A Hybrid Touch Sensing AFE with Common-CVQ (Currents, Voltages, and Charges) Subtraction to Improve Display Noise Immunity for Large Sensing Load up to 820pF

Flexible on-cell touch OLED displays face significant display noise challenges due to large parasitic capacitance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(C_{P})$</tex>. To address the limitations of conventional methods, this paper proposes improved common-current subtraction (CCS) incorporating common-voltage subtraction (CVS) and common-charge subtraction (CQS) techniques. CVS enhances SNR by up to 6.72 dB in self-capacitance (SC) sensing and 6.33 dB in mutual capacitance (MC) sensing, while CQS increases the operational load capacity from 390 pF to 820 pF. Fabricated in 65 nm CMOS, the proposed AFE achieves a twofold improvement in input dynamic range (DR) and consistent performance under display noise (D-noise) injection.