Mutual-capacitive touch sensing circuit and noise suppressing method applied to mutual-capacitive touch panel

A mutual-capacitive touch sensing circuit, applied to a mutual-capacitive touch panel, for sensing a capacitance variation of a capacitor when the mutual-capacitive touch panel is touched and suppressing an external environmental noise, the mutual-capacitive touch sensing circuit comprising:

• an operational amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to a terminal of the capacitor and the second input terminal is coupled to ground, and the output terminal outputs an output voltage;
• an analog-to-digital converter coupled to the output terminal of the operational amplifier;
• a digital signal processor coupled to the analog-to-digital converter;
• a first polarity unit, coupled between the analog-to-digital converter and the digital signal processor, for receiving the output voltage having digital form converted from analog form by the analog-to-digital converter and then outputting the output voltage to the digital signal processor by maintaining a polarity of the output voltage;
• a second polarity unit, coupled between the analog-to-digital converter and the digital signal processor, for receiving the output voltage having digital form converted from analog form by the analog-to-digital converter and then outputting the output voltage to the digital signal processor by reversing the polarity of the output voltage;
• an internal capacitor coupled between the output terminal and the first input terminal of the operational amplifier;
• a first switch having a terminal coupled to a first external charging voltage and another terminal coupled between the capacitor and the first input terminal;
• a second switch having a terminal coupled to a second external charging voltage and another terminal coupled to another terminal of the capacitor;
• a third switch having a terminal coupled to a third external charging voltage and another terminal coupled to the another terminal of the second switch and the another terminal of the capacitor;
• a first capacitor having a terminal coupled between the capacitor and the first input terminal and another terminal coupled to ground;
• and
• a second capacitor having a terminal coupled to the another terminal of the capacitor and another terminal coupled to ground;
• wherein the second external charging voltage and the third external charging voltage have the same magnitude but opposite polarities;
• the first switch, the second switch and the third switch are switched in a specific order to make the first external charging voltage and the second external charging voltage to charge the capacitor, the first external charging voltage and the third external charging voltage to charge the capacitor, or only the second external charging voltage or the third external charging voltage to charge the capacitor.

A mutual-capacitive touch sensing circuit, applied to a mutual-capacitive touch panel, for sensing a capacitance variation of a capacitor when the mutual-capacitive touch panel is touched and suppressing an external environmental noise, the mutual-capacitive touch sensing circuit comprising:

• an operational amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to a terminal of the capacitor and the second input terminal is coupled to ground, and the output terminal outputs an output voltage;
• an analog-to-digital converter coupled to the output terminal of the operational amplifier;
• a digital signal processor coupled to the analog-to-digital converter;
• a first polarity unit, coupled to the digital signal processor, for receiving the output voltage having digital form converted from analog form by the analog-to-digital converter and processed by the digital signal processor and then maintaining a polarity of the output voltage;
• a second polarity unit, coupled to the digital signal processor, for receiving the output voltage having digital form converted from analog form by the analog-to-digital converter and processed by the digital signal processor and then reversing the polarity of the output voltage;
• an internal capacitor coupled between the output terminal and the first input terminal of the operational amplifier;
• a first switch having a terminal coupled to a first external charging voltage and another terminal coupled between the capacitor and the first input terminal;
• a second switch having a terminal coupled to a second external charging voltage and another terminal coupled to another terminal of the capacitor;
• a third switch having a terminal coupled to a third external charging voltage and another terminal coupled to the another terminal of the second switch and the another terminal of the capacitor;
• a first capacitor having a terminal coupled between the capacitor and the first input terminal and another terminal coupled to ground;
• and
• a second capacitor having a terminal coupled to the another terminal of the capacitor and another terminal coupled to ground;
• wherein the second external charging voltage and the third external charging voltage have the same magnitude but opposite polarities;
• the first switch, the second switch and the third switch are switched in a specific order to make the first external charging voltage and the second external charging voltage to charge the capacitor, the first external charging voltage and the third external charging voltage to charge the capacitor, or only the second external charging voltage or the third external charging voltage to charge the capacitor.