CAPACITIVE VOLTAGE DIVIDER TOUCH SENSOR

• US 20090295409A1
• Filed: 05/27/2008
• Published: 12/03/2009
• Est. Priority Date: 05/27/2008
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Irkliy, Alex
• Granted Patent: US 9,367,179 B2
• Time in Patent Office: Days
• US Class Current: 324/658
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

A system for measuring capacitance has a measurement circuit with a first reference capacitor connected to a first node and to a second node. Each of the nodes is connected to a unit operable to apply a reference voltage or ground to one of the nodes. Each node has a first pad connected to the first node and a unit operable to measure voltage between the first node and second node.

Claims

1. A system for measuring capacitance, comprising a measurement circuit comprising:

a first reference capacitor connected to a first node and to a second node;

each said nodes connected to a unit operable to apply a reference voltage or ground to one of said nodes;

a first pad connected to the first node; and

a unit operable to measure voltage between the first node and second node.

2. The system of claim 1, further comprising a second pad connected to the second node.

3. The system of claim 1, wherein the units operable for applying reference voltages and ground to nodes are comprised of:

A first switch connected to the node and to the reference voltage; and

a second switch connected to the node and to ground.

4. The system of claim 2, further comprising:

a plurality of third nodes, fourth nodes, third pads, second reference capacitors, and units operable to measure voltage;

each said second reference capacitor connected to a third node and a fourth node;

each said third and fourth node connected to a unit operable to apply a reference voltage or ground to the node;

each said third pad connected to the third node;

each said fourth pad connected to the fourth node; and

a unit operable to measure voltage between the third node and the fourth node.

5. The system of claim 1, wherein the units operable for applying reference voltages and ground to nodes are embedded on a chip.

6. The system of claim 5, wherein the units operable for applying reference voltages and ground to nodes can be enabled through configuration of said chip.

7. The system of claim 1, wherein the units operable for measuring voltage between the first node and second node are embedded on a chip.

8. The system of claim 6, wherein the units operable for measuring voltage between the first node and second node can be enabled through configuration of said chip.

9. The system of claim 1, wherein the units operable for measuring voltage between the first node and second node are embodied by an analog-to-digital circuit.

10. The system of claim 1, wherein the system comprises a proximity sensor.

11. A method of measuring capacitance of a pad comprising:

applying a voltage to the pad and to a reference capacitor;

grounding the reference capacitor to create a circuit comprising the reference capacitor couple in series with the pad, and measuring the resulting voltage across the reference capacitor, said resulting voltage corresponding to the capacitance value of said first pad.

12. The method of claim 11, wherein the action of applying voltage across said pad is automated by a microcontroller.

13. The method of claim 11, wherein the action of applying voltage across said reference capacitor is automated by a microcontroller.

14. The method of claim 11, wherein the action of grounding said reference capacitor to create a circuit comprising the reference capacitor coupled in series with the pad is automated by a microcontroller.

15. The method of claim 11, wherein the measurement of capacitance is accomplished by comparing the voltage of said reference capacitor against a baseline voltage.

16. The method of claim 11 applied to the measurement of capacitance of a plurality of pads.

17. A method of calculating the capacitance of a plurality of pads connected across a reference capacitor, comprising:

applying a voltage across a first pad;

applying said voltage across a reference capacitor;

grounding said reference capacitor to create a circuit comprising said reference capacitor coupled in series with said first pad;

measuring the first resulting voltage across said reference capacitor, said resulting voltage corresponding to the capacitance value of said first pad;

applying a voltage across a second pad;

applying said voltage across said reference capacitor;

grounding said reference capacitor to create a circuit comprising said reference capacitor coupled in series with said second pad; and

capturing the second resulting voltage across said reference capacitor, said resulting voltage corresponding to the capacitance value of said second pad.

18. A method of determining the relative capacitance of two or more pads, comprising:

applying a voltage across a first pad;

applying said voltage across a reference capacitor;

grounding said reference capacitor to create a circuit comprising said reference capacitor coupled in series with said first pad;

measuring the first resulting voltage across said reference capacitor, said resulting voltage corresponding to the capacitance value of said first pad;

for each second pad, applying a voltage across said second pad;

applying said voltage across said reference capacitor;

grounding said reference capacitor to create a circuit comprising said reference capacitor coupled in series with said second pad;

capturing the second resulting voltage across said reference capacitor, said resulting voltage corresponding to the capacitance value of said second pad; and

comparing the resulting voltages or capacitance calculations from the two or more pads.