US20160282991A1 - Capacitive touch device with high sensitivity and operating method thereof - Google Patents

Abstract

There is provided a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an emulation circuit and a subtraction circuit. The emulation circuit is configured to output a reference signal. The subtraction circuit is coupled to the emulation circuit and the detection electrode, subtracts the reference signal outputted by the emulation circuit from a detected signal outputted by the detection electrode to output a differential detected signal, and identifies a touch event according to an amplified differential detected signal so as to improve the touch sensitivity.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application claims the priority benefit of Taiwan Patent Application Serial Number 104109783, filed on Mar. 26, 2015, the full disclosure of which is incorporated herein by reference.
BACKGROUND
• 1. Field of the Disclosure
• This disclosure generally relates to a touch device, more particularly, to a capacitive touch device with high sensitivity and an operating method thereof.
• 2. Description of the Related Art
• Because a user can operate a touch panel by intuition, the touch panel has been widely applied to various electronic devices. In general, the touch panel is classified into capacitive, resistive and optical touch panels.
• The capacitive touch sensor is further classified into self-capacitive touch sensors and mutual capacitive touch sensors. These two kinds of touch sensors have different characteristics of the capacitive variation, so they are adaptable to different functions. For example, the mutual capacitive touch sensors are adaptable to the multi-touch detection, and the self-capacitive touch sensors have a higher sensitivity to hovering operations and a lower sensitivity to water drops. However, how to improve the touch sensitivity of these two kinds of capacitive touch sensors is an important issue.
SUMMARY
• Accordingly, the present disclosure provides a capacitive touch device with high sensitivity and an operating method thereof.
• The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a size of a detection capacitor in the control chip is reduced.
• The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a touch sensitivity is improved.
• The present disclosure provides a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode forming a self-capacitor. The control chip includes a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit form a first filter circuit, the emulation circuit forms a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
• The present disclosure further provides a capacitive touch device including a touch panel and a control chip. The touch panel includes a plurality of detection electrodes respectively forming a self-capacitor. The control chip includes an emulation circuit, a plurality of programmable filters and a subtraction circuit. The emulation circuit outputs a reference signal. The programmable filters are respectively coupled to the detection electrodes. The subtraction circuit is coupled to the emulation circuit, and configured to be sequentially coupled to the programmable filters in a self-capacitive mode and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.
• The present disclosure further provides an operating method of a capacitive touch device. The capacitive touch device includes a touch panel and a control chip. The touch panel includes a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions. The control chip includes a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter. The operating method includes: respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.
• A capacitive touch device of the present disclosure is adaptable to a touch device which uses only a self-capacitive detection mode, and to a touch device which uses a dual-mode detection including the self-capacitive detection mode and a mutual capacitive detection mode.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other objects, advantages, and novel features of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
• FIG. 1 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
• FIG. 2 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
• FIG. 3 is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.
• FIG. 4A is the waveform of a detection signal and a reference signal in the capacitive touch device of the embodiments ofFIGS. 2 and 3.
• FIG. 4B is a waveform of a differential detected signal of the detection signal and the reference signal inFIG. 4A.
• FIG. 5 is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure.
