JP2010250522A - Coordinate input device and display device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance detection circuit for detecting a minute input capacitance by a high signal noise rate, in a coordinate input device for detecting a capacitance. <P>SOLUTION: The capacitance detection circuit is configured of: a capacitance sensor electrode; a switch element SA for applying a fixed potential to the capacitance sensor electrode to detect a capacitance related to the capacitance sensor electrode; a switch element SB for transferring charges stored in the capacitance sensor electrode; and an integration circuit for detecting charges to be transferred from the capacitance sensor electrode through the switch element SB. A voltage source which supplies a fixed potential is connected through the switch element SA to the capacitance sensor electrode, and the capacitance sensor electrode is connected through the switch element SB to the input terminal of the integration circuit. The switch element SC and an adjustment capacitance Ca to be short-circuited to the reference level of the integration circuit are connected to the input terminal of the integration circuit of the capacitance detection circuit, and a signal ADJ for adjustment is applied to the other terminal of the adjustment capacitance Ca. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coordinate input device for inputting coordinates to a screen and a display device including the coordinate input device, and more particularly to a technique suitable for increasing the accuracy of coordinate detection in a capacitively coupled coordinate input device.

  An input device (hereinafter also referred to as a touch sensor or a touch panel) having a screen input function for inputting information by performing a touch operation (contact pressing operation, hereinafter simply referred to as touch) using a user's finger or the like on the display screen is provided. Such display devices are used in mobile electronic devices such as PDAs and portable terminals, various home appliances, and stationary customer guidance terminals such as unmanned reception machines. As such an input device by touching, a resistive film method for detecting a change in resistance value of a touched portion, or a capacitive coupling method for detecting a capacitance change, an optical sensor for detecting a light amount change in a portion shielded by the touch The method is known.

  Among these methods, a capacitively coupled touch panel has recently attracted attention. When an input is performed on the input device by touch using a button or a slider displayed on the display device of the mobile electronic device, the input device needs to be disposed on the front surface of the display device. In this case, it is necessary to incorporate an input function while maintaining a display image quality by reducing a decrease in display brightness of the display device. Here, the transmittance is generally as low as about 80% in the resistive film type or the optical sensor method, whereas the transmittance is as high as about 90% in the capacitive coupling method. Therefore, it is advantageous in that the display image quality is not deteriorated. In the resistive film type, the touch position is detected by mechanical contact of the resistive film. Therefore, when the number of touches (mechanical contact) increases and the resistive film deteriorates or breaks, there are problems that the detection error becomes large and the detection becomes impossible. On the other hand, the capacitive coupling method is advantageous in terms of durability because there is no mechanical contact such that the detection electrode contacts other electrodes.

  As a capacitance detection circuit in the capacitive coupling method, for example, there is a method as disclosed in Patent Document 1. In this disclosed method, a sensor electrode capacitor for detecting a capacitance is charged with a constant voltage, and the charge amount is detected by an integrating circuit at a subsequent stage. In order to cancel the offset of the operational amplifier used in the integration circuit, the integrated voltage at the time of charging from the sensor electrode capacitance and the integrated voltage at the time of discharging are alternately measured by switch control.

US Pat. No. 7,235,983

  The problem of the capacitance detection method disclosed in Patent Document 1 will be described with reference to FIGS. FIG. 17 is a diagram schematically showing a conventional capacitance detection circuit DCKT. The conventional detection circuit DCKT includes a switch SA for charging a constant voltage VDD to the sensor electrode (capacitance) Cs for capacitance detection, and a switch SB for transferring the charge charged to the sensor electrode capacitance Cs to the integration circuit. And an integration circuit composed of an integration capacitor Ci, a switch SR for resetting the integration value, and an operational amplifier. The terminal vi is an input terminal that connects the detection circuit DCKT and the sensor electrode capacitor Cs, and the terminal vo is an output voltage terminal of the detection circuit DCKT.

  FIG. 18 is a waveform diagram in the case where an integrated voltage obtained by one charge / discharge of the sensor electrode capacitor Cs is used as an output signal for capacitance detection. FIG. 18A is a waveform diagram when only the sensor electrode capacitor Cs is connected to the input terminal vi in FIG. 17, and FIG. It is a wave form diagram when input capacity Cf is added. In the detection cycle Tdec_r, the period ta_r is a reset period of the integration capacitor Ci, and the integration voltage accumulated in the integration capacitor Ci is reset when the switch SR is turned on. Next, in the period tb_r, only the switch SA is turned on to charge the sensor electrode capacitor Cs and the input capacitor Cf with the constant voltage VDD. Finally, in the period tc_r, the switch SA is turned off and the switch SB is turned on, so that the charges charged in Cs and Cf are transferred to the integration circuit. Here, when only the sensor electrode capacitance Cs is as shown in FIG. 18A, the integrated voltage is −VDD · Cs / Ci. When there is an input capacitance Cf as shown in FIG. 18B, the integrated voltage is −VDD. -(Cs + Cf) / Ci. In the coordinate input device, after these integrated voltage values (output signals) are digitized by AD conversion, the difference between the digital signal when there is no input and the digital signal when there is an input is detected as an input signal, and touch coordinates Calculate

  Here, the input capacitance Cf due to electrostatic capacitance such as a finger is as small as several pF or less, whereas the sensor electrode capacitance Cs is as large as several tens pF depending on the size of the input screen. Therefore, even if the output voltage of the integrating circuit is amplified by an amplifier before AD conversion, the integrated value by the sensor electrode capacitance Cs is offset, so that sufficient amplification cannot be obtained, and the dynamics of the input signal after AD conversion There is a problem that the range becomes narrow and the input coordinates cannot be detected with high accuracy.

  An object of the present invention is to realize a capacitance detection circuit capable of detecting a minute input capacitance with a high signal-to-noise ratio in a coordinate input device that detects capacitance.

