A capacitive sensing integrated circuit for detection of micromotor critical angles

Author

Garverick, Steven L. ; Nagy, Michael L. ; Rao, Naresh K. ; Hartsfield, David K. ; Purushotham, Aravind

Author_Institution

Dept. of Electr. Eng. & Appl. Phys., Case Western Reserve Univ., Cleveland, OH, USA

Volume

32

Issue

1

fYear

1997

fDate

1/1/1997 12:00:00 AM

Firstpage

23

Lastpage

30

Abstract

The theory, design, and measured performance of an integrated circuit which enables closed-loop control of electrostatic micromotors is presented. The micromotor control integrated circuit (MCIC) consists of low-noise sense electronics designed to detect critical rotor angles to a resolution of 0.5° (0.05 fF) at a 1-MHz sampling rate, and control logic which cycles the micromotor drive state during continuous rotation to maintain maximum torque, independent of loading. Noise due to MOSFET switches and amplifiers in the analog section is modeled and shown to be 32 μV referred to the system input, i.e., about half the desired switching resolution. The MCIC was fabricated using a 2-μm, n-well CMOS process and functions as expected. The noise probability density function was measured using MCIC´s digital output for different values of input-to-ground capacitance in order to verify the noise model. Good agreement with theory was observed, although the comparator exhibited some offset and hysteresis

Keywords

CMOS analogue integrated circuits; capacitance; closed loop systems; electric sensing devices; electrostatic devices; micromotors; switched capacitor networks; 1 MHz; 2 micron; MOSFET switches; capacitive sensing integrated circuit; closed-loop control; continuous rotation; drive state; electrostatic micromotors; hysteresis; input-to-ground capacitance; micromotor control integrated circuit; micromotor critical angles; n-well CMOS process; noise probability density function; offset; rotor angles; sampling rate; switching resolution; Electrostatic measurements; Integrated circuit measurements; Integrated circuit noise; Logic circuits; Logic design; MOSFET circuits; Micromotors; Sampling methods; Semiconductor device modeling; Torque control;

fLanguage

English

Journal_Title

Solid-State Circuits, IEEE Journal of

Publisher

ieee

ISSN

0018-9200

Type

jour

DOI

10.1109/4.553172

Filename

553172