Semiconductor device

• US 9,292,137 B2
• Filed: 05/21/2013
• Issued: 03/22/2016
• Est. Priority Date: 05/21/2012
• Status: Expired due to Fees

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: Kogo, Teruyuki
• Primary Examiner(s): Balaoing, Ariel
• Assistant Examiner(s): Oehrlein, Stefan M
• Application Number:
  US13/899,445
• Publication Number:
  US 20130307821A1
• Time in Patent Office: 1,036 Days
• Field of Search: 345/173, 345/174
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A semiconductor device for use in a touch panel is capable of uniquely identifying the touched coordinates over the touch panel. When a multi-touch state is detected over the touch panel by a self-capacitance method, the semiconductor device isolates the multiple touch electrodes found to be in the touch state and has these electrodes identified by a mutual capacitance method.

Claims

1. A semiconductor device coupled to a first touch electrode group in a first direction and to a second touch electrode group in a second direction intersecting with said first direction, the two touch electrode groups configuring a touch panel, said semiconductor device comprising:

a first detection circuit detecting whether stray capacitance of each of the touch electrodes configuring said first and said second touch electrode groups has increased compared with when said touch panel is not touched;

a control circuit determining whether there is a multi-touch state in which the stray capacitance of a plurality of touch electrodes in said first touch electrode group and the stray capacitance of a plurality of touch electrodes in said second touch electrode group have increased;

a voltage application circuit applying a voltage to the touch electrodes of which the stray capacitance has increased in said first touch electrode group when said multi-touch state is in effect; and

a second detection circuit detecting a voltage change of each of the touch electrodes of which the stray capacitance has increased in said second touch electrode group when said voltage application circuit applies the voltage, wherein

when said multi-touch state is in effect, said control circuit identifies a touched area over said touch panel based on the result of the detection by said second detection circuit,

for detecting the stray capacitance of a given touch electrode in the first and second touch electrode groups, the first detection circuit detects a divided voltage of the given touch electrode when a predetermined voltage is applied to one of the ends of a first capacitive element of which the other end is serially coupled to the given touch electrode,

for detecting the stray capacitance of the given touch electrode, the first detection circuit performs a precharging operation to precharge a second capacitive element coupled to the other end of the first capacitive element via a resistive element,

after the precharging operation, the first detection circuit alternately performs a discharging operation and a detecting operation, the discharging operation fully discharging the given touch electrode, fully discharging the first capacitive element, and partially discharging the second capacitive element by coupling both ends of the first capacitive element to a ground node, the detecting operation detecting the divided voltage of the given touch electrode when the voltage of the second capacitive element is applied as the predetermined voltage to the other end of the first capacitive element,

the first detection circuit includes a first counter configured to increment a first counter value every time a detected voltage of the given touch electrode exceeds a first predetermined reference voltage, during the detecting operation,

the control circuit determines whether the stray capacitance of the given touch electrode has increased on the basis of the number of times the discharging operation is performed until the voltage of the given touch electrode drops below the predetermined first reference voltage, based on the first counter value of the first counter,

when the first and second touch electrode groups each include touch electrodes having an increased stray capacitance, the second detection circuit applies a voltage to one of the touch electrodes of the first touch electrode group, and detects when a voltage of a corresponding touch electrode in the second electrode group exceeds a predetermined second reference voltage,

the second detection circuit includes a second counter to increment a second counter value until the voltage of the corresponding touch electrode in the second electrode group exceeds the predetermined second reference voltage, and

the control circuit determines where on the touch panel is touched, based on the second counter value of the second detection circuit.

2. The semiconductor device according to claim 1, wherein, with said voltage application circuit applying the voltage to a given first touch electrode in said first touch electrode group, when the time required for the voltage of a given second touch electrode in said second touch electrode group to reach a predetermined first reference voltage is longer than when said touch panel is not touched, then said control circuit identifies as the touched area the area where said given first touch electrode and said given second touch electrode intersect with one another.

3. The semiconductor device according to claim 1, wherein, when there is one touch electrode of which the stray capacitance has increased in said first touch electrode group and when there is one touch electrode of which the stray capacitance has increased in said second touch electrode group, then said control circuit identifies as the touched area the area where the touch electrode of which the stray capacitance has increased in said first touch electrode group and the touch electrode of which the stray capacitance has increased in said second touch electrode group intersect with one another.