Patent Publication Number: US-9838527-B2

Title: Control circuit of electrostatic capacitive sensor and electronic device using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a continuation application of U.S. patent application Ser. No. 13/839,844, filed on Mar. 15, 2013, the entire contents of which are incorporated herein by reference. The Ser. No. 13/839,844 application claimed the benefit of the date of the earlier filed Japanese Patent Application No. JP 2012-062291, filed on Mar. 19, 2012, priority to which is also claimed herein, and the contents of which are also incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a mutual capacitance type touch panel. 
     BACKGROUND 
     In recent years, electronic equipment such as computers, mobile phones, tablet PCs (personal computers), PDAs (personal digital assistants) and so on have become mainstream and now also include touch panels as input devices for manipulating the electronic equipment through the touch of a finger. Mutual capacitance type touch panels are developed for these types of devices. 
     A mobile phone ceases to detect whether or not a touch panel is touched when a user puts his/her ear to the mobile phone for calling. In this case, the contact of his/or her head to the touch panel of the mobile phone will not be detected as the action of touching the touch panel. In addition, when the user puts his/her ear to the mobile phone for calling, a display of the mobile phone is turned off in order to save power. Such type of a mobile phone has an optical proximity sensor disposed at a position corresponding to the head of the user when calling. The proximity sensor includes a pair of a light emitting device and a light receiving device. The light receiving device detects light emitted from the light emitting device and reflected by a detection target such as a user&#39;s head. 
     However, the use of the optical proximity sensors increases the number of components and production costs of the mobile phone. In addition, a light passage needs to be provided in the housing of the mobile phone, which restricts the design of the mobile phone. 
     SUMMARY 
     The present disclosure provides some embodiments of a mutual capacitance type electrostatic capacitive sensor which can be also used as a proximity sensor. 
     According to one aspect of the present disclosure, there is provided a control circuit of an electrostatic capacitive sensor including a plurality of transmitter electrodes disposed in parallel in a first direction and a plurality of receiver electrodes disposed in parallel in a second direction and spaced apart from the plurality of transmitter electrodes by specific intervals. The control circuit includes: a transmitter circuit configured to apply a periodical transmission signal to each of the plurality of transmitter electrodes; and a receiver circuit configured to generate, based on a reception signal generated in each of the plurality of receiver electrodes in response to the transmission signal, a detection signal indicating a change in electrostatic capacitance formed at each of intersections of the plurality of transmitter electrodes and the plurality of receiver electrodes. The transmitter circuit is configured to switch between a first mode where the transmission signal is sequentially applied to the plurality of transmitter electrodes and a second mode where the plurality of transmitter electrodes is grouped and the same transmission signal is applied to a plurality of transmitter electrodes belonging to the same group. 
     In the second mode, the plurality of transmitter electrodes belonging to the same group acts as a single electrode having a large area. As a result, detection sensitivity of the change in capacitance can be increased and accordingly it is possible to detect a condition where a detection target is in proximity to the panel and not directly contacting to the panel. 
     In some embodiments, the transmitter circuit may be set to the first mode when the electrostatic capacitive sensor is operated as a touch panel and may be set to the second mode when the electrostatic capacitive sensor is operated as a proximity sensor. 
     In some embodiments, the transmitter circuit may be configured such that the number of groups can be changed in the second mode. In other words, the number of electrodes belonging to the same group may be changed. Thus, it is possible to change sensitivity and a spatial resolution in the first direction which are in a trade-off relationship gradually. 
     In some embodiments, the control circuit may further include a controller configured to control an operation mode of the transmitter circuit. The controller may switch between a first condition where the transmitter circuit is fixedly set to the first mode and a second condition where the transmitter circuit is set to alternate between the first mode and the second mode in a time-divisional manner. Before the user contacts the panel, both of proximity and touch can be monitored by setting the transmitter circuit to the second condition. After the touch is detected, a touched coordinate can be detected with a spatial resolution by setting the transmitter circuit to the first condition. 
     In some embodiments, the receiver circuit may be configured to switch between a first mode where the reception signal generated in each of the plurality of receiver electrodes is sequentially monitored to generate the detection signal for each of the receiver electrodes and a second mode where the plurality of receiver electrodes are grouped and a plurality of receiver electrodes belonging to the same group is connected in common to generate the detection signal for each group. In the second mode, the plurality of receiver electrodes belonging to the same group acts as a single electrode having a large area. As a result, detection sensitivity of the change in capacitance can be increased and accordingly it is possible to detect a condition where a detection target is in proximity to the panel and not directly contacting to the panel. Further, a combination of the mode of the receiver circuit and the mode of the transmitter circuit can change the detection sensitivity and the spatial resolution. 
     In some embodiments, the receiver circuit may be configured such that the number of groups can be changed in the second mode. In other words, the number of electrodes belonging to the same group may be changed. Thus, it is possible to change sensitivity and a spatial resolution in the second direction which are in a trade-off relationship gradually. 
     In some embodiments, the control circuit may further include a controller configured to control operation modes of the transmitter circuit and the receiver circuit. The controller may switch between a first condition where the transmitter circuit and the receiver circuit are fixedly set to the first mode and a second condition where the transmitter circuit and the receiver circuit are set to alternate between the first mode and the second mode in a time-divisional manner. 