• FIG. 6 is a frequency response of a filter circuit of a capacitive touch device according to one embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENT
• It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
• Please refer toFIG. 1, it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. Thecapacitive touch device1 includes acontrol chip100 and atouch panel13, wherein thecapacitive touch device1 is preferably able to detect by a self-capacitive mode. In some embodiments, thecapacitive touch device1 is able to detect approaching objects and distinguish touch positions by successively using a self-capacitive mode and a mutual capacitive mode. For example, in some embodiments, because a scanning interval of the self-capacitive mode is short, thecapacitive touch device1 is able to identify whether any object is approaching using the self-capacitive mode. After an approaching object is identified, a touch position is identified using the mutual capacitive mode. In other embodiments, thecapacitive touch device1 is able to identify a rough position of an approaching object and determine a window of interest (WOI) on thetouch panel13 with the self-capacitive mode, and then identify a fine position within the window of interest with the mutual capacitive mode to reduce data amount to be processed in the mutual capacitive mode. It should be mention that implementations of the self-capacitive mode and the mutual capacitive mode mentioned above are only intended to illustrate, but not to limit the present disclosure.
• Thetouch panel13 includes a plurality ofdetection electrodes131 to respectively form a self-capacitor C_s, wherein thedetection electrodes131 include a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, e.g., perpendicular to each other. Mutual capacitors C_m(referring toFIGS. 2 and 3) are formed between the drive electrodes and the receiving electrodes. The principle of forming self-capacitors and mutual capacitors in a capacitive touch panel is known and is not an object of the present disclosure, and thus details thereof is not described herein.
• Thecontrol chip100 includes a plurality ofdrive circuits11, a plurality of detection capacitors C_inand anemulation circuit150, wherein theemulation circuit150 is used to emulate the characteristics of the detection line in a self-capacitive mode (described hereinafter). In the self-capacitive mode, thedrive circuits11 and the detection capacitors C_inare electrically coupled to signal inputs of thedetection electrodes131 via pins. Thedrive circuits11 output a drive signal Sd, e.g., a sine wave, a cosine wave or a square wave to thedetection electrodes131. In a mutual capacitive mode, only thedrive circuit11 corresponding to the drive electrode outputs the drive signal Sd, whereas thedrive circuit11 corresponding to the receiving electrode is bypassed.
• Please refer toFIG. 2, it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. As mentioned above, thecapacitive touch device1 includes atouch panel13 and acontrol chip100. Thecontrol chip100 includes a plurality ofdrive circuits11, a plurality of detection capacitors C_in, ananalog front end15 and adigital back end16, wherein as thedigital back end16 is not an object of the present disclosure, details thereof are not described herein. In the present disclosure, thedrive circuits11 are able to be electrically coupled to signal inputs of thedetection electrodes131 via the detection capacitors C_in(e.g. in the self-capacitive mode) or bypassing the detection capacitors C_in(e.g. in the mutual capacitive mode), wherein said coupled to and bypassing the detection capacitors C_inis able to be implemented by arranging a plurality of switches SW₁between thedrive circuits11 and thetouch panel13.
• The analogfront end15 includes anemulation circuit150, a plurality ofprogrammable filters151, a subtraction circuit52, again circuit153 and an anti-aliasing filter (AAF)154. Theprogrammable filters151, the detection capacitors C_inand the self-capacitors C_sof thedetection electrodes131 form a first filter circuit, wherein the first filter circuit is, e.g., a band-pass filter (BPF) or a high-pass filter (HPF). The first filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by theanti-aliasing filter154. In one embodiment, the signal output of eachdetection electrode131 is coupled to (e.g. via a switch) oneprogrammable filter151. It should be mentioned that although only the horizontally arrangeddetection electrodes131 shown inFIGS. 2 and 3 are coupled to theprogrammable filters151, in other embodiments theprogrammable filters151 are also coupled to the longitudinally arrangeddetection electrodes131, and the present disclosure is not limited to those shown inFIGS. 2 and 3.