  In order to achieve the solution of the above problem, the present invention provides a capacitance sensor electrode for detecting capacitance and a capacitance sensor electrode for detecting a capacitance related to the capacitance sensor electrode. 1 switch element, a second switch element for transferring the charge accumulated in the capacitance sensor electrode, and an integration circuit for detecting the charge transferred from the capacitance sensor electrode via the second switch element The voltage source configured to supply the constant potential is connected to the capacitive sensor electrode via the first switch element, and the capacitive sensor electrode is connected to the input terminal of the integrating circuit via the second switch element. In the capacitance detection circuit, the input terminal of the integration circuit of the capacitance detection circuit has a third switch element and an adjustment capacitor for short-circuiting to a reference level of the integration circuit. There are connected, to the other terminal of the regulating capacitor is used capacitance detection circuit adjustment signal is applied. As a procedure for operating the capacitance detection circuit, first, the first switch element, the second switch element, and the three switch element are turned off, the output signal of the integration circuit is reset, and secondly, The first switch element is turned on, the constant potential is applied to the capacitor related to the capacitive sensor electrode, and thirdly, the first switch element is turned off and the second switch element is turned on. , Transferring the electric charge accumulated in the capacitance relating to the capacitance sensor electrode to the integrating circuit, fourthly, turning off the second switch element, changing the adjustment signal by the adjustment voltage, and fifth, The third switch element is turned on, the adjustment signal is reset to the potential before the change, and sixth, the third switch element is turned off, and the first to sixth Procedures to operate as a capacitance detection period according to the capacitance sensor electrodes at. Here, in the state where there is no input operation with respect to the capacitance sensor electrode, the output voltage of the integration circuit obtained in the first to third procedures, and the fourth procedure flows to charge the adjustment capacitor. The amount of change in the output voltage of the integration circuit caused by detecting the current by the integration circuit is substantially equal, and as a result, the output signal of the capacitance detection circuit in a state where there is no input operation to the capacitance sensor electrode is almost zero Thus, by setting the adjustment capacitor and the adjustment voltage, only the input capacitance that increases due to the touch is detected as an output signal.

  According to the present invention, only the input capacitance that increases by touch can be detected as an output signal, so that the dynamic range of the detectable input capacitance is widened, and the detection accuracy is improved.

Circuit diagram of the capacitance detection circuit in the first embodiment of the present invention Voltage waveform diagram of capacitance detection circuit at one charge / discharge in the first embodiment of the present invention Voltage waveform diagram of capacitance detection circuit in charge / discharge twice in the first embodiment of the present invention FIG. 1 is a system block diagram of a coordinate input device according to a first embodiment of the present invention and a display device using the same. Capacitance detection sequence of coordinate input device in first embodiment of the present invention Digital output signal of coordinate input device in first embodiment of the present invention Capacitance detection timing chart of the coordinate input device according to the first embodiment of the present invention Circuit diagram of the capacitance detection circuit in the second embodiment of the present invention Voltage waveform diagram of capacitance detection circuit at one charge / discharge in the second embodiment of the present invention Voltage waveform diagram of capacitance detection circuit in charge / discharge twice in the second embodiment of the present invention System block diagram of coordinate input device and display device using the same according to second embodiment of the present invention Capacitance detection sequence of coordinate input device in second embodiment of the present invention Digital output signal of coordinate input device in second embodiment of the present invention Capacitance detection timing chart of the coordinate input device in the second embodiment of the present invention Circuit diagram of the capacitance detection circuit in the third embodiment of the present invention Voltage waveform diagram of capacitance detection circuit at one charge / discharge in the third embodiment of the present invention Circuit diagram of capacitance detection circuit in the prior art Voltage waveform diagram of capacitance detection circuit with one charge / discharge in the prior art

  Hereinafter, embodiments of the present invention will be described in detail.

  A capacitance detection circuit used in the coordinate input device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit diagram of a capacitance detection circuit according to the first embodiment of the present invention. The capacitance detection circuit DCKT is a circuit for detecting the sensor electrode capacitance Cs connected to the input terminal vi and the input capacitance Cf that increases by touching the sensor electrode.

  The capacitance detection circuit DCKT includes a switch SA for charging the constant voltage VDD to the sensor electrode capacitance Cs, a switch SB for transferring the charged charge, an integration circuit with a reset switch SR, and an integration voltage of the sensor electrode capacitance Cs. An adjustment capacitor Ca for adjusting a value (hereinafter referred to as an electrode offset voltage) and removing it from the output signal vo. The integration circuit includes an integration capacitor Ci and an operational amplifier. The adjustment signal ADJ is applied to one terminal of the adjustment capacitor Ca.

  FIG. 2 is a voltage waveform diagram for explaining the operation of the capacitance detection circuit DCKT according to the first embodiment of the present invention. 2A shows a case where the input is only the sensor electrode capacitance Cs, and FIG. 2B shows a case where the input capacitance Cf is generated by touch. FIG. 2 is a timing chart for detecting the capacity by charging and discharging the capacity connected to the input terminal vi once. In this case, since the capacity can be detected at high speed, the number of subsequent digital filters can be increased, and the reaction time (coordinate detection time) of the input device can be shortened. In Tdec_r, which is one charge / discharge cycle, in the period ta_r, the reset switch SR is turned on to reset the integration voltage of the integration capacitor Ci. Next, in the period tb_r, the switch SA is turned on, so that the capacitor connected to the input terminal vi is charged with the constant voltage VDD. In the next period tc_r, the switch SB is turned on while the switch SA is turned off, so that the charge charged in the capacitor connected to the input terminal vi is transferred to the integrating circuit. Therefore, in the period tc_r, in the case of only the sensor electrode capacitance Cs, as shown in FIG. 2A, the integrated voltage becomes −VDD · Cs / Ci, and the input capacitance Cf is increased by the touch in the case of FIG. The integrated voltage is −VDD · (Cs + Cf) / Ci. In the next period td_r, the electrode offset voltage due to the sensor electrode capacitance Cs is adjusted. First, the adjustment signal ADJ is changed from GND to −Vadj, so that the adjustment capacitor Ca is charged. At this time, since the charge Ca * Vadj is charged in the adjustment capacitor Ca, the output of the integrating circuit increases by Vadj · Ca / Ci. Here, the adjustment voltages Vadj and Ca are set so that the electrode offset voltage VDD · Cs / Ci of the sensor electrode capacitance Cs in FIG. 2A is equal to the adjustment amount Vadj · Ca / Ci by charging the adjustment capacitor Ca. If set, the electrode offset voltage due to the sensor electrode capacitance can be removed from the output voltage vo. After that, the switch SC is turned on within the period td_r. Even if the switch SC is turned on to conduct to the ground (GND), since the negative terminal of the operational amplifier is a virtual ground, no current flows and the integrated voltage does not change. Here, it is assumed that the on-resistance of the switch SC is sufficiently low. In this state, the adjustment signal ADJ is returned to GND in order to discharge the charge of the adjustment capacitor Ca. The discharge current from the adjustment capacitor Ca generated at this time is discharged to GND via the switch SC without flowing to the integrating circuit because the ON resistance of the switch SC is sufficiently low.