     According to another aspect of the present disclosure, there is provided a control circuit of an electrostatic capacitive sensor including: a transmitter circuit configured to apply a periodical transmission signal to each of a plurality of transmitter electrodes; and a receiver circuit configured to generate, based on a reception signal generated in each of the plurality of receiver electrodes in response to the transmission signal, a detection signal indicating a change in electrostatic capacitance formed at each of intersections of the plurality of transmitter electrodes and a plurality of receiver electrodes. The receiver circuit is configured to switch between a first mode where the reception signal generated in each of the plurality of receiver electrodes is sequentially monitored to generate the detection signal for each of the receiver electrodes and a second mode where the plurality of receiver electrodes are grouped and a plurality of receiver electrodes belonging to the same group is connected in common to generate the detection signal for each group. 
     In the second mode, the plurality of receiver electrodes belonging to the same group acts as a single electrode having a large area. As a result, detection sensitivity of the change in capacitance can be increased and accordingly it is possible to detect a condition where a detection target is in proximity to the panel and not directly contacting to the panel. 
     In some embodiments, the receiver circuit may be set to the first mode when the electrostatic capacitive sensor is operated as a touch panel and may be set to the second mode when the electrostatic capacitive sensor is operated as a proximity sensor. 
     In some embodiments, the receiver circuit may be configured such that the number of groups can be changed in the second mode. 
     In some embodiments, the control circuit may further include a controller configured to control an operation mode of the receiver circuit. The controller may switch between a first condition where the receiver circuit is fixedly set to the first mode and a second condition where the receiver circuit is set to alternate between the first mode and the second mode in a time-divisional manner. 
     According to another aspect of the present disclosure, there is provided an electronic equipment including: a housing; a display panel disposed on one surface of the housing; an electrostatic capacitive sensor disposed at an overlapping portion of the housing with the display panel, the electrostatic capacitive sensor including a plurality of transmitter electrodes disposed in parallel in a first direction and a plurality of receiver electrodes disposed in parallel in a second direction and spaced apart from the plurality of transmitter electrodes by specific intervals; the control circuit according to the above aspects, which is disposed within the housing and detects a change in capacitance of the electrostatic capacitive sensor; and a processor configured to receive a digital value corresponding to the detection signal generated by the receiver circuit of the control circuit and detects a manipulation status of the electronic equipment by a user based on the digital value. 
     In some embodiments, the electronic equipment may be a mobile terminal and the electronic equipment may further include a speaker disposed at a position close to a user&#39; ear when calling. The processor may refer to the digital value obtained in the second mode and determine that the user approaches the housing to the user&#39; head for calling if a change in capacitance formed by the transmitter and the receiver electrodes disposed in the vicinity of the speaker increases. Accordingly, it is possible to detect proximity of a user&#39;s head by using the electrostatic capacitive sensor for use in a touch panel, without using an optical proximity sensor. 
     In some embodiments, the processor may refer to the digital value obtained in the second mode and determine that a user grips the housing if a change in capacitance of the transmitter and the receiver electrodes disposed at one end of the housing to which the user&#39; thumb approaches when the housing is gripped by the user and the transmitter and the receiver electrodes disposed at the other end of the housing to which the other fingers approach increase. 
     Other aspects of the present disclosures may include any combinations of the above-described elements or conversion of expression of the present disclosure between methods, apparatuses and so on. 
     According to the aspects of the present disclosure, a mutual capacitance type electrostatic capacitive sensor can be used as a proximity sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram showing a configuration of electronic equipment including a touch panel input device according to a first embodiment. 
         FIG. 2  is a circuit diagram showing a configuration of the input device having a control circuit according to the first embodiment. 
         FIGS. 3A and 3B  are operation waveform diagrams of a transmitter circuit in a first mode and a second mode, respectively. 
         FIGS. 4A to 4C  are operation waveform diagrams of a transmitter circuit where the number of groups is 1 to 3, respectively. 
         FIGS. 5A to 5C  are circuit diagrams showing example configurations of the transmitter circuit of  FIG. 2 . 
         FIGS. 6A to 6C  are views showing usage of an input device in each mode. 
         FIGS. 7A and 7B  are operation waveform diagrams in first and second conditions, respectively. 
         FIGS. 8A and 8B  are circuit diagrams showing example configurations of receiver circuits of a control circuit according to a second embodiment. 
         FIG. 9  is a perspective view showing a mobile terminal as one example of electronic equipment having a control circuit. 
         FIG. 10A  is a view showing a side head proximity condition and  FIG. 10B  is a view showing an output of a capacitive sensor unit under the side head proximity condition. 
         FIGS. 11A to 11C  are views for explaining the side head proximity condition. 
         FIGS. 12A to 12C  are views for explaining a condition where a user touches the vicinity of a calling speaker of a capacitive sensor unit. 
         FIG. 13A  is a view showing a grip condition and  FIG. 13B  is a view showing an output of a capacitive sensor unit under the grip condition. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure will now be described in detail with reference to the drawings. Throughout the drawings, the same or similar elements, members and processes are denoted by the same reference numerals, and explanations of which will not be repeated. The embodiments will be presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, all the features and configurations of the embodiments are not essential to the present disclosure. 