• Theemulation circuit150 forms a second filter circuit and outputs a reference signal S_ref, wherein the second filter circuit is, e.g., a band-pass filter or a high-pass filter. The second filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by theanti-aliasing filter154. Thesubtraction circuit152 is coupled to theemulation circuit150 and is sequentially and electrically coupled to theprogrammable filters151 via switches SW₂in a self-capacitive mode to be further electrically coupled to thedetection electrodes131. Thesubtraction circuit152 performs a differential operation on the reference signal S_refoutputted by theemulation circuit150 and a detection signal S_o1outputted by the coupledprogrammable filter151 to output a differential detected signal S_diff. To be more precisely, in the present disclosure, the detection capacitors C_inare respectively and electrically coupled to signal inputs of thedetection electrodes131 via a plurality of switches (e.g. SW₁), and thesubtraction circuit152 is respectively and electrically coupled to theprogrammable filters151 and thedetection electrodes131 via a plurality of switches (e.g. SW₂).
• In the present disclosure, the detection capacitor C_inis disposed in thecontrol chip100 to form the voltage division with the self-capacitor C_s. Accordingly, thecapacitive touch device1 identifies a touch event according to a variation of peak-to-peak values of the differential detected signal S_diff, wherein the differential detected signal S_diffis a continuous signal. Before a touch event is identified, the differential detected signal S_diffis further filtered or digitized. For example,FIG. 2 shows the touched differential detected signal S_touchand the non-touched differential detected signal S_non. However, as the self-capacitor C_sis generally very large, an effective voltage division is implemented by using a large detection capacitor C_in. Therefore, the considerable disposition space in the chip for the large capacitor is necessary such that a total size of thecontrol chip100 is unable to be reduced.
• Accordingly, in the present disclosure, the circuit characteristics of the detection line (e.g. from thedrive circuit11 via the detection capacitor C_in, thedetection electrode131 and the programmable filter151) is emulated by disposing theemulation circuit150 to output the reference signal S_refas a cancellation of the detection signal S_o1, as shown inFIG. 4. The capacitance of the detection capacitor C_inis able to be decreased by subtracting the cancellation from the detection signal S_o1. For example, the capacitance of the detection capacitor C_inis preferably smaller than 10 percent of capacitance of the self-capacitor C_s. Therefore, the size of thecontrol chip100 is effectively decreased.
• To make a difference between the touched differential detected signal S_touchand the non-touched differential detected signal S_nonbe more obvious, in some embodiments again circuit153 is employed to amplify the differential detected signal S_diff, wherein a gain of thegain circuit153 is determined according to an analytical range of an analog-to-digital convertor (ADC) of the digitalback end16, but not limited thereto. As shown inFIG. 2, the difference between the touched differential detected signal S_touchand the non-touched differential detected signal S_non, which are signals (i.e. differential detected signal) outputted by thegain circuit153, is increased such that a touch event is easier to be identified. Theanti-aliasing filter154 filters the amplified differential detected signal and, as mentioned above, theanti-aliasing filter154 is, for example, a low-pass filter.
• Please refer toFIG. 3, it is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure, whereinFIG. 3 further shows an implementation of theemulation circuit150 and theprogrammable filter151.
• In some embodiments, theprogrammable filter151 includes an input resistor R_inand anamplifying circuit15A, wherein the detection capacitor C_in, the self-capacitor C_s, the input resistor R_inand the amplifyingcircuit15A form a first filter circuit, and theemulation circuit150 forms a second filter circuit. As mentioned above, thesubtraction circuit152 performs a differential operation on a detection signal S_o1outputted by the first filter circuit and a reference signal S_refoutputted by the second filter circuit to output a differential detected signal S_diff, as shown inFIGS. 4A and 4B, whereinFIG. 4B shows a waveform of a differential detected signal S_diffof the detection signal S_o1and the reference signal S_refshown inFIG. 4A.
