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1. (WO2001031351) HIGHLY CONFIGURABLE CAPACITIVE TRANSDUCER INTERFACE CIRCUIT

Pub. No.:    WO/2001/031351    International Application No.:    PCT/US2000/041207
Publication Date: Fri May 04 01:59:59 CEST 2001 International Filing Date: Tue Oct 17 01:59:59 CEST 2000
IPC: G01R 19/25
G01R 27/26
Applicants: MICROSENSORS, INC.
HSU, Ying
SAUNDERS, Christ
SU, Kirk
Inventors: HSU, Ying
SAUNDERS, Christ
SU, Kirk
Title: HIGHLY CONFIGURABLE CAPACITIVE TRANSDUCER INTERFACE CIRCUIT
Abstract:
A transducer interface circuit (10) for use with a capacitive sensor (20). The interface circuit (10), provided on application specific IC, includes numerous trims and adjustments that permit it to operate with a differential, balanced-pair sensors (20A) or a singled-ended sensor (20B). In particular, the circuit (10) provides a capacitive adjustment section (100) and a capacitive trans-impedance amplifier section (200) that are configured with capacitor adjustment controls (110) and gain adjustment controls (210) that, along with other controls, are provided as control registers. The capacitive trans-impedance amplifier section (300) periodically reverses the voltages across the sensor (20), and the capacitive adjustment section (200), after blanking a feedback capacitance (CF) that is used to integrate excess charge caused by a difference in capacitance. A low pass filter section (300) provides bandwidth adjustment without requiring any external components. An output buffer section (400) includes further trim controls for gain and offset, is also governed by an offset selection bit SOFF that adjusts the output range to be optimally suited for the balanced-pair sensors (20A) or a singled-ended sensor (20B).