Methods and systems for detecting a capacitance using sigma-delta measurement techniques
Patent 7948245 Issued on May 24, 2011. Estimated Expiration Date: February 18, 2030. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
Methods, systems and devices are described for detecting a measurable capacitance using sigma-delta measurement techniques. According to various embodiments, a voltage is applied to the measurable capacitance using a first switch. The measurable capacitance is allowed to share charge with a passive network. If the charge on the passive network is past a threshold value, then the charge on the passive network is changed by a known amount for a sufficient number of repetitions until the measurable capacitance can be detected. Such a detection scheme may be readily implemented using conventional components, and can be particularly useful in sensing the position of a finger, stylus or other object with respect to a button, slider, touchpad or other input sensor.
Other References
Kremin, Victor et al., “Capacitance Sensing—Waterproof Capacitance Sensing—AN2398”, Cypress Perform, Document No. 001-14501 Rev., Dec. 8, 2006, pp. 1-11.
Quantum Research Group, “Secrets of a Successful QTouch™ Design”, Quantum Research Application Note AN-KD02, Rev. 1.03, Oct. 2005, pp. 1-11.
Martin, K.; A Voltage-Controlled Switch Capacitor Relaxation Oscillator; IEEE Journ. of Solid-State Circuits; Aug. 1981; pp. 412-414; vol. SC-16, No. 4.
Norsworthy, S.; Effective Dithering of Sigma-Delta Modulators; AT&T Bell Laboratories; IEEE 1992; pp. 1304-1307.
Josefsson, O.; Ask the Applications Engineer: Using Sigma-Delta Converters—Part 1; Analog Dialogue 30th Anniversay Reader Bonus; 1997; pp. 29-33.
Cao, Y. et al.; High-Accuracy Circuits for On-Chip Capacitance Ratio Testing or Sensor Readout; IEEE Transactions; Sep. 1994; pp. 637-639; vol. 41, No. 9.
Banks; Low Cost, Low Speed A/D Conversion for Embedded Systems; Byte Craft Limited (retrieved on Jul. 25, 2006); Retrieved from Internet: .
Johns, D.A.; Analog Integrated Circuit Design; 1997; pp. 542, 543; John Wiley & Sons.
Yamada, M. et al.; A Switched-Capacitor Interface for Capacitive Pressure Sensors; IEEE; Feb. 1992; pp. 81-86; vol. 31, No. 1.
Toth, F.; Design Method for Low-Cost, High-Perf. Cap. Sensors; Delft Univ. of Tech.;1997; Retrieved from Internet: .
Phillip, H.; Charge Transfer Sensing: Spread Spectrum Sensor Technology Blazes New Applications; Retrieved from Internet: —paper.php, 1997.
Huang, S.M. et al.; Electronic Transducers for Industrial Measurement of Low Value Capacitances; J. Phys. E.: Sci. Instrum. 21; 1988; pp. 242-250.
Cichocki, Andrzej et al.; A Switched Capacitor Interface for Capcaitive Sensors Based on Relaxation Oscillators; IEEE; Oct. 1990; pp. 797-799; vol. 39 No. 5.
Phillip, Hal; Fingering a Problem; New Electronics; Jan. 24, 2006; pp. 51-52; Retrieved from Internet: .
Touch Sensor IC(B6TS). Omron Corporation [retrieved on Aug. 14, 2006]. Retrieved from Internet: .
February 18, 2030. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
