Design and implementation of capacitive sensor readout circuit on glass substrate for touch panel applications

A capacitive sensor readout circuit on glass substrate for touch panel applications has been designed and fabricated in a 3-μm low temperature poly-silicon (LTPS) technology. In this work, the small voltage difference from capacitance change due to the touch event on panel is amplified by the switch-capacitor (SC) technique. In order to reduce the effect from device characteristic variation in LTPS process, the proposed readout circuit applies the corrected double-sampling (CDS) technique to reduce the offset originated from LTPS process variation. To enhance the resolution of touch panel, a 4-bit analog-to-digital converter is utilized to identify the different touch area conditions.