Capacitive touchscreen system with switchable charge acquisition circuit

摘要

Disclosed herein are various embodiments of a capacitive touchscreen system which includes switchable charge acquisition circuits and corresponding charge integrator circuits for sensing mutual capacitances associated with a touchscreen. Various embodiments of the switchable charge acquisition circuits and corresponding charge integrator circuits provide lower power consumption, increased operational stability, substantially reduced integrated circuit area, and increased temperature stability.

主权项

1. A capacitive touchscreen system, comprising:
a touchscreen comprising a first plurality of electrically conductive drive electrodes arranged in rows or columns, and a second plurality of electrically conductive sense electrodes arranged in rows or columns arranged at an angle with respect to the rows or columns of the first plurality of electrodes, mutual capacitances existing between the first and second pluralities of electrodes at locations where the first and second pluralities of electrodes intersect, the mutual capacitances changing in the presence of one or more fingers or touch devices brought into proximity thereto, stray capacitances being associated with each of the second plurality of electrodes; one or more drive circuits operably connected to the first plurality of electrodes, and a plurality of sense circuits, each of the plurality of sense circuits being operably connected to a corresponding one of the second plurality of electrodes, each sense circuit comprising a charge integrator circuit and a charge acquisition circuit comprising a plurality of capacitors arranged in parallel respecting one another, first input switches and second output switches corresponding to each of the capacitors in the charge acquisition circuit, each charge acquisition circuit being operably connected to a corresponding electrode from among the second plurality of electrodes to receive input signals therefrom through the first input switches wherein a gain of each charge acquisition circuit is determined by closing a predetermined number of the first input switches, the input signals representing mutual capacitances and stray capacitances, each charge acquisition circuit further being operably connected to a corresponding charge integrator circuit to provide output signals thereto through the second output switches; wherein when the first input switches of each charge acquisition circuit are closed the capacitive input signals provided thereto by the second plurality of electrodes are transferred to the plurality of capacitors corresponding thereto, and when the first switches are subsequently opened and the second switches are closed the stored charge signals corresponding to each of the capacitors in the charge acquisition circuit are transferred to the charge integrator circuit through the second switches.