Sensor Research
                Chemical Sensor Array for Study of Neurons in vitro
                Integrated Optical and Potentiometric Sensors
                Electron-Relay Enabled Immunosensor Using Magnetic Microprobes
                Integrated Liquid Chemical Sensors for Measuring Pollutants in Precipitation

       VLSI and MEMS Research
                Robust Low-Power Digital Circuit Design in Partially-Depleted SOI
                Distributed Capacitance LC Clock Generation
                Improving the Performance of Standard Cell Designs and Libraries
                A 900 mV Analog Front End for Low Power Mixed-Signal Applications
                A Low Power DSP Architecture for Cochlear Implant Systems on a Chip  
                Monolithic & Top-Down Clock Synthesis with Micromachined RF Reference
                Analysis and Development of Design Styles for Low Power SOI Circuits
                Micropower Digital SOI
                Low Power SOI PowerPC FXU

        MiBench: a free, commercially representative embedded benchmark suite

        UMIPS: University of Michigan Intellectual Property Source

See Also:
    Microprocessor Project
    Solid-State Chemical Sensors
    Instruction Stream Compression
    MS8: Mixed-Signal Sensor Interface Microcontroller

Overview

Prof. Brown conducts research ranging from solid-state process development through many aspects of VLSI circuit design.

His solid-state sensor work has included the introduction of refractory metal silicides as micromechanical materials, and development of arrays of potentiometric, amperometric, optical and conductometric liquid chemical sensors. All of this work is done on silicon and glass substrates using CMOS-like processing steps. Many of these sensors use polymeric membranes to provide specificity, to exclude certain molecules or to prevent protein coating. The chemical sensors detect ions, and can be made to detect larger molecules by incorporating biologically active species (enzymes and antibodies) bound to polymeric or gold layers. This work is done in collaboration with chemists at the University of Michigan and Kwangwoon University. Some of the sensors include on-chip circuitry to buffer, select, amplify, convert, and transmit the sensor signals. Pioneering work is being done in the miniaturization of sensors and reference electrodes, in new polymers having better adhesion to the sensor surfaces, in sensor encapsulation and packaging, in stabilization of the membrane/solid interface, in the patterning of small membrane sites, in the integration of electronics, and in the growth of cells on the sensor surfaces.

The VLSI research, done in conjunction with others from the Solid-State and Advanced Computer Architecture Labs, has included microprocessor design in two gallium arsenide technologies, enhancement/depletion MESFET (Vitesse HGaAs) and complementary GaAs (CGaAs). The HGaAs effort was focused on designing high-speed microprocessors, while the CGaAs designs are low-power and radiation-hard, suiting them well for space applications. This work has covered architectural design for high performance and for limited-resource processors; circuit design in exotic technologies; fine-pitch, area-I/O packaging on multichip modules; low-jitter PLL-based clock generators; high-speed, low-power current-mode I/O; semiconductor process optimization; place-and-route tools to manage cross-talk; and optimizing SRAM compilers.

In research that bridges the sensor and VLSI activities, Prof. Brown and his students have designed mixed-signal microcontrollers which can act as single-chip instruments for a variety of solid-state sensors. They include low-voltage analog interfaces for voltage, current and capacitance; a custom microprocessor core, optimized for executing C programs; and current source- and clock-control circuits to minimize power dissipation. Building on experience with SOI process development for chemical sensors and the experience of designing in advanced technologies from the GaAs microprocessor projects, Prof. Brown's group will employ SOI to extend the performance and power-efficiency of these microcontrollers.