Mobile screen capacitive touch panel controller

STAR2001 is a touch panel controller ASIC for smart phone and tablet sized projective-capacitive touch screens (PCTS). It is extremely flexible, allowing it to be operated in self or mutual capacitance modes, as well as using single-ended or differential transmit (TX) and receive (RX) functions. Fabricated in a standard CMOS 0.18µm process, STAR2001 has a proprietary design to provide maximum flexibility in terms of sampling techniques used by the RX analog front end (AFE). An optional on-chip charge pump enables TX driving voltages from 4V to 9V. Panel lines in mutual cap mode can be driven differentially with 2 or 3-level drive and sensed differentially to ensure baseline (pedestal) values remain negligible and all lines are sensed accurately. Single-ended modes have mechanisms built in to cancel baseline voltages. Low power self-cap modes can be operated in a one-dimensional fashion for touch-to-wake, or in a two-dimensional way for simple gesture recognition and water detection. Mutual and self-cap modes can be operated together to combine their features, as shown in Figure 1. STAR2001 is supported by firmware and algorithms that allow detection of up to 10 fingers. Its highly configurable nature allows for firmware programming to perform analog and digital signal processing to mitigate the effects of display, charger, finger, and other noise sources. Algorithms written for STAR2001 use proprietary techniques to update existing fingers, find and remove large objects, reject water, search for hotspots, do wobble and edge correction, and report active fingers among other enhancements. Support for frequency hopping mitigates interference from noise with frequencies at or near the ASIC's frequency of operation.