| 主权项 |
1. An apparatus comprising:
a pulse driver configured to generate a plurality of electrical pulses for transmission to a 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 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 a first electrical pulse, the first edge comprising a rising edge of the first electrical pulse; andhold 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 operable to be coupled to the sense line 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 an area of the capacitive touch sensor; a second capacitor operable to be coupled to the sense line 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 area 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. |
