Patent ID: 7804307
Filing Date: 2010-09-28
Classification: G01R,H03K

Abstract:
1. A system for measuring capacitance, said system comprising: an adjustable current source supplying a substantially constant current that charges a first capacitor and a second capacitor until voltage at said second capacitor settles to a settling voltage, wherein during said charging said first capacitor is alternately switched between said current source and ground, and wherein said first capacitor is electrically coupled to said second capacitor when switched to said current source, and wherein said first capacitor is electrically disconnected from said second capacitor when switched to ground, and wherein charging of said first capacitor is halted after said settling voltage is reached; a comparator coupled to said second capacitor that compares voltage at said second capacitor to a reference voltage, wherein after charging of said first capacitor is halted, said current source continues to charge said second capacitor until voltage at said second capacitor reaches said reference voltage; and a counter coupled to said comparator that determines an amount of time until voltage at said second capacitor reaches said reference voltage, wherein said amount of time corresponds to an amount of capacitance on said first capacitor.