US 8,896,325 B2 · Capacitance sensing circuit and method of capacitance sensing

Abstract

A capacitance sensing circuit comprises a capacitive device having a capacitance, the device initially being at a first voltage level. The capacitance sensing circuit is capable of applying one or more pull-up currents to the device during one or more corresponding pull-up periods of time, for changing the first voltage level into one or more corresponding pull-up voltage levels; applying a measurement current to the device; and measuring a measurement period of time, during which one of the pull-up voltage levels changes into a second voltage level. A method of sensing a capacitance of a capacitive device comprises applying a first voltage to the device; applying one or more pull-up currents during corresponding pull-up times, for changing the first voltage into corresponding pull-up voltages; applying a measurement current; and measuring a time, during which one pull-up voltage changes into a second voltage.

Claims13

Dependent claims

A capacitance sensing circuit, comprising

a capacitive device having a capacitance;
said capacitance sensing circuit being capable of
applying in an initialization phase a pull-up current to said capacitive device, said capacitive device initially being at a first voltage level;
measuring an initialization period of time for changing said first voltage level into a second voltage level by means of said pull-up current;
determining a pull-up voltage level as a voltage level present at said capacitive device after a fraction of said initialization period of time;
applying in a measurement phase said pull-up current to said capacitive device, said capacitive device initially being at said first voltage level, during a pull-up period of time, for changing said first voltage level into said pull-up voltage level;
applying a measurement current to said capacitive device, said capacitive device being at said pull-up voltage level;
and
measuring a measurement period of time, during which said pull-up voltage level changes into said second voltage level by means of said measurement current.

6 more elements

Dependencies are inferred from the claim text.

Capacitance sensing circuit and method of capacitance sensing

Life of this patent

Capacitance sensing circuit and method of capacitance sensing

Life of this patent

Abstract

Claims13