     Throughout the description, “a state where a member A and a member B is coupled” may include not only a state where the member A and the member B is physically directly connected but also a state where the member A and the member B is indirectly coupled via another member, unless the another member substantially affects the electrical connection state between the members A and B or damages main functions or effects of the connection between the members A and B. 
     Similarly, “a state where a member C is provided between a member A and a member B” may include not only a state where the member C is physically directly connected to the member A or the member B but also a state where the member C is indirectly connected to the member A or the member B via another member, unless the another member substantially affects the electrical connection state between the members A and C or between the members B and C or damages main functions or effects of the connection between the members A and C or between the member B and C. 
     First Embodiment 
       FIG. 1  is a circuit diagram showing a configuration of electronic equipment  1  including a touch panel input device  2  (simply referred to as an “input device  2 ”) according to a first embodiment. The input device  2  is disposed on a surface of an LCD (liquid crystal display)  8 , for example, and acts as a touch panel. The input device  2  determines X and Y coordinates of a point touched by a user&#39;s finger, a pen or the like (hereinafter representatively referred to as a “detection target  6 ”). 
     The input device  2  includes an electrostatic capacitive sensor  4 , a control circuit (capacitance detecting circuit)  100  and a processor  3 . The electrostatic capacitive sensor  4  is a mutual capacitance type touch panel in a matrix form. More specifically, the electrostatic capacitive sensor  4  includes M number of transmitter electrodes  10   [1˜M]  (M is an integer of 2 or more) disposed in parallel in a first direction in columns of the matrix and N number of receiver electrodes  12   [1˜N]  (N is an integer of 2 or more) disposed in parallel in a second direction in rows of the matrix. The allocation of the transmitter electrodes  10  and the receiver electrodes  12  at the rows and the columns may be in reverse. The transmitter electrodes  10  and the receiver electrodes  12  are arranged to be spaced apart from each other in the vertical direction. The transmitter electrodes  10  and the receiver electrodes  12  are capacitively coupled to each other at each of intersections of the transmitter electrodes  10  and the receiver electrodes  12 . More specifically, a pair of one transmitter electrode  10  and one receiver electrode  12  forms a capacitive sensor unit  5  at the intersection thereof. That is, the electrostatic capacitive sensor  4  includes a plurality of capacitive sensor units  5  arranged in a matrix form. For convenience of explanation, a capacitive sensor disposed at the i-th row and the j-th column (i and j are integers) will be denoted by a capacitive sensor unit  5   [i,j] . When an object such as a finger, a pen or the like is touched to or approaches the capacitive sensor unit  5   [i,j] , a mutual capacitance C M[i, j]  of the capacitive sensor unit  5   [i, j]  is changed. 
     The control circuit  100  detects changes in mutual capacitances C M  of the capacitive sensor units  5  having different coordinates in the capacitive sensor unit  4 . More specifically, the control circuit  100  cyclically and sequentially applies transmission signals to the plurality of transmitter electrodes  10  and selects a transmitter electrode  10  on which a capacitance detection is to be performed. Then, the control circuit  100  detects a change in electrostatic capacitance of the capacitive sensor unit  5  formed between the selected transmitter electrode  10  and each of the plurality of receiver electrodes  12 . The selected transmitter electrode  10  corresponds to a column coordinate and a receiver electrode  12  which has undergone a change in capacitance corresponds to a row coordinate. Data representing the change in capacitance is transmitted to the processor  3 . The processor  3  determines a coordinate touched by a user based on the change in capacitance of each coordinate. 
     The electronic equipment  1  has been outlined in the above. Below, the control circuit  100  according to the first embodiment will be now described in more details. 
       FIG. 2  is a circuit diagram showing a configuration of the input device  2  having the control circuit  100  according to the first embodiment. Only a portion relating to one transmitter electrode  10   [i]  is shown in  FIG. 2 . 
     The transmitter electrode  10   [i]  is capacitively coupled to a plurality of receiver electrodes  12   [1]  to  12   [N]  and forms capacitive sensor units  5   [i, 1]  to  5   [i, N]  having mutual capacitances C M  with the receiver electrodes  12   [1]  to  12   [N] , respectively. Reference symbol Rs denotes resistances of the transmitter electrode  10  and the receiver electrodes  12 , and reference symbol Cs denotes capacitances thereof. Though not shown in  FIG. 2 , the capacitive sensor units  5  may also be formed between other transmitter electrodes  10  and the receiver electrodes  12   [1]  to  12   [N]  in a similar manner as shown in  FIG. 2 . 
     The control circuit  100  includes a transmitter circuit  20 , a receiver circuit  26  and a controller  50 . 
     The control circuit  100  also has transmitter (TX) terminals TX [1 to M]  and receiver (RX) terminals RX [1 to N]  formed for the respective receiver electrodes  12 . TX terminal TX [i]  of the control circuit  100  is connected to a corresponding transmitter electrode  10   [i]  and RX terminal RX [j]  of the control circuit  100  is connected to a corresponding receiver electrode  12   [j] . 
     The transmitter circuit  20  generates a periodical transmission signal S 1  and applies it to the transmitter electrodes  10   [1 to M] . The transmitter circuit  20  has a signal generator  22  and a driver  24  provided for each transmitter electrode  10 . The signal generator  22  generates a periodical clock signal. The driver  24  receives this clock signal and outputs a transmission signal S 1  in synchronization with the clock signal to the transmitter electrode  10 . The transmission signal S 1  is a periodical signal which alternates between a first voltage level (for example, a power source voltage V dd ) and a second voltage level (for example, a ground voltage Vss). 