  2A, when the capacitance connected to the input terminal vi is the sensor electrode capacitance Cs, the offset voltage is adjusted and the output signal vo becomes 0V. On the other hand, when the input capacitance Cf is increased by the touch, the output signal vo becomes an integrated voltage −VDD · Cf / Ci proportional to the input capacitance Cf, as shown in FIG. Since the electrode offset voltage can be excluded from the output voltage in this way, even if the output voltage signal is amplified before AD conversion, the AD conversion range can be fully used, and the detectable input capacitance can be reduced. The dynamic range can be increased.

  FIG. 3 is a voltage waveform diagram showing another capacitance detection method using the capacitance detection circuit DCKT in the first embodiment of the present invention. In FIG. 3, the capacitor connected to the input terminal vi is charged and discharged twice. The period Tpd is a detection cycle of the input capacitance. The first charge / discharge period is a charge / discharge period Tdec_r in which the integration capacitor Ci is reset, and the next discharge period is a charge / discharge period Tdec in which the integration capacitor Ci is not reset. And The difference between the charge / discharge periods Tdec_r and Tdec is that the integration capacitor Ci is reset in the period ta_r, whereas the integration capacitor Ci is not reset in the period ta. Other periods tb_r and tb, periods tc_r and tc, and periods td_r and td may be set to the same setting. During these periods, as already described with reference to FIG. 2, the charge connected to the capacitor connected to the input terminal vi is charged, and after the discharged charge is integrated, the electrode offset voltage is canceled by the adjustment signal ADJ and the adjustment capacitor Ca. To perform the operation.

  As shown in FIG. 3A, in order to cancel the electrode offset voltage in each charging / discharging period, the output voltage vo becomes 0V when there is no input capacity even if the number of times of charging / discharging is two. On the other hand, when the input capacitance Cf is generated by touch, as shown in FIG. 3B, the integration voltage VDD · Cf / Ci depending on the input capacitance Cf is supplied to the integration circuit according to the number of times of charging / discharging. Since they are added, the output voltage vo is 2 · VDD · Cf / Ci. In FIG. 3, the charge / discharge period Tdec_r is set to one time, and the charge / discharge period Tdec is set to one time, so that the charge / discharge period Tdec_r is set to one time. By setting it to n-1 times, it is also possible to carry out charge / discharge detection of a total of n times (however, n is an integer greater than or equal to 2). Thereby, the output voltage can be n · VDD · Cf / Ci and n times that in the case of one charge / discharge.

  As described above, by performing signal addition in the analog circuit portion, it is possible to average and reduce noise generated during each charge / discharge. Further, even if the input capacitance Cf is very small, the output signal can be increased without amplification of the analog signal, so that a high signal-to-noise ratio can be obtained.

  As described above, in the capacitance detection circuit according to the first embodiment of the present invention, the output voltage when there is no input by touch can be canceled by the adjustment signal ADJ and the adjustment capacitance Ca, so that the minute input capacitance Cf In the coordinate input device using the capacitance detection circuit DCKT, it is possible to detect the input coordinates with high accuracy. Here, the output voltage when there is no touch input may be determined by the electrode offset voltage or may reflect various characteristics of the operational amplifier and each switch, both of which are the adjustment signal ADJ and the adjustment capacitance. Cancellation is possible by setting Ca.

  In the description of this embodiment, the output voltage when there is no touch input is assumed to be a negative potential. However, when the output voltage when there is no touch input is a positive potential, the adjustment signal ADJ is used. It is possible to cancel by changing the voltage to a positive voltage.

  Next, the coordinate input device according to the first embodiment of the present invention and a display device including the coordinate input device will be described with reference to FIGS. FIG. 4 is a system block diagram of the coordinate input device and the display device including the coordinate input device according to the first embodiment of the present invention. The coordinate input unit 101 usually has a sensor electrode TP made of a transparent electrode on a transparent substrate. Here, the sensor electrodes are arranged in a matrix, and four X-coordinate detection electrodes TP_X are arranged in the horizontal direction, and four Y-coordinate detection electrodes TP_Y are arranged in the vertical direction. However, the number of electrodes and the electrode arrangement method are not limited thereto. Each sensor electrode is connected to a capacitance detection circuit DCKT shown in FIG. 1 for detecting the capacitance of each sensor electrode. Each capacitance detection circuit DCKT operates based on various control signals (SA, SB, SR, ADJ) output from the input coordinate detection control unit 103, and is a detection result of each sensor electrode and the capacitance input thereto. The output signal vo is output to the AD converter ADC. The AD conversion unit ADC performs AD conversion on the output signal vo of each capacitance detection circuit in accordance with the AD conversion timing signal ADT output from the input coordinate detection control unit 103, and the resulting digital signal DATA is input to the input coordinate detection control unit 103. Output to. The input coordinate detection control unit 103 determines the presence / absence of input and input coordinates from the digital signal DATA, and outputs the determination result to the system 105. The system executes processing according to input coordinates and input actions, and outputs an image based on the processing to the display device control unit 104. The display device control unit 104 outputs signal data for displaying an image and a display control signal DPC for driving the display device to the display unit 102. Here, the display control signal DPC is also output to the input coordinate detection control unit 103. With the above configuration, a system application can be executed in response to an input (touch), and an image based on the execution result can be displayed on the display device.

  Next, the operation sequence of the coordinate input device according to the first embodiment of the present invention will be described with reference to FIG. In the coordinate input device according to the first embodiment of the present invention, the capacitance of each sensor electrode is sequentially detected. In FIG. 5, the detection is sequentially performed from the TP_X1 electrode to the TP_X4 electrode and from the TP_Y1 electrode to the TP_Y4 electrode, but the detection order is not limited to this. The detection method of each detection operation circuit may be detection by one charge / discharge as shown in FIG. 2, or may be detection by n charge / discharge as shown in FIG. These are items designed depending on the input detection speed as the coordinate input device. The output signal of each capacitance detection circuit outputs a digital signal DATA according to the AD conversion timing signal ADT. Therefore, DATA outputs the capacitance detection result of each sensor electrode serially.

  FIG. 6 shows a capacitance detection result of each sensor electrode in the coordinate input unit 101 shown in FIG. 4 when a capacitance increase due to touch occurs at one location of the FA. When a touch occurs at a location of FA, the input capacitance increases at the sensor electrodes TP_X2 and TP_Y2, so the digital signals DX2 and DY2 corresponding to these increase, and the coordinates corresponding to these sensor electrodes increase. It can be determined that there was an input.

