Stmicroelectronics Asia Pacific Pte Limited

Abhishek Singh

Hugo Gicquel

Dianbo Guo

EngJye Ng

Disclosed herein is a circuit including a driver circuit applying a received drive signal to a capacitive sensing line of a capacitive touch panel as a boosted drive signal, the driver circuit powered by a boosted supply voltage. A charge pump circuit receives an input supply voltage and output the boosted supply voltage, the charge pump circuit including a voltage sensing circuit to sense the boosted supply voltage and a comparison circuit to compare the sensed boosted supply voltage to a threshold and produce a comparison signal. A control circuit determines a ratio of a pulse width of the comparison signal to the drive signal, and tunes operation of the charge pump circuit to drive the ratio to match a performance threshold.

Auto-tunable drive system for high efficiency synchronized charge pump for use with touch screen system

Disclosed herein is a touch screen controller including a driver circuit applying a drive signal to a drive line of a capacitive touch sensing panel. The driver circuit is powered by an accurate supply voltage. A driver supply circuit receives an input supply voltage and outputs the accurate supply voltage. The driver supply circuit includes a clocked comparator comparing a divided version of the accurate supply voltage to a reference voltage and outputting a comparison signal based thereupon. A voltage control circuit (e.g. a charge pump circuit) generates the accurate supply voltage in response to the comparison signal. The clocked comparator and voltage control circuit are both clocked by a driver supply circuit clock.

Highly accurate synchronized charge pump for capacitive touch screen system

An alternating current (AC) drive signal having a first frequency and a high logic level at a boosted supply voltage is applied to drive a capacitive sensing line of a capacitive touch panel. The boosted supply voltage is generated by boosting an input voltage. The voltage boosting is effectuate by a charge pump circuit operating synchronous to assertion of the AC drive signal with a charge transfer time that is adaptable to different capacitive load conditions.

Highly efficient charge pump synchronized to the drive signal of a touch screen system

A microelectronic short circuit detection module is disclosed that locates and distinguishes among different types of short circuits in touch screen panels. Individual short circuit detection circuits are coupled to force and sense lines throughout a wire matrix within the touch screen. If the line is shorted to a neighboring line or any other line carrying an opposite logic state, its logic state will be corrupted by the short and will be held at a value opposite that of the intended input signal. Comparing the input and the output therefore provides an indicator of a short circuit to another force or sense line in the wire matrix. A pair of pull up/down stages is engaged to detect whether the short is coupled to power or ground. A threshold resistor can be varied to adjust detection sensitivity. By conducting a serial test, matrix coordinates of the short circuit can be identified.

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Singapore, Singapore

Abhishek Singh