     When the electrostatic capacitive sensor  4  is used as a touch panel, the transmitter circuit  20  selects (or scans) a plurality of transmitter electrodes  10   [1 to M]  in a time-divisional manner and applies the transmission signal S 1  to a selected transmitter electrode  10  while a fixed voltage level (for example, the ground voltage Vss) is applied to the remaining transmitter electrodes  10 . 
     The receiver circuit  26  generates, based on a reception signal I RX  generated in each of the plurality of receiver electrodes  12   [1 to N]  in response to the transmission signal S 1 , detection signals Vs indicating changes in mutual capacitances C M[1, 1]  to C M[M, N]  of a plurality of capacitive sensor units  5  formed at intersections of the plurality of transmitter electrodes  10   [1 to M]  and the plurality of receiver electrodes  12   [1 to N] . 
     The receiver circuit  26  includes an integration circuit  30 , a sample hold circuit  40 , an amplifier  42  and an A/D converter  44 . Some or all parts of the receiver circuit  26  may be provided for each of the receiver electrodes  12 . Some or all parts of the receiver circuit  26  may be provided every several receiver electrodes  12  and shared by the several receiver electrodes  12  in a time-divisional manner. 
     An integration circuit  30  allocated to a j-th receiver electrode  12   [j]  detects changes in mutual capacitances C M[1, j]  to C M[M, j]  of the capacitive sensor units  5   [1, j]  to  5   [M, j]  formed by the receiver electrode  12   [j]  and generates a detection signal Vs having a level according to the changes in capacitances based on a reception signal I RX[j] . Specifically, the reception signal I RX  is a current signal and the detection single Vs is a voltage signal, and the integration circuit  30  integrates the current I RX  and generates the detection voltage Vs according to the changes in capacitances. The integration circuit  30  may employ a well-known circuit or a circuit which will be described later, without being particularly limited in its configuration and type. 
     The sample hold circuit  40  samples and holds the detection voltage Vs generated from the integration circuit  30 . The amplifier  42  amplifies the sampled and held detection voltage Vs when necessary. The A/D converter  44  converts the amplified detection voltage Vs into a digital value Ds indicating a change in capacitance of each capacitive sensor unit  5 . 
     The controller  50  controls an operation sequence of the transmitter circuit  20  and the receiver circuit  26 . In addition, the controller  50  controls an operation mode of the transmitter circuit  20 , which will be described later. 
     In the first embodiment, the transmitter circuit  20  is configured to switch between a first mode and a second mode. In the first mode, the transmitter circuit  20  sequentially applies the transmission signal S 1  to the plurality of transmitter electrodes  10   [1 to M] . In the second mode, the transmitter circuit  20  virtually classifies the plurality of transmitter electrodes  10   [1 to M]  into at least one group and simultaneously applies the same transmission signal S 1  to a plurality of transmitter electrodes  10  belonging to the same group. 
       FIGS. 3A and 3B  are operation waveform diagrams of the transmitter circuit  20  in the first mode and the second mode, respectively. As shown in  FIG. 3A , in the first mode, the plurality of transmitter electrodes  10   [1 to M]  is sequentially scanned and the transmission signal S 1  is applied to a selected transmitter electrode in a time-divisional manner. In the second mode of  FIG. 3B , the plurality of transmitter electrodes  10   [1 to M]  belongs to a single group and the common transmission signal S 1  is applied to all of the transmitter electrodes  10   [1 to M] . 
     In the second mode, the number of groups of transmitter electrodes may be one or more. In some embodiments, the number of groups, in other words, the number of transmitter electrodes  10  belonging to a single group may be changed. 
       FIGS. 4A to 4C  are operation waveform diagrams of M number of the transmitter circuit  20  where the number of groups is 1 to 3, respectively. In  FIG. 4A , a single group G 1  is formed and the same transmission signal S 1  is simultaneously applied to all transmitter electrodes  10   [1 to M]  belonging to the group G 1 . In  FIG. 4B , two groups G 1  and G 2  are formed and are sequentially scanned. During a period of time when the group G 1  is selected, the transmission signal S 1  is applied to the transmitter electrodes  10   [1 to 6]  belonging to the group G 1 . During a period of time when the group G 2  is selected, the transmission signal S 1  is applied to the transmitter electrodes  10   [7 to 12]  belonging to the group G 2 .  FIG. 4C  shows a case where three groups are formed. It is also to be understood that four and six groups may be formed without departing from the spirit and scope of the present disclosure. 
       FIGS. 5A to 5C  are circuit diagrams showing configurations of the transmitter circuit  20  of  FIG. 2 . Each of transmitter circuits  20   a  and  20   b  of  FIGS. 5A and 5B , respectively, includes drivers  24   [1 to M]  provided for the respective transmitter electrodes  10   [1 to M] , a signal generator  22 , a demultiplexer  23  and a decoder  25 . The signal generator  22  generates a periodical signal (clock signal) to be applied to the transmitter electrodes  10  in each mode. The demultiplexer  23  receives the periodical signal from the signal generator  22  and distributes it to several selected ones of the drivers  24   [1 to M] . In the first mode for example, the demultiplexer  23  sequentially selects one of the plurality of drivers  24   [1 to M]  and outputs the periodical signal to the selected one of the drivers  24   [1 to M] . 
