JP7337742B2 - Capacitance detection circuit, input device - Google Patents

Description

The present invention relates to a capacitance detection circuit.

Electronic devices such as computers, smart phones, tablet terminals, and portable audio devices in recent years are equipped with touch-type input devices as user interfaces. Touch pads, pointing devices, and the like are known as touch-type input devices, and various inputs are possible by touching or bringing a finger or a stylus into contact with the touch input device.

Touch-type input devices are broadly classified into resistive type and capacitive type. In the capacitive method, the presence or absence of user input and coordinates are detected by converting changes in capacitance (hereinafter simply referred to as capacitance) formed by a plurality of sensor electrodes into electrical signals in response to user input. .

Capacitance detection methods are broadly classified into a self-capacitance method and a mutual capacitance method. The self-capacitance method has a very high sensitivity and can detect not only a touch but also the proximity of a finger. On the other hand, the mutual capacitance method has the advantage of being able to detect two-point touches (or more multi-touches) and being less susceptible to water droplets. Therefore, depending on the application, either the self-capacitance method or the mutual capacitance method is selected, or both methods are used.

JP 2015-11558 A

A thin film on which a sensor electrode is formed expands and contracts under the influence of temperature. As a result, the capacitance formed by the sensor electrodes changes according to the temperature. If the change in capacitance due to temperature is large, it cannot be distinguished from the change in capacitance due to touch or proximity, which causes erroneous detection.

The present invention has been made in such circumstances, and one exemplary object of some aspects thereof is to provide a capacitive detection circuit capable of detecting temperature.

A capacitance detection circuit according to one aspect of the present invention is a capacitance detection circuit that detects the capacitance of a sensor electrode, and includes a sense pin to which the sensor electrode is connected, and a reference capacitor. an analog front-end circuit including a leak path connected to the leaked element, which is one of the reference capacitor and the sensor electrode, and the output signal of the analog front-end circuit. into a digital value, and a temperature detection unit that detects temperature based on the output of the A/D converter.

Arbitrary combinations of the above constituent elements, or conversions of expressions of the present invention between methods, devices, etc. are also effective as aspects of the present invention.

According to the present invention, temperature can be detected without using a temperature sensor.

1 is a block diagram of a touch-type input device including a capacitive detection circuit according to an embodiment; FIG. FIGS. 2A to 2E are circuit diagrams showing configuration examples of leak paths. FIG. 4 is a diagram showing temperature dependence of leakage current; 1 is a circuit diagram of a capacitance detection circuit according to Example 1; FIG. 5A and 5B are diagrams for explaining the operation of the analog front-end circuit of FIG. 4. FIG. 5 is a diagram for explaining the operation of the capacitance detection circuit of FIG. 4; FIG. 7A and 7B are diagrams for explaining the operation of the capacitance detection circuit according to the second embodiment. FIG. 11 is a circuit diagram of a capacitance detection circuit according to Example 3; 9A and 9B are diagrams for explaining the operation of the capacitance detection circuit according to the fourth embodiment. FIG. 11 is a circuit diagram of a capacitance detection circuit according to Example 5; 11A to 11F are equivalent circuit diagrams of analog front-end circuits in the first to sixth phases. FIG. 4 is a waveform diagram showing basic operation of the analog front-end circuit; 13A and 13B are diagrams for explaining temperature detection by the capacitance detection circuit of FIG. 10. FIG. FIG. 12 is an operation waveform diagram of the capacitance detection circuit according to Example 6; 15A to 15C are diagrams showing the operation sequence of the capacitance detection circuit.

(Overview of Embodiment)
A capacitance detection circuit according to one embodiment detects the capacitance of a sensor electrode. The capacitance detection circuit includes a sense pin to which a sensor electrode is connected, an analog front end circuit, an A/D converter, and a temperature detection section. The analog front-end circuit includes a reference capacitor and converts the capacitance to a voltage signal by transferring charge between the reference capacitor and the sensor electrode. This analog front-end circuit includes an analog front-end circuit including a leak path connected to a leaked element that is one of the reference capacitor and the sensor electrode, and an A/D converter that converts the output signal of the analog front-end circuit into a digital value. and a temperature detection unit that detects temperature based on the output of the A/D converter.

