Capacitive measurement system and method
First Claim
1. An apparatus comprising:
- a capacitive touch screen panel; and
a touch screen controller having;
a capacitor circuit that includes a plurality of weighted capacitors that are coupled to each other at a node;
a first switching circuit that includes a first terminal coupled to the capacitive touch screen panel, a second terminal coupled to a reference voltage terminal, a set of terminals coupled to a first set of conductors of the capacitor circuit, and a switch coupled between the first and second terminals;
a comparator that is coupled to at least a second conductor of the capacitor circuit, each of the weighted capacitors of the capacitor circuit being coupled between the comparator and a respective terminal of the set of terminals;
a second switching circuit that is coupled to the first set of conductors of the capacitor circuit; and
successive approximation register (SAR) logic that is coupled to the comparator and is configured to control the second switching circuit.
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Accused Products
Abstract
A capacitance measurement system precharges first terminals (21-0 . . . 21-k . . . 21-n) of a plurality of capacitors (25-0 . . . 25-k . . . 25), respectively, of a CDAC (capacitor digital-to-analog converter) (23) included in a SAR (successive approximation register) converter (17) to a first voltage (VDD) and pre-charges a first terminal (3-j) of a capacitor (CSENj) to a second voltage (GND). The first terminals are coupled to the first terminal of the capacitor to redistribute charges therebetween so as to generate a first voltage on the first terminals and the first terminal of the capacitor, the first voltage being representative of a capacitance of the first capacitor (CSENj). A SAR converter converts the first voltage to a digital representation (DATA) of the capacitor. The capacitance can be a touch screen capacitance.
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Citations
7 Claims
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1. An apparatus comprising:
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a capacitive touch screen panel; and a touch screen controller having; a capacitor circuit that includes a plurality of weighted capacitors that are coupled to each other at a node; a first switching circuit that includes a first terminal coupled to the capacitive touch screen panel, a second terminal coupled to a reference voltage terminal, a set of terminals coupled to a first set of conductors of the capacitor circuit, and a switch coupled between the first and second terminals; a comparator that is coupled to at least a second conductor of the capacitor circuit, each of the weighted capacitors of the capacitor circuit being coupled between the comparator and a respective terminal of the set of terminals; a second switching circuit that is coupled to the first set of conductors of the capacitor circuit; and successive approximation register (SAR) logic that is coupled to the comparator and is configured to control the second switching circuit. - View Dependent Claims (2, 3, 4)
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5. An apparatus comprising:
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a capacitive touch screen panel having a plurality of horizontal conductors and a plurality of vertical conductors; and a touch screen controller having; a capacitor circuit that includes a plurality of weighted capacitors that are coupled to each other at a node; a switching circuit that includes a first terminal coupled to one of the horizontal or vertical conductors of the capacitive touch screen panel, a second terminal coupled to a reference voltage terminal, a set of terminals coupled to a set of conductors of the capacitor circuit, and a switch coupled between the first and second terminals; and a comparator that is coupled to the capacitor circuit, each of the weighted capacitors of the capacitor circuit being coupled between the comparator and a respective terminal of the set of terminals. - View Dependent Claims (6, 7)
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Specification