     The demultiplexer  23  of  FIG. 5A  includes a plurality of selectors SEL [1]  to SEL [M] . If a control signal CNT for an i-th selector SEL [i] , is “1”, an output of the selector SEL [i]  corresponds to the periodical signal from the signal generator  22 , which results in a state where the corresponding transmitter electrode  10   [i]  is selected. On the contrary, if the control signal CNT for the i-th selector SEL [i]  is “0”, an output of the selector SEL [i]  corresponds to zero, which results in a state where the corresponding transmitter electrode  10   [i]  is not selected. The decoder  25  generates different control signals CNT depending on the mode and the number of groups. 
     The demultiplexer  23  of  FIG. 5B  includes logic gates (AND gates) instead of the selectors SEL of  FIG. 5A . If a control signal CNT for an i-th AND gate AND [i]  is “1”, an output of the AND gate AND [i]  corresponds to the periodical signal from the signal generator  22 , which results in a state where the corresponding transmitter electrode  10   [i]  is selected. On the contrary, if the control signal CNT for the i-th AND gate AND [i]  is “0”, an output of the AND gate AND [i]  corresponds to zero, which results in a state where the corresponding transmitter electrode  10   [i]  is not selected. The AND gates may be replaced with OR gates, in which case the logic of the control signal may be inverted. 
     A transmitter circuit  20   c  of  FIG. 5C  includes a plurality of drivers  24   [1 to M]  and a signal generator  22   c . The signal generator  22   c  outputs a periodical signal to the plurality of drivers  24   [1 to M]  depending on the mode and the number of groups. 
     The configuration of the control circuit  100  has been described in the above. Subsequently, an operation thereof will be described for each mode. 
     &lt;First Mode&gt; 
     In the first mode, the plurality of transmitter electrodes  10   [1 to M]  is sequentially scanned. Accordingly, a spatial resolution for a first direction in which the transmitter electrode  10   [1 to M]  are arranged is maximized so that the electrostatic capacitive sensor  4  can be used as a typical touch panel sensor. 
     &lt;Second Mode&gt; 
     In the second mode, the plurality of transmitter electrodes  10   [1 to M]  is grouped. For example, if all of the transmitter electrodes  10   [1 to M]  are grouped in a single group, an apparent area of the transmitter electrodes  10  becomes substantially M times as large as that of the first mode. As a result, sensitivity can be greatly improved although the spatial resolution for the first direction may be lost. This allows for detection of a detection target such as a finger, a head, a stylus or the like in proximity to the panel and not contacting the panel. 
     In this manner, when the control circuit  100  according to this embodiment is set to the second mode, the electrostatic capacitive sensor  4  can be operated as a proximity sensor. 
     In addition, by changing the number of groups in the second mode, that is, the number of transmitter electrodes  10  to be simultaneously selected, it is possible to control the spatial resolution and the detection sensitivity which are in a trade-off relationship. 
       FIGS. 6A to 6C  are views showing usage of the input device  2  in each mode. In each of  FIGS. 6A to 6C , a detectable range RNG of the detection target  6  such as a user&#39;s finger is shown.  FIG. 6A  shows a case of the minimum number of groups in the second mode. In this case, the detectable range RNG is maximized so that the electrostatic capacitive sensor  4  can be used as a proximity sensor. 
       FIG. 6B  shows a case when the number of groups is increased in the second mode. In this case, the detectable range RNG is decreased. Accordingly, a coordinate of the detection target  6  can be detected with a rough precision when it becomes closer to the electrostatic capacitive sensor  4  than in the case shown in  FIG. 6A , although the coordinate can be detected while the detection target  6  does not contact with the electrostatic capacitive sensor  4 . This usage is suitable for detection of a user&#39;s input manipulation at a position distant from the panel, which is called “hovering.” 
     In addition, in the second mode, the increase in the number of groups helps to manipulation of the electronic equipment  1  by a gloved user. A gloved condition provides less change in mutual capacitances than an ungloved condition. On the other hand, the gloved condition requires no high spatial resolution. Accordingly, in this gloved condition, a comfortable input manipulation is enabled by appropriately setting the number of groups in the second mode.  FIG. 6C  shows a case where the number of groups is increased and the detectable range RNG is decreased than the case shown in  FIG. 6B   
     The following description is given to mode control. The controller  50  controls an operation mode of the transmitter circuit  20 . When the transmitter circuit  20  is set to the second mode and the input device  2  acts as a proximity sensor, the input device  2  cannot act as a typical touch sensor due to a low spatial resolution for the first direction. In this case, the controller  50  may switch the operation status of the transmitter circuit  20  between (i) a first condition where the transmitter circuit  20  is fixedly set to the first mode and (ii) a second condition where the transmitter circuit  20  is set to alternate between the first mode and the second mode in a time-divisional manner. 
       FIGS. 7A and 7B  are operation waveform diagrams in the first and second conditions, respectively. In many cases, the input device  2  is not required to function as a proximity sensor during user&#39;s input manipulation by touch. In these cases, by setting the transmitter circuit  20  to the first condition, a touch input coordinate by a user is detected with the maximum spatial resolution. In  FIGS. 7A and 7B , “A” denotes a period of time during which one frame is scanned in the first mode and “B” denotes a period of time during which one frame is scanned in the second mode. As shown in  FIG. 7A , in the first condition, in order to detect a minute touch input at a high speed, a repetition period Tp is set to be short and a temporal resolution is set to be high. For example, Tp may be set to 10 ms or so. 