The impedance of the leakage path and the leakage current flowing through it have temperature dependence. A high impedance period in which the leaked element becomes high impedance is provided in the sensing period by the analog front-end circuit or a different temperature detection period, and the charge of the leaked element is discharged through the leak path. Then, the charge amount of the leaked element (reference capacitor or sensor electrode) changes according to the leak current, and is reflected in the output of the A/D converter. Since the change in the charge amount of the leaked element has temperature dependence, the temperature detection section can detect the temperature based on the output of the A/D converter. Note that "detecting the temperature" means (i) detecting the absolute temperature, (ii) determining whether the current temperature is higher or lower than a predetermined threshold, and (iii) determining whether the current temperature is It includes determining whether the temperature has increased or decreased from the temperature at the start of operation, and broadly means obtaining information about the temperature.

The temperature detector may detect temperature based on changes in the output of the A/D converter when the analog front end circuit is operated at different frequencies. Operating at a faster frequency reduces the effect of leakage, and operating at a slower frequency increases the effect of leakage. On the other hand, touch and proximity are detected regardless of the operating frequency. Therefore, the temperature can be detected by monitoring changes in the two outputs of the A/D converter obtained by operating at two frequencies.

The leaked element may be a reference capacitor. In this case, the temperature detector may keep the reference capacitor in the high impedance state for a predetermined time, and then detect the temperature based on the output of the A/D converter. The output of the A/D converter contains information on the amount of charge leaked at a given time, and thus temperature information.

A leakage path may be connected in parallel with the reference capacitor.

A leak path may be provided between the sensor electrode and ground.

A leak path may include a resistor. A leakage path may include a diode. A leakage path may include a transistor.

The capacitance detection circuit may be monolithically integrated on one semiconductor integrated circuit. "Integrated integration" includes cases in which all circuit components are formed on a semiconductor substrate and cases in which the main components of a circuit are integrated. A resistor, capacitor, or the like may be provided outside the semiconductor substrate. By integrating the circuits on one chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

(Embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. Moreover, the embodiments are illustrative rather than limiting the invention, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention.

In this specification, "a state in which member A is connected to member B" refers to a case in which member A and member B are physically directly connected, or a case in which member A and member B are electrically connected to each other. It also includes the case of being indirectly connected via other members that do not substantially affect the connected state or impair the functions and effects achieved by their combination.

Similarly, "the state in which member C is provided between member A and member B" refers to the case where member A and member C or member B and member C are directly connected, as well as the case where they are electrically connected. It also includes the case of being indirectly connected through other members that do not substantially affect the physical connection state or impair the functions and effects achieved by their combination.

FIG. 1 is a block diagram of a touch-type input device 100 including a capacitive detection circuit 200 according to an embodiment. The touch-type input device 100 comprises a panel 110 and a capacitive detection circuit 200 . A touch-type input device 100 is a user interface that detects a touch operation by a user's finger 2 (or a stylus).

Panel 110 is a touch panel or switch panel and includes one or more sensor electrodes SE.

The host processor 120 comprehensively controls devices, devices, and systems in which the touch-type input device 100 is mounted. Capacitance detection circuit 200 detects the capacitance of each sensor electrode SE and transmits it to host processor 120 . Note that the capacitance detection circuit 200 may detect the presence or absence of a touch by comparing the detected electrostatic capacitance Cs with a threshold value, and transmit the presence or absence of the touch to the host processor 120 .

The capacitance detection circuit 200 includes a sense pin SNS, an analog front end circuit 210, an A/D converter 220, an interface circuit 230 and a controller 240. FIG. 1 shows a circuit configuration for one channel corresponding to one sensor electrode SE. A capacitance detection circuit 200 capable of detecting capacitances of a plurality of sensor electrodes SE includes a plurality of sense pins SNS and a plurality of analog front end circuits 210 corresponding to the plurality of sense pins. The A/D converter 220 may be provided for each channel or may be shared by multiple channels.

