Anthony J. Stratakos

A dynamic voltage scaled microprocessor system

A microprocessor system is presented in which the supply voltage and clock frequency can be dynamically varied so that the system can deliver high throughput when required while significantly extending battery life during the low speed periods. The system consists of a dc-dc switching regulator, an ARM V4 microprocessor with a 16-kB cache, a bank of 64-kB SRAM ICs, and an I/O interface IC. The four custom chips were fabricated in a standard 0.6-/spl mu/m 3-metal CMOS process. The system can dynamically vary the supply voltage from 1.2 to 3.8 V in less than 70 /spl mu/s. This provides a throughput range of 6-85 MIPS with an energy consumption of 0.54-5.6 mW/MIP yielding an effective energy efficiency as high as 26200 MIPS/W.

A low-voltage CMOS DC-DC converter for a portable battery-operated system

Motivated by emerging battery-operated applications that demand compact, lightweight, and highly efficient DC-DC power converters, a buck circuit is presented in which all active devices are integrated on a single chip using a standard 1.2 /spl mu/ CMOS process. The circuit delivers 750 mW at 1.5 V from a 6 V battery. To effectively eliminate switching loss at high operating frequencies, the power transistors achieve nearly ideal zero-voltage switching (ZVS) through an adjustable dead-time control scheme. The silicon area and power consumption of the gate-drive buffers are reduced with a tapering factor that minimizes short-circuit current and dynamic dissipation for a given technology and application. Measured results on a prototype IC indicate that on-chip losses at full load can be kept below 8% at 1 MHz.<<ETX>>

Design of portable systems

The increasing demand for portable operation has elevated power consumption to be one of the most critical design parameters. This paper presents various low-power techniques required for the design of portable systems. Low-power operation is achieved using reduced supply voltages (1-1.5 V) coupled with a system level optimization of the switching activity that involves logic design, re-synchronization, signal correlations and number representation. The support circuitry required for low-voltage operation is presented which includes level-shifters, DC-DC converters and D/A converters.<<ETX>>

DC Power Supply Design in Portable Systems

In portable systems, a number of low-voltage, low-power DC voltage supplies are needed. To provide these from a single battery source, some form of voltage conversion is necessary. To facilitate portability and conserve battery capacity, this conversion should be accomplished in minimal space and mass, with the high efficiency more easily realized in larger converters. A monolithic CMOS DC power supply could meet the severe size and efficiency requirements of a hand-held device. This chapter describes a design methodology for such converters.