Capacitive touch sensor control unit with sampling capacitors for differential integration

A method comprising:

• generating a first electrical pulse for transmission to a capacitive touch sensor;
• holding a first switch closed and a second switch open to couple a first capacitor to a sense line of the capacitive touch sensor for the duration of a first edge of the first electrical pulse, the first edge comprising a rising edge of the first electrical pulse, the first switch and the second switch coupled in parallel to the sense line of the capacitive touch sensor;
• receiving, at the first capacitor during the duration of the rising edge of the first electrical pulse, a first amount of charge from the sense line through a current induced by the rising edge of the first electrical pulse;
• holding the first switch open and the second switch closed to couple a second capacitor to the sense line of the capacitive touch sensor for the duration of a second edge of the electrical pulse, the second edge comprising a falling edge of the first electrical pulse, the first electrical pulse held generally constant between the falling edge and the rising edge;
• discharging, from the second capacitor while the second switch is closed during the duration of the falling edge of the first electrical pulse, a second amount of charge from the sense line through a current induced by the falling edge of the first electrical pulse;
• and
• providing, by a differential output, a measure of the voltage difference between the first capacitor and second capacitor to a portion of a backend circuit.

An apparatus, comprising:

• a capacitive touch sensor comprising a plurality of nodes;
• and
• a control unit coupled to the capacitive touch sensor, the control unit comprising:
• a pulse driver configured to generate a plurality of electrical pulses for transmission to a node of the plurality of nodes of the capacitive touch sensor;
• a timing circuit coupled to a first switch and a second switch, the first switch and the second switch coupled in parallel to a sense line associated with the node of the capacitive touch sensor, the timing circuit configured to:
• hold the first switch closed and the second switch open for the duration of a first edge of the first electrical pulse, the first edge comprising a rising edge of the first electrical pulse;
• and
• hold the second switch closed and the first switch open for the duration of a second edge of the first electrical pulse, the second edge comprising a falling edge of the first electrical pulse, the first electrical pulse held generally constant between the falling edge and the rising edge;
• a first capacitor selectively coupled to the sense line associated with the node of the capacitive touch sensor through the first switch, the first capacitor configured to receive, while the first switch is closed during the duration of the rising edge of the first electrical pulse, a first amount of charge that is indicative of a capacitance of the node of the capacitive touch sensor;
• a second capacitor selectively coupled to the sense line associated with the node of the capacitive touch sensor through the second switch, the second capacitor configured to discharge, while the second switch is closed during the duration of the falling edge of the first electrical pulse, a second amount of charge that is indicative of the capacitance of the node of the capacitive touch sensor;
• and
• a differential output coupled to the first capacitor and second capacitor, the differential output configured to provide, to a portion of a backend circuit, a measure of the voltage difference between the first capacitor and second capacitor.