A sensor electrode SE is connected to the sense pin SNS. The analog front end circuit 210 is a C/V conversion circuit that converts the electrostatic capacitance Cs formed by the sensor electrode SE into a voltage signal Vs.

Analog front end circuit 210 includes reference capacitor Cr and switch group 211 . The controller 240 detects the capacitance Cs of the sensor electrode SE by controlling the switch group 211 to transfer charge between the sensor electrode SE and the reference capacitor Cr.

The analog front-end circuit 210 may operate in three states: charge phase, transfer phase, and sampling phase. During the charging phase, at least one of the capacitance Cs or the reference capacitor Cr is charged with a known voltage. The subsequent transfer phase connects the capacitance Cs and the reference capacitor Cr to transfer charge between them. As a result, a charge amount corresponding to the capacitance Cs is stored in the reference capacitor Cr. In the sampling phase, a voltage signal Vs based on the charge amount of the reference capacitor Cr is supplied to the A/D converter 220 in the subsequent stage. The configuration of the switch group 211 is not particularly limited, and various variations are conceivable.

A/D converter 220 converts voltage signal Vs into digital signal Ds. Interface circuit 230 transmits digital signal Ds to host processor 120 .

Next, the temperature detection function of the capacitance detection circuit 200 will be described. In connection with temperature sensing, the analog front-end circuit 210 includes a leakage path 260 that connects with the leaked element, which is one of the reference capacitor Cr or the sensor electrode SE. In FIG. 1, the leaked element is the reference capacitor Cr, and the leak path 260 is connected in parallel with the reference capacitor Cr. The charge in reference capacitor Cr, which is a leaked element, is discharged by leak current I _LEAK flowing through leak path 260 .

The leakage current I _LEAK can be a sub-threshold leakage current, a gate leakage current, a junction leakage current, or the like of a transistor element, or a reverse current of a PN junction (diode). Alternatively, a current flowing through a resistive element having a large resistance value may be used as the leak current _ILEAK .

2A to 2E are circuit diagrams showing configuration examples of the leak path 260. FIG. Leakage path 260 in FIG. 2(a) includes a resistor. Leakage path 260 in FIG. 2(b) includes diode D1. Leakage path 260 in FIG. 2(c) includes anti-series diodes D1 and D2. A leak path 260 in FIG. 2(d) includes a FET (Field Effect Transistor). A bipolar transistor can also be used in place of the FET. Leakage path 260 in FIG. 2(e) includes a CMOS inverter. Leak path 260 may be a combination of the configurations of FIGS. 2(a)-(e).

FIG. 3 is a diagram showing the temperature dependence of leakage current. Leakage current has temperature dependence. The polarity (positive or negative) of the temperature coefficient can be selectively designed by the configuration of the leakage path 260 . For example, when using a resistive element, the leakage current _ILEAK has a negative temperature coefficient because the higher the temperature, the higher the impedance. When using sub-threshold leakage current, the higher the temperature, the higher the leakage current, thus having a positive temperature coefficient.

Controller 240 includes a temperature detector 242 . Temperature detector 242 detects the temperature based on the output of A/D converter 220 .

The above is the configuration of the capacitance detection circuit 200 . Next, temperature detection processing in the capacitance detection circuit 200 will be described.

As described above, the leakage current I _LEAK flowing through leakage path 260 has temperature dependence. A high impedance period is provided during the sensing period by the analog front-end circuit 210 or during the temperature detection period, in which the leaked element becomes high impedance, and the leaked element is discharged through the leak path 260 . Then, the charge amount of the leaked element changes according to the leak current I _LEAK and is reflected in the output of the A/D converter 220 . Since the change in the charge amount of the leaked element has temperature dependence, the temperature detection section 242 can acquire the temperature information based on the output Ds of the A/D converter 220 .

The above is the basic configuration and operation of the capacitance detection circuit 200 .

