrate operation over the application clock frequency range from 10 kHz to 20 MHz, and a 12 s transient response for a step change in speed from standby to maximum throughput operation.