  Next, a detection method for reducing noise from the display device in the capacitance detection circuit according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 4, the coordinate input unit 101 and the display unit 102 are arranged so as to overlap in the vertical direction. Therefore, a parasitic capacitance is generated between the image display drive electrode included in the display unit 102 and the sensor electrode TP of the coordinate input unit 101. Through this parasitic capacitance, the potential fluctuation in the image display drive electrode included in the display unit 102 propagates to the sensor electrode TP of the coordinate input unit 101, which causes noise in the output of the capacitance detection circuit. . Therefore, as shown in FIG. 7, the input coordinates are set so that the timing of the potential fluctuation in the image display drive electrode (in FIG. 7, the timing at which the display control signal DPC switches) always falls within the period td_r or td. The detection control unit 103 controls various control signals of the capacitance detection circuit based on the display control signal DPC. Accordingly, noise due to the display unit 102 does not occur in the periods ta_r, ta, tb_r, tb, tc_r, and tc in which charge and discharge for capacitance detection are performed. In addition, since the switch SB is in the OFF state during the periods td_r and td, even if noise occurs in the sensor electrode TP due to the change in the display control signal DPC in the display unit 102, the output voltage vo is affected. Does not reach. Therefore, as described above, the input coordinate detection control unit 103 is based on the display control signal DPC so that the timing at which the video display drive electrode signal of the display unit 102 is switched is within td_r or td in each detection cycle. By controlling, noise from the display unit 102 can be reduced. Thereby, the input coordinate by touch can be detected with high accuracy.

  For example, in the case of a liquid crystal display device, the video display drive electrode is a signal voltage line for supplying a signal voltage to the liquid crystal, a common electrode, or the like.

  Next, a capacitance detection circuit used in the coordinate input device according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a circuit diagram of the capacitance detection circuit according to the second embodiment of the present invention. The capacitance detection circuit includes two pairs of a scanning circuit SCKT and a detection circuit DCKT. A scanning sensor electrode TP_Y for capacitance detection is connected to the output terminal vi of the scanning circuit SCKT. A detection sensor electrode TP_X for capacitance detection is connected to the input terminal vs of the detection circuit DCKT. The terminal vo outputs the output voltage of the detection circuit DCKT. In the capacitance detection circuit according to the second embodiment of the present invention, the capacitance generated near the intersection of the scanning sensor electrode TP_Y and the detection sensor electrode TP_X is detected. The capacitance Cs is a capacitance in a state where there is no input such as a cross capacitance between the scanning sensor electrode TP_Y and the detection sensor electrode TP_X. The capacitance Cf is an input capacitance that is generated when there is an input by touch near the intersection between the scanning sensor electrode TP_Y and the detection sensor electrode TP_X.

  The scanning circuit SCKT includes a switch SA for charging the scanning sensor electrode TP_Y to a constant potential VDD and a switch SB for discharging the constant potential VDD charged to the scanning sensor electrode TP_Y to GND. The detection circuit DCKT includes a switch SR for resetting the integration voltage of the integration capacitor Ci, an integration circuit including the integration capacitor Ci and an operational amplifier, an adjustment capacitor Ca for adjusting the output voltage of the integration circuit, and a switch SC. An adjustment capacitor ADJ for driving the adjustment capacitor Ca and one terminal of the Ca adjusts an integrated voltage (hereinafter referred to as an electrode offset voltage) obtained as a result of detecting the capacitor Cs in a state where there is no input capacitor Cf due to touch. Used to remove from the output signal vo. The switch SC is used for resetting the scanning sensor electrode, resetting the adjustment capacitor Ca, and suppressing noise.

  FIG. 9 is a voltage waveform diagram for explaining the operation of SCKT and DCKT which are the capacitance detection circuits of the second embodiment of the present invention. FIG. 9A shows a case where the input is only the sensor electrode capacitance Cs, and FIG. 9B shows a case where the input capacitance Cf is generated by touch. FIG. 9 is a timing chart for detecting the capacitance by charging and discharging the capacitance near the intersection between the scanning sensor electrode TP_Y and the detection sensor electrode TP_X once. In this case, since the capacity can be detected at high speed, the number of subsequent digital filters can be increased, and the reaction time (coordinate detection time) of the input device can be shortened.

  In Tdec_r, which is one charge / discharge cycle, in the period ta_r, the reset switch SR is turned on to reset the integration voltage of the integration capacitor Ci. Further, the switch SB is turned on to reset the potential of the scanning sensor electrode to GND. Next, in the period tb_r, the switch SA is turned on, so that the constant voltage VDD is applied to the scan sensor electrode TP_Y connected to the output terminal vi. At this time, since the potential of the detection sensor electrode TP_X is connected to the negative terminal of the operational amplifier via the DCKT input terminal vs, it becomes the ground GND. For this reason, the capacitor near the intersection of the scanning sensor electrode TP_Y and the detection sensor electrode TP_X is charged with a charge corresponding to the constant potential VDD. The charge necessary for this charging is integrated in the integration circuit. For this reason, when there is no touch input as shown in FIG. 9A, the potential of the output voltage vo becomes −VDD · Cs / Ci, whereas, as shown in FIG. If there is, the potential of the output voltage vo is −VDD · (Cs + Cf) / Ci. In the next period tc_r, the electrode offset voltage is adjusted and the scan sensor electrode is reset. First, the adjustment signal ADJ is changed from GND to −Vadj, so that the adjustment capacitor Ca is charged. At this time, since the charge Ca * Vadj is charged in the adjustment capacitor Ca, the output of the integrating circuit increases by Vadj · Ca / Ci. Here, if the adjustment voltages Vadj and Ca are set so that the electrode offset voltage VDD · Cs / Ci in FIG. 9A and the adjustment amount Vadj · Ca / Ci by charging the adjustment capacitor Ca are equal, the electrode The offset voltage can be removed from the output voltage vo. After changing the adjustment signal ADJ, the switch SC is turned on. Even if the switch SC is turned on to conduct to the ground (GND), since the negative terminal of the operational amplifier is a virtual ground, no current flows and the integrated voltage does not change. Here, it is assumed that the on-resistance of the switch SC is sufficiently low. In this state, the switch SB is turned on to reset the potential of the scan sensor electrode TP_Y to GND. At this time, charges are discharged from the capacitance in the vicinity of the intersection of the scanning sensor electrode TP_Y and the detection sensor electrode TP_X, but the current caused by this flows to the GND via the switch SC, and therefore does not affect the output voltage vo of the integrating circuit. . Similarly, when the switch SC is on, the adjustment signal ADJ is returned to GND in order to discharge the charge of the adjustment capacitor Ca. The discharge current from Ca generated at this time does not flow to the integration circuit because the on-resistance of the switch SC is sufficiently low, but discharges to GND through the switch SC.