The present invention extends to various apparatus and methods grasped as the block diagram and circuit diagram of FIG. 1 or derived from the above description, and is not limited to any particular configuration. Hereinafter, more specific configuration examples and embodiments will be described not for narrowing the scope of the present invention, but for helping to understand the essence and operation of the invention and clarifying them.

(Example 1)
FIG. 4 is a circuit diagram of the capacitance detection circuit 200A according to the first embodiment. The switch group 211A includes switches SW11 to SW14.

The controller 240 controls the switches SW11 to SW14 forming the switch group 211. FIG. Specifically, the controller 240 switches the state of the analog front-end circuit 210A among three states of charging phase φ ₁ , transfer phase φ ₂ and sampling phase φ ₃ .

・Charging phase φ ₁
SW11 and SW13 are ON, SW12 and SW14 are OFF

In the charging phase _φ1 , the switch SW11 is turned on, and the electrostatic capacitance Cs formed by the sensor electrode SE is charged with the high level voltage, that is, the power supply voltage _VDD . A charge amount Qs of the capacitance Cs is Qs=V _DD ×Cs. Also, the switch SW13 is turned on, and the charge Qr of the reference capacitor Cr becomes zero.

・Transfer phase φ ₂
SW12 is on, SW11, SW13, and SW14 are off

In the transfer phase _φ2 , the switch SW12 is turned on and charge transfer occurs between the capacitance Cs and the reference capacitor Cr. If the influence of the leak path 260 can be ignored, the following equation holds from the charge conservation law before and after charge transfer.
V _DD ×Cs=Vr.(Cs+Cr)
Vs is the voltage generated in the reference capacitor Cr after charge transfer is completed. Therefore, voltage Vr is given by the following equation.
Vr= _VDD ×Cs/(Cs+Cr)

・Sampling phase φ ₃
SW14 is on, SW11 to SW13 are off

In the sampling phase _φ3 , the voltage Vr generated in the reference capacitor Cr is supplied to the subsequent A/D converter 220 as the voltage signal Vs.

In this configuration, if the length of the transfer phase _φ2 is lengthened, the leak current I _LEAK through the leak path 260 can discharge the charges in the reference capacitor Cr and the capacitance Cs.

The controller 240 can switch the operating frequency of the analog front-end circuit 210A between different frequencies f _H and f _L . Temperature detector 242 detects temperature based on changes in output Ds of A/D converter 220 obtained when operating at two frequencies f _H and f _L .

5A and 5B are diagrams for explaining the operation of the analog front-end circuit 210A of FIG. 4. FIG. FIG. 5(a) shows operation at a fast frequency _fH and FIG. 5(b) shows operation at a slow frequency _fL .

In the transfer phase _φ2 , the voltage Vr of the reference capacitor Cr decreases with a slope corresponding to the leakage current _ILEAK . As shown in FIG. 5(a), when the operating frequency of the analog front-end circuit 210A is high, the length of the transfer phase _φ2 is short, so the influence of the leakage current I _LEAK becomes small, and the influence of the leakage current I _{LEAK becomes} small. A small digital signal Ds is generated. As shown in FIG. 5(b), when the operating frequency of the analog front-end circuit 210A is lowered, the _length of the transfer phase _{φ2 becomes} longer. A highly influential digital signal Ds is generated.

FIG. 6 is a diagram for explaining the operation of the capacitance detection circuit 200A of FIG. When operated at a fast frequency _fH , the output Ds of the interface circuit 230 has a value (6500) that is approximately the same at high temperature (85° C.) in the non-touch state and at normal temperature (25° C.) in the touch state.

On the other hand, when operated at the slow frequency _f2 , the digital value Ds is affected by leakage current. In this example, it is assumed that the higher the temperature, the greater the leakage current _ILEAK .

At room temperature (25° C.), the leak current I _LEAK is small, so the amount of change in the digital value Ds between the frequencies f _H and f _L is small (for example, 10) in both the touch state and the non-touch state.

At high temperature (85° C.), leakage current _ILEAK increases. Therefore, when operated at the slow frequency _f2 , the digital value Ds obtained at the slow frequency _fL is smaller than when operated at the fast frequency _fH , and the difference is large (for example, 1000). That is, the temperature change can be detected based on the difference (change amount) between the digital values Ds obtained at two different frequencies f _H and f _L 2 .

