A generic interface chip for capacitive sensors in low-power multi-parameter microsystems

This paper presents a generic low-power sensor interface chip compatible wi th smart microsystems and a wide range of capacitive transducers. The inter face chip is highly programmable, can communicate with an external microcon troller using a nine-line sensor bus standard, contains a switched-capacito r readout circuit, supports sensor self-test, and includes a temperature se nsor. The circuit can interface with up to six external sensors and contain s three internal programmable reference capacitors in the range of 0.15-8 p F. The chip measures 3.2 x 3.2 mm in a standard 3-mu m single-metal double- poly p-well process, dissipates less than 2.2 mW from a single 5 V supply, and can resolve input capacitance variations of less than 1 fF in 10 Hz ban dwidth. (C) 2000 Elsevier Science S.A. All rights reserved.