  With the above operation, as shown in FIG. 9A, when there is no touch input, the electrode offset voltage is adjusted and the output signal vo becomes 0V. On the other hand, when the input capacitance Cf increases due to the touch, the output signal vo becomes an integrated voltage −VDD · Cf / Ci proportional to the input capacitance Cf, as shown in FIG. 9B. Since the electrode offset voltage can be excluded from the output voltage in this way, even if the output voltage signal is amplified before AD conversion, the AD conversion range can be fully used, and the detectable input capacitance can be reduced. The dynamic range can be increased.

  FIG. 10 is a voltage waveform diagram showing another capacitance detection method using the capacitance detection circuits SCKT and DCKT in the second embodiment of the present invention. In FIG. 10, charging / discharging is performed twice with respect to the capacitance near the intersection of the scanning sensor electrode TP_Y and the detection sensor electrode TP_X. The period Tpd is an input capacitance detection cycle. The first charge / discharge period is a charge / discharge period Tdec_r in which the integration capacitor Ci and the scan sensor electrode are reset, and the next discharge period is a charge / discharge period Tdec in which no reset operation is performed. And The difference between the charge / discharge periods Tdec_r and Tdec is that the integration capacitor Ci and the scan sensor electrode are reset in the period ta_r, whereas the reset operation is not performed in the period ta. Other periods tb_r and tb and periods tc_r and tc may be set to the same setting. During these periods, as already described with reference to FIG. 9, the charge is charged with respect to the capacitance near the intersection between the scanning sensor electrode TP_Y and the detection sensor electrode TP_X, and the current flowing at that time is integrated, and then the adjustment signal ADJ An operation of canceling the electrode offset voltage is performed by the adjustment capacitor Ca. As shown in FIG. 10A, in order to cancel the electrode offset voltage in each charge / discharge period of Tdec_r and Tdec, the output voltage vo is 0 V when there is no input capacity even if the number of charge / discharge is two times. It becomes. On the other hand, when the input capacitance Cf is generated by touch, as shown in FIG. 10B, the integration voltage VDD · Cf / Ci depending on the input capacitance Cf is supplied to the integration circuit according to the number of times of charging / discharging. Since they are added, the output voltage vo is 2 · VDD · Cf / Ci. In FIG. 10, the charge / discharge period Tdec_r is set to one time, and the charge / discharge period Tdec is set to one time, so that the charge / discharge period Tdec_r is set to one time. By setting it to n-1 times, it is also possible to carry out charge / discharge detection of a total of n times. Thereby, the output voltage can be n · VDD · Cf / Ci and n times that in the case of one charge / discharge.

  As described above, by performing signal addition in the analog circuit portion, it is possible to average and reduce noise generated during each charge / discharge. Further, even if the input capacitance Cf is very small, the output signal can be increased without amplification of the analog signal, so that a high signal-to-noise ratio can be obtained.

  As described above, in the capacitance detection circuit according to the second embodiment of the present invention, the output voltage when there is no touch input can be canceled by the adjustment signal ADJ and the adjustment capacitance Ca. In the coordinate input device using the capacitance detection circuit DCKT, it is possible to detect the input coordinates with high accuracy. Here, the output voltage when there is no touch input may be determined by the electrode offset voltage or may reflect various characteristics of the operational amplifier and each switch, both of which are the adjustment signal ADJ and the adjustment capacitance. Cancellation is possible by setting Ca.

  Next, a coordinate input device and a display device including the coordinate input device according to the second embodiment of the present invention will be described with reference to FIGS.

  FIG. 11 is a system block diagram of a coordinate input device and a display device including the coordinate input device according to the second embodiment of the present invention. The coordinate input unit 101 usually has a sensor electrode TP made of a transparent electrode on a transparent substrate. Here, the sensor electrodes are arranged in a matrix, and four X-coordinate detection electrodes TP_X are arranged in the horizontal direction, and four Y-coordinate detection electrodes TP_Y are arranged in the vertical direction. However, the number of electrodes is not limited to this. Here, the Y coordinate detection electrode TP_Y is connected to the scanning circuit SCKT as a scanning sensor electrode, and the X coordinate detection electrode TP_X is connected to the detection circuit DCKT as a detection sensor electrode.

  Each scanning circuit SCKT operates based on control signals (SA, SB) output from the input coordinate detection control unit 103. Here, each scanning sensor electrode is sequentially selected from TP_Y1 to TP_Y4, and a constant voltage is charged to the capacitance near the intersection of the selected scanning sensor electrode TP_Y and each detection sensor electrode TP_X. Each detection circuit DCKT operates based on control signals (SC, SR, ADJ) output from the input coordinate detection control unit 103, and the scanning sensor electrode TP_Y selected by the scanning circuit SCKT and each detection sensor electrode A current charged in a capacitor near the intersection with TP_X is detected, and an output signal vo that is a detection result of the input capacitance by touch is output to the AD converter ADC. The AD conversion unit ADC performs AD conversion on the output signal vo of each detection circuit DCKT in accordance with the AD conversion timing signal ADT output from the input coordinate detection control unit 103, and the resulting digital signal DATA is input to the input coordinate detection control unit. To 103. The input coordinate detection control unit 103 determines the presence / absence of input and input coordinates from the digital signal DATA, and outputs the determination result to the system 105. The system executes processing according to input coordinates and input actions, and outputs an image based on the processing to the display device control unit 104. The display device control unit 104 outputs signal data for displaying an image and a display control signal DPC for driving the display device to the display unit 102. Here, the display control signal DPC is also output to the input coordinate detection control unit 103. With the above configuration, a system application can be executed in response to an input (touch), and an image based on the execution result can be displayed on the display device.

  Next, the operation sequence of the coordinate input device according to the second embodiment of the present invention will be described with reference to FIG. In the coordinate input device according to the second embodiment of the present invention, the scanning sensor electrode TP_Y is sequentially selected by the scanning circuit SCKT, and the input capacitance near the intersection between the selected scanning sensor electrode TP_Y and each detection sensor electrode TP_X is obtained. To detect. Therefore, when the scanning sensor electrode TP_Y1 is selected by SCKT1, the results detected by the detection circuits DCKT1 to DCKT4 are the results of detecting the input capacitances near the intersections of the detection sensor electrodes TP_X1 to TP_X4, respectively. . Therefore, by sequentially selecting scanning circuits and performing detection from the scanning sensor electrodes TP_Y1 to TP_Y4, it is possible to detect input capacitances near all the intersections. The detection method of each detection operation may be detection by one charge / discharge as shown in FIG. 9, or may be detection by n charge / discharge as shown in FIG. The output signal of each detection circuit outputs a digital signal DATA according to the AD conversion timing signal ADT. Therefore, DATA outputs the input capacitance detection result in the vicinity of the intersection between the selected scanning sensor electrode and each detection sensor electrode in parallel. Here, the input capacitance detection result near the intersection between the scanning sensor electrode TP_Y1 and each detection sensor electrode is represented by DX1 (Y1) to DX4 (Y1).