• In one embodiment, the amplifyingcircuit15A includes an operational amplifier OP, a feedback resistor Rf and a compensation capacitor Cf. The feedback resistor Rf and the compensation capacitor Cf are connected between a negative input and an output of the operational amplifier OP. The input resistor R_inis coupled between a second end (i.e. the signal output) of thedetection electrode131 and the negative input of the operational amplifier OP. A first end (i.e. the signal input) of thedetection electrode131 is coupled to the detection capacitor C_in. In this embodiment, a frequency response of the first filter circuit is indicated by equation (1) and the Bode diagram ofFIG. 6, wherein the first filter circuit has two poles and a zero, which is located at 0.
• 
  (V_out/V_in)=−(Rf/R_in)×(s·C_in·R_in)/(1+s·Rf·Cf)×(1+s·R_in·C_s+s·R_in·C_in)  (1)
• As mentioned above, because an output of theemulation circuit150 is used as a cancellation of the first filter circuit, the frequency response of theemulation circuit150 is preferably similar to that of the first filter circuit, i.e. the frequency response of theemulation circuit150 is determined according to a frequency response of the first filter circuit. In some embodiments, the two frequency responses are similar is referred to, for example, two poles of theemulation circuit150 being close to two poles of the first filter circuit, but not limited thereto. For example, the two poles of theemulation circuit150 are determined according to the two poles of the first filter circuit, and because the zero is not affected, only the pole frequencies are considered. For example, differences between pole frequencies of two poles of theemulation circuit150 and frequencies of poles, which correspond to the two poles of theemulation circuit150, of the second filter circuit is designed to be below 35 percent of the pole frequencies of theemulation circuit150, and preferably to be below 20 percent. Although the two poles of theemulation circuit150 are close to the two poles of the first filter circuit as much as possible, since it is difficult to precisely know the self-capacitor C_sof eachdetection electrode131 in advance, theemulation circuit150 is designed by estimation.
• In one embodiment, theemulation circuit150 includes an emulation detection capacitor C_{ref_in}, an emulation self-capacitor C_{ref_s}, an emulation input resistor R_{ref_in}and anemulation amplifying circuit15B, and connections between the emulation detection capacitor C_{ref_in}, the emulation self-capacitor C_{ref_s}, the emulation input resistor R_{ref_in}and theemulation amplifying circuit15B are arranged based on connections between the detection capacitor C_in, the self-capacitor C_s, the input resistor R_inand the amplifyingcircuit15A to obtain a similar frequency response without particular limitations, e.g., having identical connections. That is, the emulation self-capacitor C_{ref_s}is used to emulate self-capacitor C_sof thedetection electrode131, the emulation detection capacitor C_{ref_in}is used to emulate the detection capacitor C_in, the emulation input resistor R_{ref_in}corresponds to the input resistor R_in, and theemulation amplifying circuit15B corresponds to the amplifyingcircuit15A. It should be mentioned that the circuit parameter of the emulation circuit150 (i.e. RC value) is not necessary to be completely the same as the circuit parameter of the first filter circuit, as long as the frequency response of theemulation circuit150 is similar to the frequency response of the first filter circuit, and the detection capacitor C_sis decreased without particular limitations.
• Theemulation amplifying circuit15B also includes an operational amplifier OP′, an emulation feedback resistor R_{ref_f}and an emulation compensation capacitor C_{ref_f}, wherein connections of elements in theemulation amplifying circuit15B are arranged based on those of the amplifyingcircuit15A without particular limitations, e.g., having identical connections. Therefore, a second filter circuit formed by theemulation circuit150 also has a similar frequency response as the equation (1) and the Bode diagram ofFIG. 6. The difference is that all element parameters of theemulation circuit150 are predesigned. Accordingly, positions of two poles are adjustable by changing the element parameters, i.e. resistance and capacitance, of theemulation circuit150.
• Please refer toFIG. 5, it is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure, including a self-capacitive mode (step S₅₁) and a mutual capacitive mode (step S₅₂). In this embodiment, the self-capacitive mode and the mutual capacitive mode is separately operated, e.g., firstly identifying an approaching object and/or a window of interest (WOI) using the self-capacitive mode and identifying a touch positions and/or a gesture using the mutual capacitive mode.
