Touch detecting circuit and semiconductor integrated circuit using the same
A touch detecting circuit is allowed to adaptively operate in accordance with an interconnection length to a sensor capacitor of an object to be detected. For example, the touch detecting circuit has a configuration capable of adjusting a threshold value for determination touch and non-touch or a configuration capable of adjusting detection sensitivity of a detection circuit that is connected to the sensor capacitor. For example, the touch detecting circuit has a configuration which includes an adjustment resistor that is connected in series to a signal line for input from the sensor capacitor at an input portion of the detection circuit, and which is capable of performing adjustment to cancel a difference in an interconnection resistance from a sensor capacitor on a far end side to a sensor capacitor on a near end side.
1. A touch panel controller configured to be coupled to a plurality of sensor capacitors arranged on a touch panel through an interconnection, the touch panel controller comprising:
a terminal configured to connect to the interconnection; and
circuit elements configured to:
detect capacitance values of the plurality of sensor capacitors by sequentially setting each of the plurality of sensor capacitors as a target capacitor and measuring electric charge of the target capacitor through the terminal; and
vary a detection characteristic corresponding to the target capacitor based on an interconnection length from the terminal to the target capacitor compensate for variation in interconnection resistances of the plurality of sensor capacitors.
2. The touch panel controller according to claim 1 , wherein:
the circuit elements comprise a touch recognition circuit configured to detect touch or non-touch to the target capacitor based on a threshold value, where the threshold value is adjusted based on the interconnection length.
3. The touch panel controller according to claim 2 , wherein the circuit elements comprise:
a touch drive circuit configured to charge the target capacitor;
a detection circuit configured to detect electric charge discharged from the target capacitor; and
an AD conversion circuit configured to convert an output of the detection circuit into a digital value correspondinq to a capacitive value of the target capacitor,
wherein the touch recognition circuit is configured to detect touch coordinates based on a plurality of digital values output from the AD conversion circuit.
4. The touch panel controller according to claim 3 , further comprising:
a storage device configured to store parameters for calculation of the threshold value,
wherein the touch recognition circuit is configured to read out the parameters from the storage device in accordance with the interconnection length to the target capacitor.
5. The touch panel controller according to claim 3 , wherein:
the touch recognition circuit includes a processor.
6. The touch panel controller according to claim 1 , further comprising:
a touch drive circuit configured to charge the target capacitor; and
a detection circuit configured to detect electric charge discharged from the target capacitor, and to adjust detection sensitivity based on an interconnection length to the target capacitor.
7. The touch panel controller according to claim 1 , further comprising:
a detection circuit configured to detect electric charge from the target capacitor; and
a resistor coupled in series in between the terminal and an input terminal of the detection circuit, wherein the resistor is configured to adjust a resistance value based on the interconnection length of the target capacitor.
8. The touch panel controller of claim 1 , wherein:
the circuit elements are disposed on a single semiconductor substrate.
9. The touch panel controller according to claim 8 , further comprising:
a display drive circuit configured to be coupled to a display panel configured to overlap the touch panel, the display drive circuit configured to drive and control the display panel, wherein the display drive circuit is disposed on the semiconductor substrate.
10. An input device comprising:
a touch panel controller configured to be coupled to a plurality of sensor capacitors arranged on a touch panel through an interconnection, the touch panel controller comprising:
circuit elements configured to:
a terminal configured to connect to the interconnection; and circuit elements configured to:
detect capacitance values of the plurality of sensor capacitors by sequentially setting each of the plurality of sensor capacitors as a target capacitor and measuring electric charge of the target capacitor through the terminal; and
vary a detection characteristic corresponding to the target capacitor based on an interconnection length from the terminal to the target capacitor compensate for variation in interconnection resistances of the plurality of sensor capacitors.
11. The input device according to claim 10 , wherein:
the circuit elements comprise a touch recognition circuit configured to detect touch or non-touch to the target capacitor based on a threshold value, where the threshold value is adjusted based on the interconnection length.
12. The input device according to claim 11 , wherein the circuit elements comprise:
a touch drive circuit configured to charge the target capacitor;
a detection circuit configured to detect electric charge discharged from the target capacitor; and
an AD conversion circuit configured to convert an output of the detection circuit into a digital value corresponding to a capacitive value of the target capacitor,
wherein the touch recognition circuit is configured to detect touch coordinates based on a plurality of digital values output from the AD conversion circuit.
13. The input device according to claim 12 , further comprising:
a storage device configured to store parameters for calculation of the threshold value,
wherein the touch recognition circuit is configured to read out the parameters from the storage device in accordance with the interconnection length to the target capacitor.
14. The input device according to claim 12 , wherein:
the touch recognition circuit includes a processor.
15. The input device according to claim 10 , further comprising:
a touch drive circuit configured to charge the target capacitor; and
a detection circuit configured to detect electric charge discharged from the target capacitor, and to adjust detection sensitivity based on an interconnection length to the target capacitor.
16. The input device according to claim 10 , further comprising:
a detection circuit configured to detect electric charge from the target capacitor; and
a resistor coupled in series in between the terminal and an input terminal of the detection circuit, wherein the resistor is configured to adjust a resistance value based on the interconnection length of the target capacitor.
17. The input device of claim 10 , wherein:
the circuit elements are disposed on a single semiconductor substrate.
18. The input device according to claim 17 , further comprising:
a display drive circuit coupled to a display panel configured to overlap the touch panel and configured to drive and control the display panel, wherein the display drive circuit is disposed on the semiconductor substrate.
19. A method comprising:
detecting, capacitance values of a plurality of sensor capacitors arranged on a touch panel through an interconnection by sequentially setting each of the plurality of sensor capacitors as a target capacitor and measuring electric charge of the target capacitor through a terminal configured to connect to the interconnection ; and
varying a detection characteristic corresponding to the target capacitor based on an interconnection length from the terminal to the target capacitor to compensate for variation in interconnection resistances of the plurality of sensor capacitors.
20. The method of claim 19 , further comprising:
detecting touch or non-touch to the target capacitor based on a threshold value, where the threshold value is adjusted based on the interconnection length.