A readout IC for capacitive touch screen panels with 33.9 dB charge-overflow reduction using amplitude-modulated multi-frequency excitation

JS An, JH Ra, E Kang, MAP Pertijs… - IEEE Journal of Solid …, 2021 - ieeexplore.ieee.org
IEEE Journal of Solid-State Circuits, 2021ieeexplore.ieee.org
This article presents a readout integrated circuit (ROIC) for capacitive touch-screen panels
(TSPs) employing an amplitude-modulated multiple-frequency excitation (AM-MFE)
technique. To prevent charge overflow, which occurs periodically at the beat frequency of
the excitation frequencies, the ROIC modulates the amplitude of the excitation voltages at a
mixing frequency derived from the excitation frequencies. Thus, the ROIC can sense the
charge signal without charge overflow and maximize the signal-to-noise ratio (SNR) by …
This article presents a readout integrated circuit (ROIC) for capacitive touch-screen panels (TSPs) employing an amplitude-modulated multiple-frequency excitation (AM-MFE) technique. To prevent charge overflow, which occurs periodically at the beat frequency of the excitation frequencies, the ROIC modulates the amplitude of the excitation voltages at a mixing frequency derived from the excitation frequencies. Thus, the ROIC can sense the charge signal without charge overflow and maximize the signal-to-noise ratio (SNR) by increasing the amplitude of the excitation voltages up to the sensing range of the readout circuit. The proposed ROIC was fabricated in a 0.13- standard CMOS process and was measured with a 32-in 104 64 touch-screen panel using 1 and 10 mm metal pillars. It reduces charge overflow up to 33.9 dB compared to operation without AM-MFE. In addition, the ROIC achieves a frame rate of 2.93 kHz, and SNRs of 41.7 and 61.6 dB with 1 and 10 mm metal pillars, respectively.
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