INPUT DEVICE INTERFERENCE DETERMINATION

• US 20120206154A1
• Filed: 02/10/2011
• Published: 08/16/2012
• Est. Priority Date: 02/10/2011
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Shahparnia, Shahrooz, Pant, Vivek, Shahrokhi, Farzaneh
• Granted Patent: US 9,762,234 B2
• Time in Patent Office: Days
• US Class Current: 324/613
• 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 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/94026 Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input
• CPC Class Codes: H03K 2217/96071 characterised by the detection principle

Abstract

An interference determining circuit for a capacitive sensor device comprises an amplifier, absolute differential circuitry, and comparator circuitry. The amplifier is configured for receiving a reference voltage at a first input and for receiving a resulting signal at a second input. The resulting signal is from a sensor electrode of the capacitive sensor device. The absolute differential circuitry is coupled with an output of the amplifier and configured for outputting a difference signal. The difference signal represents an absolute differential between currents utilized in the amplifier. The comparator circuitry is coupled with the absolute differential circuitry and configured for generating a non-linearity indication based on a comparison of the difference signal with at least one reference signal.

Claims

1. An interference determining circuit for a capacitive sensor device, said circuit comprising:

an amplifier configured for receiving a reference voltage at a first input and for receiving a resulting signal at a second input, wherein the resulting signal is from a sensor electrode of said capacitive sensor device;

absolute differential circuitry coupled with an output of said amplifier and configured for outputting a difference signal, wherein said difference signal represents an absolute differential between currents utilized in said amplifier; and

comparator circuitry coupled with said absolute differential circuitry and configured for generating a non-linearity indication based on a comparison of said difference signal with at least one reference signal.

2. The circuit of claim 1, further comprising:

control logic coupled with said comparator circuitry and configured to selectively accept or reject said resulting signal based upon said non-linearity indication.

3. The circuit of claim 1, further comprising:

control logic coupled with said comparator circuitry and configured to make a change based upon said non-linearity indication, wherein said change is selected from the group consisting of;

changing an integration time of said amplifier, and changing a reset time associated with said amplifier.

4. The circuit of claim 1, further comprising:

control logic coupled with said comparator circuitry and configured to make a change to a transmitter signal of said capacitive sensor device based upon said non-linearity indication, wherein said change is selected from the group consisting of;

a change to a frequency of said transmitter signal, a change to an amplitude of said transmitter signal, and a change to a phase of said transmitter signal.

5. The circuit of claim 1, wherein said absolute differential circuitry is further configured for receiving a voltage output from said output of said amplifier.

6. The circuit of claim 1, wherein said comparator circuitry comprises a plurality of comparators, wherein each of said comparators is configured for generating said non-linearity indication based on a comparison made to said difference signal.

7. The circuit of claim 1, wherein said comparator circuitry is further configured for generating said non-linearity indication based on comparison of said difference signal with a plurality of reference signals.

8. The circuit of claim 1, wherein said non-linearity indication characterizes saturation of said amplifier.

9. The circuit of claim 1, wherein said non-linearity indication characterizes settling of said amplifier.

10. A method of interference determination in a capacitive sensor device, said method comprising:

measuring a resulting signal received from a receiver electrode of a capacitive sensor device, wherein said measuring is performed with an amplifier;

determining a difference signal, wherein said difference signal represents an absolute differential between currents utilized in said amplifier during said measuring; and

generating a non-linearity indication based upon a comparison of said difference signal with at least one reference signal.

11. The method as recited in claim 10, further comprising:

changing a duration of said measuring of said resulting signal based upon said non-linearity indication.

12. The method as recited in claim 10, further comprising:

changing an aspect of a transmitter signal driven on a transmitter electrode of said capacitive sensor device, wherein said aspect is selected from the group consisting of;

a frequency of said transmitter signal, an amplitude of said transmitter signal, and a phase of said transmitter signal; and

wherein said changing is based upon said non-linearity indication.

13. The method as recited in claim 10, further comprising:

selectively accepting or rejecting said resulting signal based upon said non-linearity indication.

14. The method as recited in claim 10, wherein said generating a non-linearity indication based upon a comparison of said difference signal with at least one reference signal further comprises:

generating said non-linearity indication based on a comparison of said difference signal with a plurality of reference signals.

15. The method as recited in claim 10, wherein said generating a non-linearity indication based upon a comparison of said difference signal with at least one reference signal comprises:

generating said non-linearity indication to characterize saturation of said amplifier.

16. The method as recited in claim 10, wherein said generating a non-linearity indication based upon a comparison of said difference signal with at least one reference signal comprises:

generating said non-linearity indication to characterize settling of said amplifier.

17. An input device comprising:

a sensor pattern including a transmitter electrode and a receiver electrode;

a processing system coupled with said sensor pattern and configured to;

drive a transmitter signal onto said transmitter electrode;

receive a resulting signal from a receiver electrode with an amplifier of said processing system;

output a difference signal, wherein said difference signal represents an absolute differential between currents utilized in said amplifier;

generate a non-linearity indication based on a comparison of said difference signal with at least one reference signal; and

take one of a plurality of actions based on said non-linearity indication.

18. The input device of claim 17, wherein said processing system is further configured to:

generate said non-linearity indication based on a comparison of said difference signal with a plurality of reference signals.

19. The input device of claim 17, wherein said processing system being configured to take one of a plurality of actions based on said non-linearity indication, comprises said processing system being configured to:

change a frequency of sampling said resulting signal with said amplifier.

20. The input device of claim 17, wherein said processing system being configured to take one of a plurality of actions based on said non-linearity indication, comprises said processing system being configured to:

change an aspect of said transmitter signal.

21. The input device of claim 17, wherein said processing system being configured to take one of a plurality of actions based on said non-linearity indication, comprises said processing system being configured to:

selectively accept and reject said resulting signal based upon said non-linearity indication.