A Readout IC for Capacitive Touch Screen Panels With 33.9 dB Charge-Overflow Reduction Using Amplitude-Modulated Multi-Frequency Excitation

Jae Sung An, Jong Hyun Ra, Eunchul Kang, Michiel A.P. Pertijs, Sang Hyun Han

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Abstract

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- $\mu \text{m}$ standard CMOS process and was measured with a 32-in 104 $\times $ 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.

Original languageEnglish
Pages (from-to)3486-3498
Number of pages13
JournalIEEE Journal of Solid-State Circuits
Volume56
Issue number11
DOIs
Publication statusPublished - 2021

Bibliographical note

Accepted Author Manuscript

Keywords

  • Amplitude-modulated multi-frequency excitation (AM-MFE)
  • capacitive touch system (CTS)
  • charge overflow reduction
  • frame rate
  • readout IC (ROIC)
  • signal-to-noise ratio (SNR)
  • touch screen panel (TSP).

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