High voltage, High-sensitivity Self-capacitance Sensing

Abstract

Apparatuses and methods of high-voltage capacitance-sensing circuits are described. One apparatus includes a capacitance-sensing circuit coupled to a capacitive-sense array of electrodes. The capacitance-sensing circuit includes a self-capacitance sensing channel, a first voltage source (e.g., a low-voltage drive source) to drive a reference voltage, and a second voltage source (e.g., high-voltage drive source) to drive a sensing voltage. The sensing voltage is greater in magnitude than the reference voltage. The capacitance-sensing circuit also includes 1) a first set of switches to selectively couple the self-capacitance sensing channel or the second voltage source to a sensing electrode of the capacitance-sensing array; and 2) a second set of switches to selectively couple the first voltage source or the second voltage source to a shielding electrode of the capacitance-sensing array.

What is claimed is: 
     
         1 .- 20 . (canceled) 
     
     
         21 . An apparatus comprising:
 a first portion of a capacitance-sensing circuit, the first portion being configured to generate an output corresponding to a capacitance measured at a first electrode of a plurality of electrodes included in a capacitive-sense array;   a plurality of signal sources including a first signal source and a second signal source, the first signal source being configured to generate a first signal, and the second signal source configured to generate a second signal having a voltage magnitude greater than the first signal; and   switching circuitry configured to couple the first portion of the capacitance-sensing circuit or the second signal source to the first electrode of the plurality of electrodes, and further configured to couple the first signal source or the second signal source to a second electrode of the plurality of electrodes.   
     
     
         22 . The apparatus of  claim 21 , wherein the first signal generated by the first signal source is a reference voltage, and wherein the second signal generated by the second signal source is a sensing voltage. 
     
     
         23 . The apparatus of  claim 21 , wherein the first electrode is a sensing electrode configured to sense, at least in part, a capacitance associated with an object proximate to the capacitive-sense array, and wherein the second electrode is a shielding electrode capacitively coupled to the first electrode. 
     
     
         24 . The apparatus of  claim 23 , wherein the first portion of the capacitance-sensing circuit comprises a self-capacitance sensing channel coupled to the first electrode. 
     
     
         25 . The apparatus of  claim 24 , wherein the self-capacitance sensing channel comprises:
 an integrator;   a capacitor; and   an analog-to-digital converter (ADC).   
     
     
         26 . The apparatus of  claim 21 , wherein the switching circuitry comprises first switching circuitry and second switching circuitry, wherein the first switching circuitry is configured to couple the first portion of the capacitance-sensing circuit, the second signal source, or a ground potential to the first electrode, and wherein the second switching circuitry is configured to couple the first signal source, the second signal source, or the ground potential to the second electrode. 
     
     
         27 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit is configured to control the switching circuitry in a four-phase, full-wave mode. 
     
     
         28 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit is configured to control the switching circuitry in a two-phase, half-wave mode. 
     
     
         29 . The apparatus of  claim 21 , wherein the capacitance-sensing circuit is configured to control the switching circuitry in a three-phase, half-wave mode. 
     
     
         30 . A method comprising:
 applying a first signal to a first electrode and a second electrode, the first signal being generated by a first signal source;   discharging the first electrode to a voltage associated with a second signal, the discharging being based on positive charge transfer from the first electrode to a portion of a capacitive-sensing circuit, the second signal being generated by a second signal source, and the second signal having a lesser voltage magnitude than the first signal;   converting the positive charge transfer to a first digital value; and   accumulating the first digital value.   
     
     
         31 . The method of  claim 30 , wherein the first electrode is a sensing electrode, wherein the second electrode is a shielding electrode capacitively coupled to the first electrode, wherein the first signal source is a sensing voltage source, and wherein the second signal source is a reference voltage source. 
     
     
         32 . The method of  claim 30 , wherein the applying, setting, converting, and accumulating are included in a four-phase, full-wave mode. 
     
     
         33 . The method of  claim 30 , wherein the applying, setting, converting, and accumulating are included in a two-phase, half-wave mode. 
     
     
         34 . The method of  claim 30 , wherein the applying, setting, converting, and accumulating are included in a three-phase, half-wave mode. 
     
     
         35 . A system comprising:
 a capacitive-sense array comprising a plurality of electrodes, the plurality of electrodes including a first electrode and a second electrode; and   a capacitance-sensing circuit coupled to the capacitive-sense array, the capacitance-sensing circuit comprising:
 a first portion configured to generate an output corresponding to a capacitance measured at the first electrode; 
 a plurality of signal sources including a first signal source and a second signal source, the first signal source being configured to generate a first signal, and the second signal source configured to generate a second signal having a voltage magnitude greater than the first signal; and 
 switching circuitry configured to couple the first portion or the second signal source to the first electrode of the plurality of electrodes, and further configured to couple the first signal source or the second signal source to the second electrode of the plurality of electrodes. 
   
     
     
         36 . The system of  claim 35 , wherein the first signal generated by the first signal source is a reference voltage, and wherein the second signal generated by the second signal source is a sensing voltage. 
     
     
         37 . The system of  claim 35 , wherein the first electrode is a sensing electrode configured to sense, at least in part, a capacitance associated with an object proximate to the capacitive-sense array, and wherein the second electrode is a shielding electrode capacitively coupled to the first electrode. 
     
     
         38 . The system of  claim 37 , wherein the first portion of the capacitance-sensing circuit comprises a self-capacitance sensing channel coupled to the first electrode. 
     
     
         39 . The system of  claim 38 , wherein the self-capacitance sensing channel comprises:
 an integrator;   a capacitor; and   an analog-to-digital converter (ADC).   
     
     
         40 . The system of  claim 35 , wherein the switching circuitry comprises first switching circuitry and second switching circuitry, wherein the first switching circuitry is configured to couple the first portion of the capacitance-sensing circuit, the second signal source, or a ground potential to the first electrode, and wherein the second switching circuitry is configured to couple the first signal source, the second signal source, or the ground potential to the second electrode.