  FIG. 13 shows the result of detecting the input capacitance in the vicinity of the intersection of each sensor electrode in the coordinate input unit 101 shown in FIG. 11 when the capacitance increase due to touch occurs at two locations FA and FB. When the touch occurs at the FA location, data DX2 (Y2) near the intersection between the scanning sensor electrode TP_Y2 and the detection sensor electrode TP_X2, and data near the intersection between the scanning sensor electrode TP_Y4 and the detection sensor electrode TP_X4. Two data of DX4 (Y4) become high according to the input capacitance Cf, and it can be determined that there is an input at coordinates corresponding to these two points.

  Next, a detection method for reducing noise from the display device in the capacitance detection circuit according to the second embodiment of the present invention will be described with reference to FIG. In FIG. 8, the coordinate input unit 101 and the display unit 102 are arranged so as to overlap in the vertical direction. Therefore, as described in the first embodiment, a parasitic capacitance is generated between the image display drive electrode included in the display unit 102 and the sensor electrode TP of the coordinate input unit 101. Through this parasitic capacitance, the potential fluctuation in the image display drive electrode included in the display unit 102 propagates to the sensor electrode TP of the coordinate input unit 101, which causes noise in the output of the capacitance detection circuit. .

  Therefore, as shown in FIG. 14, the timing of the potential change in the image display drive electrode (the timing at which the display control signal DPC is switched in FIG. 14) is always the switch SC in the period tc_r or tc. The input coordinate detection control unit 103 controls various control signals of the capacitance detection circuit based on the display control signal DPC so as to fall within the period (tsc_r in FIG. 14). Accordingly, noise due to the display unit 102 does not occur in the periods ta_r, ta, tb_r, and tb in which charge charging for capacitance detection is performed. In addition, since the switch SC is in an on state during the periods tc_r and tc, even if a current is generated in the detection sensor electrode TP_X due to a change in the display control signal DPC in the display unit 102, the switch SC is turned on. Therefore, the output voltage vo of the integrating circuit is not affected. Therefore, as described above, based on the display control signal DPC, the input coordinate detection control unit 103 determines the timing at which the video display drive electrode signal of the display unit 102 is switched by tc_r in each detection cycle, or the switch SC in tc. By controlling so as to be within the period of being in the on state, noise from the display portion 102 can be reduced. Thereby, the input coordinate by touch can be detected with high accuracy.

  Next, a capacitance detection circuit used in the coordinate input device according to the third embodiment of the present invention will be described with reference to FIGS. The capacitance detection circuit according to the third embodiment of the present invention uses the adjustment capacitor Ca and the adjustment signal ADJ as the integration voltage in the capacitance detection circuit when there is no electrode offset voltage or touch input in the first and second embodiments. In contrast, the method is controlled by the current source IA. The capacitance detection circuit DCKT is a circuit for detecting the sensor electrode capacitance Cs connected to the input terminal vi and the input capacitance Cf that increases by touching the sensor electrode.

  FIG. 15 is a circuit diagram of a capacitance detection circuit according to the third embodiment of the present invention. The capacitance detection circuit DCKT includes a switch SA for charging the constant voltage VDD to the sensor electrode capacitance Cs, a switch SB for transferring the charged charge, an integration circuit with a reset switch SR, and an integration voltage of the sensor electrode capacitance Cs. An adjustment current source IA for adjusting a value (hereinafter referred to as an electrode offset voltage) and removing it from the output signal vo. The integration circuit includes an integration capacitor Ci and an operational amplifier. The current source IA controls the amount of current according to the timing.

  FIG. 16 is a voltage waveform diagram for explaining the operation of the capacitance detection circuit DCKT according to the third embodiment of the present invention. FIG. 16A shows a case where the input is only the sensor electrode capacitance Cs, and FIG. 16B shows a case where the input capacitance Cf is generated by touch. FIG. 16 is a timing chart for detecting the capacity by charging and discharging the capacity connected to the input terminal vi once. In Tdec_r, which is one charge / discharge cycle, in the period ta_r, the reset switch SR is turned on to reset the integrated voltage of the integration capacitor Ci. Next, in the period tb_r, the switch SA is turned on, so that the capacitor connected to the input terminal vi is charged with the constant voltage VDD. In the next period tc_r, the switch SB is turned on while the switch SA is turned off, so that the charge charged in the capacitor connected to the input terminal vi is transferred to the integrating circuit. Therefore, in the period tc_r, in the case of only the sensor electrode capacitance Cs, the integrated voltage becomes −VDD · Cs / Ci as shown in FIG. The integrated voltage is −VDD · (Cs + Cf) / Ci. During the period so far, the output current of the adjustment current source IA is made sufficiently small so as not to affect the integration voltage of the integration circuit.

  In the period tc_r, the electrode offset voltage due to the sensor electrode capacitance Cs is adjusted. Here, the current source IA generates the constant current ia only for a certain period of time tia. In the case of FIG. 15, since the current ia flows from the integrating circuit to the current source, the integrated voltage increases by ia · tia / Ci. Here, the adjustment current ia and the period tia are set so that the electrode offset voltage VDD · Cs / Ci of the sensor electrode capacitance Cs in FIG. 16A is equal to the adjustment amount ia · tia / Ci by the current source IA. Then, the electrode offset voltage due to the sensor electrode capacitance can be removed from the output voltage vo. After that, the switch SC is turned on within the period td_r. Even if the switch SC is turned on to conduct to the ground (GND), since the negative terminal of the operational amplifier is a virtual ground, no current flows and the integrated voltage does not change. Here, it is assumed that the on-resistance of the switch SC is sufficiently low.

  By the above operation, as shown in FIG. 16A, when the capacitance connected to the input terminal vi is the sensor electrode capacitance Cs, the offset voltage is adjusted and the output signal vo becomes 0V. On the other hand, when the input capacitance Cf is increased by touch, the output signal vo becomes an integrated voltage −VDD · Cf / Ci proportional to the input capacitance Cf, as shown in FIG. Since the electrode offset voltage can be excluded from the output voltage in this way, even if the output voltage signal is amplified before AD conversion, the AD conversion range can be fully used, and the detectable input capacitance can be reduced. The dynamic range can be increased.

