Patent ID: 8659306
Filing Date: 2014-02-25
Classification: G01D,G01R,H03K

Abstract:
1. An integrated circuit for measuring capacitance of a sense plate structure, said integrated circuit comprising: a reference capacitor; means for periodically applying a fixed charging voltage to said sense plate structure; a charge transfer circuit for periodically charging said reference capacitor, said charge transfer circuit including at least one current mirror structure having an input for receiving a current from said sense plate structure and generating an output current that is a scaled version of said input current; a switch for periodically connecting said sense plate structure to said current mirror input, wherein the periodic charging of the sense plate structure, charging said reference capacitor and connecting the sense plate to the current mirror input form a charge transfer cycle; and means for determining the capacitance of said sense plate based on the accumulated amount of charge in the reference capacitor.