This method has the advantage that it is only necessary to switch the operating frequency of the analog front-end circuit 210A, and the control sequence by the controller 240 does not need to be changed.

(Example 2)
The configuration of the analog front-end circuit 210 of the second embodiment is the same as that of the first embodiment, but the control sequence is different.

In Example 2, a leak phase φ _LEAK for temperature detection is inserted between the transfer phase φ ₂ and the sampling phase φ ₃ . In the leak phase φ _LEAK , all switches SW11 to SW14 are turned off.

7A and 7B are diagrams for explaining the operation of the capacitance detection circuit according to the second embodiment. The operation of FIG. 7(a) is the same as that of FIG. 5(a).

FIG. 7(b) shows a sequence including a leak phase φ _LEAK . In the leak phase φ _LEAK , only the charge of the reference capacitor Cr is discharged, so the voltage Vr decreases faster than in the transfer phase φ ₂ . That is, the amount of change in voltage Vr that depends on temperature can be detected with high sensitivity. However, it is necessary to switch the control sequence between normal operation and temperature detection.

(Example 3)
FIG. 8 is a circuit diagram of a capacitance detection circuit 200C according to the third embodiment. In Example 3, the leakage path 260 is provided between the sense pin SNS and ground. Other configurations and operations are the same as those of the first embodiment.

During the transfer period φ ₂ , the capacitance Cs and the reference capacitor Cr are connected and their charges are discharged through the leak path 260 . This is the same as the transfer period _φ2 of the first embodiment. Therefore, the operation of the capacitance detection circuit 200C will be similarly described with reference to FIGS. 5(a) and 5(b).

(Example 4)
In Example 4, the configuration of the capacitance detection circuit is the same as in FIG. 8, but the control sequence is different. In Example 4, a leak phase φ _LEAK is inserted between the charging phase φ ₁ and the transfer phase φ ₂ . All the switches SW11 to SW14 are off in the leak phase φ _LEAK .

9A and 9B are diagrams for explaining the operation of the capacitance detection circuit according to the fourth embodiment. In FIG. 9(a), charging phase φ ₁ , transfer phase φ ₂ and sampling phase φ ₃ are repeated. In the charging phase _φ1 , the power supply voltage _VDD is applied to the sense pin SNS to charge the capacitance Cs.

In the subsequent transfer phase _φ2 , the capacitance Cs and the reference capacitor Cr are connected to smooth the charge. As a result, the two voltages _VSNS and Vr transition to the same voltage level Vs. The voltage level Vs is output in the subsequent sampling phase _φ3 .

In FIG. 9(b), charging phase φ ₁ , leak phase φ _LEAK , transfer phase φ ₂ and sampling phase φ ₃ are repeated. In the charging phase _φ1 , the power supply voltage _VDD is applied to the sense pin SNS to charge the capacitance Cs. In the leakage phase φ _LEAK , the capacitance Cs is discharged by the leakage current I _LEAK and the sense pin voltage V _SNS drops to V _DD ′. The amount of decrease ΔV in voltage V _SNS depends on the amount of leakage current I _LEAK , ie temperature.

In the subsequent transfer phase _φ2 , the capacitance Cs and the reference capacitor Cr are connected to smooth the charge. As a result, the two voltages V _SNS and Vr transition to the same voltage level Vs'. This voltage level Vs' is given by the following equation.
Vs'= _VDD '×Cs/(Cs+Cr)
=(V _DD -ΔV)×Cs/(Cs+Cr)

A voltage signal Vs' is output in the subsequent sampling phase _φ3 .

ΔV depends on the magnitude of the leakage current, that is, on temperature. Therefore, the digital value Ds' corresponding to the voltage signal Vs' includes temperature information.