  Even in the capacity detection circuit according to the third embodiment of the present invention, although not shown, the capacity detection by charging and discharging a plurality of times is possible as in the first embodiment. Further, the current source IA used for adjusting the electrode offset voltage in the capacitance detection circuit according to the third embodiment of the present invention can also be applied to the capacitance detection circuit according to the second embodiment of the present invention. In this case, the current source IA is applied instead of the adjustment capacitor Cs in FIG. In this case, the adjustment of the electrode offset voltage by the current source IA is performed in the period tc_r or tc in the voltage waveform diagram of FIG. Specifically, in the period tc_r, a period in which the switch SC is in the OFF state is a period tia in which the current source IA generates the current ia. Thereby, after adjusting the electrode offset voltage, the switch SC is turned on to perform the reset operation of the scanning sensor electrode. By the above control, the adjustment of the output voltage vo using the current source IA in the third embodiment of the present invention can be applied to the capacitance detection circuit of the second embodiment.

  The coordinate input device using the capacitance detection circuit according to the third embodiment of the present invention and the display device including the same are the same as those in the first embodiment and the second embodiment described above, and thus the description thereof is omitted. .

  As described above, in the capacitance detection circuit according to the third embodiment of the present invention, since the output voltage when there is no input by touch can be canceled by the current source IA, a minute input capacitance Cf can be detected. In the coordinate input device using this capacitance detection circuit DCKT, it becomes possible to detect the input coordinates with high accuracy.

  Here, the output voltage when there is no input by touch may be determined by the electrode offset voltage or may reflect various characteristics of the operational amplifier and each switch, both of which are the adjustment current ia and the period tier. Can be canceled by setting. In the description of this embodiment, the output voltage when there is no input by touch is assumed to be a negative potential, but when the output voltage when there is no input by touch is a positive potential, the current source IA It is possible to cancel by reversing the current direction.

  In the first to third embodiments of the present invention, the switch is used to adjust the output current amount from the operational amplifier used in the capacitance detection circuit shown in FIG. 1, FIG. 8, or FIG. 15 or the detection circuit DCKT. An adjustment resistor may be inserted between the terminal of the element SC and the negative input terminal of the operational amplifier.

  According to the embodiment of the present invention, only the input capacitance that is increased by touch can be detected as an output signal, so that the dynamic range of the detectable input capacitance is widened and the detection accuracy is improved. In addition, it is possible to add only analog signals related to input capacity by repeating charging and discharging multiple times, so that noise generated at each charging and discharging is averaged and noise components are reduced, and a detection result with a high signal-to-noise ratio is obtained. can get. In addition, since a signal can be increased by increasing the number of times of charging / discharging even with a very small input capacitance, a higher signal-to-noise ratio can be obtained compared with a case where an analog signal is simply amplified by an operational amplifier. Thereby, a highly accurate coordinate detection result can be obtained.

  Furthermore, since noise components from the display device can be removed within the normal charge / discharge cycle, the detection time can be shortened compared to the case where the noise components are simply masked, and high-speed coordinate detection is realized as a coordinate input device. I can do it.

  It is used as an input device that detects a position input by a touch operation as input coordinates.

Cf Input capacitance by touch Cs Capacitance SA switch when there is no touch input, its control signal SB switch, its control signal SC switch, its control signal SR switch, and its control signal Ci integration capacitance Ca adjustment capacitance ADJ For adjustment Signal Tdec_r Charging / discharging cycle Tdec Charging / discharging cycle Tpd Detection cycle when charging / discharging n times TP_X X-coordinate detection sensor electrode TP_Y Y-coordinate detection sensor electrode ADC AD conversion unit DATA Digital output data 101 Coordinate input unit 102 Display unit 103 Input coordinate detection control unit 104 Display device control unit 105 System (CPU)
DPC Display control signal FA Touch input location FB Touch input location DCKT Capacitance detection circuit or detection circuit SCKT Scanning circuit IA Adjustment current source ia Adjustment current

Claims (18)