     On the other hand, if there is no touch input, the transmitter circuit  20  is set to the second mode and alternates between the first mode and the second mode in a time-divisional manner, so that the input device  2  can detect touch input while monitoring proximity of the detection target to the panel. i.e., acting as a proximity sensor. This can provide the same manipulation feeling as the case where a conventional touch sensor and an optical proximity sensor are used in combination. In addition, as shown in  FIG. 7B , a repetition period Tp in the second condition may be set to be longer than that in the first condition. For example, the repetition period Tp in the second mode may be set to 100 ms or so. This can prevent power consumption in the second condition from being increased. When the touch input is detected in the second condition, the transmitter circuit  20  immediately makes a transition to the first condition to detect a subsequent touch input at a high speed. 
     Second Embodiment 
     In the first embodiment, the transmitter circuit  20  has been configured to switch between modes. On the contrary, in the second embodiment, the receiver circuit  26  is configured to switch between modes for control of sensitivity. In the following description, portions common to the first and second embodiments are incorporated by reference and explanation of which is not repeated. 
     The receiver circuit  26  is configured to switch between a first mode and a second mode. In the first mode, the receiver circuit  26  monitors reception signals I RX[1]  to I RX[N]  generated in a plurality of receiver electrodes  12   [1 to N] , respectively, and generates a detection signal Vs for each of the receiver electrodes  12 . 
     In the second mode, the receiver circuit  26  groups the plurality of receiver electrodes  12   [1-N] , connects the receiver electrodes  12  belonging to the same group in common, and generates a detection signal for each group. In addition, the receiver circuit  26  may be configured to change the number of groups in the second mode. In other words, the number of receiver electrodes  12  connected in common may be changed. 
     The controller  50  may switch the operation status of the receiver circuit  26  between a first condition where the receiver circuit  26  is fixedly set to the first mode and a second condition where the receiver circuit  26  is set to alternate between the first mode and the second mode in a time-divisional manner. The switching operation is the same as that in the first embodiment. 
       FIGS. 8A and 8B  are circuit diagrams showing example configurations of the receiver circuits  26  of the control circuit  100  according to the second embodiment. A receiver circuit  26   a  of  FIG. 8A  includes integration circuits  30   [1 to N]  provided for the respective receiver electrodes  12   [1 to N] , a plurality of first analog switches SW 1   [1 to N] , a plurality of second analog switches SW 2   [1 to N-1]  and a decoder  27   a.    
     A j-th first analog switch SW 1   [j]  is interposed between a corresponding receiver (RX) terminal RX [j]  and an input terminal of a corresponding integration circuit  30   [j] . A j-th second analog switch SW 2   [j]  is interposed between the input terminal of the corresponding integration circuit  30   [j]  and an adjacent integration circuit  30   [j+1] . A decoder  27   a  controls the analog switches SW 1  and SW 2  depending on the mode. Specifically, in the first mode, all of the first analog switches SW 1   [1 to N]  are switched on and all of the second analog switches SW 2   [1 to N]  are switched off. 
     In the second mode, one integration circuit  30  is allocated for each group. When an integration circuit  30   [j]  is allocated to a group, the switches SW 1  and SW 2  interposed between all receiver electrodes  12  and the integration circuit  30   [j]  are switched on. 
     In a receiver circuit  26   b  of  FIG. 8B , the plurality of receiver electrodes  12   [1˜N]  shares the less number of integration circuits  30 . The number of integration circuits  30  may be one, two or four. A j-th third analog switch SW 3   [j]  is interposed between the corresponding RX terminal RX [j]  and an input terminal of a corresponding integration circuit  30 . A decoder  27   b  controls the third analog switches SW 3   [1 to N] . 
     In the first mode, N number of third analog switches SW 3   [1 to N]  are sequentially switched on. In the second mode, if the number of groups is one, all of the N number of third analog switches SW 3   [1 to N]  are switched on simultaneously. In the second mode, if the number of groups is two or more, these groups are processed in a time-divisional manner. During a period of time when a j-th group is processed, the third analog switches SW 3  interposed between the plurality of receiver electrodes  12  belonging to the j-th group and the integration circuit  30  belonging to the j-th group is switched on. 
     The configuration of the control circuit  100  according to the second embodiment has been described in the above. The following description is given to an operation of the control circuit  100  for each mode. 
     &lt;First Mode&gt; 
     In the first mode, reception signals I RX[1 to N]  generated by the plurality of receiver electrodes  12   [1 to N]  are individually integrated to generate detection voltages Vs [1 to N] . Accordingly, a spatial resolution for the second direction in which the receiver electrodes  12   [1 to N]  are arranged is maximized so that the electrostatic capacitive sensor  4  can be used as a typical touch panel sensor. 
     &lt;Second Mode&gt; 
     In the second mode, the plurality of receiver electrodes  12   [1 to N]  is grouped. For example, if all of the receiver electrodes  12   [1 to N]  are grouped in a single group, the apparent area of the receiver electrodes  12  becomes substantially N times as large as that of the first mode. As a result, sensitivity can be greatly improved although the spatial resolution for the second direction may be lost. This allows for detection of a detection target such as a finger, a head, a stylus or the like in proximity to the panel and not contacting the panel. 
