Increasing the Dynamic Range of an Integrator Based Mutual-Capacitance Measurement Circuit

摘要

In one embodiment, a method includes deactivating an integrator of a mutual-capacitive measurement circuit and configuring the mutual-capacitive measurement circuit according to a first voltage configuration. The first voltage configuration results in a charge on a sensor capacitor and a compensation capacitor when a supply voltage is applied to the mutual-capacitive measurement circuit. The method also includes adjusting a variable reference voltage input of the integrator to a first reference voltage, wherein the first reference voltage is selected to increase an output range of the mutual-capacitive measurement circuit. The method also includes applying the supply voltage to the mutual-capacitive measurement circuit and obtaining a first reference measurement from an analog-digital-converter coupled to an output of the mutual-capacitance measurement circuit.

主权项

1. A method of detecting a change in capacitance, comprising:
adjusting a variable reference voltage input of an integrator of a mutual-capacitive measurement circuit to a first reference voltage, wherein the first reference voltage is selected to increase an output range of the mutual-capacitive measurement circuit during a first half of a differential measurement cycle; configuring the mutual-capacitive measurement circuit for obtaining a first reference measurement during the first half of the differential measurement cycle; obtaining the first reference measurement from an analog-digital-converter coupled to an output of the mutual-capacitance measurement circuit; configuring the mutual-capacitive measurement circuit for obtaining a first output measurement during the first half of the differential measurement cycle; obtaining the first output measurement from the analog-digital-converter; adjusting the variable reference voltage input to a second reference voltage, wherein the second reference voltage is selected to increase the output range of the mutual-capacitive measurement circuit during a second half of the differential measurement cycle; configuring the mutual-capacitive measurement circuit for obtaining a second reference measurement during the second half of the differential measurement cycle; obtaining the second reference measurement from the analog-digital-converter; configuring the mutual-capacitive measurement circuit for obtaining a second output measurement during the second half of the differential measurement cycle; obtaining the second output measurement from the analog-digital-converter; and calculating a differential measurement using the first reference measurement, the first output measurement, the second reference measurement, and the second output measurement.