A capacitance sensor electrode for detecting capacitance, a first switch element for applying a constant potential to the capacitance sensor electrode, and a second switch element for transferring the charge accumulated in the capacitance sensor electrode; An integration circuit for detecting charges transferred from the capacitive sensor electrode via the second switch element, and the voltage source for supplying the constant potential is connected to the capacitive sensor via the first switch element. A capacitive coupling type coordinate input device connected to an electrode, wherein the capacitive sensor electrode is connected to an input terminal of the integrating circuit via the second switch element;
A third switch element and an adjustment capacitor for short-circuiting to a reference level of the integration circuit are connected to an input terminal of the integration circuit, and an adjustment signal is applied to the other terminal of the adjustment capacitor. A coordinate input device. The coordinate input device according to claim 1,
In the first procedure, the first switch element, the second switch element, and the three switch elements are turned off to reset the output signal of the integration circuit,
In the second procedure, the first switch element is turned on, and the constant potential is applied to a capacitor related to the capacitor sensor electrode;
In the third procedure, by turning off the first switch element and turning on the second switch element, the charge accumulated in the capacitor related to the capacitor sensor electrode is transferred to the integrating circuit,
In the fourth procedure, the second switch element is turned off, and the adjustment signal is changed by the adjustment voltage.
In the fifth procedure, the third switch element is turned on, the adjustment signal is reset to the potential before the change,
In the sixth procedure, the third switch element is turned off,
The coordinate input device according to claim 1, wherein the first to sixth procedures are set as a capacitance detection cycle related to the capacitance sensor electrode. The coordinate input device according to claim 1,
The coordinate input device, wherein the adjustment voltage is set so that an output signal of the capacitance detection circuit in a state where there is no input operation with respect to the capacitance sensor electrode is small. The coordinate input device according to claim 2,
When detecting the capacitance relating to the capacitance sensor electrode by repeating the capacitance detection cycle n times (where n is an integer of 2 or more),
At the first time of the capacitance detection cycle, the output signal reset operation of the integration circuit is performed in the first procedure, and after the second time of the capacitance detection cycle, the output signal reset operation of the integration circuit is stopped in the first procedure. Coordinate input device characterized by this. In a display apparatus provided with the coordinate input device of Claim 2,
Provided with a display unit for displaying video by a display control signal output from the display control unit,
The coordinate input device includes:
A coordinate input unit in which a plurality of X electrodes in which the capacitance sensor electrodes are arranged in a horizontal direction and a Y electrode in which a plurality of the capacitance sensor electrodes are arranged in a vertical direction intersect with each other via an insulating layer;
A plurality of capacitance detection circuits for respectively detecting capacitances related to the X electrode and the Y electrode;
An input coordinate detection control unit that generates a control signal for controlling the capacitance detection circuit,
The display device, wherein the coordinate input unit is transparent, the coordinate input unit and the display unit are overlapped, and the touch position coordinates on the display area are detected by capacitance detection. The display device according to claim 5,
The display device characterized in that the control signal of the capacitance detection circuit is generated so that the timing of the potential change of the display electrode of the display device is within the period of the fifth procedure of the capacitance detection cycle. A scanning sensor electrode, a detection sensor electrode arranged to intersect the scanning sensor electrode through an insulating layer, a first switch element for applying a constant potential to the scanning sensor electrode, and a potential of the scanning sensor electrode In a capacitively coupled coordinate input device, comprising: a scanning circuit having a second switch element for resetting a detection circuit; and a detection circuit comprising an integration circuit for detecting a charge flowing through the detection sensor electrode. ,
The input terminal of the integration circuit of the detection circuit is connected to a third switch element and an adjustment capacitor for short-circuiting to the reference level of the integration circuit, and an adjustment signal is connected to the other terminal of the adjustment capacitor. A coordinate input device characterized by being applied. The coordinate input device according to claim 7, wherein
In the first procedure, the first switch element and the third switch element are turned off, the second switch element is turned on, the potential of the scanning sensor electrode is reset, and the output signal of the integrating circuit is reset,
In the second procedure, the second switch element is turned off, the first switch element is turned on, and the constant potential is applied to the capacitance relating to the scan sensor electrode. At this time, the scan sensor electrode and the detection are applied. The integration circuit detects the current flowing through the capacitance near the intersection with the sensor electrode,
In the third procedure, the first switch element is turned off, and then the adjustment signal is changed by the adjustment voltage,
In the fourth procedure, the third switch element is turned on, the adjustment signal is reset to the potential before the change, the second switch element is turned on, the scan sensor electrode is reset,
In the fifth procedure, the second switch element and the third switch element are turned off,
A coordinate input device characterized in that the first procedure to the fifth procedure are set as a capacitance detection cycle in which the capacitance detection circuit detects a capacitance. The coordinate input device according to claim 7, wherein
The coordinate input is characterized in that the adjustment voltage is set so that an output signal of the detection circuit is small when there is no input operation with respect to an input capacitance detection unit composed of the scanning sensor electrode and the detection sensor electrode. apparatus. The coordinate input device according to claim 8, wherein
When detecting the input capacitance input to the input capacitance detection unit by repeating the capacitance detection cycle n times (where n is an integer of 2 or more),
At the first time of the capacitance detection cycle, the output signal of the integration circuit and the scan sensor electrode are reset in the first procedure, and the output of the integration circuit is output in the first procedure after the second capacitance detection cycle. A coordinate input device, wherein the reset operation of the signal and the scanning sensor electrode is stopped. A display device comprising the coordinate input device according to claim 8.
Provided with a display unit for displaying video by a display control signal output from the display control unit,
The coordinate input device includes:
A coordinate input unit in which a plurality of X electrodes in which the detection sensor electrodes are arranged in a horizontal direction and a Y electrode in which a plurality of the scanning sensor electrodes are arranged in a vertical direction intersect with each other via an insulating layer;
A plurality of the detection circuits connected to the X electrode;
A plurality of the scanning circuits connected to the Y electrode;
An input coordinate detection control unit that generates a control signal for controlling the detection circuit and the scanning circuit;
By making the coordinate input unit transparent, the coordinate input unit and the display unit are overlapped, and the touch position coordinates on the display area are detected by capacitance detection. The display device according to claim 11,
Control of the capacitance detection circuit so that the change timing of the display electrode of the display device falls within a period in which the third switch element is in an ON state from the fourth procedure to the fifth procedure of the capacitance detection cycle. A display device characterized by generating a signal. The coordinate input device according to claim 1,
An adjustment current source is connected instead of the adjustment capacitor, and an adjustment current is caused to flow by the adjustment current source instead of applying an adjustment signal to the other terminal of the adjustment capacitor. apparatus. The coordinate input device according to claim 13, wherein in the first step, the first switch element, the second switch element, and the three switch elements are turned off, the output signal of the integration circuit is reset, and the adjustment The current source is controlled so that the output current becomes zero,
In the second procedure, the first switch element is turned on, and the constant potential is applied to a capacitor related to the capacitor sensor electrode;
In the third procedure, by turning off the first switch element and turning on the second switch element, the charge accumulated in the capacitor related to the capacitor sensor electrode is transferred to the integrating circuit,
In the fourth procedure, the second switch element is turned off, and the adjustment current is output from the adjustment current source for a certain period.
In the fifth procedure, the third switch element is turned on,
In the sixth procedure, the third switch element is turned off,
The coordinate input device according to claim 1, wherein the first to sixth procedures are set as a capacitance detection cycle related to the capacitance sensor electrode. The coordinate input device according to claim 13,
The coordinate input device characterized in that the adjustment current is set so that an output signal of the capacitance detection circuit in a state where there is no input operation to the capacitance sensor electrode is small. The coordinate input device according to claim 7, wherein
An adjustment current source is connected instead of the adjustment capacitor, and an adjustment current is caused to flow by the adjustment current source instead of applying an adjustment signal to the other terminal of the adjustment capacitor. apparatus. The coordinate input device according to claim 16, wherein
In the first procedure, the first switch element and the third switch element are turned off, the second switch element is turned on to reset the potential of the scanning sensor electrode, and the output signal of the integration circuit is reset.
In the second procedure, the second switch element is turned off, the first switch element is turned on, and the constant potential is applied to the capacitance relating to the scan sensor electrode. At this time, the scan sensor electrode and the detection are applied. The integration circuit detects the current flowing through the capacitance near the intersection with the sensor electrode,
In the third procedure, the first switch element is turned off, and then the adjustment current is output from the adjustment current source for a certain period,
In the fourth procedure, the third switch element is turned on, the adjustment signal is reset to the potential before the change, the second switch element is turned on, the scan sensor electrode is reset,
In the fifth procedure, the second switch element and the third switch element are turned off,
A coordinate input device characterized in that the first procedure to the fifth procedure are set as a capacitance detection cycle in which the capacitance detection circuit detects a capacitance. The coordinate input device according to claim 16, wherein
The coordinate input device characterized in that the adjustment current is set so that an output signal of the capacitance detection circuit in a state where there is no input operation to the capacitance sensor electrode is small.

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