Generating a baseline compensation signal based on a capacitive circuit

• US 10,429,998 B2
• Filed: 06/26/2015
• Issued: 10/01/2019
• Est. Priority Date: 07/23/2014
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Ogirko, Roman, Ellis, Denis, Hosseini, Kaveh, Lawton, Brendan
• Primary Examiner(s): Jansen, II, Michael J
• Application Number:
  US14/752,687
• Publication Number:
  US 20160026295A1
• Time in Patent Office: 1,558 Days
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A capacitance-sensing circuit may include a plurality of channel inputs associated with measuring a capacitance of a unit cell of a capacitive sense array. The capacitance-sensing circuit may also include a baseliner component that is coupled to the plurality of channel inputs. The baseliner component may generate a baseline compensation signal using a capacitive circuit and may provide the baseline compensation signal to each of the plurality of channel inputs of the capacitive sense array.

Claims

1. A capacitive touch-sensing device comprising:

a plurality of sense channels associated with a plurality of unit cells of a capacitive sense array; and

a baseliner component coupled to the plurality of sense channels, wherein the baseliner component includes;

a sensor model coupled to an output of a buffer and a current conveyor coupled to an output of the sensor model;

wherein the baseliner component is configured to;

receive a transmit input (TX) signal by the buffer and a reference voltage input signal by the current conveyor to generate one or more baseline compensation signals using the sensor model; and

provide the one or more baseline compensation signals to inputs of the plurality of sense channels;

wherein the sensor model is separate and different from the capacitive sense array, and wherein the sensor model is used to approximate a current that is generated in response to the TX signal received by the buffer.

2. The device of claim 1, wherein the current conveyor comprises:

a plurality of current mirrors coupled to receive a current based on the output of the sensor model and to provide mirrored output currents to the plurality of sense channels, wherein the one or more baseline compensation signals correspond to the mirrored output currents.

3. The device of claim 2, wherein the current conveyor further comprises:

a gain component coupled to the plurality of current mirrors to apply a gain factor to the mirrored output currents.

4. The device of claim 2, wherein the current conveyor further comprises:

a differential amplifier to receive the output of the sensor model and the reference voltage input signal and to generate the current received by the plurality of current mirrors based on the output of the sensor model and the reference voltage input signal.

5. The device of claim 1, wherein each of the plurality of sense channels is a receive (RX) channel coupled to an RX electrode of a respective unit cell of the plurality of unit cells, wherein the RX channel comprises a first input coupled to the RX electrode and an output of the baseliner component, and wherein a second input of the RX channel is coupled to a voltage source.

6. The device of claim 1, wherein the sensor model comprises:

a first capacitor corresponding to an operation of the device in a first mode; and

a second capacitor corresponding to the operation of the device in a second mode, wherein an input of the sensor model corresponds to the TX signal.

7. A method comprising:

receiving a transmit (TX) signal by a buffer in a baseliner circuit associated with a capacitive sense array;

receiving a reference voltage signal by a current conveyor in the baseliner circuit;

generating, by the baseliner circuit, a baseline compensation signal based on the TX signal and the reference voltage signal by using a sensor model of the baseliner circuit, wherein the sensor model is coupled to an output of the buffer and the current conveyor is coupled to an output of the sensor model;

wherein the sensor model is separate and different from the capacitive sense array, and wherein the sensor model is used to approximate a current that is generated in response to the TX signal; and

providing the baseline compensation signal to an input of a sense channel associated with the capacitive sense array.

8. The method of claim 7, wherein generating the baseline compensation signal comprises:

receiving an output of the current conveyor; and

copying the output of the current conveyor to generate a mirrored output current, wherein the baseline compensation signal corresponds to the mirrored output current.

9. The method of claim 8, wherein generating the baseline compensation signal comprises:

applying a gain factor to the mirrored output current.

10. The method of claim 7, wherein the sense channel is a receive (RX) channel coupled to an RX electrode of a unit cell of the capacitive sense array, the method further comprising:

receiving, by the RX channel, a first input corresponding to a combination of the baseline compensation signal and an input signal from the unit cell of the capacitive sense array; and

receiving, by the RX channel, a second input corresponding to a reference signal from a voltage source.

11. The method of claim 7, wherein generating the baseline compensation signal comprises:

generating an output current based on a first capacitor corresponding to an operation of the capacitive sense array in a first mode or a second capacitor corresponding to the operation of the sensor model in a second mode, wherein the baseline compensation signal is based on the output current.

12. A capacitive touch-sensing system comprising:

a plurality of unit cells, each unit cell comprising an electrode or a pair of electrodes;

a plurality of sense channels coupled to the plurality of unit cells; and

a baseliner component coupled to the plurality of sense channels, wherein the baseliner component includes;

a sensor model coupled to an output of a buffer and a current conveyor coupled to an output of the sensor model;

wherein the baseliner component is configured to;

receive a transmit (TX) signal by the buffer and a reference voltage signal by the current conveyor to generate one or more baseline compensation signals using the sensor model; and

provide the one or more baseline compensation signals to inputs of the plurality of sense channels;

wherein the sensor model is separate and different from the plurality of unit cells, and wherein the sensor model is used to approximate a current that is generated in response to the TX signal received by the buffer.

13. The capacitive touch-sensing system of claim 12, wherein the current conveyor comprises:

a plurality of current mirrors coupled to receive a current based on the output of the sensor model and to provide mirrored current outputs to the plurality of sense channels, wherein the one or more baseline compensation signals correspond to the mirrored current outputs.

14. The capacitive touch-sensing system of claim 13, wherein the current conveyor further comprises:

a gain component coupled to the plurality of current mirrors.

15. The capacitive touch-sensing system of claim 13, wherein the current conveyor further comprises:

a differential amplifier to receive the output of the sensor model and the reference voltage signal and to generate the current received by the plurality of current mirrors based on the output of the sensor model and the reference voltage signal.

16. The capacitive touch-sensing system of claim 12, wherein each of the plurality of sense channels is a receive (RX) channel coupled to an RX electrode of a respective unit cell of the plurality of unit cells, wherein the RX channel comprises a first input coupled to the RX electrode and an output of the baseliner component, and wherein a second input of the RX channel is coupled to a voltage source.