• In the self-capacitive mode, thedrive circuits11 are respectively and electrically coupled to first ends of the drive electrodes via the detection capacitors C_in, and thesubtraction circuit152 is respectively and electrically coupled to second ends of the drive electrodes. Meanwhile, because thesubtraction circuit152 receives a reference signal S_refoutputted by theemulation circuit150 and thesubtraction circuit152 is electrically coupled to the second end of the drive electrodes via aprogrammable filter151, thesubtraction circuit152 performs a differential operation on a detection signal S_o1outputted by theprogrammable filter151 and the reference signal S_refoutputted by theemulation circuit150 to output a differential detected signal S_diff, as shown inFIGS. 4A and 4B. Then, again circuit153 amplifies the differential detected signal S_diffto make a difference between a touched differential detected signal S_touchand a non-touched differential detected signal S_nonbe more significant, as shown inFIG. 2. Furthermore, in one embodiment, a touch event is identified by detecting detection signals outputted by a plurality of drive electrodes or a plurality of receiving electrodes to operate in a shorter scanning period.
• In another embodiment, detection signals outputted by a plurality of drive electrodes and a plurality of receiving electrodes are detected to identify a window of interest (WOI) on the touch panel in a self-capacitive mode. Therefore, in the self-capacitive mode, thedrive circuits11 are respectively and electrically coupled to the first ends (i.e. signal inputs) of the receiving electrodes via the detection capacitors C_in, and thesubtraction circuit152 is sequentially and electrically coupled to second ends (i.e. signal outputs) of the receiving electrodes. The window of interest is determined after identifying the drive electrode and the receiving electrode that sense an approaching object. As mentioned above, in the present disclosure the drive electrodes and the receiving electrodes are both belong to thedetection electrodes131 to generate mutual capacitors C_mtherebetween.
• In the mutual capacitive mode, thedrive circuits11 are respectively and electrically coupled to the first ends of the drive electrodes without passing the detection capacitors C_in. For example inFIGS. 2 and 3, thedrive circuits11 bypass the detection capacitor C_inusing a switch SW₁and directly input the drive signal S_dto thedetection electrode131. Besides, theanti-aliasing filter154 is respectively and electrically coupled to the second ends of the drive electrodes without passing thesubtraction circuit152. For example inFIGS. 2 and 3, theanti-aliasing filter154 bypasses the subtraction circuit152 (and the gain circuit153) using another switch SW₂to allow the detection signal S_o1outputted by theprogrammable filter151 to be directly outputted to theanti-aliasing filter154. The filter parameter of theanti-aliasing filter154 is determined according to actual applications without particular limitation.
• In the present disclosure, in the self-capacitive mode because signals sent to the detection lines do not pass resistors and capacitors of the panel, a phase difference between the reference line (i.e. emulation circuit) and the detection line is not obvious. Therefore, the reference signal S_refis used as a cancellation to be subtracted from a detection signal.
• It should be mentioned that, although the amplitude (or peak-to-peak value) of a non-touched differential detected signal S_nonis shown to be larger than the amplitude (or peak-to-peak value) of a touched differential detected signal S_touchinFIG. 2, it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit150 (i.e. RC value), it is possible that the amplitude of the touched differential detected signal S_touchis larger than the amplitude of the non-touched differential detected signal S_non.
• It should be mentioned that although the amplitude (or peak-to-peak value) of a detection signal S_o1is shown to be larger than the amplitude (or peak-to-peak value) of a reference signal S_refinFIG. 4A, it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit150 (i.e. RC value), it is possible that the amplitude of the reference signal S_refis larger than the amplitude of the detection signal S_o1.
• As mentioned above, how to improve the touch sensitivity of a capacitive touch device is an important issue. Therefore, the present disclosure provides a capacitive touch device (FIGS. 1 to 3) and an operating method thereof (FIG. 5) that generate a cancellation by disposing an emulation circuit in a control chip to decrease a size of a capacitor in the control chip used in the self-capacitive mode and improve the touch sensitivity.
• Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed.

