Granted Patent B1

US 10,209,833 · App. 13/975,078 · Granted Feb 19, 2019

Abstract

Claims (38)

1. A capacitance sensor comprising:

a capacitive sensor array for detecting a presence of a conductive object, the capacitive sensor array comprising at least one first sensor element, at least one second sensor element, and at least one third sensor element, wherein the at least one first sensor element and the at least one second sensor element are single and independent sensor element respectively, wherein the third sensor element comprises of a first portion and a second portion having sensing area equal to sensing area of the first portion, wherein a sensing area of the first sensor element, a sensing area of the second sensor element, and a sensing area of the third sensor element are equal to each other, wherein the sensing area of the first portion of the third sensor element is less than the sensing area of the first sensor element, and the sensing area of the second portion of the third sensor element is less than the sensing area of the first sensor element, wherein the first sensor element and the first portion of the third sensor element are permanently connected together, and the second sensor element and the second portion of the third sensor element are permanently connected together that is electrically isolated from the first conductive material, wherein the first and second portions of the third sensor element are electrically isolated;

a relaxation oscillator respectively coupled to the first sensor element and the second sensor element to receive input signals representing capacitances on the first, second and third sensor elements, the relaxation oscillator further configured to generate an output signal, wherein the capacitances on the third sensor element is represented by simultaneously receiving the capacitances on the first and second sensor elements; and

a digital counter coupled to receive the output signal of the relaxation oscillator, the digital counter configured to measure at least one of a frequency and a period of the output signal of the relaxation oscillator.

2. The capacitance sensor of claim 1 , wherein the capacitive sensor array is coupled to the relaxation oscillator via an analog bus having a plurality of pins.

3. The capacitance sensor of claim 1 , further comprising a selection circuit that is coupled between the capacitive sensor array and the relaxation oscillator.

4. The capacitance sensor of claim 3 , wherein the selection circuit is configured to sequentially select a sensor element from the multiple sensor elements to provide charge current to the selected sensor element or to receive an input signal representing capacitance of the selected sensor element.

5. The capacitance sensor of claim 1 , wherein the capacitance sensor is configured to simultaneously scan the multiple sensor elements.

6. The capacitance sensor of claim 5 , wherein the plurality of rows are scanned simultaneously, and wherein the plurality of columns are scanned simultaneously.

7. The capacitance sensor of claim 5 , wherein voltages on the plurality of rows are simultaneously moved while voltages on the plurality of columns are held at a constant voltage in order to obtain a profile of the conductive object in a first dimension.

8. The capacitance sensor of claim 5 , wherein voltages on the plurality of rows are simultaneously moved in a positive direction while voltages on the plurality of columns are moved in a negative direction in order to obtain a profile of the conductive object in a first dimension.

9. The capacitance sensor of claim 1 , wherein the digital counter comprises a pulse width modulator (PWM) and a timer, the PWM coupled to enable the timer.

10. The capacitance sensor of claim 9 wherein, in order to measure the frequency of the output signal of the relaxation oscillator, the PWM is clocked for a fixed period based on a system clock to generate a gate time and an output of the timer is read to obtain a number of counts during the gate time.

11. The capacitance sensor of claim 9 wherein, in order to measure the period of the output signal of the relaxation oscillator, the PWM is clocked by the output signal of the relaxation oscillator and an output of the timer is read to obtain a number of counts when the PWM is interrupted.

12. A system comprising:

a capacitive sensor array comprising at least one first sensor element, at least one second sensor element, and at least one third sensor element, wherein the at least one first sensor element and the at least one second sensor element are single and independent sensor element respectively, wherein the third sensor element comprises of a first portion and a second portion having sensing area equal to sensing area of the first portion, wherein a sensing area of the first sensor element, a sensing area of the second sensor element, and a sensing area of the third sensor element are equal to each other, wherein the sensing area of the first portion of the third sensor element is less than the sensing area of the first sensor element, and the sensing area of the second portion of the third sensor element is less than the sensing area of the first sensor element, wherein the first sensor element and the first portion of the third sensor element are permanently connected together, and the second sensor element and the second portion of the third sensor element are permanently connected together that is electronically isolated from the first conductive material, wherein the first and second portions of the third sensor element are electrically isolated;

a processing device configured to detect presence of a conductive object on the capacitive sensor array; and

a capacitance sensor coupled to the processing device and to the capacitive sensor array, wherein the capacitance sensor comprises:

a relaxation oscillator configured to receive input signals, from the first and second sensor elements, representing capacitances on the first, second, and third sensor elements, the relaxation oscillator further configured to generate an output signal, wherein the capacitances on the third sensor element is represented by simultaneously receiving the capacitances on the first and second sensor elements; and

a digital counter coupled to receive the output signal of the relaxation oscillator, the digital counter coupled to receive the output signal of the relaxation oscillator, the digital counter configured to measure at least one of a frequency and a period of the output signal of the relaxation oscillator.

13. The system of claim 12 , further comprising a selection circuit that is coupled between the capacitive sensor array and the relaxation oscillator, wherein the selection circuit is configured to sequential select a sensor element from the multiple sensor elements to provide charge current to the selected sensor element or to receive an input signal representing capacitance of the selected sensor element.

14. The system of claim 13 , wherein the capacitance sensor is configured to simultaneously scan the plurality of rows, and wherein the capacitance sensor is configured to simultaneously scan the plurality of columns.

15. A method comprising:

receiving, by a relaxation oscillator, input signals from a first sensor element and a second sensor element representing capacitances on a first sensor element, a second sensor element, and a third sensor element wherein the third sensor element comprises of a first portion and a second portion having sensing area equal to sensing area of the first portion, wherein a sensing area of the first sensor element, a sensing area of the second sensor element, and a sensing area of the third sensor element are equal to each other, wherein the sensing area of the first portion of the third sensor element is less than the sensing area of the first sensor element, and the sensing area of the second portion of the third sensor element is less than the sensing area of the first sensor element;

generating, by the relaxation oscillator, an output signal based on one or more of the received input signals;

applying the output signal of the relaxation oscillator to a digital counter; and

measuring, by the digital counter, at least one of a frequency and a period of the output signal of the relaxation oscillator;

detecting a presence of a conductive object on the third sensor element by simultaneously receiving the capacitances on the first and second sensor elements.

16. The method of claim 15 , wherein the digital counter comprises a pulse width modulator (PWM) coupled to a timer, and wherein measuring the frequency of the output signal of the relaxation oscillator comprises:

enabling the timer by the PWM; and

reading an output of the timer during the gate time to obtain a number of counts, wherein the number of counts represents the frequency of the output signal of the relaxation oscillator.

17. The system of claim 15 , wherein the digital counter comprises a pulse width modulator (PWM) coupled to a timer, and wherein measuring the period of the output signal of the relaxation oscillator comprises:

clocking the PWM by using the output signal of the relaxation oscillator;

enabling the timer by the PWM; and

reading an output of the timer when the PWM is interrupted to obtain a number of counts, wherein the number of counts represents the period of the output signal of the relaxation oscillator.

18. The system of claim 15 , further comprising generating the input signals that represent the capacitances on the multiple sensor elements by sequentially scanning the multiple sensor elements.

19. The system of claim 15 , further comprising generating the input signals that represent the capacitances on the multiple sensor elements by first simultaneously scanning the plurality of rows and then simultaneously scanning the plurality of columns.

20. The system of claim 15 , further comprising generating baseline values for the multiple sensor elements, the baseline values representing no actuation of the multiple sensor elements.

Assignments (9)