GENERATING A BASELINE COMPENSATION SIGNAL BASED ON A CAPACITIVE CIRCUIT

• US 20160026295A1
• Filed: 06/26/2015
• Published: 01/28/2016
• 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, Hosseini, Kaveh, Ellis, Denis, Lawton, Brendan
• Granted Patent: US 10,429,998 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 capacitance-sensing circuit comprising:

a plurality of channel inputs associated with measuring a capacitance of a unit cell of a capacitive sense array; and

a baseliner component coupled to the plurality of channel inputs, the baseliner component to generate a baseline compensation signal using a capacitive circuit and to provide the baseline compensation signal to each of the plurality of channel inputs of the capacitive sense array.

2. The capacitance-sensing circuit of claim 1, wherein the baseliner component comprises:

the capacitive circuit; and

a current conveyor coupled to an output of the capacitive circuit.

3. The capacitance-sensing circuit of claim 2, wherein the current conveyor comprises:

a plurality of current mirrors coupled to receive a current based on the output of the capacitive circuit and to provide mirrored output currents to the plurality of channel inputs, wherein the baseline compensation signal corresponds to the mirrored output currents.

4. The capacitance-sensing circuit of claim 3, wherein the current conveyor further comprises:

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

5. The capacitance-sensing circuit of claim 3, wherein the current conveyor further comprises:

a differential amplifier to receive the output of the capacitive circuit and a reference signal associated with a voltage source and to generate the current received by the plurality of current mirrors based on the output of the capacitive circuit and the reference signal.

6. The capacitance-sensing circuit of claim 2, wherein each of the plurality of channel inputs is a receive (RX) channel coupled to an RX electrode of the unit cell, 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.

7. The capacitance-sensing circuit of claim 1, wherein the capacitive circuit comprises:

a first capacitor corresponding to an operation of the capacitance-sensing circuit in a first mode; and

a second capacitor corresponding to the operation of the capacitance-sensing circuit in a second mode, wherein an input of the capacitive circuit corresponds to a transmit (TX) signal.

8. A method comprising:

generating, by a baseliner circuit associated with a capacitive sense array, a baseline compensation signal based on a capacitive circuit; and

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

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

providing an output of the capacitive circuit to a current conveyor.

10. The method of claim 9, wherein the generating of the baseline compensation signal based on the capacitive circuit further 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.

11. The method of claim 10, wherein the generating of the baseline compensation signal based on the capacitive circuit further comprises:

applying a gain factor to the mirrored output current.

12. The method of claim 10, wherein the generating of the baseline compensation signal based on the capacitive circuit comprises:

receiving, at the current conveyor and the channel input, a reference signal associated with a voltage source; and

generating the output of the current conveyor based on an output of the capacitive circuit and the reference signal that is received by the channel input.

13. The method of claim 8, wherein channel input is a receive (RX) channel coupled to an RX electrode of a unit cell of the capacitive sense array, the method further comprising:

receiving 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 a second signal corresponding to a reference signal from a voltage source.

14. The method of claim 8, wherein the generating of the baseline compensation signal based on the capacitive circuit 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 capacitive circuit in a second mode, wherein the baseline compensation signal is based on the output current.

15. A capacitive sense array system comprising:

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

a plurality of channel inputs to measure capacitances of the plurality of unit cells; and

a baseliner component coupled to the plurality of channel inputs, the baseliner component to generate a baseline compensation signal using a capacitive circuit and to provide the baseline compensation signal to each of the plurality of channel inputs of the capacitive sense array system.

16. The capacitive sense array system of claim 15, wherein the baseliner component comprises:

the capacitive circuit; and

a current conveyor coupled to an output of the capacitive circuit.

17. The capacitive sense array system of claim 16, wherein the current conveyor comprises:

a plurality of current mirrors coupled to receive a current based on the output of the capacitive circuit and to provide mirrored current outputs to the plurality of channel inputs, wherein the baseline compensation signal corresponds to the mirrored current outputs.

18. The capacitive sense array system of claim 17, wherein the current conveyor further comprises:

a gain component coupled to the current mirrors.

19. The capacitive sense array system of claim 17, wherein the current conveyor further comprises:

a differential amplifier to receive the output of the capacitive circuit and a reference signal associated with a voltage source and to generate the current received by the plurality of current mirrors based on the output of the capacitive circuit and the reference signal.

20. The capacitive sense array system of claim 15, wherein each of the plurality of channel inputs is a receive (RX) channel coupled to an RX electrode of the unit cell, 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.