     In this manner, when the control circuit  100  according to this embodiment is set to the second mode, the electrostatic capacitive sensor  4  can be operated as a proximity sensor. 
     In addition, by changing the number of groups in the second mode, that is, the number of receiver electrodes  12  connected in common, it is possible to control the spatial resolution and the detection sensitivity which are in a trade-off relationship. 
     Third Embodiment 
     A third embodiment is a combination of the first and second embodiments, in which the transmitter circuit  20  and the receiver circuit  26  are independently configured to switch between the first mode and the second mode. 
     When both of the transmitter circuit  20  and the receiver circuit  26  are set to the first mode, the resolutions for the first and second directions are maximized so that the electrostatic capacitive sensor  4  can be used as a typical touch panel sensor. When the transmitter circuit  20  and the receiver circuit  26  are set to the first mode and the second mode, respectively, sensitivity can be improved with a high resolution for the first direction. When the transmitter circuit  20  and the receiver circuit  26  are set to the second mode and the first mode, respectively, sensitivity can be improved with a high resolution for the second direction. When both of the transmitter circuit  20  and the receiver circuit  26  are set to the second mode, sensitivity can be further improved. 
     According to the third embodiment, by controlling a combination of the modes of the transmitter circuit  20  and the receiver circuit  26 , it is possible to control the sensitivity and the spatial resolution more flexibly than the first and second embodiments. 
     The control circuit  100  according to the first to third embodiments has been described in the above. The following description is given to usage of the control circuit  100 . 
       FIG. 9  is a perspective view showing a mobile phone  700  as one example of the electronic equipment  1  having the control circuit  100 . The mobile phone  700  includes a housing  702 , a speaker  704 , a microphone  706 , a protective glass  708 , manipulation buttons  710 , the electrostatic capacitive sensor  4  and the control circuit  100 . The speaker  704  outputs a voice of a called party in calling. The microphone  706  collects voice of a user of the mobile phone  700  in calling. The electrostatic capacitive sensor  4  is disposed on the top side of a display panel (not shown), and the surface of the electrostatic capacitive sensor  4  is covered by the protective glass  708 . The manipulation buttons  710  serve as an input device to allow a user to operate the mobile phone  700 . The control circuit  100  is connected with transmitter electrodes  10  and the receiver electrodes  12  via wires (not shown). In  FIG. 9 , the transmitter electrodes  10  extend in parallel to a short side of the housing  702  (that is, in an x-axis direction) and the receiver electrodes  12  extend in parallel to a long side thereof (that is, a y-axis direction). This arrangement of the transmitter electrodes  10  and the receiver electrodes  12  may be interchangeable. 
     The configuration of the mobile phone  700  has been described in the above. The mobile phone  700  eliminates a need of a dedicated proximity sensor using a light emitting device or the like, because the electrostatic capacitive sensor  4  can be operated as both a touch panel and a proximity sensor through mode switching. Accordingly, production costs of the mobile phone  700  can be reduced and the housing  702  of the mobile phone  700  can be flexibly designed without being restricted by a proximity sensor. 
     Subsequently, unique characteristics of proximity detection of the mobile phone  700  or similar electronic equipment will be described. 
     &lt;Side Head Proximity Detection&gt; 
     Although the electrostatic capacitive sensor  4  can be used as a proximity sensor in the input device  2  according to the above described embodiments, the mobile phone  700  shown in  FIG. 9  requires a function of detecting proximity of the housing  702  to a side head of a user. In this case, there is a need to distinguish a condition where a user puts the housing  702  in proximity to the side head (hereinafter referred to as a “side head proximity condition”) from other conditions such as a condition where a user covers the input device  2  with hands at the vicinity of the surface of the protective glass  708  or a condition where the user grips the housing  702 . A technique for detecting the side head proximity condition will be described below. 
       FIG. 10A  is a view showing a side head proximity condition and  FIG. 10B  is a view showing an output of the electrostatic capacitive sensor  4  under the side head proximity condition. As shown in  FIG. 10A , in the side head proximity condition during a calling, the speaker  704  approaches a user&#39; ear. Accordingly, as shown in  FIG. 10B , a change in capacitance at the vicinity of the speaker  704  increases and a change in capacitance in the side of the microphone  706  decreases. 
     Thus, when detecting the side head proximity condition, at least one of the transmitter circuits  20  and the receiver circuit  26  of the control circuit  100  is set to the second mode so that it can have a spatial resolution in the long side direction (y-axis direction) of the housing  702 . In the example of  FIG. 10B , the receiver circuit  26  is set to the second mode and all of the receiver electrodes  12  are grouped into the same group. On the other hand, the transmitter circuit  20  is set to the first mode so that it can have a spatial resolution in the y-axis direction. 
     If the transmitter electrodes  10  and the receiver electrodes  12  are arranged in reverse, the transmitter circuit  20  and the receiver circuit  26  may be set to the second mode and the first mode, respectively. 