(Example 5)
FIG. 10 is a circuit diagram of a capacitance detection circuit 200D according to the fifth embodiment. The switch group 211D includes switches SW21 to SW28. The controller 240 controls the switches SW21 to SW28 forming the switch group 211. FIG. Specifically, the controller 240 switches the state of the analog front-end circuit 210D between six states of the first phase φ ₁ to the sixth phase φ ₆ .

FIGS. 11A to 11F are equivalent circuit diagrams of the analog front-end circuit 210 in the first phase φ ₁ to sixth phase φ ₆ . A first phase φ ₁ to a third phase φ ₃ is a unit of sensing, and a fourth phase φ ₄ to a sixth phase φ ₆ is a unit of sensing.

The first phase φ ₁ to third phase φ ₃ correspond to the charging phase φ ₁ , transfer phase φ ₂ and sampling phase φ ₃ described above.

As shown in FIG. 11(a), in the first phase _φ1 , the switch SW21 is turned on, and the electrostatic capacitance Cs is charged with the high level voltage _VH , that is, the power supply voltage _VDD . Also, the switches SW25 and SW27 are turned on to discharge the reference capacitor Cr.

As shown in FIG. 11(b), in the second phase _φ2 , the switches SW23 and SW27 are turned on, charge transfer occurs between the capacitance Cs and the reference capacitor Cr, and the charge amounts Qs and Qr are smoothed. be.
Cs×V _DD =(Cs+Cr)×Vr
The internal voltage Vr at this time is represented by Equation (1).
Vr=Cs/(Cs+Cr)× _VDD (1)

As shown in FIG. 11(c), in the third phase _φ3 , the switches SW27 and SW28 are turned on, and the voltage Vr is supplied to the subsequent A/D converter 220 as the voltage signal Vs.

As shown in FIG. 11(d), in the fourth phase _φ4 , the switch SW22 is turned on and the charge amount Qs of the capacitance Cs becomes zero. Also, the switches SW24 and SW26 are turned on, and the charge amount Qr of the reference capacitor Cr becomes zero.

As shown in FIG. 11(e), the switches SW23 and SW26 are turned on in the fifth phase _φ5 . In this state, internal voltage Vr is represented by equation (2).
Vr=Cr/(Cs+Cr)× _VDD
=V _DD -Cs/(Cs+Cr)×V _DD (2)

As shown in FIG. 11(f), the switches SW26 and SW28 are turned on in the sixth phase _φ6 . As a result, the voltage Vr is supplied to the subsequent A/D converter 220 as the voltage signal Vs.

FIG. 12 is a waveform diagram showing the basic operation of the analog front-end circuit 210D.

The above is the basic operation of the analog front-end circuit 210D. Next, temperature detection in the capacitance detection circuit 200 will be described.

13A and 13B are diagrams for explaining temperature detection by the capacitance detection circuit 200D in FIG. Controller 240 causes analog front-end circuit 210D to operate at different operating frequencies f _H and f _L . FIG. 13(a) shows the waveform of voltage Vr when operated at fast frequency _fH .

FIG. 13(b) shows the waveform of the voltage Vr when operating at the slow frequency _fL . When operated at a slow frequency, the length of the second phase _φ2 and the fifth phase _φ5 corresponding to the transfer phase is lengthened, and the charge of the reference capacitor Cr is discharged by the leak current I _LEAK . Therefore, the voltage signal Vs obtained in the third phase φ ₃ and the sixth phase φ ₆ corresponding to the sampling phase is affected by the leakage current I _LEAK , that is, temperature, and temperature information can be obtained.

(Example 6)
The configuration of the capacitance detection circuit 200 according to the sixth embodiment is the same as that of the fifth embodiment (the capacitance detection circuit 200D in FIG. 10).

In Example 6, controller 240 operates analog front-end circuit 210 at the same frequency _fH . Then, the controller 240 (temperature detector 242) inserts the leak phase φ _LEAK after the second phase or the fifth phase. The leak phase φ _LEAK may be inserted once in multiple sensings. In the leak phase φ _LEAK , the states of the switches SW21 to SW28 are determined so that the reference capacitor Cr becomes high impedance. For example, all switches SW21 to SW28 may be turned off.

