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US 6,583,632 B2Granted
Method of determining very small capacitances
AssigneeMicronas GmbH
InventorsPaul-Werner Von Basse, Josef Willer
Life of this patent
Estimating the term…
Abstract
A grid of capacitor surfaces is connected to read lines and control lines. The read lines are connected alternately to the output of a feedback operational amplifier and to a collecting capacitor. The capacitances to be measured are charged repeatedly and the charges are collected on the collecting capacitors. Between the charging operations, the potential on the read lines is kept constant through the use of the low-resistance output of the operational amplifier. The use of this method in the case of a fingerprint sensor makes it possible to evaluate all the read lines together.
Claims8
A method of determining capacitances, the method which comprises:
- (a) providing a grid-shaped configuration of capacitors, the capacitors being formed by pairs of electrical conductor surfaces;
- (b) dividing the electrical conductor surfaces into groups;
- (c) electrically conductively connecting the electrical conductor surfaces of in each case one of the groups to one another by a respective read line;
- (d) electrically conductively connecting the electrical conductor surfaces of in each case one of the groups separately from one another to a respective control line;
- (e) applying, during a given time, an electric potential to the respective control line such that a potential difference is present between the respective control line and a plurality of read lines and charging, with the potential difference, the capacitors formed in each case by at least one of the electrical conductor surfaces connected to the respective control line and at least one of the electrical conductor surfaces connected to one of the read lines;
- (f) carrying off a charge via each of the read lines separately to a respective collecting capacitor;
- (g) switching off the electric potential applied to the respective control line and impressing, at low resistance, a respective potential onto a respective one of the read lines by using a circuit, the respective potential defining a charge state of the respective collecting capacitor with respect to a reference potential;
- (h) repeating steps (e) to (g) until a given number of charge operations has taken place;
- and
- (i) subsequently determining for each of the read lines one of a charge of the respective collecting capacitor and a potential difference of the respective collecting capacitor.
7 more elements
A method of determining capacitances, the method which comprises:
- (a) providing a grid-shaped configuration of capacitors, the capacitors being formed by pairs of electrical conductor surfaces;
- (b) dividing the electrical conductor surfaces into groups;
- (c) electrically conductively connecting the electrical conductor surfaces of in each case one of the groups to one another by a respective read line;
- (d) electrically conductively connecting the electrical conductor surfaces of in each case one of the groups separately from one another to a respective control line;
- (e) applying, during a given time, an electric potential to the respective control line such that a potential difference is present between the respective control line and a plurality of read lines and charging, with the potential difference, the capacitors formed in each case by at least one of the electrical conductor surfaces connected to the respective control line and at least one of the electrical conductor surfaces connected to one of the read lines;
- (f) carrying off a charge via each of the read lines separately to a respective collecting capacitor;
- (g) switching off the electric potential applied to the respective control line and impressing, at low resistance, a respective potential onto a respective one of the read lines by using a circuit, the respective potential defining a charge state of the respective collecting capacitor with respect to a reference potential;
- (h) repeating steps (e) to (g) until a potential difference which is greater than a given value is present at the respective collecting capacitor;
- and
- (i) subsequently determining for each of the read lines a number of performed charge operations.
7 more elements
Dependencies are inferred from the claim text.