Claims (20)

What is claimed is:

1. A capacitive touch device comprising:

a touch panel comprising a detection electrode configured to form a self-capacitor; and

a control chip comprising a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein

the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit are configured to form a first filter circuit,

the emulation circuit is configured to form a second filter circuit, and

a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

2. The capacitive touch device as claimed inclaim 1, further comprising a subtraction circuit configured to perform a differential operation on a detection signal outputted by the first filter circuit and a reference signal outputted by the second filter circuit to output a differential detected signal.

3. The capacitive touch device as claimed inclaim 2, further comprising a gain circuit configured to amplify the differential detected signal.

4. The capacitive touch device as claimed inclaim 3, wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

5. The capacitive touch device as claimed inclaim 1, wherein capacitance of the detection capacitor is smaller than 10 percent of capacitance of the self-capacitor.

6. The capacitive touch device as claimed inclaim 1, wherein differences between pole frequencies of two poles of the first filter circuit and frequencies of poles, which correspond to the two poles of the first filter circuit, of the second filter circuit is lower than 35 percent of the pole frequencies of the first filter circuit.

7. The capacitive touch device as claimed inclaim 1, wherein

the amplifying circuit comprises an operational amplifier, a feedback resistor and a compensation capacitor,

the feedback resistor and the compensation capacitor are connected between a negative input and an output of the operational amplifier,

the input resistor is coupled between a second end of the detection electrode and the negative input of the operational amplifier, and

a first end of the detection electrode is coupled to the detection capacitor.

8. The capacitive touch device as claimed inclaim 7, wherein

the emulation circuit comprises an emulation detection capacitor, an emulation self-capacitor, an emulation input resistor and an emulation amplifying circuit, and

connections between the emulation detection capacitor, the emulation self-capacitor, the emulation input resistor and the emulation amplifying circuit are arranged based on connections between the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit.

9. A capacitive touch device comprising:

a touch panel comprising a plurality of detection electrodes configured to respectively form a self-capacitor; and

a control chip comprising:

an emulation circuit configured to output a reference signal;

a plurality of programmable filters respectively coupled to the detection electrodes; and

a subtraction circuit, coupled to the emulation circuit, configured to be sequentially coupled to the programmable filters in a self-capacitive mode, and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.

10. The capacitive touch device as claimed inclaim 9, wherein the control chip further comprises a gain circuit configured to amplify the differential detected signal.

11. The capacitive touch device as claimed inclaim 10, wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

12. The capacitive touch device as claimed inclaim 9, further comprising a plurality of detection capacitors configured to be electrically coupled to signal inputs of the detection electrodes in the self-capacitive mode.

13. The capacitive touch device as claimed inclaim 12, wherein the programmable filter, the self-capacitor and the detection capacitor are configured to form a first filter circuit.

14. The capacitive touch device as claimed inclaim 13, wherein the emulation circuit is configured to form a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

15. The capacitive touch device as claimed inclaim 12, wherein capacitance of the detection capacitors is smaller than 10 percent of capacitance of the self-capacitor.

16. The capacitive touch device as claimed inclaim 12, wherein

the detection capacitors are respectively coupled to the detection electrodes via a plurality of switches, and

the subtraction circuit is coupled to the programmable filters respectively via a plurality of switches.

17. An operating method of a capacitive touch device, the capacitive touch device comprising a touch panel and a control chip, the touch panel comprising a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, and the control chip comprising a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter, the operating method comprising:

respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and

respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.

18. The operating method as claimed inclaim 17, further comprising:

respectively coupling, in the self-capacitive mode, the drive circuits to first ends of the receiving electrodes via the detection capacitors, and

respectively coupling, in the self-capacitive mode, the subtraction circuit to the second ends of the receiving electrodes.

19. The operating method as claimed inclaim 17, wherein the control chip further comprises an emulation circuit and a programmable filter, the subtraction circuit is electrically coupled to the second ends of the drive electrodes via the programmable filter, and the operating method further comprises:

performing a differential operation on a detection signal outputted by the programmable filter and a reference signal outputted by the emulation circuit to output a differential detected signal;

amplifying the differential detected signal; and

identifying a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

20. The operating method as claimed inclaim 19, wherein

the programmable filter, the detection capacitors and self-capacitors of the drive electrodes form a first filter circuit,

the emulation circuit forms a second filter circuit, and

a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

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