FIG. 14 is an operation waveform diagram of the capacitance detection circuit 200 according to the sixth embodiment. In the leak phase φ _LEAK , the voltage Vr fluctuates according to the magnitude of the leak current I _LEAK , that is, the temperature. Therefore, the digital signal Ds obtained in the sampling phase following the leak phase φ _LEAK contains temperature information.

Next, the operation sequence of the multi-channel capacitance detection circuit 200 will be described. 15A to 15C are diagrams showing the operation sequence of the capacitance detection circuit 200. FIG. A shows high frequency _fH sensing and B shows low frequency _fL sensing.

In FIG. 15A, for all channels Ch1 to ChN, sensing A at frequency _fH is performed, and then sensing B at frequency _fL is performed. The temperature can be detected based on the difference between the signal Ds obtained by sensing A and the signal Ds obtained by sensing B for the same channel. According to this sequence, the temperature of each sensor electrode SE can be detected individually.

In FIG. 15B, after performing sensing A at frequency _fH for all channels Ch1 to ChN, sensing B at frequency _fL is performed for one channel CHN. The temperature can be detected based on the difference between the signal Ds obtained by sensing A and the signal Ds obtained by sensing B for channel CHN. Since the sensing cycle can be shortened compared to FIG. 15A, the responsiveness can be improved. Moreover, in the sequence of FIG.15(b), power consumption can be reduced compared with FIG.15(a).

In FIG. 15(c), sensing B at frequency _fL is performed after repeating sensing at frequency _fH over a plurality of cycles. In the sequence of FIG. 15(c), the temperature of each sensor electrode of each channel can be detected. In addition, the responsiveness can be improved and the power consumption can be reduced as compared with FIG. 15(a).

Although the present invention has been described using specific terms based on the embodiment, the embodiment only shows one aspect of the principle and application of the present invention, and the embodiment does not include the claims. Many variations and rearrangements are permissible without departing from the spirit of the invention as defined in its scope.

REFERENCE SIGNS LIST 100 touch input device 110 panel SE sensor electrode 120 host processor Cs electrostatic capacitance Cr reference capacitor 200 capacitance detection circuit 210 analog front end circuit 211 switch group 220 A/D converter 230 interface circuit 240 controller 242 temperature detector 260 leak path

Claims (10)

A capacitance detection circuit that detects the capacitance of a sensor electrode,
a sense pin to which the sensor electrode is connected;
a reference capacitor for transferring charge between the reference capacitor and the sensor electrode to convert the capacitance into a voltage signal and in communication with a leaked element that is one of the reference capacitor and the sensor electrode; an analog front-end circuit including a leakage path to
an A/D converter that converts the output signal of the analog front-end circuit into a digital value;
a temperature detection unit that detects temperature based on the output of the A/D converter;
A capacitance detection circuit comprising: 2. The capacitance detection according to claim 1, wherein said temperature detection unit detects said temperature based on a change in the output of said A/D converter when said analog front end circuit is operated at different frequencies. circuit. the leaked element is the reference capacitor;
2. The capacitance detection circuit according to claim 1, wherein said temperature detection unit keeps said reference capacitor in a high impedance state for a predetermined period of time, and thereafter detects the temperature based on the output of said A/D converter. 4. The capacitance detection circuit according to claim 1, wherein said leakage path is connected in parallel with said reference capacitor. 3. The capacitance detection circuit according to claim 1, wherein the leak path is provided between the sensor electrode and ground. 6. The capacitance detection circuit according to claim 1, wherein said leak path includes a resistor. 6. The capacitance detection circuit according to claim 1, wherein said leakage path includes a diode. 6. The capacitance detection circuit according to claim 1, wherein said leakage path includes a transistor. 9. The capacitance detection circuit according to claim 1, wherein the capacitance detection circuit is monolithically integrated on one semiconductor integrated circuit. A panel that includes sensor electrodes and changes the capacitance of the sensor electrodes near the coordinates touched by the user;
a capacitance detection circuit according to any one of claims 1 to 9, connected to the sensor electrode;
An input device comprising:

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