     The controller  50  of the control circuit  100  or the processor  3  receiving an output from the control circuit  100  detects the side head proximity condition based on a digital value Ds corresponding to a sensor output (also referred to as “sensor output Ds”). Specifically, if a change in capacitance in the y-axis direction is large in the vicinity of the speaker  704  that approaches the user&#39; ear when calling and small in the vicinity of the microphone  706 , it is determined that the mobile phone  700  is in the side head proximity condition. This determination may be made by comparing the digital value Ds having a spatial resolution in the y-axis direction with a predetermined pattern. 
     In this manner, when the electrostatic capacitive sensor  4  is operated as a proximity sensor, the side head proximity condition can be detected by providing the electrostatic capacitive sensor  4  with a spatial resolution in the long side of the housing  702 . 
       FIGS. 11A to 11C  are views for explaining the side head proximity condition.  FIG. 11A  shows a state of the mobile phone  700 ,  FIG. 11B  shows a sensor output Ds from a proximity sensor having a spatial resolution in the y-axis direction, and  FIG. 11C  shows a sensor output Ds from a touch sensor.  FIGS. 12A to 12C  are views for explaining a condition where a user touches the vicinity of the speaker  704  of the electrostatic capacitive sensor  4 .  FIG. 12A  shows a state of the mobile phone  700 ,  FIG. 12B  shows a sensor output Ds from a proximity sensor having a spatial resolution in the y-axis direction, and  FIG. 12C  shows a sensor output Ds from a touch sensor. 
     As shown in  FIGS. 11B and 12B , there may be some cases where the two conditions shown in  FIGS. 11A and 12A  cannot be distinguished with only a spatial resolution in the y-axis direction. In these cases, as shown in  FIG. 12C , the two conditions can be distinguished by operating the electrostatic capacitive sensor  4  as a touch sensor so that it can have spatial resolutions in both the x-axis and y-axis directions. When the electrostatic capacitive sensor  4  is operated in the second condition as shown in  FIG. 7B , the electrostatic capacitive sensor  4  can distinguish the condition of  FIG. 11A  and the condition of  FIG. 12A  because the electrostatic capacitive sensor unit  4  acts as a proximity sensor having a spatial resolution in the y-axis direction and as a touch sensor having spatial resolutions in the x-axis and y-axis directions. 
     &lt;Grip Detection&gt; 
     In electronic equipment such as the mobile phone  700 , there are some cases in which a condition where a user grips a housing is required to be detected.  FIGS. 13A and 13B  show that an input device  2  according to the embodiments can be also used for a grip sensor.  FIG. 13A  is a view showing a grip condition and  FIG. 13B  is a view showing an output of the electrostatic capacitive sensor  4  under the grip condition. In the grip condition as shown in  FIG. 13A , a change in capacitance of the receiver electrodes  12  at one end of a display to which a user&#39; thumb approaches and of the receiver electrodes  12  at the other end of the display to which the other fingers approach increases, while a change in capacitance of the receiver electrodes  12  disposed in the center of the display decreases. 
     Thus, when the grip condition is detected, at least one of the transmitter circuit  20  and the receiver circuit  26  of the control circuit  100  is set to the second mode so that it can have a spatial resolution in the short side direction (x-axis direction) of the housing  702 . In the example of  FIG. 13B , the transmitter circuit  20  is set to the second mode and all of the transmitter electrodes  10  are grouped into the same group. On the other hand, the receiver circuit  26  is set to the first mode so that it can have a spatial resolution in the x-axis direction. 
     If the transmitter electrodes  10  and the receiver electrodes  12  are arranged in reverse, the transmitter circuit  20  and the receiver circuit  26  may be set to the first mode and the second mode, respectively. 
     The controller  50  of the control circuit  100  or the processor  3  receiving an output from the control circuit  100  detects the grip condition based on the digital value Ds corresponding to the sensor output. Specifically, if a change in capacitance in both ends at the vicinity of the lower and the upper limit of x coordinates is large, it is determined that the mobile phone  700  is in the grip condition. This determination may be made by comparing the digital value Ds having a spatial resolution in the x-axis direction with a predetermined pattern. 
     In this manner, when the electrostatic capacitive sensor  4  is operated as a proximity sensor, the grip condition can be detected by providing the electrostatic capacitive sensor  4  with a spatial resolution in the short side of the housing  702 . 
     In the above, the present disclosure has been described by way of specific embodiments. The disclosed embodiments are merely examples and it is to be understood by those skilled in the art that combinations of elements and processes of the embodiments can be modified in various ways and such modification falls within the scope of the present disclosure. The following description is given to such modification. 
     Although an operation of setting the transmitter circuit  20  or the receiver circuit  26  to the second mode when the electrostatic capacitive sensor  4  is used as a proximity sensor has been illustrated in the above embodiments, the present disclosure is not limited thereto. For example, when the electrostatic capacitive sensor  4  is used as a touch sensor, the transmitter circuit  20  or the receiver circuit  26  may be set to the second mode and a plurality (for example, two) of the transmitter circuits  20  or the receiver circuits  26  may be allocated for each group. In this case, the amplitude of the reception signal I RX  is increased, which may result in reduction of the number of integrations performed by the integration circuit  30  and power consumption in the integration circuit  30 . In this case, since a spatial resolution in the touch sensor is decreased, such setting may be performed under a condition where a high spatial resolution is not required (for example, in a case where an icon on a home screen of the mobile phone  700  is selected). 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel methods and apparatuses described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.