CAPACITIVE TOUCH SYSTEM

• US 20160179249A1
• Filed: 08/19/2014
• Published: 06/23/2016
• Est. Priority Date: 08/20/2013
• Status: Active Grant

• Current Assignee: Advanced Silicon SA
• Original Assignee: Advanced Silicon SA
• Inventors: BALLAN, Hussein, BAUSER, Philippe
• Granted Patent: US 9,933,904 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• 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 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• 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

The invention concerns a capacitive touch system comprising: an active stylus (800) configured so as to continuously emit a signal a capacitive touch device (200) configured to be in a reset phase (1000), followed by a finger touch sensing phase (2000), the finger touches being sensed exclusively during the finger touch sensing phase (2000). The capacitive touch device (200) is configured to sense the signal from the active stylus (800) during the reset phase (1000). The capacitive touch device (200) comprises at least one charge sensor (208, 213) comprising a charge sensor amplifier (305) comprising an input (CSi) and an output (csaout), and a switch (Sw1) between this input (CSi) and this output (csaout). The charge sensor amplifier (305) is arranged for conveying the signal of the active stylus (800) through a non-zero resistance value (Ron) of the switch (Sw1) during the reset phase (1000).

Claims

1. A capacitive touch system comprising:

an active stylus, said active stylus comprising an oscillator, said oscillator being configured so as to continuously emit a signal,

a capacitive touch device configured to be in a reset phase, followed by a finger touch sensing phase, different from said reset phase, finger touches being sensed exclusively during said finger touch sensing phase,

wherein said capacitive touch device is configured to sense said signal from said active stylus during said reset phase,

wherein said capacitive touch device comprises at least one charge sensor, said charge sensor comprising

a charge sensor amplifier, said charge sensor amplifier comprising an input and an output, and

a switch between said input and said output, said switch being arranged to be open and closed,

the charge sensor amplifier being arranged for conveying the signal of the active stylus from said input to said output through a non-zero resistance value of said switch when said switch is closed, so as to connect said input with said output, wherein said reset phase corresponds to the time period during which said switch is closed, so as to connect said input with said output.

3. The capacitive touch system of claim 1, wherein the capacitive touch device comprises a plurality of lines being enabled sequentially by a token, in which each time a line is enabled, it is configured to be in said reset phase followed by said finger touch sensing phase, finger touches being sensed exclusively during said finger touch sensing phase, active stylus being sensed exclusively during said reset phase.

4. The capacitive touch system of one of claim 1, wherein said charge sense amplifier comprises a feedback capacitor, and wherein the frequency of the signal emitted from said active stylus belongs to the frequency range of the band pass characteristics of said charge sense amplifier in said reset mode.

5. The capacitive touch system of claim 1, wherein each charge sensor comprises a Stylus Signal Amplitude Detection and Conversion module for calculating the X coordinates of said active stylus.

6. The capacitive touch system of claim 1, comprising at least one N to 1 multiplexer, arranged for sequentially connecting the outputs of N charge sensors to a single Stylus Signal Amplitude Detection and Conversion module for calculating the X coordinates of said active stylus.

7. The capacitive touch system of claim 1, comprising at least one charge driver, each charge driver being configured for addressing a driving signal to a corresponding row of said capacitive touch device in response to an input signal, wherein said charge driver is configured to be in a high impedance mode during a time slot during which it is not used for the finger touch detection, so as to read the signal coming from said active stylus.

8. The capacitive touch system of claim 7, wherein each charge driver comprises:

a high side switch,

a low side switch,

a rest side switch,

a high side driver,

a low side driver,

a rest side driver,

a Boolean AND logic gate placed between the high side driver and the high side switch,

a Boolean AND logic gate placed between the low side driver and the low side switch,

a Boolean AND logic gate placed between the rest side driver and the rest side switch,

a high impedance control input, arranged to force the high side switch, the low side switch and the rest side switch in an OFF state, and then in said high impedance mode.

9. The capacitive touch system of claim 7, wherein said time slot during which said charge driver is not used for the finger touch detection correspond to said reset phase.

10. The capacitive touch system of claim 7, wherein each charge driver comprises a Stylus Signal Amplitude Detection and Conversion module for calculating the Y coordinates of said active stylus.

11. The capacitive touch system of claim 7, comprising a single Stylus Signal Amplitude Detection and Conversion module for all the charge drivers for calculating the Y coordinates of said active stylus.

12. The capacitive touch system of claim 11, comprising a wired-OR line connected to the output of each charge driver by a switch which is arranged to be activated when a token and a signal defining the time slot during which said charge driver is not used for the finger touch detection are asserted, said wired-OR line being connected to said single Stylus Signal Amplitude Detection and Conversion module.

13. The capacitive touch system of claim 1, wherein said active stylus comprises an encoder and/or a modulator for transmitting encoded and/or modulated pen digital data into said capacitive touch device, said capacitive touch device being arranged so as to extract said data during the time that separates two consecutive frames, each frame corresponding to the time during which said token circulates from a first row to a last row of said capacitive touch panel.

2. (canceled)

14. A method for a capacitive touch system comprising an active stylus and a capacitive touch device,

said active stylus comprising an oscillator, said oscillator being configured so as to continuously emit a signal,

said capacitive touch device comprises at least one charge sensor, said charge sensor comprising

a charge sensor amplifier, said charge sensor amplifier comprising an input and an output, and

a switch between said input and said output, said switch being arranged to be open and closed

comprising the following steps:

sensing said one or more finger touches exclusively during a finger touch sensing phase,

sensing said signal from said active stylus during a reset phase different from said finger touch sensing phase,

said sensing said signal from said active stylus comprising;

conveying the signal of the active stylus from said input to said output through a non-zero resistance value of said switch when said switch is closed so as to connect said input with said output

wherein said reset phase corresponds to the time period during which said switch is closed, so as to connect said input with said output.

15. The method of claim 14, comprising:

transmitting encoded and/or modulated pen digital data from said active stylus into said capacitive touch device,

extracting by said capacitive touch device said data during the time that separates two consecutive frames, each frame corresponding to the time during which a token circulates from a first row to a last row of said capacitive touch panel.