Patent attributes
A device (116) for processing signals from a projected capacitance touch panel (43) is described. The projected capacitance touch panel (43) includes a layer of piezoelectric material (9) disposed between a number of sensing electrodes (7, 27) and at least one counter electrode (8). The device (116) includes a capacitive touch controller (84) having a number of measurement ports (122). The device (116) also includes a number of charge amplifiers (123). The device (116) also includes a number of terminals (C1, . . . , C5, D1, . . . , D5) for connection to the sensing electrodes (7, 27) of the projected capacitance touch panel (43). Each terminal (C1, . . . , C5, D1, . . . , D5) is connected to one of the measurement ports (122). Each terminal (C1, . . . , C5, D1, . . . , D5) is also connected to an input of one of the charge amplifiers (123) via a corresponding switch (SW) of a number of switches (117a, 117b). The device (116) also includes a controller (121) configured to synchronise the capacitive touch controller (84) and the number of switches (SW, 117a, 117b) so that during a first portion ([t1, t2]) of a cycle the capacitive touch controller (84) outputs a capacitance measurement signal (91) to one or more of the terminals (C1, . . . , C5, D1, . . . , D5), and the plurality of charge amplifiers (123) are disconnected from the terminals (C1, . . . , C5, D1, . . . , D5) by the respective switches (SW, 117a, 117b). The controller (121) is also configured to synchronise the capacitive touch controller (84) and the number of switches (SW, 117a, 117b) so that during a second portion ([t2, t7]) of the cycle the capacitive touch controller (84) does not output the capacitance measurement signal (91), and one or more of the charge amplifiers (123) are connected to the corresponding terminals (C1, . . . , C5, D1, . . . , D5) by the respective switches (SW, 117a, 117b).
