Freescale Semiconductor,inc.

Marcos Augusto De Goes

Stefano Pietri

Alfredo Olmos

Roberto Angelo Bertoli

A method includes driving a current through a touch screen that is based on contact of the touch screen, generating a proportional second current, and detecting contact of the touch screen from the second current. Another method includes providing a touch screen with parallel plates, disabling contact detection when a plate voltage is lower than a threshold voltage, and enabling contact detection when the plate voltage is at least equal to the threshold voltage. A device includes a first node and a second node coupled to a touch screen, a third node, a first current mirror coupled to the second node and the third node configured to generate a current at the third node that is proportional to a second current at the second node, and a detection circuit that provides a signal based on the first current that indicates contact of the touch screen.

Touch screen detection and diagnostics

A multi-stage voltage multiplication circuit and methodology are provided which use a multi-stage charge pump boosting circuit () and two-stage pass gate circuit () having complementary power switches (M, M, M, M) to efficiently develop an output voltage (V) that is higher than the input supply voltage (V). By using a two-stage complementary switch to connect boosted clock signals (P, P) from a charge pump () to the multiplier output (V), return current from the storage capacitor (C) to the pumping capacitor (C, C) is blocked, thereby increasing power transfer efficiency, even at high clock frequencies. In addition, a boosted auxiliary voltage is generated by an additional boosting stage () and applied to the PMOS wells of the pass gate circuit (), thereby preventing latch-up and backflow.

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Paulinia, Brazil

Marcos Augusto De Goes